Luca Cocchi - Academia.edu (original) (raw)

Papers by Luca Cocchi

Cerebral Cortex, 2010

Repetition of environmental sounds, like their visual counterparts, can facilitate behavior and m... more Repetition of environmental sounds, like their visual counterparts, can facilitate behavior and modulate neural responses, exemplifying plasticity in how auditory objects are represented or accessed. It remains controversial whether such repetition priming/suppression involves solely plasticity based on acoustic features and/or also access to semantic features. To evaluate contributions of physical and semantic features in eliciting repetition-induced plasticity, the present functional magnetic resonance imaging (fMRI) study repeated either identical or different exemplars of the initially presented object; reasoning that identical exemplars share both physical and semantic features, whereas different exemplars share only semantic features. Participants performed a living/manmade categorization task while being scanned at 3T. Repeated stimuli of both types significantly facilitated reaction times versus initial presentations, demonstrating perceptual and semantic repetition priming. There was also repetition suppression of fMRI activity within overlapping temporal, premotor, and prefrontal regions of the auditory ''what'' pathway. Importantly, the magnitude of suppression effects was equivalent for both physically identical and semantically related exemplars. That the degree of repetition suppression was irrespective of whether or not both perceptual and semantic information was repeated is suggestive of a degree of acoustically independent semantic analysis in how object representations are maintained and retrieved.

Neuropsychologia, 2011

Increasing evidence suggests that working memory and perceptual processes are dynamically interre... more Increasing evidence suggests that working memory and perceptual processes are dynamically interrelated due to modulating activity in overlapping brain networks. However, the direct influence of working memory on the spatio-temporal brain dynamics of behaviorally relevant intervening information remains unclear. To investigate this issue, subjects performed a visual proximity grid perception task under three different visual-spatial working memory (VSWM) load conditions. VSWM load was manipulated by asking subjects to memorize the spatial locations of 6 or 3 disks. The grid was always presented between the encoding and recognition of the disk pattern. As a baseline condition, grid stimuli were presented without a VSWM context. VSWM load altered both perceptual performance and neural networks active during intervening grid encoding. Participants performed faster and more accurately on a challenging perceptual task under high VSWM load as compared to the low load and the baseline condition. Visual evoked potential (VEP) analyses identified changes in the configuration of the underlying sources in one particular period occurring 160-190 ms post-stimulus onset. Source analyses further showed an occipito-parietal down-regulation concurrent to the increased involvement of temporal and frontal resources in the high VSWM context. Together, these data suggest that cognitive control mechanisms supporting working memory may selectively enhance concurrent visual processing related to an independent goal. More broadly, our findings are in line with theoretical models implicating the engagement of frontal regions in synchronizing and optimizing mnemonic and perceptual resources towards multiple goals.

Psychiatry Research, 2007

Recent findings suggest that the visuo-spatial sketchpad (VSSP) may be divided into two sub-compo... more Recent findings suggest that the visuo-spatial sketchpad (VSSP) may be divided into two sub-components processing dynamic or static visual information. This model may be useful to elucidate the confusion of data concerning the functioning of the VSSP in schizophrenia. The present study examined patients with schizophrenia and matched controls in a new working memory paradigm involving dynamic (the Ball Flight Task -BFT) or static (the Static Pattern Task -SPT) visual stimuli. In the BFT, the responses of the patients were apparently based on the retention of the last set of segments of the perceived trajectory, whereas control subjects relied on a more global strategy. We assume that the patients' performances are the result of a reduced capacity in chunking visual information since they relied mainly on the retention of the last set of segments. This assumption is confirmed by the poor performance of the patients in the static task (SPT), which requires a combination of stimulus components into object representations. We assume that the static/dynamic distinction may help us to understand the VSSP deficits in schizophrenia. This distinction also raises questions about the hypothesis that visuo-spatial working memory can simply be dissociated into visual and spatial sub-components.

Australian and New Zealand Journal of Psychiatry, 2009

Objective: Patients with schizophrenia show deficits in visuospatial working memory and visual pu... more Objective: Patients with schizophrenia show deficits in visuospatial working memory and visual pursuit processes. It is currently unclear, however, whether both impairments are related to a common neuropathological origin. The purpose of the present study was therefore to examine the possible relations between the encoding and the discrimination of dynamic visuospatial stimuli in schizophrenia. Method: Sixteen outpatients with schizophrenia and 16 control subjects were asked to encode complex disc displacements presented on a screen. After a delay, participants had to identify the previously presented disc trajectory from a choice of six static linear paths, among which were five incorrect paths. The precision of visual pursuit eye movements during the initial presentation of the dynamic stimulus was assessed. The fixations and scanning time in definite regions of the six paths presented during the discrimination phase were investigated. Results: In comparison with controls, patients showed poorer task performance, reduced pursuit accuracy during incorrect trials and less time scanning the correct stimulus or the incorrect paths approximating its global structure. Patients also spent less time scanning the leftmost portion of the correct path even when making a correct choice. The accuracy of visual pursuit and head movements, however, was not correlated with task performance. Conclusions: The present study provides direct support for the hypothesis that active integration of visuospatial information within working memory is deficient in schizophrenia. In contrast, a general impairment of oculomotor mechanisms involved in smooth pursuit did not appear to be directly related to lower visuospatial working memory performance in schizophrenia.

Psn-psychiatrie Sciences Humaines Neurosciences, 2007

Le rapport entre les facultés psychologiques de l’être humain et les caractéristiques biologiques... more Le rapport entre les facultés psychologiques de l’être humain et les caractéristiques biologiques qui les sous-tendent s’ancre dans le questionnement philosophique traditionnel des rapports de la matière et de l’esprit, avec son corollaire éthique de la question de la liberté et du déterminisme. L’appréhension neurobiologique des activités mentales se trouve ainsi être une nouvelle manière, celle de notre époque, d’articuler les rapports du biologique et du psychique. Dans ce domaine, force est de constater que c’est souvent à partir de postulats ontologiques implicites, ou tout au moins de partis pris épistémologiques, pas toujours conscients, que vont découler les différentes positions observées moniste ou dualiste, fonctionnaliste, réductionniste, éliminativiste, identité des types... et autres variations plus ou moins raffinées. Ayant conscience de ces écueils, on peut toutefois chercher à mettre en évidence des analogies de structures au travers des différents niveaux du vivant et du mental. Ainsi, en vat-il du déséquilibre énergétique « entretenu » pour la survive de la cellule; des rapports dynamiques et complémentaires entre les fonctions homéostatiques et allostatiques des organismes vivants; de la tension entre les mécanismes complémentaires cérébraux, nécessaires à toute cognition, qui sont ceux servant à la représentation et ceux servant à la localisation d’un object dans l’espace. Tous ces phénomènes présentent certaines analogies de structures, bien qu’étant à l’œuvre à des niveaux différents du vivant. The relationship between the human psychological faculties and their underlying biological foundation is traditionally addressed within the mind-matter philosophical framework and its ethical extension regarding freedom and determinism. Neurobiology represents a new method, reflective of our times, to articulate the relationships between biological and psychological phenomena. The various points of view in this field are often based on implicit ontological presuppositions and, at least sometimes, unconscious epistemological assumptions: monism vs dualism, functionalism, reductionism, eliminativism, type identity and other more or less sophisticated variations. Bearing in mind the pitfalls these create, we can try to determine structural analogies across the different levels of the living being and the mind: the energy imbalance maintained for cell survival; the dynamic and complementary relationship between homeostatic and allostatic functions in living organisms; the tension between essential and complementary cognitive brain processes, such as the processes used to represent an object and those used to locate an object in space. Those phenomena all bear structural analogies, even though they work at different levels.

Behavioural Brain Research, 2008

In the Morris water maze (MWM) task, proprioceptive information is likely to have a poor accuracy... more In the Morris water maze (MWM) task, proprioceptive information is likely to have a poor accuracy due to movement inertia. Hence, in this condition, dynamic visual information providing information on linear and angular acceleration would play a critical role in spatial navigation. To investigate this assumption we compared rat's spatial performance in the MWM and in the homing hole board (HB) tasks using a 1.5 Hz stroboscopic illumination. In the MWM, rats trained in the stroboscopic condition needed more time than those trained in a continuous light condition to reach the hidden platform. They expressed also little accuracy during the probe trial. In the HB task, in contrast, place learning remained unaffected by the stroboscopic light condition. The deficit in the MWM was thus complete, affecting both escape latency and discrimination of the reinforced area, and was thus task specific. This dissociation confirms that dynamic visual information is crucial to spatial navigation in the MWM whereas spatial navigation on solid ground is mediated by a multisensory integration, and thus less dependent on visual information.

Psn-psychiatrie Sciences Humaines Neurosciences, 2007

Le rapport entre les facultés psychologiques de l’être humain et les caractéristiques biologiques... more Le rapport entre les facultés psychologiques de l’être humain et les caractéristiques biologiques qui les sous-tendent s’ancre dans le questionnement philosophique traditionnel des rapports de la matière et de l’esprit, avec son corollaire éthique de la question de la liberté et du déterminisme. L’appréhension neurobiologique des activités mentales se trouve ainsi être une nouvelle manière, celle de notre époque, d’articuler les rapports du biologique et du psychique. Dans ce domaine, force est de constater que c’est souvent à partir de postulats ontologiques implicites, ou tout au moins de partis pris épistémologiques, pas toujours conscients, que vont découler les différentes positions observées moniste ou dualiste, fonctionnaliste, réductionniste, éliminativiste, identité des types... et autres variations plus ou moins raffinées. Ayant conscience de ces écueils, on peut toutefois chercher à mettre en évidence des analogies de structures au travers des différents niveaux du vivant et du mental. Ainsi, en vat-il du déséquilibre énergétique « entretenu » pour la survive de la cellule; des rapports dynamiques et complémentaires entre les fonctions homéostatiques et allostatiques des organismes vivants; de la tension entre les mécanismes complémentaires cérébraux, nécessaires à toute cognition, qui sont ceux servant à la représentation et ceux servant à la localisation d’un object dans l’espace. Tous ces phénomènes présentent certaines analogies de structures, bien qu’étant à l’œuvre à des niveaux différents du vivant. The relationship between the human psychological faculties and their underlying biological foundation is traditionally addressed within the mind-matter philosophical framework and its ethical extension regarding freedom and determinism. Neurobiology represents a new method, reflective of our times, to articulate the relationships between biological and psychological phenomena. The various points of view in this field are often based on implicit ontological presuppositions and, at least sometimes, unconscious epistemological assumptions: monism vs dualism, functionalism, reductionism, eliminativism, type identity and other more or less sophisticated variations. Bearing in mind the pitfalls these create, we can try to determine structural analogies across the different levels of the living being and the mind: the energy imbalance maintained for cell survival; the dynamic and complementary relationship between homeostatic and allostatic functions in living organisms; the tension between essential and complementary cognitive brain processes, such as the processes used to represent an object and those used to locate an object in space. Those phenomena all bear structural analogies, even though they work at different levels.

Journal of Geophysical Research, 2006

We present an algorithm for the linear inversion of two-dimensional (2-D) surface magnetic data t... more We present an algorithm for the linear inversion of two-dimensional (2-D) surface magnetic data to obtain 3-D models of the susceptibility of the source. The forward model is discretized by a mesh of prismatic cells with constant magnetization that allows the recovery of a complete 3-D generating source. As the number of cells are normally greater than the amount of available data, we have to solve an underdetermined linear inverse problem. A Tikhonov regularization of the solution is introduced as a depth-weighting function adapted from Li and Oldenburg (1996) to close the source toward the bottom. The main novelty of this method is a first-stage optimization that gives information about the depth to the bottom of the generating source. This parameter permits both the evaluation of the appropriate vertical extension of the mesh and the definition of the shape of the regularizing depth-weighting distribution. After discussing the performance of this method by showing the results of various synthetic tests, we invert the magnetic anomalies of the volcanic edifices in the Latium region in central Italy to define their 3-D source distribution.

Marine Geophysical Researches, 2003

This paper shows the results of a detailed reprocessing of aeromagnetic data, obtained by the dow... more This paper shows the results of a detailed reprocessing of aeromagnetic data, obtained by the downward projection to the seabed. The area of interest is centered over the Tyrrhenian Basin, whose bathymetric–topographic lay-out is characterized by a somewhat irregular trend. The origin of the intense depth variations depends on the Tyrrhenian structural setting, that is associated with the presence of several tectonic lineaments, seamounts or volcanic islands. The data were characterized by good quality and dense sampling, but they have been reprocessed in order either to solve some problems in the original compilation, and to reduce the distortion of the geomagnetic anomaly field caused by the difference of distance between the survey level and the magnetic source. The reprocessed magnetic map is proposed as an effective analysis tool for the Tyrrhenian area that is characterized by high susceptibility lithotypes. Downward projection of the aeromagnetic data by BTM algorithm increases the definition of the anomalous magnetic signal without distortions in the geometric pattern of the field, thus showing a more stable and effective association between the magnetic anomalies and their geological sources. This effect is particularly true for high frequency anomalies that are directly comparable after the topographic projection because the depth filtering effect is attenuated. Moreover, the BTM method has been applied for the first time to a regional scale survey that shows substantial advantages because no fictitious anomalies in the high frequency sector of the spectrum were generated. This has been a typical effect of the traditional downward projection methods widely used before. The final result is a BTM anomaly map that is able to show the structural connections between the geological magnetic sources of the Tyrrhenian Sea area.

Geophysical Journal International, 2007

We have used free-air gravity satellite data from GEOSAT and ERS-1 missions to compile a Bouguer ... more We have used free-air gravity satellite data from GEOSAT and ERS-1 missions to compile a Bouguer gravity map of the Mediterranean Sea. The complete Bouguer correction has been applied by using the method of Parker, that acts in the Fourier domain and permits the exact evaluation of the gravity contribution from an highly sampled topographic model of the land. The density used for the Bouguer reduction has been obtained from the gravity data set itself, by using two different optimization methods that have given the same optimal result of 2400 kg m −3 . We have studied the radial power spectrum of the data, choosing the optimal Bouguer density from its slope, as the one which minimizes the fractal dimension of the resulting gravity map. The second approach consists of studying the correlation between topography and Bouguer anomaly by spatial cross-plots for a significant subset of the data. Both these approaches are aimed at reducing the short-wavelength effects of topography in the gravity map, but in the past they have been traditionally used alternatively since they gave different optimization values, especially the second method that seems to ignore large-wavelength isostatic effects. Actually, we have revisited both the methodologies, proposing slight modifications to make their efforts compatible. Their coincident results confirm their validity of application and give reliability to the recovered value of the Bouguer optimal density. Moreover, modifying the second approach allows us to compile a sort of normalized correlation map, which we propose in this paper, defining the 2-D isostatic setting of the investigated region without introducing any further lithospheric model. The final result is a revised Bouguer map compiled using a grid with a resolution of 2 min, that is useful for large-scale geological studies and gives important information about the compensation mechanism of the Mediterranean Sea: in a direct way we have found that the overall region seems to be in a complete isostatic equilibrium apart from the young basins of Tyrrhenian Sea and Aegean Sea, confirming previous similar results.

Journal of Geophysical Research, 2006

1] We present an algorithm for the linear inversion of two-dimensional (2-D) surface magnetic dat... more 1] We present an algorithm for the linear inversion of two-dimensional (2-D) surface magnetic data to obtain 3-D models of the susceptibility of the source. The forward model is discretized by a mesh of prismatic cells with constant magnetization that allows the recovery of a complete 3-D generating source. As the number of cells are normally greater than the amount of available data, we have to solve an underdetermined linear inverse problem. A Tikhonov regularization of the solution is introduced as a depth-weighting function adapted from to close the source toward the bottom. The main novelty of this method is a first-stage optimization that gives information about the depth to the bottom of the generating source. This parameter permits both the evaluation of the appropriate vertical extension of the mesh and the definition of the shape of the regularizing depth-weighting distribution. After discussing the performance of this method by showing the results of various synthetic tests, we invert the magnetic anomalies of the volcanic edifices in the Latium region in central Italy to define their 3-D source distribution.

Terra Nova, 2009

Inversion of new high-resolution magnetic data from the Marsili seamount and the surrounding basi... more Inversion of new high-resolution magnetic data from the Marsili seamount and the surrounding basin in the Tyrrhenian Sea reveals NNE–SSW magnetization stripes ranging from the Matuyama chron to the Brunhes chron, including the short positive Jaramillo subchron. The detailed magnetic chronology shows that from the late Matuyama (1.77 Ma), the average half spreading rate was about 1.5 cm yr−1, with a slight decrease between the Jaramillo and the Brunhes events, when the growth of the volcanic edifice overcame lateral spreading. Analysis of spreading rate and volume of erupted lava indicates that at the beginning of the Jaramillo subchron (1.07 Ma), the Marsili basin evolved from pure horizontal spreading to a superinflated seamount as a consequence of tearing of the Ionian slab. Our data give us a snapshot of the geodynamic transition from an active backarc spreading phase to the vertical accretion of the seafloor because of a radical change in the subduction dynamics.

Geophysical Research Letters, 2010

Physics of The Earth and Planetary Interiors, 2008

Inversion of large-scale potential-field anomalies, aimed at determining density or magnetization... more Inversion of large-scale potential-field anomalies, aimed at determining density or magnetization, is usually made in the Fourier domain. The commonly adopted geometry is based on a layer of constant thickness, characterized by a bottom surface at a fixed distance from the top surface. We propose a new method to overcome this limiting geometry, by inverting in the usual iterating scheme using top and bottom surfaces of differing, but known shapes. Randomly generated synthetic models will be analyzed, and finally performance of this method will be tested on real gravity data describing the isostatic residual anomaly of the Southern Tyrrhenian Sea in Italy. The final result is a density model that shows the distribution of the oceanic crust in this region, which is delimited by known structural elements and appears strongly correlated with the oceanized abyssal basins of Vavilov and Marsili.

Journal of Geophysical Research, 2009

1] We show a set of forward model equations in the Fourier domain for calculating the 3-D gravity... more 1] We show a set of forward model equations in the Fourier domain for calculating the 3-D gravity and magnetic anomalies of a given 3-D distribution of density or magnetization. One property of the potential field equations is that they are given by convolution products, providing a very simple analytic expression in the Fourier domain. Under this assumption, the domain of the density or magnetization parameters is connected by a biunivoc relationship with the data space, and potential field anomalies can be seen as filtered versions of the corresponding density or magnetization distributions. A very fine spatial discretization can be obtained by using a large number of points within a unique 3-D grid, where both the source distributions and field data are defined. The main advantage of this formulation is that it dramatically reduces execution times, providing a very fast forward model tool useful for modeling anomalies at different altitudes. We use this method to evaluate an average magnetization of 8 A/m for the Palinuro Seamount in the Tyrrhenian Sea (southern Italy), thus performing a joint interpretation of morphological and newly acquired magnetic data.

Journal of Geophysical Research, 2009

1] We show a set of forward model equations in the Fourier domain for calculating the 3-D gravity... more 1] We show a set of forward model equations in the Fourier domain for calculating the 3-D gravity and magnetic anomalies of a given 3-D distribution of density or magnetization. One property of the potential field equations is that they are given by convolution products, providing a very simple analytic expression in the Fourier domain. Under this assumption, the domain of the density or magnetization parameters is connected by a biunivoc relationship with the data space, and potential field anomalies can be seen as filtered versions of the corresponding density or magnetization distributions. A very fine spatial discretization can be obtained by using a large number of points within a unique 3-D grid, where both the source distributions and field data are defined. The main advantage of this formulation is that it dramatically reduces execution times, providing a very fast forward model tool useful for modeling anomalies at different altitudes. We use this method to evaluate an average magnetization of 8 A/m for the Palinuro Seamount in the Tyrrhenian Sea (southern Italy), thus performing a joint interpretation of morphological and newly acquired magnetic data.

Geophysical Research Letters, 2010

Geophysical Journal International, 2010

New high-resolution bathymetric and magnetic data from the western Aeolian sector, southern Tyrrh... more New high-resolution bathymetric and magnetic data from the western Aeolian sector, southern Tyrrhenian Sea, provide insights into structural and volcanic development of the area, suggesting a strong interaction between volcanism and tectonics. The analysis of these data combined with relocated earthquake distribution, focal plane solutions and strain rate evaluation indicates that the dextral strike-slip Sisifo-Alicudi shear zone is a complex and wide area of active deformation, representing the superficial expression of the deep seated lithospheric tear fault separating the subduction slab below Sicily and Calabria. Most of the observed volcanic features are aligned along a NW–SE trend, such as the Filicudi island-Alicudi North Seamount and Eolo-Enarete alignments, and are dissected by hundred-metre-high scarps along conjugate NNE–SSW trending fault systems. The magnetic field pattern matches the main trends of volcanic features. Spectral analysis and Euler deconvolution of magnetic anomalies show the existence of both deep and shallow sources. High-amplitude, high-frequency anomalies due to shallow sources are dominant close to the volcanic edifices of Alicudi and Filicudi, while the main contribution on the surrounding Eolo, Enarete, Alicudi North and Filicudi North seamounts is given by low-amplitude anomalies and/or deeper magnetic sources. This is probably related to different ages of the volcanic rocks, although hydrothermal processes may have played an important role in blanketing magnetic anomalies, in particular at Enarete and Eolo seamounts. Relative chronology of the eruptive centres and the inferred deformation pattern outline the Quaternary evolution of the western Aeolian Arc: Sisifo, Alicudi North and Filicudi North seamounts might have developed in an early stage, following the Late Pliocene–Early Pleistocene SE-ward migration of arc-related volcanism due to the Ionian subduction hinge retreat; Eolo, Enarete and Filicudi represent later manifestations that led volcanoes to develop during Mid-Late Pleistocene, when the stress regime in the area changed, due to the SSE-ward propagation of the subduction slab tear fault and the consequent reorientation and decrease of trench migration velocity. Finally, volcanic activity occurred in a very short time span at Alicudi, where an almost conical volcanic edifice emerged, suggesting negligible interactions with regional fault systems.

Marine Geophysical Researches, 2008

We show the magnetic model of the Selli-Vavilov region. The Selli Line is known as the northweste... more We show the magnetic model of the Selli-Vavilov region. The Selli Line is known as the northwestern edge of the southern Tyrrhenian Basin. The tectonic evolution of the Tyrrhenian Basin is dominated by a Tortonian-Quaternary extension through the eastward movement of the Apennine subduction system. This migration has generated a diffuse stretching of the continental crust with the emplacement of new oceanic material. This latter occurred in several localized zones where the eastward retreating of the Ionian subduction system produced a strong depletion of the crust with formation of basins and correlated spreading. Nowadays the presence of oceanic crust is confirmed through direct drilling investigation but a complete mapping of the oceanic crustal distribution is still lacking. The Selli-Vavilov region shows a differentiated crustal setting where seamount structures, the oceanic basement portions and continental crust blocks are superimposed. To this aim, a 2D inversion of the magnetic data of this region was conducted to define buried structures. The magnetic susceptibility pattern was computed by solving the least squares problem of the misfit between the predicted and real data for separated wavebands. This method produced two 2D models of the high and low frequency fields of the Selli-Vavilov region. The two apparent susceptibility maps provide different information for distinct ranges of depth. The results of the inversions were also combined with seismic data of the Selli region highlighting the position of the highly magnetized buried bodies. The results confirm a role for the Selli Line as a deep crustal boundary dividing the Sardinian passive domain from the easternmost active region where different oceanic structures are located. The Selli Line has worked as a detachment fault system which has moved eastward. Finally, the Selli-Vavilov region may be interpreted as a tectonic result due to a passive asymmetrical rift occurred between the Tortonian and Pliocene.

Psychiatry Research-neuroimaging, 2010

We used magnetic resonance imaging to examine the effect of ethyl-eicosapentaenoic acid (E-EPA) o... more We used magnetic resonance imaging to examine the effect of ethyl-eicosapentaenoic acid (E-EPA) on hippocampal T(2) relaxation time in first episode psychosis patients at baseline and after 12 weeks of follow-up. There was an increase in T(2) in the placebo group but not in the E-EPA group, suggesting a neuroprotective effect of E-EPA treatment. In addition, the smaller the increase in T(2), the greater the improvement in negative symptoms.

Cerebral Cortex, 2010

Repetition of environmental sounds, like their visual counterparts, can facilitate behavior and m... more Repetition of environmental sounds, like their visual counterparts, can facilitate behavior and modulate neural responses, exemplifying plasticity in how auditory objects are represented or accessed. It remains controversial whether such repetition priming/suppression involves solely plasticity based on acoustic features and/or also access to semantic features. To evaluate contributions of physical and semantic features in eliciting repetition-induced plasticity, the present functional magnetic resonance imaging (fMRI) study repeated either identical or different exemplars of the initially presented object; reasoning that identical exemplars share both physical and semantic features, whereas different exemplars share only semantic features. Participants performed a living/manmade categorization task while being scanned at 3T. Repeated stimuli of both types significantly facilitated reaction times versus initial presentations, demonstrating perceptual and semantic repetition priming. There was also repetition suppression of fMRI activity within overlapping temporal, premotor, and prefrontal regions of the auditory ''what'' pathway. Importantly, the magnitude of suppression effects was equivalent for both physically identical and semantically related exemplars. That the degree of repetition suppression was irrespective of whether or not both perceptual and semantic information was repeated is suggestive of a degree of acoustically independent semantic analysis in how object representations are maintained and retrieved.

Neuropsychologia, 2011

Increasing evidence suggests that working memory and perceptual processes are dynamically interre... more Increasing evidence suggests that working memory and perceptual processes are dynamically interrelated due to modulating activity in overlapping brain networks. However, the direct influence of working memory on the spatio-temporal brain dynamics of behaviorally relevant intervening information remains unclear. To investigate this issue, subjects performed a visual proximity grid perception task under three different visual-spatial working memory (VSWM) load conditions. VSWM load was manipulated by asking subjects to memorize the spatial locations of 6 or 3 disks. The grid was always presented between the encoding and recognition of the disk pattern. As a baseline condition, grid stimuli were presented without a VSWM context. VSWM load altered both perceptual performance and neural networks active during intervening grid encoding. Participants performed faster and more accurately on a challenging perceptual task under high VSWM load as compared to the low load and the baseline condition. Visual evoked potential (VEP) analyses identified changes in the configuration of the underlying sources in one particular period occurring 160-190 ms post-stimulus onset. Source analyses further showed an occipito-parietal down-regulation concurrent to the increased involvement of temporal and frontal resources in the high VSWM context. Together, these data suggest that cognitive control mechanisms supporting working memory may selectively enhance concurrent visual processing related to an independent goal. More broadly, our findings are in line with theoretical models implicating the engagement of frontal regions in synchronizing and optimizing mnemonic and perceptual resources towards multiple goals.

Psychiatry Research, 2007

Recent findings suggest that the visuo-spatial sketchpad (VSSP) may be divided into two sub-compo... more Recent findings suggest that the visuo-spatial sketchpad (VSSP) may be divided into two sub-components processing dynamic or static visual information. This model may be useful to elucidate the confusion of data concerning the functioning of the VSSP in schizophrenia. The present study examined patients with schizophrenia and matched controls in a new working memory paradigm involving dynamic (the Ball Flight Task -BFT) or static (the Static Pattern Task -SPT) visual stimuli. In the BFT, the responses of the patients were apparently based on the retention of the last set of segments of the perceived trajectory, whereas control subjects relied on a more global strategy. We assume that the patients' performances are the result of a reduced capacity in chunking visual information since they relied mainly on the retention of the last set of segments. This assumption is confirmed by the poor performance of the patients in the static task (SPT), which requires a combination of stimulus components into object representations. We assume that the static/dynamic distinction may help us to understand the VSSP deficits in schizophrenia. This distinction also raises questions about the hypothesis that visuo-spatial working memory can simply be dissociated into visual and spatial sub-components.

Australian and New Zealand Journal of Psychiatry, 2009

Objective: Patients with schizophrenia show deficits in visuospatial working memory and visual pu... more Objective: Patients with schizophrenia show deficits in visuospatial working memory and visual pursuit processes. It is currently unclear, however, whether both impairments are related to a common neuropathological origin. The purpose of the present study was therefore to examine the possible relations between the encoding and the discrimination of dynamic visuospatial stimuli in schizophrenia. Method: Sixteen outpatients with schizophrenia and 16 control subjects were asked to encode complex disc displacements presented on a screen. After a delay, participants had to identify the previously presented disc trajectory from a choice of six static linear paths, among which were five incorrect paths. The precision of visual pursuit eye movements during the initial presentation of the dynamic stimulus was assessed. The fixations and scanning time in definite regions of the six paths presented during the discrimination phase were investigated. Results: In comparison with controls, patients showed poorer task performance, reduced pursuit accuracy during incorrect trials and less time scanning the correct stimulus or the incorrect paths approximating its global structure. Patients also spent less time scanning the leftmost portion of the correct path even when making a correct choice. The accuracy of visual pursuit and head movements, however, was not correlated with task performance. Conclusions: The present study provides direct support for the hypothesis that active integration of visuospatial information within working memory is deficient in schizophrenia. In contrast, a general impairment of oculomotor mechanisms involved in smooth pursuit did not appear to be directly related to lower visuospatial working memory performance in schizophrenia.

Psn-psychiatrie Sciences Humaines Neurosciences, 2007

Le rapport entre les facultés psychologiques de l’être humain et les caractéristiques biologiques... more Le rapport entre les facultés psychologiques de l’être humain et les caractéristiques biologiques qui les sous-tendent s’ancre dans le questionnement philosophique traditionnel des rapports de la matière et de l’esprit, avec son corollaire éthique de la question de la liberté et du déterminisme. L’appréhension neurobiologique des activités mentales se trouve ainsi être une nouvelle manière, celle de notre époque, d’articuler les rapports du biologique et du psychique. Dans ce domaine, force est de constater que c’est souvent à partir de postulats ontologiques implicites, ou tout au moins de partis pris épistémologiques, pas toujours conscients, que vont découler les différentes positions observées moniste ou dualiste, fonctionnaliste, réductionniste, éliminativiste, identité des types... et autres variations plus ou moins raffinées. Ayant conscience de ces écueils, on peut toutefois chercher à mettre en évidence des analogies de structures au travers des différents niveaux du vivant et du mental. Ainsi, en vat-il du déséquilibre énergétique « entretenu » pour la survive de la cellule; des rapports dynamiques et complémentaires entre les fonctions homéostatiques et allostatiques des organismes vivants; de la tension entre les mécanismes complémentaires cérébraux, nécessaires à toute cognition, qui sont ceux servant à la représentation et ceux servant à la localisation d’un object dans l’espace. Tous ces phénomènes présentent certaines analogies de structures, bien qu’étant à l’œuvre à des niveaux différents du vivant. The relationship between the human psychological faculties and their underlying biological foundation is traditionally addressed within the mind-matter philosophical framework and its ethical extension regarding freedom and determinism. Neurobiology represents a new method, reflective of our times, to articulate the relationships between biological and psychological phenomena. The various points of view in this field are often based on implicit ontological presuppositions and, at least sometimes, unconscious epistemological assumptions: monism vs dualism, functionalism, reductionism, eliminativism, type identity and other more or less sophisticated variations. Bearing in mind the pitfalls these create, we can try to determine structural analogies across the different levels of the living being and the mind: the energy imbalance maintained for cell survival; the dynamic and complementary relationship between homeostatic and allostatic functions in living organisms; the tension between essential and complementary cognitive brain processes, such as the processes used to represent an object and those used to locate an object in space. Those phenomena all bear structural analogies, even though they work at different levels.

Behavioural Brain Research, 2008

In the Morris water maze (MWM) task, proprioceptive information is likely to have a poor accuracy... more In the Morris water maze (MWM) task, proprioceptive information is likely to have a poor accuracy due to movement inertia. Hence, in this condition, dynamic visual information providing information on linear and angular acceleration would play a critical role in spatial navigation. To investigate this assumption we compared rat's spatial performance in the MWM and in the homing hole board (HB) tasks using a 1.5 Hz stroboscopic illumination. In the MWM, rats trained in the stroboscopic condition needed more time than those trained in a continuous light condition to reach the hidden platform. They expressed also little accuracy during the probe trial. In the HB task, in contrast, place learning remained unaffected by the stroboscopic light condition. The deficit in the MWM was thus complete, affecting both escape latency and discrimination of the reinforced area, and was thus task specific. This dissociation confirms that dynamic visual information is crucial to spatial navigation in the MWM whereas spatial navigation on solid ground is mediated by a multisensory integration, and thus less dependent on visual information.

Psn-psychiatrie Sciences Humaines Neurosciences, 2007

Le rapport entre les facultés psychologiques de l’être humain et les caractéristiques biologiques... more Le rapport entre les facultés psychologiques de l’être humain et les caractéristiques biologiques qui les sous-tendent s’ancre dans le questionnement philosophique traditionnel des rapports de la matière et de l’esprit, avec son corollaire éthique de la question de la liberté et du déterminisme. L’appréhension neurobiologique des activités mentales se trouve ainsi être une nouvelle manière, celle de notre époque, d’articuler les rapports du biologique et du psychique. Dans ce domaine, force est de constater que c’est souvent à partir de postulats ontologiques implicites, ou tout au moins de partis pris épistémologiques, pas toujours conscients, que vont découler les différentes positions observées moniste ou dualiste, fonctionnaliste, réductionniste, éliminativiste, identité des types... et autres variations plus ou moins raffinées. Ayant conscience de ces écueils, on peut toutefois chercher à mettre en évidence des analogies de structures au travers des différents niveaux du vivant et du mental. Ainsi, en vat-il du déséquilibre énergétique « entretenu » pour la survive de la cellule; des rapports dynamiques et complémentaires entre les fonctions homéostatiques et allostatiques des organismes vivants; de la tension entre les mécanismes complémentaires cérébraux, nécessaires à toute cognition, qui sont ceux servant à la représentation et ceux servant à la localisation d’un object dans l’espace. Tous ces phénomènes présentent certaines analogies de structures, bien qu’étant à l’œuvre à des niveaux différents du vivant. The relationship between the human psychological faculties and their underlying biological foundation is traditionally addressed within the mind-matter philosophical framework and its ethical extension regarding freedom and determinism. Neurobiology represents a new method, reflective of our times, to articulate the relationships between biological and psychological phenomena. The various points of view in this field are often based on implicit ontological presuppositions and, at least sometimes, unconscious epistemological assumptions: monism vs dualism, functionalism, reductionism, eliminativism, type identity and other more or less sophisticated variations. Bearing in mind the pitfalls these create, we can try to determine structural analogies across the different levels of the living being and the mind: the energy imbalance maintained for cell survival; the dynamic and complementary relationship between homeostatic and allostatic functions in living organisms; the tension between essential and complementary cognitive brain processes, such as the processes used to represent an object and those used to locate an object in space. Those phenomena all bear structural analogies, even though they work at different levels.

Journal of Geophysical Research, 2006

We present an algorithm for the linear inversion of two-dimensional (2-D) surface magnetic data t... more We present an algorithm for the linear inversion of two-dimensional (2-D) surface magnetic data to obtain 3-D models of the susceptibility of the source. The forward model is discretized by a mesh of prismatic cells with constant magnetization that allows the recovery of a complete 3-D generating source. As the number of cells are normally greater than the amount of available data, we have to solve an underdetermined linear inverse problem. A Tikhonov regularization of the solution is introduced as a depth-weighting function adapted from Li and Oldenburg (1996) to close the source toward the bottom. The main novelty of this method is a first-stage optimization that gives information about the depth to the bottom of the generating source. This parameter permits both the evaluation of the appropriate vertical extension of the mesh and the definition of the shape of the regularizing depth-weighting distribution. After discussing the performance of this method by showing the results of various synthetic tests, we invert the magnetic anomalies of the volcanic edifices in the Latium region in central Italy to define their 3-D source distribution.

Marine Geophysical Researches, 2003

This paper shows the results of a detailed reprocessing of aeromagnetic data, obtained by the dow... more This paper shows the results of a detailed reprocessing of aeromagnetic data, obtained by the downward projection to the seabed. The area of interest is centered over the Tyrrhenian Basin, whose bathymetric–topographic lay-out is characterized by a somewhat irregular trend. The origin of the intense depth variations depends on the Tyrrhenian structural setting, that is associated with the presence of several tectonic lineaments, seamounts or volcanic islands. The data were characterized by good quality and dense sampling, but they have been reprocessed in order either to solve some problems in the original compilation, and to reduce the distortion of the geomagnetic anomaly field caused by the difference of distance between the survey level and the magnetic source. The reprocessed magnetic map is proposed as an effective analysis tool for the Tyrrhenian area that is characterized by high susceptibility lithotypes. Downward projection of the aeromagnetic data by BTM algorithm increases the definition of the anomalous magnetic signal without distortions in the geometric pattern of the field, thus showing a more stable and effective association between the magnetic anomalies and their geological sources. This effect is particularly true for high frequency anomalies that are directly comparable after the topographic projection because the depth filtering effect is attenuated. Moreover, the BTM method has been applied for the first time to a regional scale survey that shows substantial advantages because no fictitious anomalies in the high frequency sector of the spectrum were generated. This has been a typical effect of the traditional downward projection methods widely used before. The final result is a BTM anomaly map that is able to show the structural connections between the geological magnetic sources of the Tyrrhenian Sea area.

Geophysical Journal International, 2007

We have used free-air gravity satellite data from GEOSAT and ERS-1 missions to compile a Bouguer ... more We have used free-air gravity satellite data from GEOSAT and ERS-1 missions to compile a Bouguer gravity map of the Mediterranean Sea. The complete Bouguer correction has been applied by using the method of Parker, that acts in the Fourier domain and permits the exact evaluation of the gravity contribution from an highly sampled topographic model of the land. The density used for the Bouguer reduction has been obtained from the gravity data set itself, by using two different optimization methods that have given the same optimal result of 2400 kg m −3 . We have studied the radial power spectrum of the data, choosing the optimal Bouguer density from its slope, as the one which minimizes the fractal dimension of the resulting gravity map. The second approach consists of studying the correlation between topography and Bouguer anomaly by spatial cross-plots for a significant subset of the data. Both these approaches are aimed at reducing the short-wavelength effects of topography in the gravity map, but in the past they have been traditionally used alternatively since they gave different optimization values, especially the second method that seems to ignore large-wavelength isostatic effects. Actually, we have revisited both the methodologies, proposing slight modifications to make their efforts compatible. Their coincident results confirm their validity of application and give reliability to the recovered value of the Bouguer optimal density. Moreover, modifying the second approach allows us to compile a sort of normalized correlation map, which we propose in this paper, defining the 2-D isostatic setting of the investigated region without introducing any further lithospheric model. The final result is a revised Bouguer map compiled using a grid with a resolution of 2 min, that is useful for large-scale geological studies and gives important information about the compensation mechanism of the Mediterranean Sea: in a direct way we have found that the overall region seems to be in a complete isostatic equilibrium apart from the young basins of Tyrrhenian Sea and Aegean Sea, confirming previous similar results.

Journal of Geophysical Research, 2006

1] We present an algorithm for the linear inversion of two-dimensional (2-D) surface magnetic dat... more 1] We present an algorithm for the linear inversion of two-dimensional (2-D) surface magnetic data to obtain 3-D models of the susceptibility of the source. The forward model is discretized by a mesh of prismatic cells with constant magnetization that allows the recovery of a complete 3-D generating source. As the number of cells are normally greater than the amount of available data, we have to solve an underdetermined linear inverse problem. A Tikhonov regularization of the solution is introduced as a depth-weighting function adapted from to close the source toward the bottom. The main novelty of this method is a first-stage optimization that gives information about the depth to the bottom of the generating source. This parameter permits both the evaluation of the appropriate vertical extension of the mesh and the definition of the shape of the regularizing depth-weighting distribution. After discussing the performance of this method by showing the results of various synthetic tests, we invert the magnetic anomalies of the volcanic edifices in the Latium region in central Italy to define their 3-D source distribution.

Terra Nova, 2009

Inversion of new high-resolution magnetic data from the Marsili seamount and the surrounding basi... more Inversion of new high-resolution magnetic data from the Marsili seamount and the surrounding basin in the Tyrrhenian Sea reveals NNE–SSW magnetization stripes ranging from the Matuyama chron to the Brunhes chron, including the short positive Jaramillo subchron. The detailed magnetic chronology shows that from the late Matuyama (1.77 Ma), the average half spreading rate was about 1.5 cm yr−1, with a slight decrease between the Jaramillo and the Brunhes events, when the growth of the volcanic edifice overcame lateral spreading. Analysis of spreading rate and volume of erupted lava indicates that at the beginning of the Jaramillo subchron (1.07 Ma), the Marsili basin evolved from pure horizontal spreading to a superinflated seamount as a consequence of tearing of the Ionian slab. Our data give us a snapshot of the geodynamic transition from an active backarc spreading phase to the vertical accretion of the seafloor because of a radical change in the subduction dynamics.

Geophysical Research Letters, 2010

Physics of The Earth and Planetary Interiors, 2008

Inversion of large-scale potential-field anomalies, aimed at determining density or magnetization... more Inversion of large-scale potential-field anomalies, aimed at determining density or magnetization, is usually made in the Fourier domain. The commonly adopted geometry is based on a layer of constant thickness, characterized by a bottom surface at a fixed distance from the top surface. We propose a new method to overcome this limiting geometry, by inverting in the usual iterating scheme using top and bottom surfaces of differing, but known shapes. Randomly generated synthetic models will be analyzed, and finally performance of this method will be tested on real gravity data describing the isostatic residual anomaly of the Southern Tyrrhenian Sea in Italy. The final result is a density model that shows the distribution of the oceanic crust in this region, which is delimited by known structural elements and appears strongly correlated with the oceanized abyssal basins of Vavilov and Marsili.

Journal of Geophysical Research, 2009

1] We show a set of forward model equations in the Fourier domain for calculating the 3-D gravity... more 1] We show a set of forward model equations in the Fourier domain for calculating the 3-D gravity and magnetic anomalies of a given 3-D distribution of density or magnetization. One property of the potential field equations is that they are given by convolution products, providing a very simple analytic expression in the Fourier domain. Under this assumption, the domain of the density or magnetization parameters is connected by a biunivoc relationship with the data space, and potential field anomalies can be seen as filtered versions of the corresponding density or magnetization distributions. A very fine spatial discretization can be obtained by using a large number of points within a unique 3-D grid, where both the source distributions and field data are defined. The main advantage of this formulation is that it dramatically reduces execution times, providing a very fast forward model tool useful for modeling anomalies at different altitudes. We use this method to evaluate an average magnetization of 8 A/m for the Palinuro Seamount in the Tyrrhenian Sea (southern Italy), thus performing a joint interpretation of morphological and newly acquired magnetic data.

Journal of Geophysical Research, 2009

1] We show a set of forward model equations in the Fourier domain for calculating the 3-D gravity... more 1] We show a set of forward model equations in the Fourier domain for calculating the 3-D gravity and magnetic anomalies of a given 3-D distribution of density or magnetization. One property of the potential field equations is that they are given by convolution products, providing a very simple analytic expression in the Fourier domain. Under this assumption, the domain of the density or magnetization parameters is connected by a biunivoc relationship with the data space, and potential field anomalies can be seen as filtered versions of the corresponding density or magnetization distributions. A very fine spatial discretization can be obtained by using a large number of points within a unique 3-D grid, where both the source distributions and field data are defined. The main advantage of this formulation is that it dramatically reduces execution times, providing a very fast forward model tool useful for modeling anomalies at different altitudes. We use this method to evaluate an average magnetization of 8 A/m for the Palinuro Seamount in the Tyrrhenian Sea (southern Italy), thus performing a joint interpretation of morphological and newly acquired magnetic data.

Geophysical Research Letters, 2010

Geophysical Journal International, 2010

New high-resolution bathymetric and magnetic data from the western Aeolian sector, southern Tyrrh... more New high-resolution bathymetric and magnetic data from the western Aeolian sector, southern Tyrrhenian Sea, provide insights into structural and volcanic development of the area, suggesting a strong interaction between volcanism and tectonics. The analysis of these data combined with relocated earthquake distribution, focal plane solutions and strain rate evaluation indicates that the dextral strike-slip Sisifo-Alicudi shear zone is a complex and wide area of active deformation, representing the superficial expression of the deep seated lithospheric tear fault separating the subduction slab below Sicily and Calabria. Most of the observed volcanic features are aligned along a NW–SE trend, such as the Filicudi island-Alicudi North Seamount and Eolo-Enarete alignments, and are dissected by hundred-metre-high scarps along conjugate NNE–SSW trending fault systems. The magnetic field pattern matches the main trends of volcanic features. Spectral analysis and Euler deconvolution of magnetic anomalies show the existence of both deep and shallow sources. High-amplitude, high-frequency anomalies due to shallow sources are dominant close to the volcanic edifices of Alicudi and Filicudi, while the main contribution on the surrounding Eolo, Enarete, Alicudi North and Filicudi North seamounts is given by low-amplitude anomalies and/or deeper magnetic sources. This is probably related to different ages of the volcanic rocks, although hydrothermal processes may have played an important role in blanketing magnetic anomalies, in particular at Enarete and Eolo seamounts. Relative chronology of the eruptive centres and the inferred deformation pattern outline the Quaternary evolution of the western Aeolian Arc: Sisifo, Alicudi North and Filicudi North seamounts might have developed in an early stage, following the Late Pliocene–Early Pleistocene SE-ward migration of arc-related volcanism due to the Ionian subduction hinge retreat; Eolo, Enarete and Filicudi represent later manifestations that led volcanoes to develop during Mid-Late Pleistocene, when the stress regime in the area changed, due to the SSE-ward propagation of the subduction slab tear fault and the consequent reorientation and decrease of trench migration velocity. Finally, volcanic activity occurred in a very short time span at Alicudi, where an almost conical volcanic edifice emerged, suggesting negligible interactions with regional fault systems.

Marine Geophysical Researches, 2008

We show the magnetic model of the Selli-Vavilov region. The Selli Line is known as the northweste... more We show the magnetic model of the Selli-Vavilov region. The Selli Line is known as the northwestern edge of the southern Tyrrhenian Basin. The tectonic evolution of the Tyrrhenian Basin is dominated by a Tortonian-Quaternary extension through the eastward movement of the Apennine subduction system. This migration has generated a diffuse stretching of the continental crust with the emplacement of new oceanic material. This latter occurred in several localized zones where the eastward retreating of the Ionian subduction system produced a strong depletion of the crust with formation of basins and correlated spreading. Nowadays the presence of oceanic crust is confirmed through direct drilling investigation but a complete mapping of the oceanic crustal distribution is still lacking. The Selli-Vavilov region shows a differentiated crustal setting where seamount structures, the oceanic basement portions and continental crust blocks are superimposed. To this aim, a 2D inversion of the magnetic data of this region was conducted to define buried structures. The magnetic susceptibility pattern was computed by solving the least squares problem of the misfit between the predicted and real data for separated wavebands. This method produced two 2D models of the high and low frequency fields of the Selli-Vavilov region. The two apparent susceptibility maps provide different information for distinct ranges of depth. The results of the inversions were also combined with seismic data of the Selli region highlighting the position of the highly magnetized buried bodies. The results confirm a role for the Selli Line as a deep crustal boundary dividing the Sardinian passive domain from the easternmost active region where different oceanic structures are located. The Selli Line has worked as a detachment fault system which has moved eastward. Finally, the Selli-Vavilov region may be interpreted as a tectonic result due to a passive asymmetrical rift occurred between the Tortonian and Pliocene.

Psychiatry Research-neuroimaging, 2010

We used magnetic resonance imaging to examine the effect of ethyl-eicosapentaenoic acid (E-EPA) o... more We used magnetic resonance imaging to examine the effect of ethyl-eicosapentaenoic acid (E-EPA) on hippocampal T(2) relaxation time in first episode psychosis patients at baseline and after 12 weeks of follow-up. There was an increase in T(2) in the placebo group but not in the E-EPA group, suggesting a neuroprotective effect of E-EPA treatment. In addition, the smaller the increase in T(2), the greater the improvement in negative symptoms.