Stefania Della Penna | Università degli Studi "G. d'Annunzio" Chieti Pescara (original) (raw)

Papers by Stefania Della Penna

The authors developed a new method in order to automatically segment magnetic resonance images (M... more The authors developed a new method in order to automatically segment magnetic resonance images (MRIs) of the head. The main tissues, such as scalp, brain and skull, are recognised. The method is based on a Kohonen self organising feature map which performs a cluster of the image areas into three main classes. The network, after being trained, is successfully operated on the test set. The network performances do not depend on the MRI apparatus producing the images set. The network classes are properly matched and processed in order to obtain slices containing the desired tissues. The proposed method has been developed in the frame of a project for the 3-dimensional reconstruction of selected surfaces

Proceedings of the National Academy of Sciences, 2015

Fundamental problems in neuroscience today are understanding how patterns of ongoing spontaneous ... more Fundamental problems in neuroscience today are understanding how patterns of ongoing spontaneous activity are modified by task performance and whether/how these intrinsic patterns influence task-evoked activation and behavior. We examined these questions by comparing instantaneous functional connectivity (IFC) and directed functional connectivity (DFC) changes in two networks that are strongly correlated and segregated at rest: the visual (VIS) network and the dorsal attention network (DAN). We measured how IFC and DFC during a visuospatial attention task, which requires dynamic selective rerouting of visual information across hemispheres, changed with respect to rest. During the attention task, the two networks remained relatively segregated, and their general pattern of within-network correlation was maintained. However, attention induced a decrease of correlation in the VIS network and an increase of the DAN→VIS IFC and DFC, especially in a top-down direction. In contrast, within the DAN, IFC was not modified by attention, whereas DFC was enhanced. Importantly, IFC modulations were behaviorally relevant. We conclude that a stable backbone of within-network functional connectivity topography remains in place when transitioning between resting wakefulness and attention selection. However, relative decrease of correlation of ongoing "idling" activity in visual cortex and synchronization between frontoparietal and visual cortex were behaviorally relevant, indicating that modulations of resting activity patterns are important for task performance. Higher order resting connectivity in the DAN was relatively unaffected during attention, potentially indicating a role for simultaneous ongoing activity as a "prior" for attention selection.

Proceedings of the 20th Annual International Conference of the IEEE Engineering in Medicine and Biology Society. Vol.20 Biomedical Engineering Towards the Year 2000 and Beyond (Cat. No.98CH36286), 1998

Presents an in vivo SQUID susceptometer using a nonhomogeneous magnetising field which is null at... more Presents an in vivo SQUID susceptometer using a nonhomogeneous magnetising field which is null at the sensing coil and increases towards the patient position with a constant gradient plus a cubic term at large distances. This shape of the magnetising field enhances the signal due to internal organs with respect to the signal due to superficial tissue. A high signal-to-noise

Physics in Medicine and Biology, 2002

In this paper we generalize the approach of Ahonen et al (1993 IEEE Trans. Biomed. Eng. 40 859-69... more In this paper we generalize the approach of Ahonen et al (1993 IEEE Trans. Biomed. Eng. 40 859-69) to two-dimensional non-uniform sampling. The focus is on two main topics: (1) searching for the optimal sensor configuration on a planar measurement surface; and (2) reconstructing the magnetic field (a continuous function) from a discrete set of data points recorded with a

The Neuroradiology Journal, 1999

Functional Neurology, 2014

To progress toward understanding of the mechanisms underlying the functional organization of the ... more To progress toward understanding of the mechanisms underlying the functional organization of the human brain, either a bottom-up or a top-down approach may be adopted. The former starts from the study of the detailed functioning of a small number of neuronal assemblies, while the latter tries to decode brain functioning by considering the brain as a whole. This review discusses the top-down approach and the use of magnetoencephalography (MEG) to describe global brain properties. The main idea behind this approach is that the concurrence of several areas is required for the brain to instantiate a specific behavior/functioning. A central issue is therefore the study of brain functional connectivity and the concept of brain networks as ensembles of distant brain areas that preferentially exchange information. Importantly, the human brain is a dynamic device, and MEG is ideally suited to investigate phenomena on behaviorally relevant timescales, also offering the possibility of capturing behaviorally-related brain connectivity dynamics.

Il Nuovo Cimento D, 1994

Summary A preliminary study is here reported on a new potential marker for biomagnetic measureme... more Summary A preliminary study is here reported on a new potential marker for biomagnetic measurements. The marker consists of superparamagnetic polymer microspheres which were detected in the presence of external steady magnetic fields by means of an r.f.-SQUID magnetometer. The particles were prepared in samples differing in the concentration value and immersed in a homogeneous magnetic field of variable intensity. A simple model was taken into account for the distribution of the microspheres in the samples, so that the theoretical values were compared to the marker field values measured by the biomagnetic sensor. The overall sensitivity of the experimental apparatus and the minimum concentration value of the marker were then estimated.

ChemInform, 2005

ABSTRACT For Abstract see ChemInform Abstract in Full Text.

The Journal of neuroscience : the official journal of the Society for Neuroscience, Jan 14, 2015

Using repetitive transcranial magnetic stimulation (rTMS), we have recently shown a functional an... more Using repetitive transcranial magnetic stimulation (rTMS), we have recently shown a functional anatomical distinction in human parietal cortex between regions involved in maintaining attention to a location [ventral intraparietal sulcus (vIPS)] and a region involved in shifting attention between locations [medial superior parietal lobule (mSPL)]. In particular, while rTMS interference over vIPS impaired target discrimination at contralateral attended locations, interference over mSPL affected performance following shifts of attention regardless of the visual field (Capotosto et al., 2013). Here, using rTMS interference in conjunction with EEG recordings of brain rhythms during the presentation of cues that indicate to either shift or maintain spatial attention, we tested whether this functional anatomical segregation involves different mechanisms of rhythm synchronization. The transient inactivation of vIPS reduced the amplitude of the expected parieto-occipital low-α (8-10 Hz) desy...

Neuron, 2012

We used magneto-encephalography to study the temporal dynamics of band-limited power correlation ... more We used magneto-encephalography to study the temporal dynamics of band-limited power correlation at rest within and across six brain networks previously defined by prior fMRI studies. Epochs of transiently high within-network BLP correlation were identified and correlation of BLP time-series across networks was assessed in these epochs. These analyses demonstrate that functional networks are not equivalent with respect to cross-network interactions. The defaultmode network and the posterior cingulate cortex, in particular, exhibit the highest degree of transient BLP correlation with other networks especially in the 14-25 Hz (beta band) frequency range. Our results indicate that the previously demonstrated neuroanatomical centrality of the PCC and DMN has a physiological counterpart in the temporal dynamics of network interaction at behaviorally relevant time scales. This interaction involved subsets of nodes from other networks during periods in which their internal correlation was low. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript.

NeuroImage, 2014

Several neuroimaging studies reported that a common set of regions are recruited during 15 action... more Several neuroimaging studies reported that a common set of regions are recruited during 15 action observation and execution and it has been proposed that the modulation of the µ rhythm, 16 in terms of oscillations in the alpha and beta bands might represent the electrophysiological 17 correlate of the underlying brain mechanisms. However, the specific functional role of these bands 18 within the µ rhythm is still unclear. Here, we used magnetoencephalography (MEG) to analyze the 19 spectral and temporal properties of the alpha and beta bands in healthy subjects during an action 20 observation and execution task. 21

Philosophical Magazine B-Physics of Condensed Matter Statistical Mechanics Electronic Optical and Magnetic Properties, 2000

We present two multichannel systems based on a superconducting quantum interference device (SQUID... more We present two multichannel systems based on a superconducting quantum interference device (SQUID) for biomagnetic measurements, installed at the University of Chieti. Both systems have been designed for clinical and routine use and have been developed owing to an international cooperation. The main issues in the instrument implementation were ® eld sensitivity and spatial resolution, as well as¯exibility and stability during operation. The ® rst system is a planar system and is devised for magnetocardiographic measurements. This system is composed of 74 dc SQUID integrated magnetometers contained in a low-noise dewar: 55 sensors are measurement channels and 21 are placed far from the subject and are used as reference channels to create software gradiometers. The second system is a helmet system and consists of 165 dc SQUID integrated magnetometers to perform magnetoencephalographic recordings; 153 channels are distributed over a surface covering the whole scalp and 12 channels are used as references. The ® eld noise of the SQUID magnetometers is about 5 fT Hz ¡1=2 . Each system is placed in a magnetically shielded room for eddy current shielding and magnetic shielding. The magnetic ® eld is recorded with sampling frequencies up to 10 kHz. The analogue-to-digital converted data are processed on line by means of an array of digital signal processors, allowing bandpass ® ltering, decimation and noise compensation.

Neuroimage, 2013

The principles of functional specialization and integration in the resting brain are implemented ... more The principles of functional specialization and integration in the resting brain are implemented in a complex system of specialized networks that share some degree of interaction. Recent studies have identified wider functional modules compared to previously defined networks and reported a small-world architecture of brain activity in which central nodes balance the pressure to evolve segregated pathways with the integration of local systems. The accurate identification of such central nodes is crucial but might be challenging for several reasons, e.g. inter-subject variability and physiological/pathological network plasticity, and recent works reported partially inconsistent results concerning the properties of these cortical hubs. Here, we applied a whole-brain data-driven approach to extract cortical functional cores and examined their connectivity from a resting state fMRI experiment on healthy subjects. Two main statistically significant cores, centered on the posterior cingulate cortex and the supplementary motor area, were extracted and their functional connectivity maps, thresholded at three statistical levels, revealed the presence of two complex systems. One system is consistent with the default mode network (DMN) and gradually connects to visual regions, the other centered on motor regions and gradually connects to more sensory-specific portions of cortex. These two large scale networks eventually converged to regions belonging to the medial aspect of the DMN, potentially allowing inter-network interactions.

NeuroImage, 2004

In this MEG study, we investigated cortical alpha/sigma and beta ERD/ ERS induced by median nerve... more In this MEG study, we investigated cortical alpha/sigma and beta ERD/ ERS induced by median nerve stimulation to extend previous evidence on different resonant and oscillatory behavior of SI and SII (Neuro-Image 13 [2001] 662). Here, we tested whether a simple somatosensory stimulation could induce a distinctive sequence of alpha/sigma and beta ERD/ERS over SII compared to SI. We found that for both alpha/ sigma (around 10 Hz) and beta (around 20 Hz) rhythms, the latencies of ERD and ERS were larger in bilateral SII than in contralateral SI. In addition, the peak amplitude of alpha/sigma and beta ERS was smaller in bilateral SII than in contralateral SI. These results indicate a delayed and prolonged activation of SII responses, reflecting a protracted information elaboration possibly related to SII higher order role in the processing of somatosensory information. This temporal dynamics of alpha/sigma and beta rhythms may be related to a sequential activation scheme of SI and SII during the somatosensory information processes. Future studies should evaluate in SII the possible different functional significance of alpha/sigma with respect to beta rhythms during somatosensory processing. D 2004 Elsevier Inc. All rights reserved.

Proceedings of the Second Joint 24th Annual Conference and the Annual Fall Meeting of the Biomedical Engineering Society] [Engineering in Medicine and Biology, 2002

We studied MEG and fMRI responses to electric median and tibial nerve stimulation in five healthy... more We studied MEG and fMRI responses to electric median and tibial nerve stimulation in five healthy volunteers. The aim was to compare the fMRI activation and MEG equivalent current dipole (ECD) localisations in the primary (SI) and secondary (SII) somatosensory cortices. EPI functional images were acquired with a SIEMENS 1.5 T scanner according to a block paradigm. MEG data were acquired with a 165-channel whole head neuromagnetometer. Matching of MEG and fMRI subject reference frames was performed with current carrying coils whose signal was recorded in MEG and whose position was identified in structural MRI with oil capsules. Stimuli were rectangular pulses with duration 200 to 400 microseconds and frequency 0.3 Hz for MEG and 1.9 Hz for fMRI. A higher stimulus rate in fMRI was used to increase regional cerebral blood flow. The stimulus intensity was settled at a level producing a painless, clearly visible thumb opposition or foot flexion. A somatotopic organization of SII was seen both with MEG and fMRI, with the upper limb areas located more anteriorly and more inferiorly than the lower limb areas. ECD locations and fMRI activation were substantially consistent, with an average mismatch of about 1 cm. Similar differences were observed in SI.

NeuroImage, 2009

32 SU-PM High resolution functional MRI of subliminal and conscious vision at 7 Tesla, V. Schöpf ... more 32 SU-PM High resolution functional MRI of subliminal and conscious vision at 7 Tesla, V. Schöpf , F.

Review of Scientific Instruments, 1992

The paper describes an electron paramagnetic resonance apparatus for spectroscopy and imaging at ... more The paper describes an electron paramagnetic resonance apparatus for spectroscopy and imaging at very low frequency (283 MHz). The bridge operates in a reflection cavity homodyne configuration and can be used on a very broad frequency range. The sample cavity is a one loop-two gap resonator and accepts samples up to 5 cm in diameter and 10 cm long. These sample dimensions make the apparatus suitable for observing living samples such as rats. For the main field and gradients the apparatus uses a newly designed multipolar magnet that can provide the main field and gradients for 2D image reconstruction. The third gradient is obtained by coils mounted in the bore of the magnet. Tests on peroxilamine disulfonate samples have shown micromolar sensitivity. The minimum spatial resolution is limited by the sample linewidth and by the signal/noise. In living samples the toxicity of nitroxide radicals restricts the maximum label concentrations to values of the order of 10U4 M, and the resolution seems to be limited by sensitivity to fractions of cm3.

Superconductor Science and Technology, 2014

ABSTRACT This paper provides an overview on the basic principles and applications of magnetoencep... more ABSTRACT This paper provides an overview on the basic principles and applications of magnetoencephalography (MEG), a technique that requires the use of many SQUIDs and thus represents one of the most important applications of superconducting electronics. Since the development of the first SQUID magnetometers, it was clear that these devices could be used to measure the ultra-low magnetic signals associated with the bioelectric activity of the neurons of the human brain. Forty years on from the first measurement of magnetic alpha rhythm by David Cohen, MEG has become a fundamental tool for the investigation of brain functions. The simple localization of cerebral sources activated by sensory stimulation performed in the early years has been successively expanded to the identification of the sequence of neuronal pool activations, thus decrypting information of the hierarchy underlying cerebral processing. This goal has been achieved thanks to the development of complex instrumentation, namely whole head MEG systems, allowing simultaneous measurement of magnetic fields all over the scalp with an exquisite time resolution. The latest trends in MEG, such as the study of brain networks, i.e. how the brain organizes itself in a coherent and stable way, are discussed. These sound applications together with the latest technological developments aimed at implementing systems able to record MEG signals and magnetic resonance imaging (MRI) of the head with the same set-up pave the way to high performance systems for brain functional investigation in the healthy and the sick population.

Applied Magnetic Resonance, 1992

ABSTRACT This paper presents the preliminary results obtained using an Electron Paramagnetic Reso... more ABSTRACT This paper presents the preliminary results obtained using an Electron Paramagnetic Resonance imaging apparatus operating at 280 MHz. The acquisition technique and the procedure used to obtain the spin density spatial localization are presented and specimen images of extended samples are given. The accuracy of the images and the spatial resolution are also discussed.