Jens Schwarzbach | University of Trento (original) (raw)

Papers by Jens Schwarzbach

American Journal of Clinical Nutrition, 2003

Moving dots can evoke a percept of the spatial structure of a three-dimensional object in the abs... more Moving dots can evoke a percept of the spatial structure of a three-dimensional object in the absence of other visual cues. This phenom- enon, called structure from motion (SFM), suggests that the motion flowfield represented in the dorsal stream can form the basis of object recognition performed in the ventral stream. SFM processing is likely to contribute to object perception

We present an experiment designed to test whether experienced regret and rejoicing evoked in a ri... more We present an experiment designed to test whether experienced regret and rejoicing evoked in a risk choice have an impact on subsequent intertemporal choice. We found that regret and rejoicing experienced prior to an intertemporal choice influenced considerably the way people relate to future: when regret was experienced participants preferred not to wait, whereas when rejoicing was experienced, participants were willing to wait longer. We show that in the framework of the discounted utility model experienced regret lowered and experienced rejoicing increased the discount factor.

The Journal of neuroscience : the official journal of the Society for Neuroscience, Jan 2, 2014

Neuropsychological studies have described patients with a selective impairment of finger identifi... more Neuropsychological studies have described patients with a selective impairment of finger identification in association with posterior parietal lesions. However, evidence of the role of these areas in finger gnosis from studies of the healthy human brain is still scarce. Here we used functional magnetic resonance imaging to identify the brain network engaged in a novel finger gnosis task, the intermanual in-between task (IIBT), in healthy participants. Several brain regions exhibited a stronger blood oxygenation level-dependent (BOLD) response in IIBT than in a control task that did not explicitly rely on finger gnosis but used identical stimuli and motor responses as the IIBT. The IIBT involved stronger signal in the left inferior parietal lobule (IPL), bilateral precuneus (PCN), bilateral premotor cortex, and left inferior frontal gyrus. In all regions, stimulation of nonhomologous fingers of the two hands elicited higher BOLD signal than stimulation of homologous fingers. Only in ...

Right hand finger tapping performed for 10 sec at a rate of 3-4 taps per second alternating with ... more Right hand finger tapping performed for 10 sec at a rate of 3-4 taps per second alternating with a mean rest period of 25 sec (sd = 1.39) repeated for 20 blocks. Data acquisition and processing: Data for one participant was collected at the Stanford NIRS Lab [2,3] with an ETG-4000 Hitachi System. One 4x4 probe covered the motor cortex contralateral to the effector activated. We applied a bandpass filter (0.01 -0.5Hz). We examined 4 channels that showed the typical delayed hemodynamic response time-locked to stimulus presentation (peak around 8 sec). Two of them (channels 13 and 20) showed a decrease in the oxy-Hb component peaking at 1.5 sec, whereas in channels 10 and 9 the initial dip was absent. We used the slope of the timecourse of these respective concentration parameters as summary statistics. HbO and HbD (difference between oxy-and deoxy-Hb [4]) slopes were computed for 4 time windows of interest: from 0 to 2 sec in steps of 0.5 sec Classification analysis: We trained a line...

Theoretical and empirical body of research have exposed the powerful role of experiencing regret ... more Theoretical and empirical body of research have exposed the powerful role of experiencing regret in guiding choice behavior. In this paper, we examined the impact of experienced regret and rejoicing induced by feedback provided on a risk decision prior to a two-period intertemporal choice. To our knowledge, this is the rst attempt to bring together experienced regret and choice over time. We used the two-component discounted utility model approach as a framework. We applied previous research ndings on the eect of experienced regret on utility, and we performed an experiment to test whether experienced regret and rejoicing have an impact on the discount factor. We found that both experienced regret and rejoicing have an impact on the way people discount future: when regret is experienced the discount factor decreases, whereas when rejoicing is experienced the discount factor increases.

We typically fixate targets such that they are projected onto the fovea for best spatial resoluti... more We typically fixate targets such that they are projected onto the fovea for best spatial resolution. Macular degeneration patients often develop fixation strategies such that targets are projected to an intact eccentric part of the retina, called pseudofovea. A longstanding debate concerns which pseudofovea location is optimal for non-foveal vision. We examined how pseudofovea position and eccentricity affect performance in visual search when vision is restricted to an offfoveal retinal region by a gaze-contingent display that dynamically blurs the stimulus except within a small viewing window (forced field location). Trained normally sighted participants were more accurate when forced field location was congruent with the required scan path direction; this contradicts the view that a single pseudofovea location is generally best. Rather, performance depends on the congruence between pseudofovea location and scan path direction.

Journal of Cognitive Neuroscience, 2011

Neuropsychological evidence has highlighted the role of the anterior temporal lobes in the proces... more Neuropsychological evidence has highlighted the role of the anterior temporal lobes in the processing of conceptual knowledge. That putative role is only beginning to be investigated with fMRI as methodological advances are able to compensate for well-known susceptibility artifacts that affect the quality of the BOLD signal. In this article, we described differential BOLD activation for pictures of animals and

Natural scenes contain more information than the human visual system can efficiently process at o... more Natural scenes contain more information than the human visual system can efficiently process at once. Visual attention is the perceptual mechanism by which observers select important aspects of a scene for further cognitive processing 1-5 . Evidence from neurophysiology and functional neuroimaging shows that the neural representation of a visual object is suppressed when it is presented along with other competing objects, relative to when it is presented alone, reflecting competitive interactions among sensory representations. This competitive suppression is thought to occur through inhibitory neural connections. When an object is attended through the action of a top-down biasing signal, this suppression is effectively lifted, and the item is 'selected' 6-8 .

Perception, 2007

Our visual world can be thought of as organised in a hierarchical manner. Studies on hierarchical... more Our visual world can be thought of as organised in a hierarchical manner. Studies on hierarchical letter stimuli (a large letter composed of smaller letters) suggest that processing of a visual scene is global to local, a phenomenon known as the global-precedence effect. Elaborating on this global-to-local hypothesis we tested whether global interference will increase with increasing level of globality. For this, we used three-level hierarchical letter stimuli with a global, middle, and local level. When attending to the local level of the stimulus, only the middle level showed an interference effect, whereas the global level did not interfere at all. We argue that, considering the perceptual and attentional contributions to this effect, the hypothesis of global-to-local processing of a visual scene may only hold within a limited spatial attentional window.

Psychological Science, 2010

Tool use depends on processes represented in distinct regions of left parietal cortex. We studied... more Tool use depends on processes represented in distinct regions of left parietal cortex. We studied the role of visual experience in shaping neural specificity for tools in parietal cortex by using functional magnetic resonance imaging with sighted, late-blind, and congenitally blind participants. Using a region-of-interest approach in which tool-specific areas of parietal cortex were identified in sighted participants viewing pictures, we found that specificity in blood-oxygen-level-dependent responses for tools in the left inferior parietal lobule and the left anterior intraparietal sulcus is independent of visual experience. These findings indicate that motor-and somatosensory-based processes are sufficient to drive specificity for representations of tools in regions of parietal cortex. More generally, some aspects of the organization of the dorsal object-processing stream develop independently of the visual information that forms the major sensory input to that pathway in sighted individuals.

Proceedings of the National Academy of Sciences, 2003

Visual stimuli may remain invisible but nevertheless produce strong and reliable effects on subse... more Visual stimuli may remain invisible but nevertheless produce strong and reliable effects on subsequent actions. How well features of a masked prime are perceived depends crucially on its physical parameters and those of the mask. We manipulated the visibility of masked stimuli and contrasted it with their influence on the speed of motor actions, comparing the temporal dynamics of visual awareness in metacontrast masking with that of action priming under the same conditions. We observed priming with identical time course for reportable and invisible prime stimuli, despite qualitative changes in the masking time course. Our findings indicate that experimental variations that modify the subjective visual experience of masked stimuli have no effect on motor effects of those stimuli in early processing. We propose a model that provides a quantitative account of priming effects on response speed and accuracy.

NeuroImage, 2005

If attending to a target in a rapid stream of visual stimuli within the next 400 ms or so, a seco... more If attending to a target in a rapid stream of visual stimuli within the next 400 ms or so, a second target in the stream is frequently not detected by an observer. This so-called attentional blink can provide a comparison of neural signals elicited by identical stimuli that, in one condition, reach conscious awareness and, in the other, fail to be selected for awareness. In the present study, using event-related functional magnetic resonance imaging (fMRI), differences of neural activation were studied in an attentional blink experiment in order to identify brain regions putatively involved in controlling the access of information to consciousness. Subjects viewed a rapid stream of black letters in which the second target (T2) was either presented within or outside the attentional blink period, or not at all. We observed an increase in activation for detected as compared to missed T2 presented during the attentional blink in frontal and parietal cortices. In contrast, in occipitotemporal regions activation was increased for missed as compared to detected T2. Furthermore, in several frontal and parietal areas, missed targets were associated with increased activity if compared to the condition in which no second target was presented. Finally, a selective decrease in activation for detected T2 presented during the attentional blink was observed in areas associated with emotional and predominantly automatic processing. While activations in occipitotemporal regions might mainly reflect duration of attentive search, the frontoparietal areas seem to be involved in a highly distributed network controlling visual awareness. D

NeuroImage, 2009

Recent psychophysics studies suggest that the behavioral impact of a visual stimulus and its cons... more Recent psychophysics studies suggest that the behavioral impact of a visual stimulus and its conscious visual recognition underlie two functionally dissociated neuronal processes. Previous TMS studies have demonstrated that certain features of a visual stimulus can still be processed despite TMS-induced disruption of perception. Here, we tested whether symbolic action priming also remains intact despite TMSinduced masking of the prime. We applied single-pulse TMS over primary visual cortex at various temporal intervals from 20 ms to 120 ms during a supraliminal action priming paradigm. This TMS protocol enabled us to identify at what exact time point a TMS-induced activity disruption of primary visual cortex interferes with conscious visual perception of the prime versus (un)conscious behavioral priming of the visual target stimulus. We also introduced spatial uncertainty by presenting visual stimuli either above or below the fixation cross, while the TMS pulse was always targeting the prime presented below fixation. We revealed that TMS over primary visual cortex interferes with both conscious visual perception and symbolic behavioral priming in a temporarily and spatially specific manner, i.e., only when disrupting primary visual cortex at approximately the same temporal stage between 60 and 100 ms after prime onset, and only for those prime stimuli presented below fixation. These findings are in disagreement with the idea of subliminal action priming being mediated by neural pathways bypassing striate cortex, and rather suggest that symbolic action priming relies on an intact neural transmission along the retino-geniculo-striate pathway. The implications of our findings for previous reports of residual visual processing during striate TMS are discussed.

NeuroImage, 2003

Allocating attention to a spatial location in the visual field is associated with an increase in ... more Allocating attention to a spatial location in the visual field is associated with an increase in the cortical response evoked by a stimulus at that location, compared to when the same stimulus is unattended. We used event-related functional magnetic resonance imaging to investigate attentional modulation of the cortical response to a stimulus probe at an attended location and to multiple probes at unattended locations. A localizer task and retinotopic mapping were used to precisely identify the cortical representations of each probe within striate (V1) and extrastriate cortex (V2, VP, V3, V4v, and V3A). The magnitude and polarity of attentional modulation were assessed through analysis of event-related activity time-locked to shifts in spatial attention. Attentional facilitation at the attended location was observed in striate and extrastriate cortex, corroborating earlier findings. Attentional inhibition of visual stimuli near the attended location was observed in striate cortex, and attentional inhibition of more distant stimuli occurred in both striate and extrastriate cortex. These findings indicate that visual attention operates both through facilitation of visual processing at the attended location and through inhibition of unattended stimulus representations in striate and extrastriate cortex.