We review recent methodological advances in electromagnetic source imaging and present EEG data f... more We review recent methodological advances in electromagnetic source imaging and present EEG data from our laboratory obtained by application of these methods. There are two principal steps in our analysis of multichannel electromagnetic recordings: (i) the determination of functionally relevant time periods in the ongoing electric activity and (ii) the localization of the sources in the brain that generate these
There is growing evidence that the visual processing of human body stimuli is particular and dist... more There is growing evidence that the visual processing of human body stimuli is particular and distinct from that of other objects. This is due to implicit knowledge of anatomical and biomechanical constraints of the human body. The question arises whether body stimuli in which biomechanical constraints are violated are processed in the same way as realistic bodies. This study investigated the neural mechanisms of anatomically plausible and implausible body stimuli. Event-related potentials (ERP) were recorded in healthy participants during mental rotation of body parts. Subjects were shown pictures of body parts or whole bodies in which one element (finger, arm) could be anatomically accurate or inaccurate (e.g., left forearm attached to right upper arm). Furthermore, the body parts were rotated in 7 different orientations, from 0 degrees to 180 degrees in 30 degrees increments, resulting in some possible and some impossible positions of the body parts. Analysis of the 123-channel ER...
Neuropsychology is a scientific discipline, born in the XIX century, and bridges the fields of ne... more Neuropsychology is a scientific discipline, born in the XIX century, and bridges the fields of neurology and psychology. Neuropsychologists apply scientific knowledge about the relationship between brain function and mental performances. The major clinical role of a neuropsychological evaluation is to help to establish medical and functional diagnosis in patients (adults or infants) with different neurological pathologies such as stroke, traumatic brain injury, dementia, epilepsy.... Such analysis necessitates accurate observation of behaviour and administration of tests of mental abilities (e.g. language, memory...). Test results can also help to clarify the nature of cognitive difficulties and to support the formulation of plans for neuropsychological therapy and functional adjustment in every day life.
Using visual half-field presentations of words to the right (RVF) and to the left visual field (L... more Using visual half-field presentations of words to the right (RVF) and to the left visual field (LVF), this study investigated the time course of the hemispheric involvement in the processing of semantic category information. Multi-channel event related brain potentials (ERPs) were recorded from 15 healthy subjects during a categorisation task of sequentially presented word pairs. Subjects had to judge mentally after the appearance of the second word whether the words of a pair were semantically related (SR) or not (SU). ERPs were computed, from 100 ms before the onset of the second word to 600 ms, for SR and SU conditions in the LVF and in the RVF separately. The temporal segmentation of ERP map series into sequences of quasi-stable map configurations revealed a total of seven segments in each visual field of which only the first five (S1-S5, appearing between 70 and 400 ms) showed different map configurations as a function of visual field but presented a similar temporal sequence i...
Mental imagery is a powerful mechanism that may facilitate visual perception as well as compensat... more Mental imagery is a powerful mechanism that may facilitate visual perception as well as compensate for it. The role of V1 in mental imagery is still a matter of debate. Our goal here was to investigate whether visual imagery was still possible in case of bilateral V1 destruction behaviorally evidenced by total clinical blindness and if so, whether it might boost residual visual perception. In a factorial fMRI design, faces, scenes or scrambled images were presented while a rare patient with cortical blindness over the whole visual field due to bilateral V1-lesions (TN) was instructed to imagine either an angry person or a neutral object (tree). The results show that visual imagery of a person activates frontal, parietal and occipital brain regions similar to control subjects and hence suggest that V1 is not necessary for visual imagery. In addition, the combination of visual stimulation and visual imagery of socio-emotional stimuli triggers activation in superior parietal lobule (SPL) and ventromedial and dorsolateral prefrontal cortex. Finally, activation during residual vision, visual imagery and their interaction overlapped in the SPL, arguing for a central role of feeling in V1-independent vision and imagery.
We review recent methodological advances in electromagnetic source imaging and present EEG data f... more We review recent methodological advances in electromagnetic source imaging and present EEG data from our laboratory obtained by application of these methods. There are two principal steps in our analysis of multichannel electromagnetic recordings: (i) the determination of functionally relevant time periods in the ongoing electric activity and (ii) the localization of the sources in the brain that generate these
There is growing evidence that the visual processing of human body stimuli is particular and dist... more There is growing evidence that the visual processing of human body stimuli is particular and distinct from that of other objects. This is due to implicit knowledge of anatomical and biomechanical constraints of the human body. The question arises whether body stimuli in which biomechanical constraints are violated are processed in the same way as realistic bodies. This study investigated the neural mechanisms of anatomically plausible and implausible body stimuli. Event-related potentials (ERP) were recorded in healthy participants during mental rotation of body parts. Subjects were shown pictures of body parts or whole bodies in which one element (finger, arm) could be anatomically accurate or inaccurate (e.g., left forearm attached to right upper arm). Furthermore, the body parts were rotated in 7 different orientations, from 0 degrees to 180 degrees in 30 degrees increments, resulting in some possible and some impossible positions of the body parts. Analysis of the 123-channel ER...
Neuropsychology is a scientific discipline, born in the XIX century, and bridges the fields of ne... more Neuropsychology is a scientific discipline, born in the XIX century, and bridges the fields of neurology and psychology. Neuropsychologists apply scientific knowledge about the relationship between brain function and mental performances. The major clinical role of a neuropsychological evaluation is to help to establish medical and functional diagnosis in patients (adults or infants) with different neurological pathologies such as stroke, traumatic brain injury, dementia, epilepsy.... Such analysis necessitates accurate observation of behaviour and administration of tests of mental abilities (e.g. language, memory...). Test results can also help to clarify the nature of cognitive difficulties and to support the formulation of plans for neuropsychological therapy and functional adjustment in every day life.
Using visual half-field presentations of words to the right (RVF) and to the left visual field (L... more Using visual half-field presentations of words to the right (RVF) and to the left visual field (LVF), this study investigated the time course of the hemispheric involvement in the processing of semantic category information. Multi-channel event related brain potentials (ERPs) were recorded from 15 healthy subjects during a categorisation task of sequentially presented word pairs. Subjects had to judge mentally after the appearance of the second word whether the words of a pair were semantically related (SR) or not (SU). ERPs were computed, from 100 ms before the onset of the second word to 600 ms, for SR and SU conditions in the LVF and in the RVF separately. The temporal segmentation of ERP map series into sequences of quasi-stable map configurations revealed a total of seven segments in each visual field of which only the first five (S1-S5, appearing between 70 and 400 ms) showed different map configurations as a function of visual field but presented a similar temporal sequence i...
Mental imagery is a powerful mechanism that may facilitate visual perception as well as compensat... more Mental imagery is a powerful mechanism that may facilitate visual perception as well as compensate for it. The role of V1 in mental imagery is still a matter of debate. Our goal here was to investigate whether visual imagery was still possible in case of bilateral V1 destruction behaviorally evidenced by total clinical blindness and if so, whether it might boost residual visual perception. In a factorial fMRI design, faces, scenes or scrambled images were presented while a rare patient with cortical blindness over the whole visual field due to bilateral V1-lesions (TN) was instructed to imagine either an angry person or a neutral object (tree). The results show that visual imagery of a person activates frontal, parietal and occipital brain regions similar to control subjects and hence suggest that V1 is not necessary for visual imagery. In addition, the combination of visual stimulation and visual imagery of socio-emotional stimuli triggers activation in superior parietal lobule (SPL) and ventromedial and dorsolateral prefrontal cortex. Finally, activation during residual vision, visual imagery and their interaction overlapped in the SPL, arguing for a central role of feeling in V1-independent vision and imagery.
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Papers by Alan Pegna