A study on cerebral activity by means of combined EEG-fMRI in neuropsychological disorders in childhood

This study is composed by two parts, both focusing on post-calcarine ventral, occipito-temporal visual pathway (“ventral stream”), and on occipito- temporal cortex, structures involved in images and in face processing. In the first part of the study I have analyzed gamma-band ERSP (event-related spectral perturbations) and fMRI BOLD activations in response to recognizable and not recognizable visual stimuli, in typical children and in children affected by "ventral type" Cerebral Visual Impairment, trying to show how the deficits in "ventral" tasks could be investigated using both a neurophysiological and a neuroimaging approach. However I was not able to reproduce preliminary, promising data on gamma-band ERSP because of excessive electrical noise during EEG recordings, most likely because of an equipment radical and unexpected change. Despite these issues, taking advantage of the peculiar features and strength points of the new equipment (a dense-array EEG machine), I continued my work on visual perception and the occipito- temporal visual network using ERPs recordings (part 2), that are substantially less affected from the AC electrical noise usually present in every EEG recording. In particular, I recorded high density ERP responses to neutral and emotional visual face stimuli in typical children and in children affected by Autism Spectrum Disorder, a condition in which face-processing neural networks have been often found dysfunctional in neurophysiological and functional neuroimaging studies. However, evidence regarding face processing in Autism Spectrum Disorders is still contradictory and neurophysiological methods used are heterogeneous. Therefore I designed and applied an experimental paradigm trying to control most of the known or suspected confounding variables in this kind of studies. Using neutral and emotional faces, and trees as non-face stimuli, I was able to modulate both latency and amplitude of the main face-sensitive ERPs (N170, P1, peak-to-peak N170) as a function of stimulus and group conditions. These findings support the hypothesis of an early (first 200 msec) impairment in both neutral and emotional face processing in children affected by Autism Spectrum Disorders.