‘Phylogenetic scale: an introductive ERPs research

Neuroimaging and neuropsychological literature show functional dissociations in brain activity during processing of stimuli belonging to different semantic categories (e.g., animals, tools, faces, places). The aim of the study was to provide informations about the processing of stimuli from different phylogenetic domains, in order to observe the emergence of non-linguistic conceptual knowledge perceptualand categorizational pathway. Event related potentials (ERPs), N200 and P300, were recorded with an odd ball paradigm, in 24healthy right-handed individuals as they performed a perceptual recognition task on 56 of images of animals, man-made objects (i.e., artifacts) and background-color.The animals were grouped according to the phylogenetic scale in Fish (F), Reptiles (R) and Mammals (M). All stimuli were matched according to the familiarity of representation. The Task consisted in 4 sessions, one for every stimulus.The task was to press a button when the subject saw the stimulus between the background colors. Univariate ANOVAs were computed separately for each ERP component in amplitude (V) and latency (L) for Electrode and for Lateralization. Both N200 and P300 had shown significant differences in Frontal Channels (Fp2, F4, F8) V (p<,05) and in Frontal L as well (p<,05). Post hoc Analysis (Bonferroni) for N200 showed thatF and R stimuli elicited a decrement in V (p<,05) and an increment inL in N200 (p<,05) waves and in Right Lateralization (p<,05). Post hoc Analysis for P300 showed that F, R and M stimuli elicited an increment in P300 L (p<,05) and in Right Lateralization (p<,05). Phylogenetically distant stimuli have differently activated the cortical processing,regardless of familiarity with the stimulus presented. The right hemisphere appears to be more sensitive to differences related to the visual representation of the stimuli that are processed more slowly, which correspond to stimuli furthest by evolutive level.