Effects of moderate hypobaric hypoxia on evoked categorical visuocognitive responses

OBJECTIVE Aim of the current study is to provide electrophysiological evidence about the effects of moderate hypobaric hypoxia on human visual cognition. METHODS We investigate ERPs at occipitoparietal cortical areas in an ultra-rapid categorical discrimination task with psychomotor responses under the conditions of normoxia vs. moderate hypobaric hypoxia. Subjects had to produce motor response upon the categorization of target images containing animals, while suppress it for nontarget images containing only nonanimals. RESULTS Statistical analysis on peak amplitudes and latencies of ERP components indicated significant: (i) attenuation of P1 and enhancement of N1-P3 amplitudes, (ii) delay of P2 latency for both stimuli whereas the delay of P3 latency only for nontargets, (iii) reduction in behavioral performance rates only for nontargets. CONCLUSIONS For both categorical stimuli, impairment of early visual sensory and compensation through late cognitive processes was noticed. For targets, compensatory discrimination-categorization processes (reflected on P3 amplitudes) were sufficient to override our mild transient hypoxic challenge. For nontargets, differential P3 latencies and behavioral performance manifested the early impeding effects of systemic hypoxaemia. SIGNIFICANCE Evoked brain responses allow for early detection of subtle electrophysiological modulations coupled to cognitive-behavioral alterations, assessment of 'functional' hypobaric hypoxic sensitivity thresholds for 'altinauts' and reveal the susceptibilities of complex visuocognitive processes even to moderate hypoxic insults.