title: Neurophysiological correlates of visual stimulus recognition in man.
abstract: This study investigated the components of evoked impulse activity of neurons and neuronal populations (NIA) in the human brain. Subjects were 5 parkinsonian patients, two patients with skull trauma and an epileptic, diagnosed and treated with implanted electrodes. NIA was recorded during the following psychological tests: (1) identification of letters and digits presented at near-threshold exposures; (2) recognition of polygonal shapes with and without semantic meaning. Peri-stimulus time histograms (PSTHs) for the cases of recognition and non-recognition in the first test and for cases of presentation of familiar and unfamiliar patterns in the second test were computed and compared with each other. PSTH components in the stimulus-response interval were classified into 3 groups: the earliest components with the latency 60-200 ms; the late components with latency 300-400 ms; and slow count rate shifts revealed 300-500 ms after stimulus presentation. No significant differences were found between the short-latency components for cases of recognition and non-recognition in the first test and for cases of presentation of familiar and unfamiliar patterns in the second test, while late components depended upon subjective estimation by the patient of the stimulus. Early components are supposed to be related to physical characteristics of the stimulus, while the late components with semantic meaning.
mesh_terms: D000328:Adult; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping; D002421:Caudate Nucleus / Q000502:physiology; D002540:Cerebral Cortex / Q000502:physiology; D003342:Corpus Striatum / Q000502:physiology; D004567:Electrodes, Implanted; D005074:Evoked Potentials, Visual; D005556:Form Perception / Q000502:physiology*; D006801:Humans; D008875:Middle Aged; D010364:Pattern Recognition, Visual / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D013787:Thalamic Nuclei / Q000502:physiology