Neurophysiological Features of Perception of Roman and Arabic Numerals in Paranoid Schizophrenia Patients

Latencies and amplitudes of the Р100, N170 and P200 components of event-related potentials (ERPs) derived during visual presentation of Roman and Arabic numerals from healthy subjects and in patients with paranoid schizophrenia were studied. The activation level was estimated as the ratio of the values in response to Arabic and Roman numerals. The Р100 latency in response to Arabic numerals in controls was shorter in the occipital and parietal areas, while the amplitude was higher in the left posterior temporal area. In schizophrenia patients, the Р100 amplitude in response to Arabic numerals was higher in the left temporal area and lower in the right central area. The intergroup analysis showed that the Р100 amplitude in the central parietal, left temporal and right posterior temporal areas in response to Arabic numerals in the control was greater than in schizophrenia patients. The N170 latency in response to Arabic numerals in the control group was shorter in the left occipital, right temporal and parietal areas, while the amplitude was lower in the right posterior temporal area. In schizophrenia patients, the N170 latency of response to Arabic numerals was shorter only in the middle parietal area. Intergroup analysis showed that the N170 latency of responses to both types of stimuli was shorter in the occipital areas in controls compared to the patients, and the amplitude of this wave in response to Roman numerals was higher in the right posterior temporal area. The P200 latency in response to Arabic numerals in control group was shorter in the left frontal area, while the amplitude was higher in the middle frontal and left temporal areas. In schizophrenia patients, the P200 latency in response to Arabic numerals was longer in the left occipital region and the amplitude was lower in the middle central and right occipital areas. Intergroup analysis showed that the latency in response to Arabic numerals was shorter in the left parietal area in the control group compared to the patients, and the amplitude in the right central and left temporal areas was higher. The P200 amplitude in response to Roman numerals in the right prefrontal and left frontal areas was higher in the control compared to the patients. Thus, in norm and in schizophrenia patients different levels of cortical areas activation to the two types of stimuli were revealed reflecting the differences of these stimuli characteristics.