Cognitive Evoked Potentials (P300): Is the Decision To Press a Button Always Conscious?

Evoked cognitive potentials are a promising experimental technique that can be useful in diagnosis of various cognitive disorders, especially connected to the various memory impairments. Of particular interest to researchers is the study of the cognitive evoked potentials’ latency when recognition of various stimuli isinvolved. To study the physiological nature and functional role of evoked cognitive potentials observed during the reaction to stimuli, and to determine the degree of conscious control involved in this reaction, the experimental data were statistically analyzed to determine the numerical correlation between the working memory capacity and the cognitive potential’s latency. The cognitive EPs were measured for 166 healthy subjects and 63 others that had some pathological brain condition (discirculatory encephalopathy and other brain discirculatory disorders), varied by the age and gender. Measurements were done with the Neurosoft Neuro-MEP 4 computerized encephalography system, which implemented the standard method of large latency neural response measurement for P300 waves. Measurements were done in the setup where the subject had to recognize the significant stimuli and react to them by pressing a button. The significant stimulus was represented by a 2 kHz tone, while the insignificant stimuli were the frequently repeated 1 kHz tones.The brainwaves were registered in Cz-M1 and Cz-M2 outputs. This method allowed detection and latency measurements of the main response components N2, P3a P3ab and N3. Working memory capacity was determined by the number of words from a 10–15 word sets correctly reproduced shortly after exposures, as outlined by Luria. A statistically significant nonlinear correlation was observed between the memory capacity and the EP’s latency, which was fitted by a modified hyperbolic function. Additionally, greater latencies were observed for subjects suffering from the memory disorders, and much shorter latencies were in general noted for the male subjects as opposed to the female ones. One more interesting observation was that in manycases the absolute reaction time was less than the cognitive potential peak taken as a conscious decision, suggesting that it is in many cases an automatic reaction. Cognitive potentials measurements, being an instrumental method, allow a clinical psychologist much greater flexibility in his diagnostic repertory, as it can be used even in the cases where word tests cannot. Also, the reaction times shorter than the latency of conscious reaction to stimuli adds weight to the simultaneous codes theory of automatic reactions. Keywords: working memory capacity (WMC), regression line, nonlinear correlation, test less WMC estimates, cognitive processes, working memory, cognitive evoked potentials simultaneous codes, positional game, conscious cognitive comparison, P30

Cognitive Evoked Potentials (P300): is the Decision to Press A Button Always Conscious?

Evoked cognitive potentials are a promising experimental technique that can be useful in diagnosis of various cognitive disorders, especially connected to the various memory impairments. Of particular interest to researchers is the study of the cognitive evoked potentials' latency when recognition of various stimuli isinvolved. To study the physiological nature and functional role of evoked cognitive potentials observed during the reaction to stimuli, and to determine the degree of conscious control involved in this reaction, the experimental data were statistically analyzed to determine the numerical correlation between the working memory capacity and the cognitive potential's latency. The cognitive EPs were measured for 166 healthy subjects and 63 others that had some pathological brain condition (discirculatory encephalopathy and other brain discirculatory disorders), varied by the age and gender. Measurements were done with the Neurosoft Neuro-MEP 4 computerized encephalography system, which implemented the standard method of large latency neural response measurement for P300 waves. Measurements were done in the setup where the subject had to recognize the significant stimuli and react to them by pressing a button. The significant stimulus was represented by a 2 kHz tone, while the insignificant stimuli were the frequently repeated 1 kHz tones.The brainwaves were registered in Cz-M1 and Cz-M2 outputs. This method allowed detection and latency measurements of the main response components N2, P3a P3ab and N3. Working memory capacity was determined by the number of words from a 10–15 word sets correctly reproduced shortly after exposures, as outlined by Luria. A statistically significant nonlinear correlation was observed between the memory capacity and the EP's latency, which was fitted by a modified hyperbolic function. Additionally, greater latencies were observed for subjects suffering from the memory disorders, and much shorter latencies were in general noted for the male subjects as opposed to the female ones. One more interesting observation was that in manycases the absolute reaction time was less than the cognitive potential peak taken as a conscious decision, suggesting that it is in many cases an automatic reaction. Cognitive potentials measurements, being an instrumental method, allow a clinical psychologist much greater flexibility in his diagnostic repertory, as it can be used even in the cases where word tests cannot. Also, the reaction times shorter than the latency of conscious reaction to stimuli adds weight to the simultaneous codes theory of automatic reactions. Keywords: working memory capacity (WMC), regression line, nonlinear correlation, test less WMC estimates, cognitive processes, working memory, cognitive evoked potentials simultaneous codes, positional game, conscious cognitive comparison, P30

The clinical and neurophysiological characteristics of the deja vu phenomenon in epilepsy

Objective: to study the clinical and neurophysiological characteristics of the deja vu phenomenon in epilepsy. Patients and methods. The manifestations of the dВjЕ vu phenomenon were compared in 154 examinees in two groups: 1) 139 healthy individuals and 2) 25 patients with epilepsy (mean age 25.17±9.19 years; women, 63.2%) The characteristics of the phenomenon were determined, by questioning the examinees; 12—16-hour ambulatory electroencephalogram (EEG) monitoring was made. Results. The deja vu phenomenon occurred with cryptogenic and symptomatic focal epilepsy with equal frequency; however, the phenomenon was also seen in the idiopathic generalized form of the latter and could be concurrent virtually with any types of seizures and observed as an individual seizure and in the structure of a partial and secondarily generalized seizure. In epileptic patients, the main clinical characteristics of the deja vu vu phenomenon are its frequency, fear before its onset, and emotional coloring. The most important criterion is a change in the characteristics of deja vu vu: prolongation, more frequencies, and the emergence of negative emotions. On EEG, the phenomenon was characterized by the onset of polyspike activity in the right temporal leads and, in some cases, ended with slow-wave, theta-delta activity in the right hemisphere

DEREALIZATION DISORDERS IN EPILEPSY

Derealization is mental disorder, manifested in a feeling of unreality and strangeness of the surrounding real world, a form of impairment of consciousness. The most common and recognizable such disorder is the phenomenon of «déjà vu» – deja vu (DV). Objective: to study the clinical and diagnostic value derealization disorders (DD) in epilepsy. Materials and Methods: the total study group was 152 persons (mean age 25,17±9,19; 63,2% of women). The phenomena of derealization were compared in groups of healthy subjects (n = 139) and patients with epilepsy (n = 23). Patients were interviewed on the DV characteristics and long-term (12-16 hours) ambulatory EEG monitoring was conducted. Results: the same frequency of DV in patients with cryptogenic and symptomatic focal epilepsy was demonstrated. DV could be combined with any types of seizures, it could be aura of a seizure or own seizure. The main clinical characteristics that differentiate DV in healthy from DV in patients with epilepsy are: frequency, fear of the onset DV and emotional coloring. The most important criterion is the dynamic characteristics of the DV: elongation increased the appearance of negative emotions. The DV phenomenon characterized in EEG by start with polyspiking activity in the right temporal leads and, in some cases, ended by slow wave, theta-delta activity in the right hemispher