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Biomedical subjects

T Vladova

Publications and source records attributed to T Vladova.

4 recordsLinked to original sources
PubMed1997

Event-related potentials in parkinsonian patients under auditory discrimination tasks.

Seventeen non-demented idiopathic medicated Parkinsonian patients and 17 age- and education-matched controls participated in auditory discrimination tasks. The study aimed at revealing the differences in their ability for auditory information processing. Series comprising 1000 Hz and 800 Hz tones were used as stimuli. The accuracy in the tones' discrimination was determined by means of counting the high tone or recording a binary sensomotor reaction. The results based on the mean group values of event-related potential components show that the Parkinsonian patients had lower amplitude for the exogenous N1 and endogenous P3 components of the evoked responses. In the sensomotor task series the patients had longer N2 latency than controls. In the counting series the patients recognized the tones well and gave an exact count but during the sensomotor task they had longer reaction time, more erroneous answers and depressed P3. The data show differences in the information processing between the two groups and reveal cognitive impairment in the Parkinsonian patients.

Acoustic Stimulation↗
PubMed1981

Changes in the P3-wave in a situation of verbal stimulus prediction.

The changes in the P3-wave of averaged auditory evoked potentials (AEP) from Fz, Cz and Pz were studied under conditions when: (I) the subject was required to predict which of the two alternative sound stimuli would appear. After presentation of a series of 50 high (1200 Hz) and 50 low (800 Hz) tones, in random order (mixed signal series) we proceeded suddenly to the presentation of the low tone only, without warning the subject (pseudo-mixed series); (II) the same mixed signal series was presented again requiring quick motor response by the subject only to the appearance of the high tone and not requiring verbal prediction (choice RT task). It has been found that in the three recordings: (1) the P3-wave increases for both types of stimuli, both in the situation of verbal stimulus prediction without motor response and in the situation of choice RT task; (2) the increase in P3 (assessed by the N1-P3 amplitude) is greater in AEP from stimuli disconfirming the prediction compared with stimuli confirming it; (3) preforming of the verbal prediction, in the course of the pseudo-mixed series, to prediction of the appearance of the low tone only is accompanied by a sharp decrease or disappearance of the P3-wave. The results show that the P3-wave is not connected with the development of motor potentials but with the processes of verbal prediction, in particular with the non-coincidence between the event expected by the subject and the really appearing one.

Electroencephalography↗
PubMed1981

Dependence between the P3-wave and the prestimulus EEG negative shift under conditions of probability prediction.

The connection between the prestimulus slow potential shift (SPS) and the P3-wave of auditory averaged evoked potentials (AEP) from Fz and Cz is studied upon changing the probability and signal characteristics of the stimuli. It has been found that while the changes in the P3-wave, depending on the character of the experimental tasks, are unidirectional for all subjects studied in both recordings and repeat our earlier results, the changes in SPS have different directions. The same changes in P3 are accompanied in some cases by a slightly expressed negativization, in other cases by a certain positivization and in a third group of cases by lack of SPS. The results obtained show that the observed changed in the P3-wave under the conditions of our experiments are not connected with pre-stimulus SPS of the CNV type, being generated in the central nervous system irrespectively of them. They support our hypothesis that the P3-wave is connected with the processes of probability prediction in the brain functioning.

Electroencephalography↗