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At least 757 records · Page 42Linked to original sources
PubMed1975

The frontal CNV: its dissimilarity to CNVs recorded from other sites.

Two new techniques were used to study the distribution of the CNV recorded from the scalp of humans. One technique was for the suppression of eye movements and the elimination of them fron the average data. The other technique was for the recognition of differences in the form of CNVs recorded from different sites. The latter technique utilized an average vertex CNV as a template pattern against which CNVs from the vertex, left and right frontal, central and parietal sites were matched. The results showed that the frontal CNV was different in form from the vertex, central and parietal Cnvs and that the vertex, central and parietal CnvS were similar in form. An analysis of the amplitudes of CNVs showed that the frontal CNVs were significantly smaller than the CNVs from all other sites, that the vertex CNV was significantly larger than the parietal or central CNVs and that the central CNV was significantly larger than the parietal CNV. There were no differences in amplitude between hemispheres within Condition A responding with the right hand) or Condition B (responding with the left hand) or between Conditions A and B. The results are discussed with respect to their possible theoretical implications.

Adult↗
PubMed1975

On the independence of the CNV and the P300 components of the human averaged evoked potential.

We report an experiment designed to assess the interactions between the CNV and the P300 components of human event-related potential. Eight subjects were each presented with series of experimental trials on all of which either a 1200 c/sec or an 800 c/sec tone was presented. There were three independent variables: (a) The presence or absence of a warning flash 1000 msec prior to the tone. (b) The task assigned to the subject--that is subjects were either to make a discriminative response to the tone or, on half the series, to predict prior to the tiral which of the two tones would be presented. (c) The predictability of the tone frequency. On half the series high and low tones alternated from trial to trial. On the other series, tones were chosen randomly on each trial. The data show that the amplitude of the P300 component is not affected by the presence or absence of a warning stimulus. Furthermore, the distributions of P300 and the CNV over the scalp are quite different. These conclusions are supported by a principal component and a discriminant analysis of the data. We conclude that the CNV and the P300 reflect the activity of functionally distinct cortical mechanisms.

Analysis of Variance↗
PubMed1977

Ethanol and marihuana effects on event-related potentials in a memory retrieval paradigm.

Twelve men performed the Sternberg memory retrieval task under three experimental conditions: after oral doses of marihuana extract calibrated to contain 0.7 mg/kg delta9-tetrahydrocannabinol (THC), 1.0 ml/kg 95% ethanol, or placebo. Simultaneously, the EEG was recorded from Ca to linked ears and the EOG from leads above and below the right eye. In this task, subjects saw a set of 1 to 4 digits follwed by a warning tone that was followed 1.5 sec later by a test digit. Subjects indicated by pressing one of two buttons whether the test digit was in-set or out-of-the-set. There were no drug effects on N1 in the evoked potential to the warning tone, but P3 amplitude was smaller under THC and ethanol than under placebo. CNV amplitude in the interval between the warning tone and the test digit showed no drug effects, indicating that the subject was equally prepared for the test digit regardless of drug received. However, the latency of 50% resolution of the CNV was longer under THC than under placebo. THC also increased the reaction time for each set size by about 75 msec above the values for ethanol and placebo, the latter two not differing significantly. Set size affected N1 and P3 amplitudes and latencies and CNV amplitude, as well as 50% CNV resolution latency and reaction time, but there were no drug chi set size interactions.

Adolescent↗
PubMed1978

Occipital rhythmic activity within the alpha band during conditioned externally paced movement.

The time-dependent behaviour of the power within the alpha band during conditioned movement was studied from the scalp EEG of 9 normal humans. Two tasks were used: (1) button pressing at imperative signal S1 and release at signal S2; (2) button pressing at imperative signal S2, preceded by warning signal S1. Together with a complex correlate of the CNV and EPs, the components of power decrease related to initiation of movement were not clearly identifiable in the central areas. They were sharply isolated in the occipital areas, using tone as the imperative signal. During initiation of movement a significant short-lasting decrease in power of the occipital alpha activities was observed in all 9 subjects. However, 'mu activity', tested in the classical manner and with help of power spectra, was not present in some of these subjects.

Acoustic Stimulation↗
PubMed1979

A CNV rebound effect.

Fifty normal volunteers were tested in two conditions: (1) a constant-foreperiod reaction time situation consisting of a flash-tone-key press sequence (control trials); (2) a '50%-letters' condition, in which two types of trials occurred randomly--no letters trials, which were identical to control trials, and letters trials, which were similar to control trials but also involved the presentation of four auditory letters within the flash-tone interval as part of a short-term memory task. Compared to control trials, CNV amplitude showed a pattern of reduction in letters trials accompanied by slower reaction times to tone (CNV distraction effect). Compared to control trials, CNV amplitude showed an unexpected supranormal increase in no-letters trials. The CNV rebound effect observed in no-letters trials was interpreted as reflecting a switching of attention from the divided attention set intrinsic to letters trials (listening for letters and preparing for response to tone) to an undivided attention set in no-letters trials (simply preparing for response to tone). The CNV rebound effect, which is diminished in aging individuals and absent in psychosurgery patients, appears to represent a non-invasive technique of possible value in assessing pathophysiology of human brain functioning.

Adult↗