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Biomedical subjects

A Aranibar

Publications and source records attributed to A Aranibar.

13 recordsLinked to original sources
PubMed1979

Amplitude of evoked potentials and degree of event-related desynchronization (ERD) during photic stimulation.

The variations in amplitude of visual evoked potentials (VEPs) and parallel changes in amount of event-related desynchronization (ERD) of the rhythmic activity within the alpha band were studied in central derivations of scalp EEG, in 10 normal subjects. Two methods were used to estimate the amplitude of VEPs in small groups of 10 responses: (1) inverse and matched filtering techniques; (2) two-way rank analysis of variance by the Friedman test. The two methods gave similar results and two groups, statistically different, emerged. The first, with large VEP amplitude, having at the same time large ERD, and the second, with small VEP amplitude and small ERD.

Adult↗
PubMed1979

Evaluation of event-related desynchronization (ERD) preceding and following voluntary self-paced movement.

A method of accurate storage and on-line preprocessing of an EEG signal, preceding and following a trigger signal, elicited by button pressing, is described. The method was used to study the changes occurring in the power of the rhythmic activity within the alpha band in central areas, during voluntary, self-paced movement in 10 normal humans. A short-lasting decrease or phasic event-related desynchronization (ERD) of alpha power, representing mu activity, was observed in all 10 subjects. During the 2 sec period preceding movement the phasic ERD was mostly bilateral, but larger prior to right than to left thumb movement. At onset and during the first second of execution of movement, the phasic ERD was mostly bilateral but predominant in ipsilateral areas. Preceding or during movement, maximum ERD was observed in most cases in central-vertex regions.

Adult↗
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↗
PubMed1978

On and off effects in the background EEG activity during one-second photic stimulation.

The changes in alpha band power of the background EEG activity during 1-sec light stimulation were investigated in 10 normal human subjects. The EEG data were band-pass filtered, centering on the alpha range, and the time-dependent power changes were evaluated for their significance. The most significant finding was a light-on power decrease (on-effect) occurring in occipital areas 250--500 msec after onset of the stimulus, observed in all subjects, and reaching values of 72.2 +/- 13.2% decrease, with reference to power in the pre-stimulus interval. In 8 subjects there was also a significant light-off power decrease occuring 250--500 msec after offset of the photic stimulus (average across subjects: 41.8 +/- 24.4%) also in the occipital region. Similar on- and off-effects were observed in central regions, with lesser statistical significance. This pattern of light-on and -off power decreases was consistent and reproducible, with small inter- and intraindividual variability.

Alpha Rhythm↗
PubMed1978

[Reactions in the brainactivity during increased carbondioxyde concentration (author's transl)].

A comparative study of two kinds of respiration (normal air and mixed with 4% CO2) was carried out in 8 healthy students. During the three experiments, each one lasting over 120 min, CO2 or air was inhaled using a mask. Blood samples were taken from the fingers, an average increase of pCO2 of 1.9 mm (p less than 0.01) and pO2 of 7.3 mm (p less than 0.01) was found during CO2-inhalation. The ECG and EEG were recorded and reaction times to tone stimuli in a foreperiod reaction time experiment were measured. During CO2-inhalation a clear reduction of the power in the alpha-band was found in frontal, central and occipital region in the order of 23% (p less than 0.05) and 12% (p less than 0.05) and 22% (p less than 0.01). The heart rate interval decreased significantly by 2.3% (p less than 0.05). No significant changes were found in CNV, reaction time and percentage event-related alpha-desynchronization.

Adult↗
PubMed1978

[Changes in the spontaneous EEG-activity before and during voluntary self-paced movement. New ways of investigation of the central mu-activity (author's transl)].

Movement-related desynchronization was investigated in the EEG from central region in human subjects, during voluntary self-paced movement of the thumb. The average dynamic time-behaviour of the power in the alpha band was calculated from 4 sec before to 2 sec after voluntary movement. In all investigated subjects (9 students and 7 patients with several forms of hemiplegia) a significant power reduction before voluntary movement of the thumb was found. This power decrease can be interpreted as desynchronization of the central mu activity. Therefore, it appears that in all subjects a mu activity can be demonstrated. In most cases, a short-lasting desynchronization of central mu activity occurred about 2 sec before movement onset and was followed by a second one, about 1 sec before movement onset which reached a maximum during initiation of movement. Frequently the first desynchronization occurred in parallel but often also before the Bereitschaftspotential.

Alpha Rhythm↗
PubMed1977

Event-related cortical desynchronization detected by power measurements of scalp EEG.

Changes in the background EEG activity occurring at the same time as visual and auditory evoked potentials, as well as during the interstimulus interval in a CNV paradigm were analysed in human subjects, using serial power measurements of overlapping EEG segments. The analysis was focused on the power of the rhythmic activity within the alpha band (RAAB power). A decrease in RAAB power occurring during these event-related phenomena was indicative of desynchronization. Phasic, i.e. short lasting, localised desynchronization was present during sensory stimulation, and also preceding the imperative signal and motor response (motor preactivation) in the CNV paradigm.

Auditory Perception↗