Biomedical subjects
Publications and source records attributed to T Radil.
The influence of conceptualization of a specific two-dimensional perceptual cue on the perception of the reversible Necker cube pattern was investigated. It was found that it reduced markedly the spontaneous reversal rate.
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Visually evoked potentials (VEPs) were compared in 7 normally reared cats (N cats) and 9 cats deprived of pattern vision during postnatal period. In 4 deprived cats (D cats) recording was done immediately after deprivation period which lasted from 6 to 24 months. In 5 cats (DE cats) 6 months of deprivation was followed by 4-18 months of visual experience. Two stimuli were used: a large stationary stimulus (a 30 per 30 degrees grating pattern illuminated by flash) and a small moving stimulus (a smaller grating pattern was located in different parts of visual field and illuminated by a moving 1 per 4 degrees light slit). The VEPs were recorded in the marginal, suprasylvian, ectosylvian and sigmoid gyri. As compared with N cats, in D cats the VEPs in all cortical areas were of simpler form, more variable and of greater amplitude. Moreover, in contrast to N cats, in D cats the VEPs were of similar amplitude when evoked from the contra or homolateral visual field. However, results in DE cats showed that these changes are largely reversible.
A heart rate biofeedback system consisting of a JPR 12 minicomputer (12 bit, 4 K), of input devices (an electronic circuit triggered by the EEG R-waves or a photoelectric ear lobe pulse detector and of output devices (a feedback indicator of successful or unsuccessful heart rate control during the preceding time interval, the teletype and the paper tape punch) is described. The actual heart rate is measured and compared with levels differing from the average by a preselected number of pulses/min. When a preset criterion is met, the levels are shifted automatically. In control session shuffled data from the preceding experimental session are used for feedback.
Eye movements during discrimination of simultaneously presented random textures pairs, differing in increasing mutual transitional probability, were recorded. Increase of difference in the "grain" between images resulted in reduction of crossing eye movements, while the number of saccadic eye movements within each image prior crossing eye movements decreased only slightly. The mean fixation time did not change at all. The principal factor determining the latencies of discrimination was the number of crossing eye movements. The schematized process of discrimination covering several steps is suggested.
The effect of electrical stimulation of the mesencephalic reticular formation and of physostigmine on hippocampal theta activity was combined in rats with implanted electrodes. The effect was not additive. The threshold for evoking motor activity by means of reticular stimulation decreased after physostigmine administration.
Ongoing unconscious processes may be influenced by related conscious processes without self-awareness. (a) When the conscious semantic interpretation of physically identical shapes changes due to their angular rotation, the sequence of saccadic movements arid the localization of eye fixations over the shapes change as well. (b) The amplitude of the P 300 wave of visual evoked potentials is related to the conscious cognitive interpretation of identical stimuli. (c) The instants of figure reversals are influenced by conscious cognitive programs delineated by means of corresponding experimental instructions. It is assumed that unconscious and conscious processes may be considered functional manifestations of the same complex and specific neuronal network at different levels of its hierarchical organization and that mutual interactions between both types of processes do not require the existence of any mediating "interface" system.
Six cats with brainstem transection at the pretrigeminal level were used. Visually evoked potentials (VEPs) to a diffused flash were recorded in the marginal, suprasylvian, ectosylvian and sigmoid gyri under three situations: the eyes were motionless in the position of rest, the eyes followed a moving object, and the eyes moved spontaneously. In the marginal and ectosylvian gyri the VEPs were smaller in the second situation, compared to the first and third. It is concluded that the VEP reduction is not produced by the eye-movement itself, but by the process of selective attention to the followed stimulus.
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Explore the source record for details and available documents.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.