Biomedical subjects
Publications and source records attributed to J Allik.
The pitch detection algorithm proposed by Duifhuis, Willems, and Sluyter [J. Acoust. Soc. Am. 71, 1568-1580 (1982)] can be made more than 20 times faster by replacing the harmonic sieve procedure by the approximate common denominator procedure, the results differing only slightly.
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To investigate the question of what happens with regard to position sense and control of the human eyes when the eyelids are closed, the contact-wire-free electromagnetic eye movement recording method was developed. It was shown that after the start of blinking of eyelid closure, the eyeball moves up as the upper eyelids come down. Experimental data show human inability to maintain a given position of the eyes in the head under the closed lids. When the subject was asked to follow a simple geometrical path, a very weak metrical and topological correspondence between desired and actual paths occurred with closed eyes. It is proposed that the poor control of eye movements behind closed eyelids is due to the lack of available information about the eye position in the head. The assumption was confirmed by providing artificial auditory feedback about the eyeball position to the subject, which can be effectively used for gaze stabilization by the subject. It is suggested that visual information is the only useful basis for eye movement regulation under normal conditions.
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Paris of geometric forms of equal area were presented, one form after another, with interstimulus intervals t ranging from 0 to 250 ms. The subject's task in experiment 1 was to recognise both stimuli. Identification of the form presented first (backward masking) across all values of t was of a nonmonotonic nature, with greatest impairment at values of t from 30 to 60 ms. Identification of the second form presented (forward masking) increased monotonically with increasing t. Different forms were recognised with different effectiveness across all values of t where masking took place. The results are interpreted on the basis of a multiple-stage processing model which assumes interaction between stimuli at different levels at different values of t. In experiment 2 the subject's task was to detect the presence or absence of a predesignated form. This condition yielded monotonic functions for both backward and forward masking. An explanation in terms of attention-dependent masking is given.