Document Detail

Persistence of the dark-background-contingent gaze upshift during visual fixations of rhesus monkeys.
MedLine Citation:
PMID:  25057145     Owner:  NLM     Status:  Publisher    
During visual fixations, the eyes are directed so that the image of the target (object of interest) falls on the fovea. An exception to this rule was described in macaque monkeys (though not in humans): dark background induces a gaze shift upwards, sometimes large enough to shift the target's image off the fovea. Here we address an aspect not previously rigorously studied, the time-course of the upshift. The time-course is critical for determining whether the upshift is indeed an attribute of visual fixation or, alternatively, of saccades that precede the fixation. These alternatives lead to contrasting predictions regarding the time-course of the upshift (durable if the upshift is an attribute of fixation, transient if caused by saccades). We studied visual fixations with dark and bright background in 3 monkeys. We confined ourselves to a single upshift-inducing session in each monkey, so as not to study changes in the upshift caused by training. Already at their first sessions, all monkeys showed clear upshift. During the first 0.5s after reaching the vicinity of the target, the upshift was on average larger, but also more variable, than later in the trial; this initial high value (1) strongly depended on target location, and was maximal at locations high in the screen, (2) appears to reflect mostly the intervals between the primary and correction saccades. Subsequently, the upshift stabilized and remained constant, well above zero, throughout the 2s fixation interval. Thus, there is a persistent background-contingent upshift genuinely of visual fixation.
Oleg Spivak; Hans-Peter Thier; Shabtai Barash
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2014-7-23
Journal Detail:
Title:  Journal of neurophysiology     Volume:  -     ISSN:  1522-1598     ISO Abbreviation:  J. Neurophysiol.     Publication Date:  2014 Jul 
Date Detail:
Created Date:  2014-7-24     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0375404     Medline TA:  J Neurophysiol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
Copyright © 2013, Journal of Neurophysiology.
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