טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentEizenberg Natanel
SubjectShort Term Adaptation in Single Cells in the Alert Monkey
Primary Visual Cortex
DepartmentDepartment of Biomedical Engineering
Supervisor Professor Moshe Gur


Abstract

The phenomenon of long-term visual adaptation is well known and many visual phenomena, such as the waterfall illusions are attributed to it. In this work we dealt with the phenomena of short-term adaptation which deems important for visual discriminability by reducing correlations between similar images.

Almost all supporting physiological was recorded in anesthetized animal but this condition is too removed from the awake human so we looked at short-term adaptation in V1 of the alert monkey. The alert monkey not only differs from the anesthetized one in its physiological state but also in that it views the target while fixating which, unlike the truly immovable eye in the anesthetized is an active process comprised of fixational saccades and drifts. Using monkeys that had different fixation characteristics enabled us to see how the fixational process affects short-term adaptation. The results of the monkeys performing many saccades are more relevant to human performance since humans, typically, perform many saccades.

We recorded eye movements and external cellular responses from single cells in V1 of macaques performing a fixation task, while presenting different repeating visual stimuli (flashing, moving bars and drifting sinusoids). Data was then analyzed to show quantitative description of the adaptation phenomena.

Our major findings are:

1) In the monkey performing a few saccades, there is a short-term adaptation in that stimuli succeeding the first one generate fewer spikes than the first stimulus.

2) In monkeys that performed a large number of saccades, no adaptation could be found.

3) The effects of saccades suggest that they may serve to reset cell responsivity and thus prevent short-term adaptation.