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The effects of adaptation to visual stimuli on the velocity of subsequent ocular following responses

โœ Scribed by M. R. Ibbotson; T. Maddess


Publisher
Springer-Verlag
Year
1994
Tongue
English
Weight
724 KB
Volume
99
Category
Article
ISSN
0014-4819

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โœฆ Synopsis


We examined the effect of prior adaptation to moving and flickering stimuli on the velocity of subsequent ocular following responses in man. Experiments consisted of two phases: an adaptation phase in which moving or flickering stimuli were presented while the eyes fixated a small spot and a test phase in which ocular following responses were free to occur. The effects resulting from prior adaptation were characterized by determining the mean initial eye velocities in the period 200-500 ms after the onset of the test stimulus. It was found that 8 s of prior exposure to a grating pattern moving at between 1.5 and 4 cycles.s-1 significantly reduced initial eye velocities in all subjects. Prior exposure to a flickering stimulus (temporal frequency 3.2 cycles.s-1) also attenuated the velocities of initial eye movements, but to a far lesser extent. These results suggest that a motion-dependent and a weaker flicker-dependent process have an adaptive influence on the generation of ocular following responses. Initial eye velocities were measured as a function of the contrast of the prior adapting gratings. The velocities were found to decrease with increasing adapting contrast. The reductions in eye velocity were well described by a decaying exponential function. The motion-dependent adaptive effect showed significant inter-ocular transfer and had the same temporal tuning when transferred (i.e. optimum adaptation at between 1.5 and 4 cycles.s-1). The flicker-dependent effect did not show inter-ocular transfer. There is a distinct similarity between the adaptive process that causes attenuation of ocular following velocities and the adaptive mechanism that induces perceptual motion after-effects. This similarity is discussed.


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