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Abstract:
Abstract: It has been established that the N1 component of
visual evoked potentials (VEPs), recorded over the occipital lobe,
exponentially habituates. That is, when inter-stimulus interval
(ISI) is reduced, the amplitude of this N1 component decreases
exponentially. The time constant of N1 habituation is usually a
fraction of a second. This study examined the spatial and
content-related specificity of N1 habituation with whole-head (64
channels) EEG recordings. During VEP recording, subjects maintained
fixation on the center of a computer screen. A standard stimulus, a
small patch of sinusoidal luminance gratings was presented at the
same location repetitively with a duration of 28 ms and an ISI of
700 ms. Occasionally, the standard stimulus was replaced by a
variant stimulus that differed from the standard in either grating
orientation or location of the patch on the screen. We found that
the N1 response to the standard stimulus immediately after a
variant is enhanced only if the variant differs from the standard
in spatial location. These results indicate that the habituation of
N1 is specific to spatial location, not to the orientation of the
gratings. The implication of these findings to visual spatial
attention and memory will be discussed.
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