|
Abstract:
As we move our eyes, new images are constantly presented to
the brain, yet we perceive the world as remaining still. This
perceptual stability may reflect the updating of an internal
representation in conjunction with eye movements. At the single
neuron level, memory traces of visual stimuli are updated during
saccades. Neurons in primate extrastriate, parietal, and frontal
cortex become active when the receptive field is moved to a
previously stimulated screen location, even when the stimulus is no
longer present. We have now used event-related fMRI to investigate
activation in human cortex associated with updating memory traces
of salient visual stimuli.
Subjects were scanned during three types of trials. (1) In
stimulus only trials, a stimulus was presented in the right or left
visual field. (2) In saccade only trials, subjects made aurally
cued saccades to the right or left. (3) In spatial updating trials,
a stimulus appeared briefly and subjects made a saccade only after
its offset.
In spatial updating trials we found that the representation of
the stimulus shifted from one hemisphere to the other. This
occurred even though the stimulus had been extinguished prior to
the eye movement. This activation may reflect the updating of the
memory trace of a stimulus when the eyes move.
Supported by NASA, NSF, James S. McDonnell Foundation
|
