Neural responses that keep the world from fading
When retinal images are stabilized the visual world fades from
perception. When we voluntarily fixate our gaze, however, the world
does not fade. The reason is that during fixation we produce tiny eye
movements of which we are unaware. These eye movements, called
microsaccades, refresh the retinal image several times a second, thus
preventing adaptation and visual fading. Neural activity correlated
with microsaccades may then be important to convey the visibility of a
stimulus. To determine the nature of this neural activity, we trained
macaque monkeys to fixate their gaze on a small spot while recording
from cells in the early visual system. We presented bars of light to
the receptive fields of the cells we recorded from. We then correlated
the occurrence of microsaccades during fixation with neural activity.
We found that microsaccades are best correlated with bursts of spikes
in the LGN and area V-1. This suggests that bursts of spikes may best
represent the visibility of a stimulus to higher visual areas.