Аннотация
Each of our movements activates our own sensory receptors, and therefore
keeping track of self-movement is a necessary part of analysing sensory
input. One way in which the brain keeps track of self-movement is
by monitoring an internal copy, or corollary discharge, of motor
commands. This concept could explain why we perceive a stable visual
world despite our frequent quick, or saccadic, eye movements: corollary
discharge about each saccade would permit the visual system to ignore
saccade-induced visual changes. The critical missing link has been
the connection between corollary discharge and visual processing.
Here we show that such a link is formed by a corollary discharge
from the thalamus that targets the frontal cortex. In the thalamus,
neurons in the mediodorsal nucleus relay a corollary discharge of
saccades from the midbrain superior colliculus to the cortical frontal
eye field. In the frontal eye field, neurons use corollary discharge
to shift their visual receptive fields spatially before saccades.
We tested the hypothesis that these two componentsa pathway for
corollary discharge and neurons with shifting receptive fieldsform
a circuit in which the corollary discharge drives the shift. First
we showed that the known spatial and temporal properties of the corollary
discharge predict the dynamic changes in spatial visual processing
of cortical neurons when saccades are made. Then we moved from this
correlation to causation by isolating single cortical neurons and
showing that their spatial visual processing is impaired when corollary
discharge from the thalamus is interrupted. Thus the visual processing
of frontal neurons is spatiotemporally matched with, and functionally
dependent on, corollary discharge input from the thalamus. These
experiments establish the first link between corollary discharge
and visual processing, delineate a brain circuit that is well suited
for mediating visual stability, and provide a framework for studying
corollary discharge in other sensory systems.
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