Excitatory synaptic feedback from the motor layer to the sensory layers of the superior colliculus.
Neural circuits that translate sensory information into motor commands are organized in a feedforward manner converting sensory information into motor output. The superior colliculus (SC) follows this pattern as it plays a role in converting visual information from the retina and visual cortex into motor commands for rapid eye movements (saccades). Feedback from movement to sensory regions is hypothesized to play critical roles in attention, visual image stability, and saccadic suppression, but in contrast to feedforward pathways, motor feedback to sensory regions has received much less attention. The present study used voltage imaging and patch-clamp recording in slices of rat SC to test the hypothesis of an excitatory synaptic pathway from the motor layers of the SC back to the sensory superficial layers. Voltage imaging revealed an extensive depolarization of the superficial layers evoked by electrical stimulation of the motor layers. A pharmacologically isolated excitatory synaptic potential in the superficial layers depended on stimulus strength in the motor layers in a manner consistent with orthodromic excitation. Patch-clamp recording from neurons in the sensory layers revealed excitatory synaptic potentials in response to glutamate application in the motor layers. The location, size, and morphology of responsive neurons indicated they were likely to be narrow-field vertical cells. This excitatory projection from motor to sensory layers adds an important element to the circuitry of the SC and reveals a novel feedback pathway that could play a role in enhancing sensory responses to attended targets as well as visual image stabilization.
Department of Neuroscience, Neuroscience Training Program.
Nima
N
Ghitani
Department of Neuroscience.
Peter O
PO
Bayguinov
Department of Neuroscience, Molecular and Cellular Pharmacology Training Program, and.
Corinne R
CR
Vokoun
Molecular Biophysics Ph.D. Program, University of Wisconsin-Madison, Madison, Wisconsin 53706, and.
Shane
S
McMahon
Department of Neuroscience, mbasso@mednet.ucla.edu mbjackso@wisc.edu.
Meyer B
MB
Jackson
Department of Neuroscience, Department of Psychiatry and Biobehavioral Sciences and Semel Institute for Neuroscience and Human Behavior University of California at Los Angeles, Los Angeles, California 90095-7332 mbasso@mednet.ucla.edu mbjackso@wisc.edu.
Michele A
MA
Basso
D000818:Animals; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology*; D025461:Feedback, Physiological / Q000502:physiology*; D005260:Female; D008297:Male; D009434:Neural Pathways / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013477:Superior Colliculi / Q000502:physiology*; D013569:Synapses / Q000502:physiology*
superior colliculus; voltage imaging