Completing the corticofugal loop: a visual role for the corticogeniculate Type 1 metabotropic glutamate receptor

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Completing the corticofugal loop: a visual role for the corticogeniculate Type 1 metabotropic glutamate receptorDate
2002-04-01Citation
Rivadulla C, Martínez LM, Varela C, Cudeiro J. Completing the corticofugal loop: a visual role for the corticogeniculate Type 1 metabotropic glutamate receptor. J Neurosci. 2002;22(7):2956-2962
Abstract
[Abstract] The way in which the brain deals with sensory information relies
not only on feedforward processing of signals from the periph-
ery but also on feedback inputs. This is the case of the massive
projection back from layer 6 in the visual cortex to the thalamus,
for which, despite being the greatest single source of synaptic
contacts, the functional role still remains unclear. In the cat
lateral geniculate nucleus, part of this cortical feedback is
mediated by type 1 metabotropic glutamate receptors
(mGluR1s), which are exclusively located on distal segments of
the relay-cell dendrites. Here we show that in adult cats the
cortex uses a synaptic drive mediated by these receptors
(mGluR1) specifically to enhance the excitatory center of the
thalamic receptive field. Moreover the effect is maximum in
response to those stimuli that effectively drive cortical cells, and
importantly, it does not affect the spatiotemporal structure of
the thalamic receptive field. Therefore, cortex, by closing this
corticofugal “loop,” is able to increase the gain of its thalamic
input within a focal spatial window, selecting key features of the
incoming signal.
Keywords
LGN
Visual cortex
Corticothalamic
Metabotropic receptors
Feddback modulation
Layer 6
Visual cortex
Corticothalamic
Metabotropic receptors
Feddback modulation
Layer 6
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Creative Commons Attribution 4.0 International Licence