Distinct properties of corticothalamic and primary sensory synapses to thalamic neurons.

An unique synaptic feature of thalamic relay neurons is that, in addition to receiving primary sensory synapses, they receive massive feedback synapses originating from the cerebral cortex (corticothalamic synapses). These two synapses are both glutamatergic and coordinate the firing responses of thalamic neurons. It has been revealed in the past decade that various glutamate receptors are involved in synaptic responses in the thalamus. However, differences in the compositions of glutamate receptors between corticothalamic and primary sensory synapses have not been fully determined. This update article aims to provide an overview of the differences in the synaptic properties, including the compositions of glutamate receptors, between primary sensory and corticothalamic synapses in the ventrobasal nucleus of the somatosensory thalamus, and then elucidate how these differences in the two synapses influence the firing properties of thalamic neurons.