Fig. 1

The neural circuit of the inferior colliculus. a Schematic diagram of main inputs to the IC of mammals. Red, blue, and green arrows indicate glutamatergic, GABAergic, and glycinergic projection. DNLL dorsal nucleus of the NLL, INLL intermediate nucleus of the NLL, VNLL ventral nucleus of the NLL. b A model of synaptic organization of the ICC. Each functional module is denoted by a different shade and represents a different excitatory brainstem input (red, ipsilateral MSO; blue, contralateral DCN; green, contralateral LSO). Inhibitory inputs (ipsilateral LSO, yellow spheres; DNLL, blue spheres) terminate in particular domains and avoid others. The distribution of some modules is highly related to the tonotopic map (stacked laminae inside the ICC), because some inputs are absent at the ends of the frequency ranges. Within each lamina, disc-shaped neurons (shown in a red lamina) extend their dendrites. Adapted, with permission, from Ref. [6]. c Schematic diagram of neural circuitry in which LG neurons (blue cells) are involved. Inside the ICC, more ventral and medial domains receive dense ascending inputs from the DCN whereas the more lateral domain receives dense inputs from the SOC and NLL. LG neurons receive glutamatergic (red) inputs from local and ascending sources. Because local excitatory neurons innervate LG neurons located in different synaptic domains and those located in the same domain, an LG neuron may mix information from multiple synaptic domains. LG neurons may control specific local circuitry in the thalamus, because LG neurons innervate stellate neurons and a subpopulation of tufted neurons in the MGB (color figure online)