Figure 6

Photic information can reach the SCN through an indirect pathway which parallels the RHT. The retinal ganglion cells which form the RHT also project to a subdivision of the lateral geniculate—the intergeniculate leaflet (IGL). Neurons in the IGL, in turn, project to the SCN through a geniculohypothalamic tract (GHT). Evidence suggests that the amino acid GABA and neuropeptide Y (NPY) act as signaling molecules at this synaptic connection.

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published 2000