The viruses used in this article from BrainVTA are in the table below

Light plays a pivotal role in the regulation of affective behaviors. However, the precise circuits that mediate the impact of light on depressive-like behaviors are not well understood. Here, we show that light influences depressive-like behaviors through a disynaptic circuit linking the retina and the lateral habenula (LHb). Specifically, M4-type melanopsin-expressing retinal ganglion cells (RGCs) innervate GABA neurons in the thalamic ventral lateral geniculate nucleus and intergen-iculate leaflet (vLGN/IGL), which in turn inhibit CaMKIIa neurons in the LHb. Specific activation of vLGN/IGL-projecting RGCs, activation of LHb-projecting vLGN/IGL neurons, or inhibition of post-synaptic LHb neurons is sufficient to decrease the depressive-like behaviors evoked by long-term exposure to aversive stimuli or chronic social defeat stress. Furthermore, we demonstrate that the antidepressive effects of light therapy require activation of the retina-vLGN/IGL-LHb pathway. These results reveal a dedicated retina-vLGN/IGL-LHb circuit that regulates depressive-like behaviors and provide a potential mechanistic explanation for light treatment of depression.

Figure 1. M4-type mRGCs Directly Innervate the vLGN/IGL-LHb Pathway

By combining conventional neurotracer and transneuronal virus tracing techniques, the authors identified a visual circuit related to the LHb that regulates depressive-like behaviors. They demonstrate that activation of the disynaptic retina-vLGN/IGL-LHb pathway underlies the antidepressive effects of light therapy.