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. 2017 May 4;8:162. doi: 10.3389/fneur.2017.00162

Figure 1.

Figure 1

(Upper panel) The connection between the eye and the suprachiasmatic nucleus (SCN) of the hypothalamus through the retinohypothalamic tract, originating in the retina from melanopsin-containing retinal ganglion cells (mRGCs) (in blue), is shown. (Lower panel) At the retina level, where are located also the mRGCs, the distinct pattern of axonal loss [retinal nerve fiber layer (RNFL) thinning] demonstrated by optical coherence tomography studies is reported for Alzheimer’s disease (AD) (21) with a more pronounced loss in the superior quadrant (left) and Parkinson’s disease (PD) with a more evident loss in the infero-temporal quadrants of the optic nerve (44, 46, 49) (right). Moreover, the figure depicts the pattern of β-amyloid deposition in AD, more evident in the superior quadrant and ganglion cell layer (GCL) [for a review, see Ref. (30)], and α-synuclein in PD in the inner retina and in particular at the inner plexiform layer (IPL)–inner nuclear layer (INL) interface (51, 52).