136 — Lateral geniculate neurons projecting to primary visual cortex show ocular dominance plasticity in adult mice

The brain responds to dramatic changes to the visual system — such as temporary blindness — by reallocating resources around the problem area: For example, monocular-blind individuals’ brains will reallocate cortical tissue to improve representation of data coming from the other eye.

The general understanding is that the primary mechanism for this plasticity is taking place in the cortex: Even if the cellular mechanism “how” is poorly understood, it’s at least widely hypothesized that cortex is the “where.”

This paper challenges that conventional wisdom: The author demonstrate that some amount of ocular-dominance plasticity is taking place upstream of cortex, in the LGN of thalamus.

In monocular-deprivation mice (i.e. blind in one eye), the cortex does indeed shift to spending more effort parsing inputs from the other eye — but Jaepel et al demonstrate that this is (at least partially) because the thalamus shifts its representation: thalamic neurons that send outputs to layer 1 of binocular V1 switch their responses to favor the unhandicapped retina.

The authors were able to determine this because of the resolution of their imaging modality: Prior studies had looked at populations of dLGN cells, but never at a cell-level dataset. Image resolution is important.