Axonal plasticity associated with perceptual learning in adult macaque primary visual cortex

Abstract

Perceptual learning is associated with changes in the functional properties of neurons even in primary sensory areas. In macaque monkeys trained to perform a contour detection task, we have observed changes in contour-related facilitation of neuronal responses in primary visual cortex that track their improvement in performance on a contour detection task. We have previously explored the anatomical substrate of experience-dependent changes in the visual cortex based on a retinal lesion model, where we find sprouting and pruning of the axon collaterals in the cortical lesion projection zone. Here, we attempted to determine whether similar changes occur under normal visual experience, such as that associated with perceptual learning. We labeled the long-range horizontal connections in visual cortex by virally mediated transfer of genes expressing fluorescent probes, which enabled us to do longitudinal two-photon imaging of axonal arbors over the period during which animals improve in contour detection performance. We found that there are substantial changes in the axonal arbors of neurons in cortical regions representing the trained part of the visual field, with sprouting of new axon collaterals and pruning of preexisting axon collaterals. Our findings indicate that changes in the structure of axonal arbors are part of the circuit-level mechanism of perceptual learning, and further support the idea that the learned information is encoded at least in part in primary visual cortex.

Ventral midbrain stimulation induces perceptual learning and cortical plasticity in primates

“…This is supported by studies of primate dopamine receptor distribution that have found more pronounced receptor densities in temporal compared to primary visual cortex 39 . In contrast, other neuromodulatory systems with stronger innervation to early visual regions 40 may also play a role in VPL-related plasticity observed in these earlier regions 33,41 . The latter hypothesis requires further testing.…”

Motor Learning Promotes Remyelination via New and Surviving Oligodendrocytes

“…Alternatively, heterogeneity 46 or regional variance between somatosensory and motor oligodendrocytes may play a role in this differential response. The role of sheath retraction throughout learning remains to be explored, though recent work suggests this may regulate conduction velocity 47,48 and allow for increased axonal branching [49][50][51] . Concurrent multi-color in vivo imaging of reach-specific neurons and myelin sheath dynamics in the context of learning will provide further information into how neurons and oligodendrocytes interact to facilitate the consolidation of neural circuits.…”

Ocular dominance plasticity: Molecular mechanisms revisited

“…Importance of the intracortical horizontal afferents is further exemplified in a meticulously executed study on the behaving monkey: it has showed that dynamic changes, pruning and sprouting, of the horizontally projecting axon collaterals of pyramidal cells took place in conjunction with perceptual training which lasted up to 8 weeks (Van Kerkoerle, Marik, Meyer Zum Alten Borgloh, & Gilbert, 2018). The extent of collateral sprouting was correlated to the monkeys' learning scores.…”