Vision Triggers an Experience-Dependent Sensitive Period at the Retinogeniculate Synapse

Abstract

In the mammalian visual system, sensory experience is widely thought to sculpt cortical circuits during a precise critical period. In contrast, subcortical regions, such as the thalamus, were thought to develop at earlier ages in a vision-independent manner. Recent studies at the retinogeniculate synapse, however, have demonstrated an influence of vision on the formation of synaptic circuits in the thalamus. In mice, dark rearing from birth does not alter normal developmental maturation of the connection between retina and thalamus. However, deprivation 20 d after birth [postnatal day 20 (p20)] resulted in dramatic weakening of synaptic strength and an increase in the number of retinal inputs that innervate a thalamic relay neuron. Here, by quantifying changes in synaptic strength and connectivity in response to different time windows of deprivation, we find that several days of vision after eye opening is necessary for triggering experience-dependent plasticity. Shorter periods of visual experience do not permit similar experience-dependent synaptic reorganization. Furthermore, changes in connectivity are rapidly reversible simply by restoring normal vision. However, similar plasticity did not occur when shifting the onset of deprivation to p25. Although synapses still weakened, recruitment of additional retinal inputs no longer occurred. Therefore, synaptic circuits in the visual thalamus are unexpectedly malleable during a late developmental period, after the time when normal synapse elimination and pruning has occurred. This thalamic sensitive period overlaps temporally with experience-dependent changes in the cortex, suggesting that subcortical plasticity may influence cortical responses to sensory experience.

A Critical Window for Experience-Dependent Plasticity at Whisker Sensory Relay Synapse in the Thalamus

“…The effects of sensory deprivation on synaptic function in the VPm are much quicker than those observed at the retinogeniculate synapse (Hooks and Chen, 2008), but are comparable to those obtained in the rat superior colliculus (SC). Eye opening increases within 24 h amplitudes of EPSC-AMPAR and AMPARmediated quantal events in SC neurons (Lu and ConstantinePaton, 2004).…”

Grey and white matter changes in children with monocular amblyopia: voxel-based morphometry and diffusion tensor imaging study

“…Undoubtedly, this is correlated with less information flow in the related fibre tracts. Long-term depression will weaken the synaptic strength,19 especially in the critical developmental period. Perhaps the underdevelopment of WM, in turn, prolongs neural transmission and impairs the connection between the visual and visual-related cortices.…”

Neuroinflammation: Ways in Which the Immune System Affects the Brain

“…Synaptic inputs from the ipsilateral and contralateral eyes compete for territory [30][31][32][33]. To achieve mature projection patterns, synaptic remodeling occurs, including synapse elimination as well as stabilization and elaboration of remaining synapses [34,35].…”