Moreover, enucleation of one eye completely restores retinotopic refinement of ventral-temporal RGC axons from the remaining eye, clearly demonstrating that ventral-temporal RGC axons are fully capable of normal retinotopic refinement in β2(TG) mice, but binocular interactions prevent this refinement. Analogous results have been reported in the ferret (Huberman et al., 2006), where binocular pharmacological blockade of retinal waves with epibatidine

significantly enlarged the receptive fields of neurons with binocular receptive fields in the visual cortex but had no effect on the receptive fields of monocular neurons. These somewhat surprising results suggest that maps for retinotopy and eye-specific segregation are fundamentally linked; conditions that are appropriate for normal retinotopic refinement in the monocular zone may be inadequate to mediate retinotopic refinement in the presence of binocular competition. In the visual cortex, EPZ 6438 the plasticity of ocular dominance maps following monocular deprivation is linked to maps for stimulus orientation (Crair et al., 1997), but the current work specifically implicates selleck chemicals llc the structure of spontaneous neuronal activity, not visual experience, in linking maps for retinotopy

and eye of origin. Our Hebbian computational model recapitulates the link between eye-specific segregation and retinotopy. In simulations where binocular interactions persist due to poor eye segregation, retinotopic refinement is impaired as well. According to the model, if inputs from the two eyes do not segregate, the pattern of input activity to the SC and dLGN is fundamentally altered because it reflects activity from both eyes instead of one eye only. Normally,

homeostatic regulation of the total synaptic input to neurons in the SC or dLGN favors the strengthening of highly correlated inputs from neighboring RGCs. However, the persistence of conflicting inputs from the two eyes interferes with the process of RGC axon pruning Methisazone from inappropriate retinotopic locations, and retinotopic refinement is impaired. By contrast, retinotopy develops normally in the monocular zone of β2(TG) mice and throughout the SC in enucleated β2(TG) mice, because conflicting signals from the two eyes do not exist under these conditions. β2-nAChRs are normally expressed throughout the developing retina (Moretti et al., 2004; Figure 1C), particularly in synapses among amacrine cells and between amacrine cells and ganglion cells (Blankenship and Feller, 2010). Retinal waves are thought to be nucleated by ChAT-positive intrinsically bursting starburst amacrine cells, and wave propagation across the retina mediated by β2-nAChR containing synapses between amacrine cells in the inner nuclear layer (Butts et al., 1999 and Zheng et al., 2006). RGC firing during a wave is coupled to starburst amacrine cell bursting through synapses containing β2-nAChRs (Blankenship and Feller, 2010).