Aim: 

We compared the effects of monocular deprivation (MD) at the level of postsynaptic potentials (PSPs) and action potentials (APs) in morphologically identified pyramidal neurons along a retinotopically defined functional column of rat binocular visual cortex (V1).

Methods: 

At this aim, we used intrinsic signal imaging-targeted in vivo whole-cell recordings followed by neuronal reconstructions. Pigmented rats were subjected to MD for 10 days at the peak of the critical period for ocular dominance plasticity (P21-P31).

Results: 

In normal animals, the ocular preference of V1 neurons was sharper at AP level compared to PSPs. The contralateral bias was unevenly distributed along a column. Indeed, layer 4 pyramids (L4Ps, n = 16) and layer 5 slender tufted pyramids (L5sPs, n = 10) had a sharper contralateral bias compared to layer 2/3 pyramids (L2/3Ps, n = 32) and layer 5 thick tufted pyramids (L5tPs, n = 11). In particular, L5tPs had the highest degree of binocularity along a V1 column. MD effects in shifting the ocular preference of V1 neurons were sharper at AP level compared to PSPs. The ocular dominance shift was mostly due to depression of responsiveness to the closed eye, which was stronger compared to potentiation of open eye responsiveness. Of relevance, MD was highly effective in L4Ps (n = 26) and L2/3Ps (n = 15), whereas it was scarcely or not effective in shifting the ocular preference of infragranular pyramids, depending on cell types. Indeed, L5tPs (n = 15) were slightly and significantly affected by MD, whereas L5sPs (n = 13) and L6Ps (n = 5) were not. Level of significance =0.05.

Conclusion: 

The preference for the dominant eye is sharper at AP level compared to PSPs. Further, the binocularity of V1 pyramidal neurons in normal controls, as well as the effects of MD during the critical period, are layer- and cell type specific along a cortical column.