Sensory deprivation changes the pattern of synaptic connectivity in rat barrel cortex

We examined whether sensory deprivation during formation of the cortical circuitry influences the pattern of intracortical single-cell connections in rat barrel cortex. Excitatory postsynaptic potentials from layer 5 pyramidal neurons were recorded in vitro using patch-clamp techniques. In order to evoke such postsynaptic potentials presumptive presynaptic neurons were stimulated by photolytically applied glutamate thus generating action potentials. Synaptic connections between the stimulated and the recorded neuron were identified by the occurrence of postsynaptic potentials following photostimulation. Sensory deprivation altered the projections from layer 2/3 neurons to layer 5 pyramidal cells (L2/3-->L5 projections). In slices of non-deprived rats the input probability of L2/3-->L5 projections showed a periodic pattern with more synaptic connections originating from the borders of the barrel columns, and less synaptic connections originating from the centres. After whisker clipping this periodic pattern disappeared completely and the input probability declined monotonically with increasing distance between stimulated and recorded neuron. These results indicate that sensory input is a prerequisite to establish a synaptic projection pattern which is correlated to the columnar organisation of the anatomical barrel structure.