Cerebral cortex
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To understand sensory representation in cortex, it is crucial to identify its constituent cellular components based on cell-type-specific criteria. With the identification of cell types, an important question can be addressed: to what degree does the cellular properties of neurons depend on cortical location? We tested this question using pyramidal neurons in layer 5 (L5) because of their role in providing major cortical output to subcortical targets. ⋯ A comprehensive investigation of anatomical and functional properties of these 2 cell types in visual and somatosensory cortex demonstrates that, with important exceptions, most properties appear to be cell-type-specific rather than dependent on cortical area. This result suggests that although cortical output neurons share a basic layout throughout the sensory cortex, fine differences in properties are tuned to the cortical area in which neurons reside.
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Spike timing precision is a fundamental aspect of neuronal information processing in the brain. Here we examined the temporal precision of input-output operation of dentate granule cells (DGCs) in an animal model of temporal lobe epilepsy (TLE). In TLE, mossy fibers sprout and establish recurrent synapses on DGCs that generate aberrant slow kainate receptor-mediated excitatory postsynaptic potentials (EPSP(KA)) not observed in controls. ⋯ Conversely in epileptic rats, blockade of EPSP(KA) or I(NaP) restores the temporal precision of EPSP-spike coupling. Importantly, EPSP(KA) not only decrease spike timing precision at recurrent mossy fiber synapses but also at perforant path synapses during synaptic integration through I(NaP) activation. We conclude that a selective interplay between aberrant EPSP(KA) and I(NaP) severely alters the temporal precision of EPSP-spike coupling in DGCs of chronic epileptic rats.