Cell-Type Specific Properties of Pyramidal Neurons in Neocortex Underlying a Layout that Is Modifiable Depending on the

To understand sensory representationincortex, itiscrucial toidentify 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. Recently developed transgenic mice with cell-type--specific enhanced green fluorescent protein labeling of neuronal subtypes allow reliable identification of 2 cortical cell types in L5 throughout the entire neocortex. A comprehensive investigation of anatomical and functional properties ofthese2 celltypes invisual andsomatosensory cortexdemonstrates that, with important exceptions, most properties appear to be celltype--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 inpropertiesare tuned to the cortical area in which neurons reside.