Towards an anatomical model of information integration in prefrontal cortex

One area of the mammalian prefrontal cortex, the prelimbic cortex (Brodmann area 32), is strategically involved in the integration of limbic, motor and autonomic activity with the working memory and cognitive processes that underlie spatiotemporal behaviour. To understand how specific information channels are integrated within prelimbic cortex, a neuroanatomical model, constrained by biological parameters, has been constructed of the quantitative neural architecture of this cortical area in rats. The model defines the densities of specific laminar classes of identified excitatory pyramidal cells and inhibitory local circuit neurons (LCNs) including their dendritic architectures. By using the model in conjunction with anatomical data detailing the laminar distribution of identified afferent synaptic input to area 32 from several functionally strategic subcortical and cortical limbic sources (basolateral amygdala, ventral CA1 hippocampus, lateral hypothalamus, mediodorsal thalamus and anterior insular cortex), it has been possible to theoretically determine, given a uniform pattern of connectivity, the number of individual synaptic contacts between a defined afferent input and the dendrites of specific classes of pyramidal cells and LCNs. The results indicate that the dendrites of individual pyramid cells and LCNs in area 32 are sparsely innervated by synaptic inputs from the identified sources. The model is currently being refined to incorporate aspects of the intrinsic microcircuitry and projection output pathways from prelimbic cortex. The emerging data provide important insights into the parallel distributed processing of afferent, internal and efferent information by this area of limbic cortex in the rat