Brain Microcircuits
The interactions between mitral and granule cells provided the basis for the concept of a brain microcircuit, set forth in a Scientific American article (Shepherd, 1978), now defined as “a set of interactions within local neuronal circuits adapted for a specific function or functions by a given brain region”. The term has also been used to describe analogous circuits in invertebrates (Byrne and Kandel, 1978). A handbook of microcircuits (Shepherd and Grillner, 2010, 2018) in over 50 brain regions has been assembled to support the identification of organizational principles shared and adapted across different systems. In the mammalian olfactory pathway, a series of microcircuits has been identified that carry out the high dimensional processing of odors underlying the perception of smell (Shepherd et al, 2021).