Combined physiological-anatomical approaches to study lateral inhibition

In the visual cortex, large basket cells form the cellular basis of long-ra nge lateral inhibition. The present paper focuses on combinations of method s with which large basket cells can be studied in the context of extensive neuronal representations. In the first approach, the topographic relationsh ip between large basket axons and known functional representations such as orientation, direction, and ocular dominance is analysed. Functional mappin g is carried out using extracellular electrode recordings or optical imagin g of intrinsic signals followed by 3-dimensional anatomical reconstruction of biocytin stained large basket cells in the same regions. In the second a pproach, the contribution of lateral inhibition to orientation and directio n selectivity is assessed using the GABA inactivation paradigm and direct i nhibitory projections from the inactivation to recording sites are demonstr ated with biocytin staining and injections of [H-3]nipecotic acid, a radioa ctive marker for GABAergic cells. The limitation of these approaches is tha t they can only be used in cortical regions which lie on the surface of the brain. (C) 2000 Published by Elsevier Science B.V.