The dorsocaudal neostriatum of the domestic chick: a structure serving higher associative functions

The dorsocaudal neostriatal (dNC) complex consists of at least three functi onally distinct subregions and is part of an 'imprinting' pathway, which in terconnects several forebrain regions that are known to be involved in juve nile learning. Based on its anatomical features, at least one subregion of the dNC complex, the neostriatum dorsocaudale (Ndc) may be considered as th e equivalent of the mammalian polysensory association cortices. Several lin es of evidence point to a role for this forebrain region in learning and me mory formation. After auditory or visual imprinting changes of stimulus-evo ked metabolic activities and of synaptic densities have been measured in th e Ndc. Pharmacological behavioral studies revealed that the activation of N MDA receptors plays a critical role during this learning process and that N MDA receptor activation is required for the associated metabolic and synapt ic changes. Ln addition to glutamatergic afferents, anatomical studies reve aled a massive input from monoaminergic and peptidergic pathways into the d NC complex, suggesting a modulatory role for these systems during imprintin g. The results presented here together with data from other avian species s upport the view that the dNc complex, and in particular the Ndc, plays an i mportant role in juvenile and adult learning. (C) 1999 Elsevier Science B.V . All rights reserved.