Anatomical connections suitable for the direct processing of neuronal information of different modalities via the rodent primary auditory cortex

During the last years it has become increasingly apparent that primary sensory cortices, like the primary auditory field AI, are not purely unisensory but also process complex information from other sensory modalities as well as non-sensory information. Here, we review our anatomical work on the connections of the auditory cortex in a small rodent, the Mongolian gerbil (Meriones unguiculatus), a common animal model in auditory research, and the related literature from other mammalian species. In particular we will show that AI has multiple connections with auditory, non-auditory sensory (visual, somatosensory, olfactory), multisensory, motor, "higher order" associative and neuromodulatory brain structures. These connections are suitable to mediate multimodal integration processes observed at the level of AI and, in turn, enable AI to influence other sensory and non-sensory systems at several cortical and subcortical levels. (C) 2009 Elsevier B.V. All rights reserved.