Organization of sensory neocortex in prairie voles (Microtus ochrogaster).

In the current investigation, the functional organization of visual, auditory, and somatosensory cortex was examined in prairie voles (Microtus ochrogaster) by using electrophysiological recording techniques. Functional boundaries of cortical fields were directly related to myeloarchitectonic boundaries. Our results demonstrated that most of the neocortex is occupied by the visual, auditory, and somatosensory areas. Specifically, a small area 17, or primary visual area (V1), was located on the caudomedial pole of the neocortex; a large auditory cortex (AC), which contains the primary auditory area (A1) and other auditory fields, encompassed almost the entire temporal pole; and a large area 3b, or primary somatosensory area (S1), contained a complete representation of the contralateral body surface. Furthermore, these areas were coextensive with distinct myeloarchitectonic appearances. We also observed that the AC appeared to be disproportionately large in the prairie vole compared with other rodents. In addition, we found that both primary and nonprimary areas contained neurons that responded to auditory stimulation. Finally, we observed within S1 a disproportionate amount of cortex that was devoted to representing the perioral hairs and the snout and also that neurons within this representation had very small receptive fields. We discuss the expanded auditory domain and the enlarged representation of perioral hairs as they relate to the specialized life style of the prairie vole.