Abstract
The perirhinal cortex is a medial temporal lobe area crucial for object memory, object recognition and the resolution of ambiguous features. Its involvement in both perceptual and mnemonic processes is reflected in its connectivity to a variety of cortical and subcortical areas, such as the hippocampus and visual areas. In rats and monkeys, the perirhinal cortex projects to visual areas via feedback projections that can modulate the visual input, but the exact functions of these connections are still unknown. Therefore, the examination of a simpler model organism, such as the mouse, could be beneficial. Recent evidence suggests that the mouse, despite the common opinion, is a suitable model for vision. In this study, anterograde and retrograde tracing was utilized to examine the connectivity between the perirhinal cortex and ventral visual stream areas (V1, V2 and TeA) with special focus on the feedback projections. To my knowledge, this study presents the first evidence showing that the mouse perirhinal cortex projects to visual areas via feedback connections, a feature thought to be exclusive to higher-developed animals. Moreover, the medial secondary visual cortex was found to be strongest connected with the perirhinal cortex, which stands in contrast to the findings in rats (strongest to lateral V2). Overall, these findings indicate that the perirhinal feedback to visual areas may be more conserved and fundamental than was assumed so far, and that the relative connective strength may be species-specific.