A new neural framework for visuospatial processing

Various proposals have defined the dorsal visual stream as a 'Where' or 'How' pathway. Synthesizing data from anatomical and functional studies, Mishkin and colleagues propose that in the posterior parietal cortex, three different pathways emerge from the dorsal stream, each supporting a different aspect of spatial processing. The division of cortical visual processing into distinct dorsal and ventral streams is a key framework that has guided visual neuroscience. The characterization of the ventral stream as a 'What' pathway is relatively uncontroversial, but the nature of dorsal stream processing is less clear. Originally proposed as mediating spatial perception ('Where'), more recent accounts suggest it primarily serves non-conscious visually guided action ('How'). Here, we identify three pathways emerging from the dorsal stream that consist of projections to the prefrontal and premotor cortices, and a major projection to the medial temporal lobe that courses both directly and indirectly through the posterior cingulate and retrosplenial cortices. These three pathways support both conscious and non-conscious visuospatial processing, including spatial working memory, visually guided action and navigation, respectively.