Object and space perception - is it a matter of hemisphere?

In the 1980s, following Newcombe's observations, Ungerleider and Mishkin put forward the functional subdivision of the visual system into a ventral stream dedicated to object perception and a dorsal stream dedicated to space perception. Ten years after this discovery, the perception-action model re-defined the dorsal stream as responsible for non-conscious visual guidance, and most recently a tripartition has been suggested to account for a variety of visuospatial functions. Here, we investigated the neural underpinnings of object and space perception by combining the administration of the Visual Object Space Perception (VOSP) battery with a voxel-based lesion symptom mapping (VLSM) approach in a large sample of patients with penetrating traumatic brain injury (pTBI). First, our results provided new support for the complementary role of both hemispheres in object recognition. The right lateral occipital complex was found to be critical in early perceptual discrimination, whereas more anterior temporal and frontal regions in the left hemisphere were found to be critical in more complex forms of object discrimination and recognition. Second, our findings confirmed that space perception depended on the integrity of the right inferior parietal lobule (IPL) and revealed that a network linking the right IPL with the right premotor cortex was critical for the perception of spatial relationships in both 2D and 3D representations. Taken together, our results supported the functional subdivision of the visual system and shed new light on the specific processes involved along both the dorsal and the ventral streams.