Beyond Retinotopic Mapping: The Spatial Representation of Objects in the Human Lateral Occipital Complex

Abstract

The spatial representation in the human ventral object-related areas (i.e., the lateral occipital complex [LOC]) is currently unknown. It seems plausible, however, that it would diverge from the strict retinotopic mapping (characteristic of V1) to a more invariant coordinate frame, thereby allowing for reliable object recognition in the face of eye, head, or body movement. To study this, we compared the fMRI activation in LOC when object displacement was limited to either the retina or the screen by manipulating eye position and object locations. We found clear adaptation in LOC when the object's screen position was fixed, regardless of the object's retinal position. Furthermore, we found significantly greater activation in LOC in the hemisphere contralateral to the object's screen position, although the visual task was constructed in a way that the objects were present equally often on each of the 2 retinal hemifields. Together, these results indicate that a sizeable fraction of the neurons in LOC may have head-based receptive fields. Such an extraretinal representation may be useful for maintenance of object coherence across saccadic eye movements, which are an integral part of natural vision.

The distribution of category and location information across object-selective regions in human visual cortex

“…Similarly, the EBA preferred lower visual field stimuli to both foveal and upper visual field stimuli, which activated the region equally. These findings, like earlier reports of contralateral biases in object-selective regions (13)(14)(15)(16) do not fit within the fovea/periphery framework, and it is not clear how the computational-demands hypothesis (35) could account for them.…”

“…At the most general level, some of these regions demonstrate contralateral field biases (13)(14)(15)(16), and some of them [e.g., the parahippocampal place area (PPA)] respond more strongly to stimuli presented in the periphery, whereas others [e.g., the fusiform face area (FFA)] respond more strongly to foveal stimuli (17,18). Studies conducted with retinotopic mapping (19,20) have shown object-selective responses in certain retinotopically defined regions, although the degree to which these maps overlap object-selective cortex is not yet known.…”

“…Elevation. Although eccentricity biases (17,18) and contralateral biases (13)(14)(15)(16) have been reported for some higher-level category-selective areas, no studies to date have systematically tested for elevation biases in regions other than LO, which shows a lower visual field bias (13). Therefore, we compared mean response magnitude in each ROI for upper and lower field stimuli at equal eccentricities.…”

Modulation of Visual Responses by Gaze Direction in Human Visual Cortex

“…Some previous studies have reported that some visual areas represent stimuli in a "spatiotopic" reference frame, linked to the location of stimuli in space (i.e., screen coordinates), independent of eye position (McKyton and Zohary, 2007;d'Avossa et al, 2007). But our results support the hypothesis that visual cortical areas represent stimulus locations in a retinotopic reference frame modulated by eye position (Gardner et al, 2008).…”

Position specificity of adaptation-related face aftereffects

“…Similarly, Merriam et al [88] found evidence of spatial remapping in higherorder retinotopic areas (specifically in area V3a and hV4) during the presentation of simple light flashes. McKyton & Zohary [89] tested similar questions in the object selective lateral occipital (LO) complex. They compared the fMRIa effect for man-made objects when their displacement was limited to either the retina or the screen, by manipulating eye position and object locations.…”