Wide-Field Retinotopy Defines Human Cortical Visual Area V6

Abstract

The retinotopic organization of a newly identified visual area near the midline in the dorsalmost part of the human parieto-occipital sulcus was mapped using high-field functional magnetic resonance imaging, cortical surface-based analysis, and wide-field retinotopic stimulation. This area was found in all 34 subjects that were mapped. It represents the contralateral visual hemifield in both hemispheres of all subjects, with upper fields located anterior and medial to areas V2/V3, and lower fields medial and slightly anterior to areas V3/V3A. It contains a representation of the center of gaze distinct from V3A, a large representation of the visual periphery, and a mirror-image representation of the visual field. Based on similarity in position, visuotopic organization, and relationship with the neighboring extrastriate visual areas, we suggest it might be the human homolog of macaque area V6, and perhaps of area M (medial) or DM (dorsomedial) of New World primates.

Reaching Activity in the Medial Posterior Parietal Cortex of Monkeys Is Modulated by Visual Feedback

“…Results of this study show that a medial posterior parietal region located at the superior end of parieto-occipital sulcus responds more during visual than non-visual reaches or saccades. Since the activated region is located just anterior to the human area V6 (Pitzalis et al, 2006), and since in the macaque the cortical region anterior to V6 is occupied by area V6A (Galletti et al, 1996;1999), we suggest that this area could be the human homolog of macaque area V6A (Cavina-Pratesi et al, 2010). Present results, showing that V6A reaching neurons are on average more responsive in the light than in the dark, agree well with this view, suggesting that also human V6A is more responsive to reaching in light.…”

Mapping multisensory parietal face and body areas in humans

“…Groupaverage retinotopic maps (Fig. S5) show that looming stimuli activated areas V1, V2, V3, and V4 in the occipital lobe (34), unnamed areas beyond the peripheral borders of V1 and V2, area V6 in the parieto-occipital sulcus (35), an area in the precuneus (PCu), areas MT, MST, and FST in the temporal lobe (36), areas V3A/V3B in the dorsal occipital lobe (37), areas in the intraparietal sulcus and superior parietal lobule (38), area polysensory zone in the precentral gyrus (2), and area FEF complex in the frontal cortex (38). The most anterior retinotopic maps overlapping with the parietal face and body areas in the superior parietal region are discussed with quantitative measures below.…”

“…In each scan, subjects fixated on a central red cross while attending to looming balls apparently passing by their faces for eight rounds at a 64-s period. Each round consisted of 40 looming balls (1.6 s per trial) that appeared at increasing (counterclockwise) or decreasing (clockwise) polar angles (at a 9°step) from the right horizon, which was a variant of the phase-encoded design used in retinotopic mapping experiments (34,35). At the beginning of each 1.6-s trial, a white ball appeared at 5.73°eccentricity and gradually expanded and moved toward the far periphery (Fig.…”

Eye Position Encoding in Three-Dimensional Space: Integration of Version and Vergence Signals in the Medial Posterior Parietal Cortex

“…In humans, the putative homolog of monkey area V6A is located in the dorsalmost part of parieto-occipital sulcus (POs), just anterior to the location of human area V6 (Pitzalis et al, 2006;Cavina-Pratesi et al, 2010). Several studies reported the presence of activations in the dorsalmost part of human POs for changes in the direction of gaze (Law et al, 1998;Williams and Smith, 2010), but to our knowledge only one reported activations in the dorsalmost POs for changes of eye vergence (Quinlan and Culham, 2007).…”