Most of our understanding of the functional organization of human visual cortex comes from lesion and functional imaging studies and by extrapolation from results obtained by neuroanatomical and neurophysiological studies in nonhuman primates. Although some single-unit and field potential recordings have been made in human visual cortex, none has provided quantitative characterization of spatial receptive fields (RFs) of individual sites. Here we use subdural electrodes implanted for clinical purposes to quantitatively measure response properties in different regions of human visual cortex. We find significant differences in RF size, response latency, and response magnitude for sites in early visual areas, versus sites in later stages of both the dorsal and ventral streams. In addition, we use this technique to estimate the cortical magnification factor in early human visual cortex. The spatial and temporal resolution of cortical surface recordings suggest that this technique is well suited to examine further issues in visual processing in humans.
Bibliographical noteFunding Information:
This work was supported by grants from the National Institutes of Health (K08NS045053) and The Methodist Hospital Foundation to D. Yoshor. J.H.R. Maunsell is a Howard Hughes Medical Institute Investigator. We thank L. Rhodes, B. Pudlo, M. King, S. Pedigo, H. Tsoi, W. Morton, A. Verma, I. Goldsmith, and E. Mizrahi for assistance with intracranial recordings and M. Beauchamp and R. Grossman for helpful comments. We also thank the patients who volunteered to participate in this study. Conflict of Interest: None declared.
- Magnification factor