A direct demonstration of functional specialization in human visual cortex

Abstract

We have used positron emission tomography (PET), which measures regional cerebral blood flow (rCBF), to demonstrate directly the specialization of function in the normal human visual cortex. A novel technique, statistical parametric mapping, was used to detect foci of significant change in cerebral blood flow within the prestriate cortex, in order to localize those parts involved in the perception of color and visual motion. For color, we stimulated the subjects with a multicolored abstract display containing no recognizable objects (Land color Mondrian) and contrasted the resulting blood flow maps with those obtained when subjects viewed an identical display consisting of equiluminous shades of gray. The comparison identified a unique area (area V4) located in the lingual and fusiform gyri of the prestriate cortex. For motion, blood flow maps when subjects viewed moving or stationary black and white random-square patterns were contrasted. The comparison identified a unique area located in the region of the temporo-parieto-occipital junction (area V5). We thus provide direct evidence to show that, just as in the macaque monkey, different areas of the human prestriate visual cortex are specialized for different attributes of vision. The striate cortex (V1) and the contiguous visual area (V2), which in the monkey brain feed both the homologous areas, were active in all 4 conditions. This pattern of activity allowed us to use an extension of the approach to assess the functional relationship between the 3 areas during color and motion stimulation. This is based on an hypothesis-led analysis of the covariance structure of the blood flow maps and promises to be a powerful tool for inferring anatomical pathways in the normal human brain.(ABSTRACT TRUNCATED AT 250 WORDS)

Generalised filtering and stochastic DCM for fMRI

“…An early visual region (V1) was identified using a contrast testing for the effect of visual stimulation. An extrastriate cortex (motion-sensitive area V5; Zeki et al, 1991) was identified using a test for motion-specific responses, and an attentional area was identified in the frontal eye fields (FEF), using a test for the effects of attention (see Fig. 1 for details).…”

Simultaneous recordings of visual evoked potentials and BOLD MRI activations in response to visual motion processing

“…It is independent of stimulus color but highly sensitive to luminance contrast. Most prominently, neurons in V5/ MTþ are highly direction selective and respond to the presentation of moving stimuli and edge-contrast as seen in pattern-reversal stimuli (5)(6)(7)(8). V5/MTþ was found to play a role concerning the well-known motion aftereffect (MAE), that is, the ongoing illusionary perception of motion in the opposite direction after a period of viewing unidirectional motion (9)(10)(11)(12).…”

Functional localization of the human color center by decreased water displacement using diffusion‐weighted fMRI

“…1989; Zeki et al. 1991; McKeefry and Zeki 1997). The stimuli were created using the Psychophysics Toolbox (Brainard 1997; RRID:rid_000041) running on MATLAB (The Mathworks, Sherborne, MA, USA) and back‐projected onto an LCD screen located inside the bore of the scanner.…”