The Processing of First- and Second-Order Motion in Human Visual Cortex Assessed by Functional Magnetic Resonance Imaging (fMRI)

Abstract

We have examined the activity levels produced in various areas of the human occipital cortex in response to various motion stimuli using functional magnetic resonance imaging (fMRI) methods. In addition to standard luminance-defined (first-order) motion, three types of second-order motion were used. The areas examined were the motion area V5 (MT) and the following areas that were delineated using retinotopic mapping procedures: V1, V2, V3, VP, V3A, and a new area that we refer to as V3B. Area V5 is strongly activated by second-order as well as by first-order motion. This activation is highly motion-specific. Areas V1 and V2 give good responses to all motion stimuli, but the activity seems to be related primarily to the local spatial and temporal structure in the image rather than to motion processing. Area V3 and its ventral counterpart VP also respond well to all our stimuli and show a slightly greater degree of motion specificity than do V1 and V2. Unlike V1 and V2, the response in V3 and VP is significantly greater for second-order motion than for first-order motion. This trend is evident, but less marked, in V3A and V3B and absent in V5. The results are consistent with the hypothesis that first-order motion sensitivity arises in V1, that second-order motion is first represented explicitly in V3 and VP, and that V5 (and perhaps also V3A and V3B) is involved in further processing of motion information, including the integration of motion signals of the two types.

Automatic volumetric segmentation of human visual retinotopic cortex

“…The layout of the cortical areas is in agreement with previous fMRI (DeYoe et al, 1996;Engel et al, 1997;Sereno et al, 1995;Smith et al, 1998;Tootell et al, 1997), positron emission tomography (Fox et al, 1987;Hasnain et al, 1998Hasnain et al, , 2001), lesion studies (Holmes, 1945;Horton and Hoyt, 1991;Wong and Sharpe, 1999), and cytoarchitectonic maps of Brodmann's area 17 and 18 (Amunts et al, 2000;Clarke and Miklossy, 1990).…”

“…The visual field sign pattern is in accordance with previous studies identifying visual areas (Sereno et al, 1995;DeYoe et al, 1996;Engel et al, 1997;Tootell et al, 1997;Smith et al, 1998). In all subjects visual areas V1, V2, V3/VP, V4v, and V3A could be identified.…”

“…These areas are at the limit of the current methodology and therefore may be only partially identified, if at all, as evidenced by inconsistent descriptions of several studies (Press et al, 2001;Smith et al, 1998;Tootell et al, 1998a,b). Press et al (2001) found an upper and lower visual field representation for both V3B and V7.…”

“…Press et al (2001) found an upper and lower visual field representation for both V3B and V7. Smith et al (1998) could determine only a lower field representation for area V3B, while Tootell et al (1998a,b) could only measure a lower field representation for area V7. Here we can confirm both an upper and a lower field representation for V7; however, for V3B only a representation of the lower visual field was found.…”

“…These results were replicated by DeYoe et al (1996) and Engel et al (1997), also utilizing a cortical surface-based analysis but manually distinguishing the borders based on polar-angle information. Further phase-encoded mapping studies with modifications of the stimulus revealed visual areas V3A (DeYoe et al, 1996;Tootell et al, 1997Tootell et al, , 1998c, V3B (Press et al, 2001;Smith et al, 1998), V7 (Mendola et al, 1999;Press et al, 2001;Tootell et al, 1998a,c;Tootell and Hadjikhani, 2001), V8 , a putative homologue of the lateral intraparietal area (LIP) (Sereno et al, 2001), and retinotopic organization in human MT/V5 (Huk et al, 2002).…”