Sensitivity to optic flow in human cortical areas MT and MST

Abstract

The macaque V5/MT complex comprises several sub-regions but little is known of their human homologues. We examined human V5/MT with fMRI in terms of specificity to optic flow stimuli, a key characteristic of macaque MST. Stimuli were large fields of moving dots, forming coherent global flow patterns. Random motion was used as a control. Retinotopic mapping was also conducted. The previously suggested existence of at least two distinct sub-regions, MT and MST, within the V5/MT complex was confirmed. Human MT is activated about equally by all moving dot patterns, including random motion, suggesting that it has little sensitivity to global flow structure. As previously described, this region shows strong signs of retinotopic organization and is only weakly activated by stimuli confined to the ipsilateral hemifield. In human MST, located immediately anterior to MT and strongly driven by ipsilateral stimuli, activation varies markedly with optic flow structure. The strongest activation is produced by complex flow that contains multiple flow components (expansion, contraction and rotation). Single components produce rather less response, while rigid translation and random motion produce less still. The results suggest that human MST is strongly specialized for encoding global flow properties, while human MT is less so.

Neural Systems in the Visual Control of Steering

“…The most basic process is to pick up the current direction of travel (heading). In monkeys, both MSTd and the VIP have been implicated in processing the current direction of travel from ground plane flow, and human homologs are suggested by the studies of Morrone et al (2000) and Smith et al (2006). Area VIP is also sensitive to multisensory inputs, and this property was used to identify a human homolog of VIP (Bremmer et al, 2001).…”

“…Research into the neural basis of sensitivity to optic flow and direction of self-motion has focused on the properties of two brain areas, dorsal medial superior temporal cortex (MSTd) and ventral intraparietal area (VIP). Neurons in macaque MSTd respond selectively to specific optic flow components (Tanaka et al, 1989;Duffy and Wurtz, 1991), and a human area with similar properties has been identified (Morrone et al, 2000;Smith et al, 2006). The sensitivity of macaque VIP to heading has been established by Bremmer et al (2002).…”

Maps of Visual Space in Human Occipital Cortex Are Retinotopic, Not Spatiotopic

“…2 A). Second, MT is identifiable relative to nearby visual areas by its distinct topographic organization Smith et al, 2006): MT is located anterolateral to LO1 and LO2 (Larsson and Heeger, 2006), has a representation of the fovea that is different from neighboring visual areas (see Fig. 2 B), and has a complete representation of the contralateral hemifield (see Fig.…”

“…This was done because MT is distinguished from MST in terms of the sizes of the underlying receptive fields (Desimone and Ungerleider, 1986;Tanaka et al, 1986). MST neurons, unlike those in MT, have very large receptive fields that extend into the ipsilateral visual field and are thus not modulated strongly by the polar angle stimulus Smith et al, 2006). Applying these criteria enabled us to reliably identify MT in both hemispheres of all five subjects studied.…”

The visual perception of motion by observers with autism spectrum disorders: A review and synthesis

“…Because specific patterns of locomotor activity produce specific patterns of optic flow, visual and motor processes are coupled such that large field optic flow typically triggers compensatory motor activity and postural adjustments in the observer. Although the neural mechanisms underlying optic flow perception by observers with ASD are unknown, part of the human MT complex known as area MST is strongly responsive during optic flow perception by typical observers (Smith, Wall, Williams, & Singh, 2006). In the study by Gepner et al, a small sample of children with ASD and age-matched control participants stood on a force plate positioned near a large screen.…”