A cortical area that responds specifically to optic flow, revealed by fMRI

Abstract

articlesThe optic flow 1 that is generated when a person moves through the environment can be locally decomposed into several basic components, including radial, circular, translation and sheer motion 2,3 . Neurons in the dorsal portion of the medial superior temporal cortex (MSTd) of macaque monkeys respond selectively to these components, alone or in combination [4][5][6][7] . Microstimulation can influence the direction of heading of a behaving monkey 8 , which demonstrates the functional importance of MST to heading. In the adjacent area MT (or V5), neurons also respond to motion and are highly directionally selective, but they do not show specific selectivity to circular or radial trajectories 9 . The neurophysiology findings are reinforced by psychophysical studies suggesting the existence of analogous neural units in humans that integrate local-motion signals along complex flow trajectories 10,11 . In agreement with the neurophysiological studies, these units have very large receptive fields 12 and sum information over periods of one or two seconds (L. Santoro and D.C. Burr, Perception 28, 90c, 1999). There is also some evidence in humans for selectivity along the 'cardinal directions' of optic flow (radial and circular) 13 , although this issue is somewhat controversial 14 .A very strong motion-selective response at the boundary of Brodmann's areas 19 and 37 is shown by human imaging [15][16][17][18][19][20][21][22][23] . This area is generally thought to be the human analogue of monkey V5/MT-MST regions, and is referred to as 'V5/MT complex' (MT+). Other motion-sensitive areas have been identified: a dorsal region referred to as V3A 16,21,22,24 and a ventral region, seemingly activated by motion boundaries and second-order motion 20,21 . Here, using fMRI, we examined the response to optic-flow stimuli, and showed selective activation of a large area within the V5/MT complex to radial and circular motion, very different from the area activated by translational motion. Activation in response to optic flow occurred only when the direction of optic flow changed-abruptly or gradually-during the presentation period; continuous radial or circular motion produced no reliable activation in any area when measured against a matched random control. RESULTS Response to optic flowWe created dynamic displays of circular, radial, spiral and translational motion from random-dot patterns. The control stimuli were locally identical to the active stimuli; each dot moved along independent, randomly chosen trajectories ( Fig. 1; Methods). Responses of subjects to flow motion were measured against these random controls, with both active and control stimuli reversing direction every two seconds. There was a clear and specific activation in the temporal-occipital cortex, with no response in V1 or any other cortical area (example, Fig. 2a). The response extended for more than 1 cm along the sulcus that separates Brodmann's area 19 and 37, within the region that is usually referred to the human analogue of V5/MT complex [15][16][...

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).…”

Spatial Navigation Impairment in Healthy Aging and Alzheimer’s Disease

“…Optic flow is the patterned visual motion seen by a moving observer (Gibson, 1950). It provides cues about heading direction and the three-dimensional structure of the visual environment (Royden et al, 1992;Warren & Hannon, 1988) and its perception activates right posterior parietal cortex (Morrone et al, 2000). An atypical form of AD with higher visuospatial impairment was described (Kiyosawa et al, 1989), based also on deficits in judging spatial relations (Cogan, 1985) and atrophy (Benson et al, 1988), hypometabolism (Pietrini et al, 1996) and neuropathology (Hof et al, 1989) of the posterior cortical regions.…”

Probing the involvement of the earliest levels of cortical processing in motion extrapolation with rapid forms of visual motion priming and adaptation

“…Corroborating the low-level-processing hypothesis arising from the findings with ambiguous motion, it has been found that transfer between the two types of motion was small or absent: rVMP and rMAE can be elicited by both first-and second-order motion, but only if both the adapting and test stimuli are of the same motion type (first-or second-order; Pavan, Campana, Guerreschi, Manassi, & Casco, 2009). Finally, by using components of the optic flow (complex motion) typically processed at intermediate and high levels of motion processing (Morrone et al, 2000;Wall, Lingnau, Ashida, & Smith, 2008) to investigate the level of processing of rapid forms of adaptation, it was shown that, whereas rMAE can be elicited by both simple translational motion and complex motion, rVMP can only be produced with simple translational motion (Pavan, Campana, Maniglia, & Casco, 2010). This finding proposes the notion that the faster the adaptation (and interstimulus interval; rVMP), the earlier the level of processing.…”