A Neural Model of Motion Processing and Visual Navigation by Cortical Area MST

Cells in the dorsal medial superior temporal cortex (MSTd) process optic flow generated by self-motion during visually-guided navigation. A neural model shows how interactions between well-known neural mechanisms (log polar cortical magnification, Gaussian motion-sensitive receptive fields, spatial pooling of motion-sensitive signals, and subtractive extraretinal eye movement signals) lead to emergent properties that quantitatively simulate neurophysiological data about MSTd cell properties and psychophysical data about human navigation. Model cells match MSTd neuron responses to optic flow stimuli placed in different parts of the visual field, including position invariance, tuning curves, preferred spiral directions, direction reversals, average response curves, and preferred locations for stimulus motion centers. The model shows how the preferred motion direction of the most active MSTd cells can explain human judgments of self-motion direction (heading), without using complex heading templates. The model explains when extraretinal eye movement signals are needed for accurate heading perception, and when retinal input is sufficient, and how heading judgments depend on scene layouts and rotation rates.Defense Research Projects Agency (N00014-92-J-4015); Office of Naval Research (N00014-92-J-1309, N00014-95-1-0409, N00014-95-1-0657, N00014-91-J-4100, N0014-94-I-0597); Air Force Office of Scientific Research (F49620-92-J-0334)

The role of the ventral intraparietal area (VIP/pVIP) in parsing optic flow into visual motion caused by self-motion and visual motion produced by object-motion

Retinal image motion is a composite signal that contains information about two behaviourally significant factors: self-motion and the movement of environmental objects. It is thought that the brain separates the two relevant signals, and although multiple brain regions have been identified that respond selectively to the composite optic flow signal, which brain region(s) perform the parsing process remains unknown. Here, we present original evidence that the putative human ventral intraparietal area (pVIP), a region known to receive optic flow signals as well as independent self-motion signals from other sensory modalities, plays a critical role in the parsing process and acts to isolate object-motion. We localised pVIP using its multisensory response profile, and then tested its relative responses to simulated object-motion and self-motion stimuli; results indicated that responses were much stronger in pVIP to stimuli that specified object-motion. We report two further observations that will be significant for the future direction of research in this area; firstly, activation in pVIP was suppressed by distant stationary objects compared to the absence of objects or closer objects. Secondly, we describe several other brain regions that share with pVIP selectivity for visual object-motion over visual self-motion as well as a multisensory response

Optic flow in human vision: MEG reveals a foveo-fugal bias in V1, specialization for spiral space in hMSTs, and global motion sensitivity in the IPS

Abstract We recorded MEG responses from 17 participants viewing random-dot patterns simulating global optic flow components (expansion, contraction, rotation, deformation, and translation) and a random motion control condition. Theta-band (3–7 Hz), MEG signal power was greater for expansion than the other optic flow components in a region concentrated along the calcarine sulcus, indicating an ecologically valid, foveo-fugal bias for unidirectional motion sensors in V1. When the responses to the optic flow components were combined, a decrease in MEG beta-band (17–23 Hz) power was found in regions extending beyond the calcarine sulcus to the posterior parietal lobe (inferior to IPS), indicating the importance of structured motion in this region. However, only one cortical area, within or near the V5/hMT+ complex, responded to all three spiral-space components (expansion, contraction, and rotation) and showed no selectivity for global translation or deformation: we term this area hMSTs. This is the first demonstration of an exclusive region for spiral space in the human brain and suggests a functional role better suited to preliminary analysis of ego-motion than surface pose, which would involve deformation. We also observed that the rotation condition activated the cerebellum, suggesting its involvement in visually mediated control of postural adjustment

A quantitative investigation of natural head movement and its contribution to spatial orientation perception.

Movement is ubiquitous in everyday life. As we exist in a physical world, we constantly account for our position in it relative to other physical features: both at a conscious, volitional level and an unconscious one. Our experience estimating our own position accumulates over the lifespan, and it is thought that this experience (often referred to as a prior) informs current perception of spatial orientation. Broadly, this perception of spatial orientation is rapidly performed by the nervous system by monitoring, interpreting, and integrated sensory information from multiple sense organs. To do this efficiently, the nervous system likely represents this sensory information in a statistically optimal manner. Some of the most important information for spatial orientation perception comes from visual and vestibular sensation, which rely on sensory organs located in the head. While statistical information about natural visual and vestibular stimuli have been characterized, natural head movement and position, which likely drives correlated dynamics across head-located senses, has not. Furthermore, sensory cues essential to spatial orientation perception are directly affected by head movement specifically. It is likely that measurement of these sensory cues taken during natural behaviors sample a significant portion of the total behaviors that comprise ones’ prior. In this dissertation, I present work quantifying characteristics of head orientation and heading, two dimensions of spatial orientation, over long-duration recordings of natural behavior in humans. Then, I use these to generate priors for Bayesian modeling frameworks which successfully predict observed patterns of orientation and heading perception bias. Given the ability to predict some patterns of bias (head roll and heading azimuth) particularly well, it is likely our data are representative of real behaviors that comprise previous experience the nervous system may have. Natural head orientation and heading distributions reveal several interesting trends that open future lines of research. First, head pitch demonstrates large amounts of inter-subject variability; likely this is due to biomechanical differences, but as these remain relatively stable over the lifespan these should bias head movements. Second, heading azimuth appears to vary significantly as a function of task. Heading azimuth distributions during low velocities (which predominantly consist of stationary activities like standing or sitting) are strongly multimodal across all subjects, while azimuth distributions during high velocities (predominantly consisting of locomotion) are unimodal with relatively low variance. Future work investigating these trends, as well as implications these trends and data have for sensory processing and other applications is discussed

Heading perception from optic flow in the presence of biological motion

© 2019 Association for Research in Vision and Ophthalmology Inc. We investigated whether biological motion biases heading estimation from optic flow in a similar manner to nonbiological moving objects. In two experiments, observers judged their heading from displays depicting linear translation over a random-dot ground with normal point light walkers, spatially scrambled point light walkers, or laterally moving objects composed of random dots. In Experiment 1, we found that both types of walkers biased heading estimates similarly to moving objects when they obscured the focus of expansion of the background flow. In Experiment 2, we also found that walkers biased heading estimates when they did not obscure the focus of expansion. These results show that both regular and scrambled biological motion affect heading estimation in a similar manner to simple moving objects, and suggest that biological motion is not preferentially processed for the perception of selfmotion

Acute alcohol administration dampens central extended amygdala reactivity.

Alcohol use is common, imposes a staggering burden on public health, and often resists treatment. The central extended amygdala (EAc)-including the bed nucleus of the stria terminalis (BST) and the central nucleus of the amygdala (Ce)-plays a key role in prominent neuroscientific models of alcohol drinking, but the relevance of these regions to acute alcohol consumption in humans remains poorly understood. Using a single-blind, randomized-groups design, multiband fMRI data were acquired from 49 social drinkers while they performed a well-established emotional faces paradigm after consuming either alcohol or placebo. Relative to placebo, alcohol significantly dampened reactivity to emotional faces in the BST. To rigorously assess potential regional differences in activation, data were extracted from unbiased, anatomically predefined regions of interest. Analyses revealed similar levels of dampening in the BST and Ce. In short, alcohol transiently reduces reactivity to emotional faces and it does so similarly across the two major divisions of the human EAc. These observations reinforce the translational relevance of addiction models derived from preclinical work in rodents and provide new insights into the neural systems most relevant to the consumption of alcohol and to the initial development of alcohol abuse in humans

Misperception of rigidity from actively generated optic flow

It is conventionally assumed that the goal of the visual system is to derive a perceptual representation that is a veridical reconstruction of the external world: a reconstruction that leads to optimal accuracy and precision of metric estimates, given sensory information. For example, 3-D structure is thought to be veridically recovered from optic flow signals in combination with egocentric motion information and assumptions of the stationarity and rigidity of the external world. This theory predicts veridical perceptual judgments under conditions that mimic natural viewing, while ascribing nonoptimality under laboratory conditions to unreliable or insufficient sensory information\u2014for example, the lack of natural and measurable observer motion. In two experiments, we contrasted this optimal theory with a heuristic theory that predicts the derivation of perceived 3-D structure based on the velocity gradients of the retinal flow field without the use of egomotion signals or a rigidity prior. Observers viewed optic flow patterns generated by their own motions relative to two surfaces and later viewed the same patterns while stationary. When the surfaces were part of a rigid structure, static observers systematically perceived a nonrigid structure, consistent with the predictions of both an optimal and a heuristic model. Contrary to the optimal model, moving observers also perceived nonrigid structures in situations where retinal and extraretinal signals, combined with a rigidity assumption, should have yielded a veridical rigid estimate. The perceptual biases were, however, consistent with a heuristic model which is only based on an analysis of the optic flow