Objects move through the environment in three dimensions, and primates are very adept at interacting with a dynamic 3D world, both with respect to moving objects and as they move their own bodies. The goal of this proposed research is to understand how neural circuits in the primate brain exploit binocular information to represent the direction of objects moving through 3D space. Our particular focus is understanding how the brain goes from differential patterns of motion falling upon the two retinae to inferences about velocities of real objects in the 3D environment. In order to understand how this critical transformation from an ?ocular? to an ?environmental? representation is performed by the brain, we propose the following suite of psychophysical and electrophysiological investigation.
Aim 1 : Test whether perceptual sensitivity re?ects ocular or environmental velocity It is critical to assess whether human perception of 3D direction re?ects the velocity of objects in the environment, or remains tied to the velocities that fall upon the retinae. We will use the characteristic patterns of perceptual sensitivity (bolstered by our geometric understanding of how motions in the environment relate to velocities projected upon the retina) to test whether perception remains tied to ocular velocities, or whether it correctly estimates (and uses) viewing distance to express sensitivity in environmental terms, independent of exactly where in space and depth the moving object is. We will also continue to generalize classical psychophysics to a novel continuous tracking task that we developed in the last cycle.
Aim 2 : Assess 3D velocity tuning across the dorsal stream (MT, MST, VIP) of awake fixating primates In the prior work supported by this grant, we showed that many neurons in area MT are tuned for differential velocities in the two eyes, consistent with 3D direction-selectivity. We now propose to characterize these responses in a broader array of brain areas (MT, MST, VIP) and to test whether these responses re?ect tuning to differential ocular velocity or sensitivity to environmental direction.
Aim 3 : Test for a selective causal roles of dorsal stream areas in binocular 3D motion perception This aim extends the behavioral tracking paradigm from Aim 1 that will allow us to link human and monkey perceptual sensitivity to 3D direction. We will then employ reversible neural inactivations and stereoscopic stimulus manipulations within this paradigm to test for selective causal roles of dorsal visual areas in 3D motion perception.
/ RELEVANCE Although much is known about how very simple visual patterns presented to the retinae are processed by the brains of primates, very little is understood about how such neural processing relates to the rich and dynamic information actually present in the 3D world. A thorough understanding of the neural basis of processing 3D motion will prove valuable for robotics/prosthetics work that tries to take in image data, and attempts to infer the dynamic structure of the environment in order to accomplish feats like controlling artificial limbs. It will also elucidate how multiple sources and modalities of sensory information are simultaneously integrated by the brain, which could inform the development of treatments for brain disorders that involve difficulty in information integration such as posterior cortical atrophy.
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| Huk, Alexander; Bonnen, Kathryn; He, Biyu J (2018) Beyond Trial-Based Paradigms: Continuous Behavior, Ongoing Neural Activity, and Natural Stimuli. J Neurosci 38:7551-7558 |
| Cormack, Lawrence K; Czuba, Thaddeus B; Knöll, Jonas et al. (2017) Binocular Mechanisms of 3D Motion Processing. Annu Rev Vis Sci 3:297-318 |
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| Joo, Sung Jun; Czuba, Thaddeus B; Cormack, Lawrence K et al. (2016) Separate Perceptual and Neural Processing of Velocity- and Disparity-Based 3D Motion Signals. J Neurosci 36:10791-10802 |
| Joo, Sung Jun; Katz, Leor N; Huk, Alexander C (2016) Decision-related perturbations of decision-irrelevant eye movements. Proc Natl Acad Sci U S A 113:1925-30 |
| Greer, Devon A; Bonnen, Kathryn; Huk, Alexander C et al. (2016) Speed discrimination in the far monocular periphery: A relative advantage for interocular comparisons consistent with self-motion. J Vis 16:7 |
| Katz, Leor N; Hennig, Jay A; Cormack, Lawrence K et al. (2015) A Distinct Mechanism of Temporal Integration for Motion through Depth. J Neurosci 35:10212-6 |
| Bonnen, Kathryn; Burge, Johannes; Yates, Jacob et al. (2015) Continuous psychophysics: Target-tracking to measure visual sensitivity. J Vis 15: |
| Goonetilleke, Samanthi C; Katz, Leor; Wood, Daniel K et al. (2015) Cross-species comparison of anticipatory and stimulus-driven neck muscle activity well before saccadic gaze shifts in humans and nonhuman primates. J Neurophysiol 114:902-13 |
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