Encoding of 3D Head Movement and Direction in Visual Cortex
MetadataShow full item record
CitationGuitchounts, Grigori. 2020. Encoding of 3D Head Movement and Direction in Visual Cortex. Doctoral dissertation, Harvard University, Graduate School of Arts & Sciences.
AbstractAnimals sample the visual world by producing complex patterns of movements that serve to stabilize or shift gaze, sample the visual scene, or estimate distance using parallax cues. Despite the myriad of movements animals make to support visual perception, this sense is typically studied in restrained animals that absorb sensory stimuli passively. As such, it is unknown what effect, if any, naturalistic movements have on neuronal dynamics in visual cortex.
We sought to investigate the encoding of movement and orientation in primary visual cortex (V1) by recording neuronal activity in V1 of freely behaving rats. We demonstrate that three-dimensional (3D) head orienting movements modulate V1 neuronal activity in a direction-specific manner that also depends on the presence or absence of light, and that V1 gains access to this motor information from secondary motor cortex. These results suggest a mechanism through which sensory signals generated by purposeful movement can be distinguished from those arising in the outside world.
Further, we address whether a related but distinct spatial signal can be found in V1: the sense of direction. Head direction (HD) signals have been reported in a number of brain regions relating to spatial navigation, one of which---the retrosplenial cortex---is densely interconnected with V1. We show that V1 dynamics encode 3D HD as well, and that individual V1 neurons are tuned to HD. We propose that HD signals in V1 may be passed down from the RSC as part of a predictive coding framework in which expected HD is compared with actual HD as estimated from visual signals in V1.
Next, we outline a working definition of brain states and propose that movement be considered a brain state. Finally, we discuss challenges in chronic recording of neuronal activity and describe the design and implementation of a 64-channel carbon fiber electrode array that addresses some of these.
Together, these results reveal a pervasive role of 3D movement and orientation in shaping sensory cortical dynamics. Understanding vision therefore will be facilitated by considering it an active process, and exploring its underlying neural codes while subjects are free to behave.
Citable link to this pagehttps://nrs.harvard.edu/URN-3:HUL.INSTREPOS:37365943
- FAS Theses and Dissertations