An investigation of visual cues and the neural mechanisms on human motor control behaviour

Abstract

Accurate perception and control of self-motion is vital for human survival. Most

animals rely on vision for navigating through complex environments. In this

thesis, I investigated how vision influence perception and guide self-motion

from two aspects: (1) what visual information humans pick up from the

environment to form their perception and guide their self-motion; (2) how the

degeneration of the basal ganglia and cerebellum, the two largest subcortical

nuclei connecting the visual and motor areas of the brain, affect the controller’s

performance.

Study 1 examined the condition under which optic-flow information

beyond velocity field helps heading perception. I systematically varied the

amount of information in velocity field through manipulations of field of view

(FOV). The amount of optic-flow information beyond velocity field was

manipulated by two types of displays. I found heading bias increased with the

reduction of FOV only when optic-flow information beyond velocity field was

not available.

Study 2 investigated whether the information investigated in Study 1 is

sufficient and necessary for active control of heading. I used the similar display

simulations as study 1 with the exception that the vehicle orientation was

perturbed pseudo-randomly. Participants used a joystick, under both velocity

and acceleration control dynamics, to continuously rotate the vehicle orientation

back to its heading direction. The results showed that participants’ accurate

performance under condition that only provided velocity field information was

further improved when optic-flow information beyond velocity field was

available.

Study 3 examined the relative contributions of three visual cues (i.e.,

heading from optic flow, bearing, and splay angle) for lane-keeping control.

Observers controlled the car’s lateral movement to stay in the center of the lane

while facing two random perturbations affecting the use of bearing or splay

angle information. I found that performance improved with enriched flow

information. In the presence of splay angles, participants ignored bearing angle

information.

Study 4 investigated the roles of the basal ganglia and cerebellum in

motor control task using brain-damaged patients. Participant’s task was to use

the joystick to keep a blob in the center of the display while the horizontal

position of the blob was perturbed pseudo-randomly. This task is not a

self-motion task but mimics real-world lane-keeping control. Both the

Parkinson’s disease patients and cerebellar patients showed impaired motor

control performance in comparison with the healthy controls.

In conclusion, the visual information used for motor control in general

depends on the task. For traveling along a curved path, the velocity field

contains sufficient information for heading perception and heading control.

Optic-flow information beyond velocity field improves heading perception

when the velocity field does not contain sufficient information. It also helps

heading control when available. For lane-keeping control, adding optic flow

information improves participants’ performance. Splay angle information plays

a more important role than does bearing angle information. The visual

information used for motor control changes when certain brain areas are

damaged. Parkinson’s disease patients and cerebellar patients show the inability

to process visual input effectively for online motor control.