Projects: Sensorimotor Neuroscience Laboratory, York University

General research plan

    In order to accurately reach for an object, one must transform a sensory signal into a complex pattern of muscle activity. The control processes employed by the brain which underlie this seemingly straightforward task are not as yet completely understood. The overall objective of my research program is to understand the cortical control signals used to coordinate the different levels of motor output (e.g. forces, spatial trajectories, hand velocity, etc.) required for these voluntary multi-joint limb movements. These studies will focus on the central representation of different aspects of movement and force generation in the control of arm reaching movements.

One line of research employs three approaches to these issues

1) Psychophysical studies

    The psychophysical studies will examine motor behaviour during target-directed reaching movements and isometric force production using the whole arm. The behavioural measures include movement kinematics (hand and joint motions), limb kinetics (forces at the hand or joints used to produce either limb motion or force at the hand), and muscle activity responsible for force generation at the joints. (see Neuroscience poster on main lab page)

2) Functional Magnetic Resonance Imaging (fMRI)

    In collaboration with the CIHR Group for Action and Perception, the fMRI research will employ similar methods to those in the psychophysical studies. These studies will examine neural activity in the human brain during the performance of sensory-guided motor tasks in which different attributes of the motor output are systematically controlled. The overall goal is to understand which aspects of motor output are reflected in the activity of different cortical areas. 

3) Transcranial Magnetic Stimulation (TMS)

    In studies complementary to the psychophysical and imaging projects, TMS will be used to transiently disrupt specific motor cortical regions. Using this technique during whole arm motor tasks, one can observe the effect on directed movement or force generation. Thus, the contribution of different cortical areas to these distinct components of motor output can be delineated.

A second line of research will involved studying the central mechanisms involved in the planning and execution of arm movements performed under increasingly arbitrary visuomotor transformations. Some of the movements that we make are directly toward stimuli of interest. However, many of the transformations that we perform require more arbitrary associations. In everyday life, we perform these types of transformations effortlessly. A common example is the use of a computer mouse to move a pointer on a monitor. Such a skill requires a remapping of motor output from a frontal plane to a horizontal one. In this situation, for example, to displace the pointer upward on the screen requires a forward movement of the hand. This learned transformation between visual presentation and motor production is not innate, and can deteriorate under neuropathological conditions such as Alzheimer’s disease. To study this issue, two complementary approaches will address the following specific questions:

i) What is the effect of increasingly complex visuomotor transformations on patterns of motor errors in humans? In this project we will examine the patterns of motor behaviour associated with tasks involving increasingly complex visuomotor transformations. A comparison of error patterns produced during reaches with increasingly dissociated visual guidance will be used to ascertain the stage at which the cognitive dissociation is being processed. The performance of neurologically healthy young versus elderly adults will be compared, as well as neurologically healthy elderly versus elderly with Alzheimer's Disease. 

ii) What is the cortical representation underlying learned visuomotor associations in humans? We will address this question by using functional Magnetic Resonance Imaging to examine neural activity in the human brain during the performance of visually guided movements. Specifically, the motor task will remain invariant while the visual stimulus guiding the movement will become progressively less direct in order to test the hypothesis that the human parietal and premotor cortex are differentially involved in visuomotor tasks that are increasingly more dissociated. (see Gorbet et al. in Publications)

 

All material ©Lauren E. Sergio, School of Kinesiology and Health Science, York University, 2005.

These projects are funded by the Canadian Institutes of Health Research, the Natural Sciences and Engineering Research Council of Canada, the Canadian Foundation for Innovation, and the Ontario Innovation Trust

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