Identifying the cognitive and neural mechanisms underlying the effects of prism adaptation on attention and perceptual biases.

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When we perform a simple motor task like throwing a ball to someone we do not always reach our intended target. However, our motor system has the capability of adjusting our future movements based on movement errors me make in order to help us reach the intended target on subsequent throws. This type of motor learning can be studied in the lab using prism glasses that shift vision in one direction, for example, to the right. If you ask someone to reach to a target while wearing these rightward shifting prisms they will initially reach too far to the right. However, after several more reaches, the person learns to adjust their movements leftward to compensate for the rightward visual shift. Early research indicated that only the parts of the body involved in adapting to prisms were affected (e.g., the eyes and the hand used). However, more recent research suggests that this simple motor learning procedure can also influence how we are able pay attention to our surroundings. For example, some of Dr. Striemer’s previous work has demonstrated that rightward prism adaptation, which leads to a leftward adjustment in movements, can actually make it easier for patients with right hemisphere brain damage to pay more attention to objects on their left side. Similarly, leftward prism adaptation, which leads to a rightward adjustment in movements, can also alter the ability of healthy adults to pay attention to their left side (for a brief period of time). This suggests that the cognitive and neural mechanisms controlling prism adaptation (a form of motor learning) are closely related to the cognitive and neural mechanisms that control attention. The long-term objective of Dr. Striemer’s research program is to better understand the cognitive and neural mechanisms that allow the attention and motor systems to interact. Thus, prism adaptation represents an ideal paradigm to investigate this interaction. The work proposed here will help scientists better understand how prism adaptation influences attention in healthy adults by focusing on three critical short-term objectives: 1) We will explore how the size of the error signal (e.g., how far to the right you initially reach when wearing right shifting prisms) generated during prism adaptation is related to the effects of prisms on attention. This will be examined in a series of experiments by manipulating the magnitude of prism shift used (i.e., 5° vs. 10° vs. 20°). 2) We will examine which adaptation procedures, and which sensory signals (e.g., vision or sensed arm position), result in the largest effects of prisms on attention. We will investigate this in a number of experiments by manipulating whether or not participants have feedback of their reaching hand during prism adaptation. And 3), in another set of experiments we will explore whether increasing neural activity in brain regions that are thought to be important for prism adaptation will lead to larger and longer lasting effects of prisms on attention. This will be accomplished using transcranial direct current stimulation (tDCS), a non-invasive brain stimulation technique. This work has important implications for a number of different areas, and will benefit Canadians in a number of ways. First, the knowledge obtained from these studies will help scientists better understand the basic mechanisms underlying motor learning, and how it can influence attention. Second, this work can be applied to designing more efficient methods to rehabilitate attention problems in patients with brain damage. Finally, this work can also be applied to engineering to help design better systems for controlling prosthetic limbs, or robots, which can utilize sensory feedback signals from movement errors to optimize future movements.