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- All Subjects: Startle-evoked Movements
- All Subjects: Behavior
- Creators: Santello, Marco
- Member of: Barrett, The Honors College Thesis/Creative Project Collection
- Resource Type: Text
Description
Most daily living tasks consist of pairing a series of sequential movements, e.g., reaching to a cup, grabbing the cup, lifting and returning the cup to your mouth. The process by which we control and mediate the smooth progression of these tasks is not well understood. One method which we can use to further evaluate these motions is known as Startle Evoked Movements (SEM). SEM is an established technique to probe the motor learning and planning processes by detecting muscle activation of the sternocleidomastoid muscles of the neck prior to 120ms after a startling stimulus is presented. If activation of these muscles was detected following a stimulus in the 120ms window, the movement is classified as Startle+ whereas if no sternocleidomastoid activation is detected after a stimulus in the allotted time the movement is considered Startle-. For a movement to be considered SEM, the activation of movements for Startle+ trials must be faster than the activation of Startle- trials. The objective of this study was to evaluate the effect that expertise has on sequential movements as well as determining if startle can distinguish when the consolidation of actions, known as chunking, has occurred. We hypothesized that SEM could distinguish words that were solidified or chunked. Specifically, SEM would be present when expert typists were asked to type a common word but not during uncommon letter combinations. The results from this study indicated that the only word that was susceptible to SEM, where Startle+ trials were initiated faster than Startle-, was an uncommon task "HET" while the common words "AND" and "THE" were not. Additionally, the evaluation of the differences between each keystroke for common and uncommon words showed that Startle was unable to distinguish differences in motor chunking between Startle+ and Startle- trials. Explanations into why these results were observed could be related to hand dominance in expert typists. No proper research has been conducted to evaluate the susceptibility of the non-dominant hand's fingers to SEM, and the results of future studies into this as well as the results from this study can impact our understanding of sequential movements.
ContributorsMieth, Justin Richard (Author) / Honeycutt, Claire (Thesis director) / Santello, Marco (Committee member) / Harrington Bioengineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
Startle-evoked-movement (SEM), the involuntary release of a planned movement via a startling stimulus, has gained significant attention recently for its ability to probe motor planning as well as enhance movement of the upper extremity following stroke. We recently showed that hand movements are susceptible to SEM. Interestingly, only coordinated movements of the hand (grasp) but not individuated movements of the finger (finger abduction) were susceptible. It was suggested that this resulted from different neural mechanisms involved in each task; however it is possible this was the result of task familiarity. The objective of this study was to evaluate a more familiar individuated finger movement, typing, to determine if this task was susceptible to SEM. We hypothesized that typing movements will be susceptible to SEM in all fingers. These results indicate that individuated movements of the fingers are susceptible to SEM when the task involves a more familiar task, since the electromyogram (EMG) latency is faster in SCM+ trials compared to SCM- trials. However, the middle finger does not show a difference in terms of the keystroke voltage signal, suggesting the middle finger is less susceptible to SEM. Given that SEM is thought to be mediated by the brainstem, specifically the reticulospinal tract, this suggest that the brainstem may play a role in movements of the distal limb when those movements are very familiar, and the independence of each finger might also have a significant on the effect of SEM. Further research includes understanding SEM in fingers in the stroke population. The implications of this research can impact the way upper extremity rehabilitation is delivered.
ContributorsQuezada Valladares, Maria Jose (Author) / Honeycutt, Claire (Thesis director) / Santello, Marco (Committee member) / Harrington Bioengineering Program (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2016-12
Description
Motor learning is the process of improving task execution according to some measure of performance. This can be divided into skill learning, a model-free process, and adaptation, a model-based process. Prior studies have indicated that adaptation results from two complementary learning systems with parallel organization. This report attempted to answer the question of whether a similar interaction leads to savings, a model-free process that is described as faster relearning when experiencing something familiar. This was tested in a two-week reaching task conducted on a robotic arm capable of perturbing movements. The task was designed so that the two sessions differed in their history of errors. By measuring the change in the learning rate, the savings was determined at various points. The results showed that the history of errors successfully modulated savings. Thus, this supports the notion that the two complementary systems interact to develop savings. Additionally, this report was part of a larger study that will explore the organizational structure of the complementary systems as well as the neural basis of this motor learning.
ContributorsRuta, Michael (Author) / Santello, Marco (Thesis director) / Blais, Chris (Committee member) / School of Mathematical and Statistical Sciences (Contributor) / School of Molecular Sciences (Contributor) / School of Human Evolution & Social Change (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05