Dissertation Defense: Factors Influencing how Electrotactile Stimuli are Consciously Perceived

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About this Dissertation

Accurately perceiving the physical interactions with objects, or touch, is critical to successfully perform daily physical activities, like holding a cup, hugging a loved one, or learning new skills such as playing a musical instrument. However, roughly 30% of individuals in the United States experience difficulty or inability in detecting and interpreting touch-related stimuli, which can lead to a decrease in quality of life and performance in everyday tasks. Consequently, understanding the various factors that influence intact touch perception is of significant interest. These factors include arm dominance, nerve stimulated, location of stimulation, biological sex, age of a participant, mental effort associated with the task, and how these all interact. In clinical settings, assessments of touch-related perception are commonly used to diagnose impairments. However, existing assessment methods often inadequately consider the various factors that influence intact perception. As a result, recent investigations suggest that these assessments are insufficient. Here, we further explore the different factors that can influence touch perception in typical populations, namely young and older adults. If we can more greatly understand the different factors that influence touch perception in individuals who are typical, then we can better identify when and why impairments occur in clinically-relevant populations.

This work first examines the various factors that influence touch perception, and how they interact. Participants were asked to report whether they could perceive an externally applied stimulus (touch-related task) while at rest. This approach utilized electrical stimulation to assess touch perception, which is easily manipulated and controlled. Utilizing this protocol in both younger and older adults, this work suggests that factors such as the nerve stimulated, location of stimulation, participant sex, and their interactions could impact touch-related perception in young adults. Additionally, this body of work suggests that in older adults factors such as age, location, nerve, and their interactions could influence touch perception. However, contrary to our preliminary findings and existing literature, no effect of arm dominance was observed. Combined, this work suggests that when assessing intact touch perception while at rest, factors such as nerve, location, age, sex, and their interactions should be considered. 

This work next explores whether the mental resources allocated to perceiving touch influence touch-related perception in younger adults. Participants were asked to complete two tasks at the same time (one touch-related and one sound-related) to determine if performing both tasks at once would affect their ability to detect or differentiate between touch-related stimuli. This approach also examined whether the type of touch task (detection versus discrimination) influenced outcomes. Findings from this body of work suggest that factors such as the nerve stimulated and arm used can impact touch-related perception. However, performing the auditory task at the same time did not influence touch perception in younger adults. Notably, small impacts were observed, raising the possibility that observed effects may not fully reflect meaningful physiological differences. These findings highlight the importance of evaluating both statistical and physiological significance when interpreting results related to touch perception.

Lastly, this work explores whether the mental resources allocated to perceiving touch influence touch-related perception in older adults. Participants were asked to complete two tasks at the same time (one touch-related and one sound-related) to determine if performing both tasks at once would affect their ability to detect or differentiate between touch-related stimuli. This approach also examined whether the type of auditory task (i.e., detection versus discrimination) and the type of touch task (i.e., detection versus discrimination) influenced outcomes. Findings from this body of work suggest that performing a more mentally demanding task (discrimination) made it harder for older adults to accurately detect touch stimuli. When the task was less demanding (detection), participants had greater variability in detecting touch stimuli. These findings suggest that as mental demands increase, touch-related perception may become less accurate or more varied in older adults.

Overall, this work emphasizes the importance of considering multiple factors when performing touch-related examinations. The findings demonstrate that characteristics such as age, location and nerve stimulated, mental demands, and their interactions can meaningfully shape how touch is experienced in both younger and older adults. These findings have implications for enhancing tactile assessments, particularly in clinical settings where precise measurements are crucial for accurate diagnoses and interventions. By incorporating these factors into evaluations for tactile perception, clinicians can provide more individualized assessments, ultimately leading to more effective and personalized treatments for those with tactile impairments.