Theses and Dissertations
This collection includes both ASU Theses and Dissertations, submitted by graduate students, and the Barrett, Honors College theses submitted by undergraduate students.
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- Creators: Santello, Marco
Description
Understanding human-human interactions during the performance of joint motor tasks is critical for developing rehabilitation robots that could aid therapists in providing effective treatments for motor problems. However, there is a lack of understanding of strategies (cooperative or competitive) adopted by humans when interacting with other individuals. Previous studies have investigated the cues (auditory, visual and haptic) that support these interactions but understanding how these unconscious interactions happen even without those cues is yet to be explained. To address this issue, in this study, a paradigm that tests the parallel efforts of pairs of individuals (dyads) to complete a jointly performed virtual reaching task, without any auditory or visual information exchange was employed. Motion was tracked with a NDI OptoTrak 3D motion tracking system that captured each subject’s movement kinematics, through which we could measure the level of synchronization between two subjects in space and time. For the spatial analyses, the movement amplitudes and direction errors at peak velocities and at endpoints were analyzed. Significant differences in the movement amplitudes were found for subjects in 4 out of 6 dyads which were expected due to the lack of feedback between the subjects. Interestingly, subjects in this study also planned their movements in different directions in order to counteract the visuomotor rotation offered in the test blocks, which suggests the difference in strategies for the subjects in each dyad. Also, the level of de-adaptation in the control blocks in which no visuomotor rotation was offered to the subjects was measured. To further validate the results obtained through spatial analyses, a temporal analyses was done in which the movement times for the two subjects were compared. With the help of these results, numerous interaction scenarios that are possible in the human joint actions in without feedback were analyzed.
ContributorsAgrawal, Ankit (Author) / Buneo, Christopher (Thesis advisor) / Santello, Marco (Committee member) / Tillery, Stephen Helms (Committee member) / Arizona State University (Publisher)
Created2016
Description
The ability to inhibit a planned but inappropriate response, and switch to executing a goal-relevant motor response, is critically important for the regulation of motor behaviors. Inhibition and switching could be mediated by various control mechanisms. Proactive control uses contextual information (cues) to plan the response for the target stimulus (probe) based on the expectation of a response inhibition or switching stimulus combination. Previous work has reported the involvement of several brain areas associated with proactive inhibition and switching, e.g., dorsolateral prefrontal cortex, anterior cingulate cortex, inferior frontal junction, and pre-supplementary motor area. However, how these areas interact and their functional role in different types of cognitive control is still debated. An AX-version of the continuous performance task (AX-CPT) was used to examine proactive inhibition and switching of motor actions. In a typical AX-CPT trial, a contextual cue stimulus is presented, followed by a probe stimulus after a specific inter-stimulus interval. As part of a trial sequence, if a target cue and target probe are presented, a target response is to be provided when the probe is observed. Otherwise, a non-target response is to be provided for all other stimuli. A behavioral switching AX-CPT experiment (48 subjects) was conducted to explore the parameters that induce a proactive shift in the motor response. Participants who performed the AX-CPT task with relatively shorter interstimulus interval predominantly and consistently exhibited proactive control behavior. A follow-up pilot study (3 subjects) of response inhibition versus response switching AX-CPT was performed using 256-channel high-density electroencephalography (HD-EEG). HD-EEG was used to identify the time course of cortical activation in brain areas associated with response inhibition. It was observed that one out of three participants used a proactive strategy for response switching based on probe response error and probe response reaction time. Instantaneous amplitude spatial maps obtained from HD-EEG revealed cortical activity corresponding to conflict between proactively-prepared incorrect responses and reactively-corrected goal-relevant responses after the probe was presented.
ContributorsMysore, Archana Shashidhar (Author) / Santello, Marco (Thesis advisor) / Blais, Christopher (Committee member) / Brewer, Gene (Committee member) / Tillery, Stephen Helms (Committee member) / Arizona State University (Publisher)
Created2020
Description
The human hand is a complex biological system. Humans have evolved a unique ability to use the hand for a wide range of tasks, including activities of daily living such as successfully grasping and manipulating objects, i.e., lifting a cup of coffee without spilling. Despite the ubiquitous nature of hand use in everyday activities involving object manipulations, there is currently an incomplete understanding of the cortical sensorimotor mechanisms underlying this important behavior. One critical aspect of natural object grasping is the coordination of where the fingers make contact with an object and how much force is applied following contact. Such force-to-position modulation is critical for successful manipulation. However, the neural mechanisms underlying these motor processes remain less understood, as previous experiments have utilized protocols with fixed contact points which likely rely on different neural mechanisms from those involved in grasping at unconstrained contacts. To address this gap in the motor neuroscience field, transcranial magnetic stimulation (TMS) and electroencephalography (EEG) were used to investigate the role of primary motor cortex (M1), as well as other important cortical regions in the grasping network, during the planning and execution of object grasping and manipulation. The results of virtual lesions induced by TMS and EEG revealed grasp context-specific cortical mechanisms underlying digit force-to-position coordination, as well as the spatial and temporal dynamics of cortical activity during planning and execution. Together, the present findings provide the foundation for a novel framework accounting for how the central nervous system controls dexterous manipulation. This new knowledge can potentially benefit research in neuroprosthetics and improve the efficacy of neurorehabilitation techniques for patients affected by sensorimotor impairments.
ContributorsMcGurrin, Patrick M (Author) / Santello, Marco (Thesis advisor) / Helms-Tillery, Steve (Committee member) / Kleim, Jeff (Committee member) / Davare, Marco (Committee member) / Arizona State University (Publisher)
Created2017