Biology subjects

Wallace, D. G.

Publications and source records attributed to Wallace, D. G..

3 recordsLinked to original sources

bioRxiv2022

Rapid loss of fine motor skills after low dose space radiation exposure

Sensorimotor function, motivation, and attentional processes are fundamental aspects of behavioral organization during skilled tasks. NASAs planned expedition to Mars will expose astronauts to space radiation (SR) that has the potential to impair performance in mission critical tasks. Impairments in task accuracy and movement kinematics have been previously reported during string-pulling behavior ~7 months after SR exposure. If similar SR-induced sensorimotor deficits emerge at earlier times, then astronauts may have compromised in-flight performance disruptions while performing skilled tasks in critical situations, such as when manipulating controls or performing seat egress. Due to the possibility that such performance losses may compromise mission success, it is critical to determine if sensorimotor, motivation, or attentional deficits occur acutely after SR exposure at a time point that corresponds to in-flight performance. Male Wistar rats were thus exposed to either 10 cGy simplified galactic cosmic radiation (GCRsim), 10 cGy 4Helium (4He), or no radiation at all (Sham), and string-pulling behavior was assessed approximately 72 hours later. Following exposure to SR, rats (4He) took more time to approach the string to initiate string-pulling behavior and to pull in the string to reach the Cheerio (4He and GCRsim) relative to Sham rats. 4He-exposed rats also exhibited a greater number of misses and less contacts relative to both Sham and GCRsim-exposed rats. Further, rats exposed to 4He demonstrated less concentrated reach endpoints with both the left and right hands compared to GCR-exposed rats. This work suggests that sensorimotor function and motivation and/or attentional processes were impaired 72 hours after 4He-radiation exposure.

animal behavior and cognition↗

bioRxiv2022

String-Pulling as a Behavioral Assessment of Skilled Forelimb Motor Function in a Middle Cerebral Artery Occlusion Rat Model

Stroke is a leading cause of long-term disability in humans and frequently results in bilateral impairments in fine motor control. Many behavioral tasks used to assess rodent models of stroke evaluate a single limb; however, recent work has demonstrated that bilateral hand-over-hand movements used to pull in a string assess skilled movement of both hands. Devascularization focused on the forelimb portion of sensorimotor cortex has been observed to produce persistent disruptions in the topographical organization of string-pulling behavior. The current study examined changes in string-pulling after a more clinically relevant rodent model of stroke via middle cerebral artery occlusion (MCAO). Detailed movement analyses revealed disruptions in the bilateral organization of string-pulling and fine motor control of both hands. Rats missed the string more often with both hands, and when the string was missed on the impaired side, rats continued to cycle through subcomponents of string-pulling behavior as if the string were grasped in the hand. Rats also failed to make a grasping motion with the impaired hand when the string was missed and instead, demonstrated an open-handed raking-like motion. No differences were found in time to approach or to complete the string-pulling task to obtain a reward, demonstrating the importance of using a detailed functional analysis of movement to detect changes in performance. String-pulling behavior is sensitive at detecting changes in bilateral rhythmical hand control following MCAO providing a foundation for future work to investigate other models of stroke and to evaluate the efficacy of therapeutic interventions that enhance neuroplasticity.

animal behavior and cognition↗

bioRxiv2019

Reach and Grasp Altered in Pantomime String-Pulling: A Test of the Action/Perception Theory in a Bilateral Reaching Task

The action/perception theory of cortical organization is supported by the finding that pantomime hand movements of reaching and grasping are different from real movements. Frame-by-frame video analysis and MATLAB(R) based tracking examined real/pantomime differences in a bilaterally movement, string-pulling, pulling down a rope with hand-over-hand movements. Sensory control of string-pulling varied from visually-direct when cued, visually-indirect when non cued and somatosensory controlled in the absence of vision. Cued grasping points were visual tracked and the pupils dilated in anticipation of the grasp, but when noncued, visual tracking and pupil responses were absent. In real string-pulling, grasping and releasing the string featured an arpeggio movement in which the fingers close and open in the sequence 5 through 1 (pinki first, thumb last); in pantomime, finger order was reversed, 1 through 5. In real string-pulling, the hand is fully opened and closed to grasp and release; in pantomime, hand opening was attenuated and featured a gradual opening centered on the grasp. The temporal structure of arm movements in real string-pulling featured up-arm movements that were faster than down-arm movement. In pantomime, up/down movements had similar speed. In real string-pulling, up/down arm movements were direct and symmetric; in pantomime, they were more circular and asymmetric. That pantomime string-pulling featured less motoric and temporal complexity than real string-pulling is discussed in relation to the action/perception theory and in relation to the idea that pantomimed string-pulling may feature the substitution of gestures for real movement.\n\nSignificant StatementMost laboratory studies investigating hand movements made by humans feature single hand movements, the current study presents a novel string-pulling task to study bimanual coordination of left and right hands in real and pantomime conditions. The results show that pantomime string-pulling featured less motoric and temporal complexity than real string-pulling. These findings are relevant to the contemporary theory of action and perception that the dorsal stream (parietal cortex) is related to actions and the ventral stream (temporal cortex) is related to perception.

neuroscience↗