Biology subjects

Ballard, H. K.

Publications and source records attributed to Ballard, H. K..

4 recordsLinked to original sources

bioRxiv2019

Using high-definition transcranial direct current stimulation to elucidate the role of the cerebello-thalamo-prefrontal network in explicit sequence learning

Though we have a general understanding of the brain areas involved in motor sequence learning, there is more to discover about the neural mechanisms underlying skill acquisition. Skill acquisition may be subserved, in part, by interactions between the cerebellum and prefrontal cortex through a cerebello-thalamo-prefrontal network. In prior work, we investigated this network by targeting the cerebellum; here, we explored the consequence of stimulating the dorsolateral prefrontal cortex using high-definition transcranial direct current stimulation (HD-tDCS) before administering an explicit motor sequence learning paradigm. Using a mixed within- and between-subjects design, we employed anodal (n = 24) and cathodal (n = 25) HD-tDCS (relative to sham) to temporarily alter brain function and examine effects on skill acquisition. The results indicate that both anodal and cathodal prefrontal stimulation impedes motor sequence learning, relative to sham. These findings suggest an overall negative influence of active prefrontal stimulation on the acquisition of a sequential pattern of finger movements. Collectively, this provides novel insight on the role of the dorsolateral prefrontal cortex in initial skill acquisition, when cognitive processes such as working memory are used. Exploring methods that may improve motor learning is important in developing therapeutic strategies for motor-related diseases and rehabilitation.

neuroscience↗

bioRxiv2019

Shaky Scaffolding: Age Differences In Cerebellar Activation Revealed Through Activation Likelihood Estimation Meta-Analysis

Cognitive neuroscience research has provided foundational insights into aging, but has focused primarily on the cerebral cortex. However, the cerebellum is subject to the effects of aging. Given the importance of this structure in the performance of motor and cognitive tasks, cerebellar differences stand to provide critical insights into age differences in behavior. But, our understanding of cerebellar functional activation in aging is limited. Thus, we completed a meta-analysis of neuroimaging studies across task domains. Unlike in the cortex where an increase in bilateral activation is seen during cognitive task performance with advanced age, there is less overlap in cerebellar activation across tasks in older adults relative to young. Conversely, we see an increase in activation overlap in older adults during motor tasks. We propose that this is due to inputs for comparator processing in the context of control theory (cortical and spinal) that may be differentially impacted in aging. These findings advance our understanding of the aging mind and brain.

neuroscience↗

bioRxiv2019

Effects of prefrontal tDCS on dopamine-mediated behavior and psychophysiology

The ability to manipulate dopamine in vivo through non-invasive, reversible mechanisms has the potential to impact clinical, translational, and basic research. Recent PET studies have demonstrated increased dopamine release in the striatum after prefrontal transcranial direct current stimulation (tDCS). We sought to extend this work by examining whether prefrontal tDCS could demonstrate an effect on behavioral and physiological correlates of subcortical dopamine activity. We conducted a between-subjects study (n = 30) with active and sham tDCS and used spontaneous eye blink rate (EBR), facial attractiveness ratings, and greyscales orienting bias as indirect proxies for dopamine functioning. The initial design and analyses were pre-registered (https://osf.io/gmnpc). Stimulation did not significantly affect any of the three measures, though effect sizes were often moderately large and were all in the predicted directions. Additional exploratory analyses suggested that stimulations effect on EBR might depend on pre-stimulation dopamine levels. Our results shed light on the sensitivity of indirect measures of dopamine in humans and add to a growing body of work demonstrating the importance of examining individual differences in tDCS response.

neuroscience↗

bioRxiv2019

The effects of cerebellar transcranial direct current stimulation on the cognitive stage of sequence learning

Though the cerebellum has been previously implicated in explicit sequence learning, the exact role of this structure in the acquisition of motor skills is not completely clear. The cerebellum contributes to both motor and non-motor behavior. Thus, this structure may contribute not only to the motoric aspects of sequence learning, but may also play a role in the cognitive components of these learning paradigms. Therefore, we investigated the consequence of both disrupting and facilitating cerebellar function using high definition transcranial direct current stimulation (HD-tDCS) prior to the completion of an explicit motor sequence learning paradigm. Using a mixed within- and between-subjects design, we employed cathodal (n=21) and anodal (n=23) tDCS (relative to sham), targeting the lateral posterior cerebellum, to temporarily modulate function and investigate the resulting effects on the acquisition of a sequential pattern of finger movements. Results indicate that cathodal stimulation has a positive influence on learning while anodal stimulation has the opposite effect, relative to sham. Though the cerebellum is presumed to be primarily involved in motor function and movement coordination, our results support a cognitive contribution that may come into play during the initial stages of learning. Using tDCS targeting the right posterior cerebellum, which communicates with the prefrontal cortex via closed-loop circuits, we found polarity-specific effects of cathodal and anodal stimulation on sequence learning. Thus, our results substantiate the role of the cerebellum in the cognitive aspect of motor learning and provide important new insights into the polarity-specific effects of tDCS in this area.\n\nNew & NoteworthyThe cerebellum contributes to motor and cognitive processes. Investigating the cognitive contributions of the cerebellum in explicit sequence learning stands to provide new insights into this learning domain, and cerebellar function more generally. Using HD-tDCS, we demonstrated polarity-specific effects of stimulation on explicit sequence learning. We speculate that this is due to facilitation of working memory processes. This provides new evidence supporting a role for the cerebellum in the cognitive aspects of sequence learning.

neuroscience↗