Biology subjects

Robertson, E. M.

Publications and source records attributed to Robertson, E. M..

4 recordsLinked to original sources

bioRxiv2023

Generalization of procedural motor sequence learning after a single practice trial

When humans begin learning new motor skills, they typically display early rapid performance improvements. It is not well understood how knowledge acquired during this early skill learning period generalizes to new, related skills. Here, we addressed this question by investigating factors influencing generalization of early learning from a skill A to a different, but related skill B. Early skill generalization was tested over four experiments (N = 2,095). Subjects successively learned two related motor sequence skills (skills A and B) over different practice schedules. Skill A and B sequences shared ordinal (i.e. - matching keypress locations), transitional (i.e. - ordered keypress pairs), parsing rule (i.e., distinct sequence events like repeated keypresses that can be used as a breakpoint for segmenting the sequence into smaller units) structures, or possessed no structure similarities. Results showed generalization for shared parsing rule structure between skills A and B after only a single 10-second practice trial of skill A. Manipulating the initial practice exposure to skill A (1 to 12 trials) and inter-practice rest interval (0 to 30s) between skills A and B had no impact on parsing rule structure generalization. Furthermore, this generalization was not explained by stronger sensorimotor mapping between individual keypress actions and their symbolic representations. In contrast, learning from skill A did not generalize to skill B during early learning when the sequences shared only ordinal or transitional structure features. These results document sequence structure that can be very rapidly generalized during initial learning to facilitate generalization of skill.

neuroscience↗

bioRxiv2022

Prefrontal stimulation disrupts motor memory consolidation at the micro timescale

Functional brain responses in hippocampo- and striato-cortical networks during initial motor sequence learning (MSL) are critical for memory consolidation. We have recently shown that prefrontal stimulation applied prior to initial MSL can alter these learning-related responses. In the present study, we investigated whether such stimulation-induced modulations of brain responses can influence motor memory consolidation at different timescales. Specifically, we examined the effect of prefrontal stimulation on the behavioral and neural responses associated to (i) fast consolidation processes occurring during short rest episodes interspersed with practice during initial learning (i.e., micro timescale) and (ii) slow consolidation process taking place across practice sessions separated by 24h (i.e., macro timescale). To do so, we applied active (inhibitory or facilitatory) or control theta-burst stimulation to the prefrontal cortex of young healthy participants before they were trained on an MSL task while their brain activity was recorded using functional magnetic resonance imaging (fMRI). Motor performance was retested, in the MRI scanner, after a night of sleep. Both our behavioral and brain imaging results indicate that while stimulation did not modulate consolidation at the macro timescale, it disrupted the micro-offline consolidation process. Specifically, our behavioral data indicate that active - as compared to control - stimulation resulted in a decrease in micro-offline gains in performance over the short rest intervals. At the brain level, stimulation disrupted activity in the caudate nucleus and the hippocampus during the micro-offline intervals. Additionally, multivariate pattern persistence from task into inter-practice rest episodes - which is thought to reflect the reactivation of learning-related patterns - was hindered by active prefrontal stimulation in the hippocampus and caudate nucleus. Importantly, stimulation also altered the link between the brain and the behavioral markers of the micro-offline consolidation process. These results collectively suggest that active prefrontal stimulation prior to MSL disrupted both the behavioral and neural correlates of motor memory consolidation at the micro timescale.

neuroscience↗

bioRxiv2021

Prefrontal stimulation prior to motor sequence learning alters multivoxel patterns in the striatum and the hippocampus

Motor sequence learning (MSL) is supported by dynamical interactions between hippocampal and striatal networks that are thought to be orchestrated by the prefrontal cortex. In the present study, we tested whether individually-tailored theta-burst stimulation of the dorsolateral prefrontal cortex (DLPFC) prior to MSL, can modulate multivoxel response patterns in the stimulated cortical area, the hippocampus and the striatum. Response patterns were assessed with multivoxel correlation structure analyses of functional magnetic resonance imaging data acquired during task practice and during resting-state scans before and after learning/stimulation. Results revealed that, across stimulation conditions, MSL induced greater modulation of task-related DLPFC multivoxel patterns than random practice. A similar learning-related modulatory effect was observed on sensorimotor putamen patterns under inhibitory stimulation. Furthermore, MSL as well as inhibitory stimulation affected (posterior) hippocampal multivoxel patterns at post-intervention rest. Exploratory analyses showed that MSL-related brain patterns in the posterior hippocampus persisted into post-learning rest preferentially after inhibitory stimulation. These results collectively show that prefrontal stimulation can alter multivoxel brain patterns in deep brain regions that are critical for the MSL process. They also suggest that stimulation influenced early offline consolidation processes as evidenced by a stimulation-induced modulation of the reinstatement of task pattern into post-learning wakeful rest.

neuroscience↗

bioRxiv2020

Hippocampal and striatal responses during motor learning are modulated byprefrontal cortex stimulation

While it is widely accepted that motor sequence learning (MSL) is supported by a prefrontal-mediated interaction between hippocampal and striatal networks, it remains unknown whether the functional responses of these networks can be modulated in humans with targeted experimental interventions. The present proof- of-concept study employed a comprehensive multimodal neuroimaging approach, including functional magnetic resonance (MR) imaging and MR spectroscopy, to investigate whether individually-tailored theta-burst stimulation of the dorsolateral prefrontal cortex can modulate responses in the hippocampus and striatum during motor learning. Our results indicate that stimulation influenced task-related connectivity patterns within hippocampo-frontal and striatal networks. Stimulation also altered the relationship between the levels of gamma-aminobutyric acid (GABA) in the stimulated prefrontal cortex and learning-related changes in both activity and connectivity in fronto-striato-hippocampal networks. This study provides the first experimental evidence that brain stimulation can alter motor learning-related functional responses in the striatum and hippocampus.

neuroscience↗