TY - JOUR
T1 - Variable neural contributions to explicit and implicit learning during visuomotor adaptation
AU - Liew, Sook Lei
AU - Thompson, Tziporah
AU - Ramirez, Joel
AU - Butcher, Peter A.
AU - Taylor, Jordan A.
AU - Celnik, Pablo A.
N1 - Funding Information:
This research was funded by the National Institutes of Health (NIH) National Institute of Neurological Disorders and Stroke (NINDS) Intramural Research Program (S-LL) and Intramural Competitive Fellowship Award (S-LL), by the NIH National Institute of Child Health and Development (NICHD) and National Center for Medical Rehabilitation Research (NCMRR) Extramural Program (R01HD073147 to PC; K01HD091283 and K12HD055929 to S-LL), the NIH NINDS (R01 NS-084948 to JT) and the Princeton Neuroscience Institute’s Innovation Fund (JT). Its contents are solely the responsibility of the author and do not necessarily represent the official views of the NIH. The authors also wish to thank Dr. Samiran Bhattacharya for experimental assistance, and Dr. Leonardo Cohen, Dr. Robert Hardwick, and Dr. Ryan Roemmich for valuable insight and discussion.
Publisher Copyright:
© 2007 - 2018 Frontiers Media S.A. All Rights Reserved.
PY - 2018/9/18
Y1 - 2018/9/18
N2 - We routinely make fine motor adjustments to maintain optimal motor performance. These adaptations have been attributed to both implicit, error-based mechanisms, and explicit, strategy-based mechanisms. However, little is known about the neural basis of implicit vs. explicit learning. Here, we aimed to use anodal transcranial direct current stimulation (tDCS) to probe the relationship between different brain regions and learning mechanisms during a visuomotor adaptation task in humans. We hypothesized that anodal tDCS over the cerebellum (CB) should increase implicit learning while anodal tDCS over the dorsolateral prefrontal cortex (dlPFC), a region associated with higher-level cognition, should facilitate explicit learning. Using a horizontal visuomotor adaptation task that measures explicit/implicit contributions to learning (Taylor et al., 2014), we found that dlPFC stimulation significantly improved performance compared to the other groups, and weakly increased explicit learning. However, CB stimulation had no effects on either target error or implicit learning. Previous work showed variable CB stimulation effects only on a vertical visuomotor adaptation task (Jalali et al., 2017), so in Experiment 2, we conducted the same study using a vertical context to see if we could find effects of CB stimulation. We found only weak effects of CB stimulation on target error and implicit learning, and now the dlPFC effect did not replicate. To resolve this discrepancy, in Experiment 3, we examined the effect of context (vertical vs. horizontal) on implicit and explicit contributions and found that individuals performed significantly worse and used greater implicit learning in the vertical screen condition compared to the horizontal screen condition. Across all experiments, however, there was high inter-individual variability, with strong influences of a few individuals, suggesting that these effects are not consistent across individuals. Overall, this work provides preliminary support for the idea that different neural regions can be engaged to improve visuomotor adaptation, but shows that each region's effects are highly context-dependent and not clearly dissociable from one another. This holds implications especially in neurorehabilitation, where an intact neural region could be engaged to potentially compensate if another region is impaired. Future work should examine factors influencing interindividual variability during these processes.
AB - We routinely make fine motor adjustments to maintain optimal motor performance. These adaptations have been attributed to both implicit, error-based mechanisms, and explicit, strategy-based mechanisms. However, little is known about the neural basis of implicit vs. explicit learning. Here, we aimed to use anodal transcranial direct current stimulation (tDCS) to probe the relationship between different brain regions and learning mechanisms during a visuomotor adaptation task in humans. We hypothesized that anodal tDCS over the cerebellum (CB) should increase implicit learning while anodal tDCS over the dorsolateral prefrontal cortex (dlPFC), a region associated with higher-level cognition, should facilitate explicit learning. Using a horizontal visuomotor adaptation task that measures explicit/implicit contributions to learning (Taylor et al., 2014), we found that dlPFC stimulation significantly improved performance compared to the other groups, and weakly increased explicit learning. However, CB stimulation had no effects on either target error or implicit learning. Previous work showed variable CB stimulation effects only on a vertical visuomotor adaptation task (Jalali et al., 2017), so in Experiment 2, we conducted the same study using a vertical context to see if we could find effects of CB stimulation. We found only weak effects of CB stimulation on target error and implicit learning, and now the dlPFC effect did not replicate. To resolve this discrepancy, in Experiment 3, we examined the effect of context (vertical vs. horizontal) on implicit and explicit contributions and found that individuals performed significantly worse and used greater implicit learning in the vertical screen condition compared to the horizontal screen condition. Across all experiments, however, there was high inter-individual variability, with strong influences of a few individuals, suggesting that these effects are not consistent across individuals. Overall, this work provides preliminary support for the idea that different neural regions can be engaged to improve visuomotor adaptation, but shows that each region's effects are highly context-dependent and not clearly dissociable from one another. This holds implications especially in neurorehabilitation, where an intact neural region could be engaged to potentially compensate if another region is impaired. Future work should examine factors influencing interindividual variability during these processes.
KW - Cerebellum
KW - Context-dependent learning
KW - Dorsolateral prefrontal cortex (DLPFC)
KW - Explicit learning
KW - Implicit learning
KW - TDCS
KW - Visuomotor adaptation-learning
UR - http://www.scopus.com/inward/record.url?scp=85055132575&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85055132575&partnerID=8YFLogxK
U2 - 10.3389/fnins.2018.00610
DO - 10.3389/fnins.2018.00610
M3 - Article
C2 - 30279645
AN - SCOPUS:85055132575
SN - 1662-4548
VL - 12
JO - Frontiers in Neuroscience
JF - Frontiers in Neuroscience
IS - SEP
M1 - 610
ER -