Stimulus uncertainty enhances motor cortical plasticity induced with a paired associative stimulation paradigm
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1
The University of Queensland, Queensland Brain Institute, Australia
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2
The University of Queensland, School of Psychology, Australia
Neuroplasticity manifests as a change in structure and function of the central nervous system, and is important for memory formation, skill acquisition and recovery following injury. A factor known to influence plasticity mechanisms is stimulus uncertainty. An uncertain stimulus can be more conducive to learning than a predictable one. In humans, neuroplasticity can be induced non-invasively in primary motor cortex with paradigms that employ transcranial magnetic stimulation (TMS). These paradigms show some promise in promoting functional recovery after stroke, but their effectiveness in the clinical domain is hampered by substantial effect variability. One such paradigm, paired associative stimulation (PAS), induces plasticity by repeatedly pairing an electrical stimulus delivered to the median nerve in the wrist, with TMS of the contralateral motor cortex 25 ms later. This study aimed to investigate whether stimulus uncertainty influences the effectiveness of PAS-induced plasticity. Participants (n = 28) attended two sessions during which a modified PAS protocol was used to introduce stimulus uncertainty by randomly including unpaired (TMS-only) stimulation throughout PAS. Prior to each paired or unpaired trial, an auditory stimulus was delivered at a contingency that was either predictive (no uncertainty) or random (maximum uncertainty) regarding the subsequent paired or unpaired stimulation. Based on evidence that probabilistic encoding of uncertainty modulates learning in low-level sensory areas, it was predicted that PAS-induced plasticity would be greater in the maximum uncertainty condition. The results demonstrated PAS-induced plasticity effects, but only for the random contingency condition. The findings have implications for research aimed at optimising plasticity paradigms for therapeutic application, and suggest that manipulating stimulus uncertainty can boost plasticity induction.
Keywords:
Learning,
Motor Cortex,
Transcranial Magnetic Stimulation,
plasticity,
predictive coding,
entropy
Conference:
XII International Conference on Cognitive Neuroscience (ICON-XII), Brisbane, Queensland, Australia, 27 Jul - 31 Jul, 2014.
Presentation Type:
Poster
Topic:
Memory and Learning
Citation:
Sale
M,
Nydam
A,
Kamke
M and
Mattingley
J
(2015). Stimulus uncertainty enhances motor cortical plasticity induced with a paired associative stimulation paradigm.
Conference Abstract:
XII International Conference on Cognitive Neuroscience (ICON-XII).
doi: 10.3389/conf.fnhum.2015.217.00336
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Received:
19 Feb 2015;
Published Online:
24 Apr 2015.
*
Correspondence:
Dr. Martin Sale, The University of Queensland, Queensland Brain Institute, Brisbane, Australia, m.sale@uq.edu.au