Poster No:
2026
Submission Type:
Late-Breaking Abstract Submission
Authors:
Hayami Nishio1, Corey Wadsley1, Chris Horton1, Aaron Gudmundson2, Richard Edden3, Ian Greenhouse1
Institutions:
1University of Oregon, Eugene, OR, 2Johns Hopkins School of Medicine, Baltimore, MD, 3Johns Hopkins University, Baltimore, MD
First Author:
Co-Author(s):
Late Breaking Reviewer(s):
Naomi Gaggi, PhD
New York University Grossman School of Medicine
Rockaway Park, NY
Wei Zhang
Washington University in St. Louis
Saint Louis, MO
Introduction:
The role of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) within the sensorimotor cortex remains a key area of investigation in motor control. GABA may facilitate efficient movement execution by resolving competition among chosen and non-chosen motor representations. The sensorimotor cortex contralateral to a moving limb is widely recognized as a primary source of descending corticospinal signals for driving voluntary movement. Recent evidence has established the role of the ipsilateral sensorimotor cortex in movement preparation and response selection...1. However, whether GABA content predicts reaction times remains unclear. This study examines the relationship between GABA concentrations and reaction times in a within-hand versus between-hand instructed delay choice response tasks to elucidate ipsilateral and contralateral contributions.
Methods:
Thirty-four healthy adults (16F, 18-36 yrs, 6 left-handed) participated in our study. GABA concentrations were measured within the left and right sensorimotor cortex and an occipital control region using a MEGA-PRESS magnetic resonance spectroscopy (MRS) sequence with an unsuppressed water reference to account for tissue composition and serve as an internal GABA reference. At a separate visit, response reaction times were measured from hand muscles during performance of two instructed delay response tasks which required participants to select finger responses either within the right hand or between hands. Pearson's r correlations were computed to assess the relationship between sensorimotor GABA and reaction times.
Results:
Higher GABA concentrations in the right sensorimotor cortex correlated with faster reaction times for the task involving response selection within the right hand (r = -0.320, BF10 = 1.866). Additionally, right sensorimotor GABA was negatively correlated with reaction times in the between hands condition when responding with the right hand (r = -0.386, BF10 = 3.937), but did not correlate with left hand reaction times (r = -0.264, BF10 = 1.095). In contrast, left sensorimotor GABA levels did not significantly predict reaction times for either condition (BF10 < 0.43), and no significant correlations were observed between occipital GABA levels and reaction times (BF < 1.0).
Conclusions:
Our results suggest GABAergic tone within the sensorimotor cortex facilitates ipsilateral hand responses, regardless of whether the response occurs within hand or between hands. This complements prior findings demonstrating sensorimotor cortex GABAergic tone correlates with intrinsic corticospinal excitability, which in turn correlates with reaction time...2. We speculate the observed relationship reflects interhemispheric specific roles in choice response tasks. The laterality aspect of our findings further suggests that inhibition within the ipsilateral sensorimotor cortex has a potential role in handedness. Moreover, it highlights a possible role for ipsilateral sensorimotor cortex GABAergic inhibition in executing prepared responses...1.
Brain Stimulation:
Non-invasive Magnetic/TMS 2
TMS
Perception, Attention and Motor Behavior:
Motor Planning and Execution 1
Keywords:
GABA
Hemispheric Specialization
Magnetic Resonance Spectroscopy (MRS)
Motor
Neurotransmitter
Transcranial Magnetic Stimulation (TMS)
1|2Indicates the priority used for review
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Please indicate below if your study was a "resting state" or "task-activation” study.
Task-activation
Healthy subjects only or patients (note that patient studies may also involve healthy subjects):
Healthy subjects
Was this research conducted in the United States?
Yes
Are you Internal Review Board (IRB) certified?
Please note: Failure to have IRB, if applicable will lead to automatic rejection of abstract.
Yes, I have IRB or AUCC approval
Were any human subjects research approved by the relevant Institutional Review Board or ethics panel?
NOTE: Any human subjects studies without IRB approval will be automatically rejected.
Yes
Were any animal research approved by the relevant IACUC or other animal research panel?
NOTE: Any animal studies without IACUC approval will be automatically rejected.
No
Please indicate which methods were used in your research:
TMS
Behavior
Other, Please specify
-
MR Spectroscopy
For human MRI, what field strength scanner do you use?
3.0T
Provide references using APA citation style.
Bundy, D.T. (2020). The Cortical Physiology of Ipsilateral Limb Movements. Trends in Neuroscience, 42(11), 825-839.
Greenhouse, I., (2017). Individual Differences in Resting Corticospinal Excitability Are Correlated with reaction time and GABA Content in Motor Cortex. Journal of Neuroscience 37(10), 2686-2696.
No