19 Exploring GABA Concentration Changes in Sensorimotor Cortex in Older Adults During Motor & Cognitive Performance

Objective:Aging is associated with changes in cortical excitability which may affect motor learning and cognitive function via selective modulation of gamma aminobutyric acid (GABA). Previous studies using magnetic resonance spectroscopy (MRS) to measure GABA in older adults found that increased baseline GABA levels in the sensorimotor cortex (M1S1) were associated with better motor performance. GABA levels in M1S1 have tended to decrease during the execution of a repeated motor sequence. The dynamic change in GABA density in M1S1 in older adults is currently unknown and represents a critical gap in our understanding of how it could impact motor learning and cognitive performance. As such, the purpose of the current study is to quantify changes in cortical GABA during motor learning in the aging brain and examine those changes in relation to motor and cognitive performance. We hypothesize that older adults with greater dynamic range in M1S1 GABA levels will display more efficient motor learning and increased cognitive scores.Participants and Methods:We report on a total of 18 healthy older adults aged 64 to 80 years (M = 70.44, SD = 4.99, 12 females). Using MRS at 3T, we measured changes in GABA concentration in M1S1 at rest, during an eight or 12 finger-movement motor entrainment task, and during a recall task. Gannett was used for GABA quantification relative to water. Change in GABA was calculated by subtracting Rest1 GABA from Recall1 GABA. In a separate session, participants completed a battery of cognitive assessments. We computed linear regressions to examine the relationship between dynamic GABA change, recall accuracy of the motor task and cognitive performance.Results:In relation to motor performance, we found that both greater baseline (Rest1) GABA levels and greater dynamic change in GABA significantly predicted better recall accuracy on the motor task. For cognitive performance, we found that greater dynamic change in GABA significantly predicted better performance on Word Reading in the Stroop Color and Word Test and Delayed Recall in the Hopkins Verbal Learning Test (HVLT). No additional significant relationships were found for the remaining cognitive assessments.Conclusions:Older adults who were able to accurately perform the task had a greater dynamic change in GABA and increased baseline GABA levels. These adults with greater dynamic change also had better cognitive performance on HVLT Delay and Stroop Word Reading. This modulation of GABA associated with better performance could be related to changes in neuroplasticity. Although these results are in the preliminary stages, they point to a greater understanding of aging related changes in motor and cognitive performance. We’ll continue to explore the relationship between sensory motor performance and changes in GABA concentration as a potential predictor for cognitive performance and future rehabilitation.