The Acute GABAergic Effects of Mindfulness Meditation in the Motor Cortex of University Students

Background: Previous research demonstrated the cortical silent period (CSP) protocol, a measure of GABAB related cortical inhibition, reliably reflects differences between psychiatric populations and healthy controls. Furthermore, cognitive behaviour therapy (CBT) and mindfulness meditation (MM) programs have been shown to affect CSP positively. In this pilot study, we assessed acute effects of MM by measuring pre-post differences in participants with minimal experience with meditation.

Methods: The CSP protocol was employed to measure cortical inhibition before and after a single 40 minute guided meditation session. Furthermore, involvement with the practice before and after the appointment was used to determine if experience affected the degree of change in cortical inhibition and whether this change could predict a participants likelihood of attending weekly meditation tutorials. Finally, increases were expected to be correlated with 5 measures of self-reports of anxiety, depression, and mindfulness.

Results: Significant pre-post differences were found after 40 minutes of MM in 67 students with minimal experience with meditation (t(66) = 2.334, p = 0.011). Students who had no prior meditation experience (< 2 hours) exhibited significant increases in CSP (delta x = 0.014 s) compared to those with more experience (F(1, 1) = 5.388, p = 0.024, η2 = 0.079). Change in CSP did not predict likelihood of continued attendance (F(1, 1) = 1.242, p = 0.269). Finally, baseline CSP measures were found to be negatively correlated with self-reports of negative automatic thoughts (r = -0.303, p = 0.008, n = 63).

Discussion: Findings indicated improved cortical inhibition in minimally experienced MM practitioners after 40 minutes of meditation and that experience plays a role in the effectiveness of a single guided mindfulness meditation session. Furthermore, the degree of change in CSP was predicted by the severity of self-reported automatic thoughts possibly as a result of the decreased difficulty of staying focused with fewer intrusive thoughts allowing for a more equanimous meditation session. This evidence suggests GABAergic neurotransmission may prove to be involved in a neurophysiological mode of action and that automatic thoughts may be a psychological variable involved in a cognitive mechanism underlying the health benefits associated with mindfulness meditation.