Relating motor cortical oscillations to motor γ-Aminobutyric acid (GABA)

Abstract

Event Abstract Back to Event Relating motor cortical oscillations to motor γ-Aminobutyric acid (GABA) William Gaetz1*, James C. Edgar1, D-J Wang1 and Timothy P. Roberts1 1 The Children's Hospital of Philadelphia and The University of Pennsylvania, Department of Radiology, United States Animal [1] and non-invasive human studies [2] demonstrate a strong relationship between cortical motor oscillations and the inhibitory neurotransmitter γ-Aminobutyric acid (GABA). A relationship between GABA concentration and cortical gamma oscillations was recently demonstrated in visual cortex [3]. Movement-related gamma (MRG), and post-movement beta rebound (PMBR) observed in humans may also depend on interneuronal GABA inhibitory currents [4]. Direct measures between motor cortex oscillations and motor cortex (MI) GABA, however, have not yet been demonstrated. The present study examined associations between PMBR and MRG and MI GABA. Adult subjects (N=8) made a right finger button response to a visual cue while whole-cortex MEG was obtained. PMBR (1-100 Hz) and PMG (65-90Hz) were estimated by first localizing contralateral MI using a differential SAM beamformer (Beta ERD; 15-30Hz). Time-frequency transforms were then applied to source waveforms from peak ERD locations, yielding frequency and power measures of PMBR and MRG oscillations. In the same subjects, single voxel (30x30x30mm) GABA magnetic response spectroscopy (MRS) was obtained using MEGA-PRESS. The MRS voxel was centered on the “hand-knob” of the left central sulcus. GABA measures were also obtained from a head coil reference phantom (50mM GABA). GABA levels were estimated as the ratio of the MI GABA integral to that of the phantom. PMBR power (% change) showed a marginally significant linear association with motor GABA concentration (r2 = 0.33, p=0.07). MRG frequency was associated with motor GABA concentration (r2 = 0.48, p=0.03). Present results support the hypothesis that motor cortical gamma power and frequency depend on MI GABA concentrations.