Abstract
Neuronal oscillatory activity in the beta band (15–30 Hz) is a prominent signal within the human sensorimotor cortex. Computational modeling and pharmacological modulation studies suggest an influence of GABAergic interneurons on the generation of beta band oscillations. Accordingly, studies in humans have demonstrated a correlation between GABA concentrations and power of beta band oscillations. It remains unclear, however, if GABA concentrations also influence beta peak frequencies and whether this influence is present in the sensorimotor cortex at rest and without pharmacological modulation. In the present study, we investigated the relation between endogenous GABA concentration (measured by magnetic resonance spectroscopy) and beta oscillations (measured by magnetoencephalography) at rest in humans. GABA concentrations and beta band oscillations were measured for left and right sensorimotor and occipital cortex areas. A significant positive linear correlation between GABA concentration and beta peak frequency was found for the left sensorimotor cortex, whereas no significant correlations were found for the right sensorimotor and the occipital cortex. The results show a novel connection between endogenous GABA concentration and beta peak frequency at rest. This finding supports previous results that demonstrated a connection between oscillatory beta activity and pharmacologically modulated GABA concentration in the sensorimotor cortex. Furthermore, the results demonstrate that for a predominantly right-handed sample, the correlation between beta band oscillations and endogenous GABA concentrations is evident only in the left sensorimotor cortex.
Highlights
Oscillatory activity in the beta (15–30 Hz) frequency range is a prominent signal in the human sensorimotor cortex, both at rest and during motor activity [1,2,3,4]
Due to cancellation of the measurements or distorted spectra, GABA+/Cr concentrations could not be estimated for the left sensorimotor, right sensorimotor and occipital Magnetic resonance spectroscopy (MRS) regions of interest (ROIs) in 4, 2, and 1 subjects, respectively
0.1034 0.0783 0.1000 0.1066 0.0110 individual HDT handedness scores as covariates yielded a significant difference between GABA+/Cr concentrations in the 3 MRS ROIs (F(2,12) = 4.024, p = 0.046, 95% CI [left sensorimotor: 0.084, 0.101; right sensorimotor: 0.09, 0.108; occipital: 0.093, 0.112])
Summary
Oscillatory activity in the beta (15–30 Hz) frequency range is a prominent signal in the human sensorimotor cortex, both at rest and during motor activity [1,2,3,4]. Beta band activity differs across areas and depends on motor output (see [5] for a review). There is increasing evidence that beta peak frequency (i.e., the frequency within the beta band with the highest power) is an important and functionally relevant parameter of oscillatory activity [9]. Neuronal activity in the motor cortex and electromyographic activity during movement is coherently coupled at ~20 Hz [11]. This 20 Hz motor cortical activity is thought to optimize motor output by maximal recruitment of motor neurons at a minimum discharge in the pyramidal tract [11]
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