Distinct Roles for Alpha- and Beta-Band Oscillations during Mental Simulation of Goal-Directed Actions

Abstract

Rhythmic neural activity within the alpha (8 -12 Hz) and beta (15-25 Hz) frequency bands is modulated during actual and imagined movements. Changes in these rhythms provide a mechanism to select relevant neuronal populations, although the relative contributions of these rhythms remain unclear. Here we use MEG to investigate changes in oscillatory power while healthy human participants imagined grasping a cylinder oriented at different angles. This paradigm allowed us to study the neural signals involved in the simulation of a movement in the absence of signals related to motor execution and sensory reafference. Movement selection demands were manipulated by exploiting the fact that some object orientations evoke consistent grasping movements, whereas others are compatible with both overhand and underhand grasping. By modulating task demands, we show a functional dissociation of the alpha-and beta-band rhythms. As movement selection demands increased, alpha-band oscillatory power increased in the sensorimotor cortex ipsilateral to the arm used for imagery, whereas beta-band power concurrently decreased in the contralateral sensorimotor cortex. The same pattern emerged when motor imagery trials were compared with a control condition, providing converging evidence for the functional dissociation of the two rhythms. These observations call for a re-evaluation of the role of sensorimotor rhythms. We propose that neural oscillations in the alpha-band mediate the allocation of computational resources by disengaging task-irrelevant cortical regions. In contrast, the reduction of neural oscillations in the beta-band is directly related to the disinhibition of neuronal populations involved in the computations of movement parameters.

Transcranial alternating current stimulation to the inferior parietal lobe decreases mu suppression to egocentric, but not allocentric hand movements

“…This rotation would arguably require a greater level of processing, and may explain Frenkel-Toledo and colleagues ' (2013) finding that an allocentric perspective of a movement induced greater -suppression compared to an egocentric perspective, as it is known that sensorimotor suppression is enhanced by task demands and cognitive load (Klimesch, Schimke, & Pfurtscheller, 1993;Klimesch et al, 1998;Brinkman et al, 2014). However, we did not observe a significant effect for the factor perspective, suggesting that this possibility is unlikely.…”

Distinct α- and β-band rhythms over rat somatosensory cortex with similar properties as in humans

“…Within cortex, the sensorimotor ␤-rhythm is classically thought to arise from motor, rather than somatosensory, regions (Brovelli et al 2002;Pfurtscheller et al 1997) and, therefore, has been mainly considered as a motor rhythm. In line with this, there is extensive evidence for a modulation of this rhythm by most aspects of movement: from movement execution (Jasper and Penfield 1949;Rougeul et al 1979), offset (Pfurtscheller et al 1997(Pfurtscheller et al , 1998, planning (Leocani et al 1997), preparation (Pfurtscheller et al 1998;Zhang et al 2008), inhibition (Pogosyan et al 2009;Swann et al 2009), and switching (Cheyne et al 2012;Gilbertson et al 2005;Stoffers et al 2001), to movement imagery (Brinkman et al 2014;Schnitzler et al 1997) and observation (Babiloni et al 2002;Koelewijn et al 2008;Orgs et al 2008, Pavlidou et al 2014. Furthermore, strong evidence for the motor function of the sensorimotor ␤-rhythm comes from the clear ␤-peak in the corticomuscular coherence: the coherence between the extracranial activity over the sensorimotor cortex and the EMG (Baker et al 1997;Salenius et al 1997).…”

Assessing Selectivity in the Basal Ganglia: The “Gearbox” Hypothesis

“…According to this popular theory, the BG 12 circuit is able to process those requests and finally select the most salient (or urgent) 13 potential action, via the direct BG pathway, while providing inhibition to the rest 14 competing channels via the indirect pathway [6,7]. 15 An increasing amount of neurophysiological evidence implicates the BG to selection 16 of voluntary motor actions and provides indirect verification of this hypothesis [8]. [9] 17 showed that the excess activation of the direct BG pathway in freely behaving mice, via 18 stimulation of MSN D1 neurons in the striatum, increases movement, while the 19 stimulation of the indirect pathway made the same animals to freeze.…”

“…In addition, 20 although both pathways are required for healthy action selection and were found to 21 contribute equally to the initiation of actions in [10], the indirect pathway is suppressed 22 during the execution of actions or action sequences [11], presumably because any 23 behavioural conflicts have already been resolved during movement [8]. 24 From another standpoint, low-frequency brain oscillations have been widely 25 implicated in both the function of the BG [12] and the process of decision 26 making [13][14][15][16][17]. Oscillations in the cortex mediate the processing of new 27 information [18], the dynamic formation of neural ensembles representing different 28 actions and the suppression of other task-irrelevant regions [19,20].…”

“…In the literature, there is cumulative evidence that strong alpha power is able to inhibit 754 task-irrelevant regions in the cortex and thus control information flow [15,20,67]. This 755 theory, which is known as gating by inhibition [68], proposes that strong alpha activity 756 is caused by GABAergic interneurons, which silence neuronal firing by providing a GABAergic inhibition, or other brain regions, and whether this mechanism can operate 762 in the same spatial scale that is required to inhibit complete neural ensembles.…”