Neuronal oscillations in deep brain structures regulate behavioral sequences
Scientists at the Charité − Universitätsmedizin Berlin have discovered which brain structures are responsible for the acquisition of sequential behaviors such as playing a piano or riding a bicycle. They have also succeeded in decoding the underlying neuronal processes. The results of their study have now been published in the scientific journal Brain*.
Once learned, behaviors such as riding a bicycle or playing a piano can be repeated automatically. The human ability to recognize, acquire and produce series of ordered events or actions is known as sequential behavior. This kind of behavior entails several individual movements, which are arranged in a specific temporal order with a starting and an end point. Following learning, sequential behavior becomes automatic and can be produced repeatedly without our conscious attention.
The Movement Disorders Unit of the Department of Neurology at the Charité's Campus Virchow-Klinikum examined which patterns of neuronal activity regulate these recurring behavioral sequences in the brain, in particular in patients with Parkinson's disease. Parkinsonian patients typically exhibit impaired sequential behavior. This manifests for instance in their difficulties initiating or terminating a simple walking sequence (gait abnormality). The so-called basal ganglia, which are structures lying deep in the brain and that substantially contribute to learning and control of movements, are partially responsible for the motor impairment in those patients.
"In our study, we investigated for the first time which neuronal processes in the basal ganglia contribute to the acquisition of sequential behavior in humans.“, explained the lead author Dr. Maria Herrojo Ruiz. This was achieved by directly recording neuronal activity in a specific structure of the basal ganglia, the nucleus subthalamicus, in patients that underwent deep brain stimulation (DBS) for the treatment of advanced Parkinson's disease. This therapy consists of implanting electrodes in the brain and using a stimulator to send electrical impulses to the targeted brain regions, which results in an improvement in some of the Parkinson's symptoms. In the context of the study, the patients were asked to practice short musical sequences on a piano while electrophysiological signals from the subthalamic nucleus were recorded.
With this approach it was possible for the scientists to demonstrate that the basal ganglia play a key role in the encoding of the start and end points of behavioral sequences. Furthermore, they determined the exact modulation of electrophysiological rhythms known as 'oscillations' that are responsible for this effect. Patients who were able to play more skillfully the musical sequences exhibited a reduction in the so-called beta oscillations (frequency range of 13-30 Hz), before the first and last elements of the sequence. These elements constitute the sequence boundaries. By contrast, patients who had difficulties in playing the pieces showed a decrease in beta oscillations at the elements within the sequence, not at the boundaries. Dr. María Herrojo Ruiz explains: "Through their ability to encode the start and end points, the basal ganglia contribute to the concatenation of series of single movements into units of action and thus play an important role in the formation of automatic behavioral patterns in the brain”. The Head of the Research Group, Prof. Dr. Andrea Kühn adds: “Our findings also underscore how the enhanced level of beta oscillations typically found in the basal ganglia of patients with Parkinson's disease contributes to the extent of impairment suffered by these patients."
* Herrojo Ruiz M, Rusconi M, Brücke C, Haynes J.-D, Schönecker T, Kühn A. A. Encoding of sequence boundaries in the subthalamic nucleus of patients with Parkinson's disease. Brain 2014 July 16. Doi: 10.1093/brain/awu191
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Dr. María Herrojo Ruiz
Department of Neurology with Experimental Neurology
Virchow-Klinikum
t: +49 30 450 560 373
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