The Impact of a Cognitive-Behavioral Therapy on Event-Related Potentials in Patients with Tic Disorders or Body-Focused Repetitive Behaviors

Abstract

Context: Tic disorders (TD) are characterized by the presence of non-voluntary contractions of functionally related groups of skeletal muscles in one or multiple body parts. Patients with body-focused repetitive behaviors (BFRB) present frequent and repetitive behaviors, such as nail biting or hair pulling. TD and BFRB can be treated with a cognitive-behavioral therapy (CBT) that regulates the excessive amount of sensorimotor activation and muscular tension. Our CBT, which is called the cognitive-psychophysiological (CoPs) model, targets motor execution and inhibition, and it was reported to modify brain activity in TD. However, psychophysiological effects of therapy are still poorly understood in TD and BFRB patients. Our goals were to compare the event-related potentials (ERP) of TD and BFRB patients to control participants and to investigate the effects of the CoPs therapy on the P200, N200, and P300 components during a motor and a non-motor oddball task.

Method: Event-related potential components were compared in 26 TD patients, 27 BFRB patients, and 27 control participants. ERP were obtained from 63 EEG electrodes during two oddball tasks. In the non-motor task, participants had to count rare stimuli. In the motor task, participants had to respond with a left and right button press for rare and frequent stimuli, respectively. ERP measures were recorded before and after therapy in both patient groups.

Results: CoPs therapy improved symptoms similarly in both clinical groups. Before therapy, TD and BFRB patients had reduced P300 oddball effect during the non-motor task, in comparison with controls participants. An increase in the P300 oddball effect was observed posttherapy. This increase was distributed over the whole cortex in BFRB patients, but localized in the parietal area in TD patients.

Discussion: These results suggest a modification of neural processes following CoPs therapy in TD and BFRB patients. CoPs therapy seems to impact patients' attentional processes and context updating capacities in working memory (i.e., P300 component). Our results are consistent with a possible role of the prefrontal cortex and corpus callosum in mediating interhemispheric interference in TD.

Keywords: Tourette syndrome; body-focused repetitive behaviors; cognitive–behavioral therapy; cognitive–psychophysiological therapy; electrophysiology; event-related potentials; habit disorder; tic disorders.

Figure 1

ERP waveforms during the counting oddball task. The initial positive deflection that arises about 200 ms after stimulus presentation corresponds to the P200 component. The negative deflection that follows is the N200, which is then followed by the P300, a positive deflection that emerges 300 ms after stimulus presentation. The oddball effect is represented by the P300 amplitude to rare (dotted line) − frequent (solid line) stimuli. Before therapy, TD and BFRB patients had reduced P300 amplitude than controls during rare trials. A significant amplitude increase was induced by the CoPs therapy. This increase occurred in all three regions in BFRB patients but was more localized in the parietal region in TD patients.

Figure 2

The P300 oddball effect (therapy by condition). The P300 oddball effect represents the subtraction of frequent condition from the rare condition across all scalp regions. With the counting oddball task, the oddball effect was significantly reduced in both clinical groups at pretherapy (black). However, there were no significant differences across groups during the motor task (gray) and no effect of therapy reached significance. At posttherapy, a normalization of the oddball effect was induced during the counting oddball task (black), especially in BFRB patients, where it almost reaches the level of control participants. Note: error bars represent the SEM.

Figure 3

P300 scalp topographies of activation changes induced by CoPs therapy. P300 data before therapy were subtracted from P300 data after CoPs therapy to illustrate the activation changes induced by CoPs therapy in frequent and rare conditions. Red color represents an activation increase following CoPs therapy, whereas blue color represents a decrease in activation in microvolts. The SLORETA number indicates the timeframe of each scalp. The timeframes were selected as the maximum peak during the 300–550 ms interval following stimulus presentation, for the frequent and rare condition. For both groups, scalp topographies show that most of the pre–posttherapy difference in P300 activation occurred during rare condition. In TD patients, the activation increase was localized in the parietal area, especially the central and left hemisphere. In BFRB patients, the increase was generalized to the whole cortex. Scalp topographies were obtained through LORETA (63).

Figure 4

ERP waveforms during the motor oddball task. No significant group differences were observed during the motor oddball task.