Neural oscillatory evidence of compensatory inhibitory mechanisms in Tourette patients

Introduction:

It has been proposed that individuals with Gilles de la Tourette syndrome (TS) gain control over their tics through the development of compensatory inhibitory self-regulation mechanisms.

Aims:

We tested the presence of inhibitory patterns in the beta (15 – 25 Hz) frequency range, a rhythm that is typically related to motor functions. Specifically, we predicted an enhanced beta rebound in Tourette subjects as a signature of increased inhibitory mechanisms.

Methods:

Magnetoelectroencephalographic (MEG) signals were measured from 12 TS patients with no comorbidities and 12 control subjects matched for gender, age and handedness. A visual stimulus (S1) cued which of 2 fingers of the right hand should be lifted in case of Go condition, while a second visual stimulus (S2) coded the Go/Nogo condition. Analyses focussed on beta brain oscillations accompanying the response preparation between S1 and S2 onsets.

Results:

While patients and controls performed similarly as for reaction time and accuracy, the two groups showed significantly different oscillatory modulations over left sensorimotor and bilateral parietoccipital areas. Specifically, patients had a strong and broadly distributed beta rebound, which interrupted the beta suppression related to response preparation comparably shown in both groups. Whereas in patients the beta rebound occurred at about 900 ms post S1 onset and lasted about 700 ms, this activation was almost absent in controls.

Summary:

The observed beta modulation suggests the presence of motor inhibitory, probably compensatory mechanisms in TS patients during an S1-S2 Go/NoGo task.