Tactile processing and vibrotactile discrimination capacity in children with Tourette Syndrome

Abstract

Tourette Syndrome (TS) is a childhood-onset developmental psychiatric disorder. Pediatric patients are diagnosed with TS if they show multiple motor tics and at least one vocal tic for at least one year. The tic severity is known to be reduced in most of the cases as the patient progress into adulthood which suggests a cerebral adaptation over time. The pathology of TS is not clear; however, neurotransmission deficits, especially of -aminobutyric acid (GABA), and structural alterations in the cerebral structures are believed to be play a role in disorder’s occurrence. Existing literature suggests the tics to arise from hyperexcitability due to GABAergic dysfunction, and the adaptive somatosensory mechanisms in TS to be disrupted. This study aimed to extend the GABAergic adaptive dysfunction in TS hypothesis by assessing the detection and difference thresholds through a psychophysical vibrotactile battery. Thirty TS children (7 female, 23 male) and 25 healthy controls (7 female, 18 male) participated in the experiments. Vibrotactile stimuli were generated by a portable device and applied to the fingertips of the subjects. The vibrotactile battery consisted of Choice Reaction Time (cRT, amplitude: 200 m, Static Detection Threshold (DT_s ), Dynamic Detection Threshold (DT_c , amplitude ramp: 2 m/s ), Amplitude Discrimination (AD, standard stimuli: 50, 100, 200 m ), and Amplitude Discrimination with single-site adaptation (cAD, the same standards, adapting stimuli: 100, 300 m, adaptation duration: 1 s) measurements. The analyses showed that both groups produced comparable detection thresholds. Amplitude discrimination tasks produced further support for the GABAergic adaptive dysfunction in TS hypothesis, since in the baseline AD tasks TS group produced significantly higher difference thresholds, and in the cAD tasks control group closed the gap by showing a more prominent adaptation.|Keywords : Tactile processing, Amplitude discrimination, Tourette Syndrome