Inter-individual differences in urge-tic associations in Tourette syndrome

Premonitory urges are a cardinal feature in Tourette syndrome (GTS) and are commonly viewed as a driving force of tics. However, inter-individual differences in experimentally measured urges, tics and urge-tic associations, as well as possible relations to clinical characteristics and abnormal perception-action processing recently demonstrated in these patients have not been investigated in detail. Here, we analyze the temporal associations between urges and tics in 21 adult patients with GTS including inter-individual differences and the relation of such associations with clinical measures and experimentally tested perception-action coupling. At the group level, our results confirm known positive associations between subjective urges and tics, with increased tic frequency and tic intensity during periods of elevated urge. Inter-individual differences in the associations between urges and tics were, however, substantial. While most participants (57-66 % depending on the specific measure) showed positive associations as expected, several participants did not, and two even had negative associations with tic occurrence and intensity being reduced at times of increased urges. Subjective urge levels and tic occurrence correlated with corresponding clinical scores, providing converging evidence. Measures of the strength of urge-tic associations did not correlate with clinical measures nor the strength of perception-action coupling. Taken together, urge-tic associations in GTS are complex and heterogenous, casting doubt on the notion that tics are primarily driven by urges.