Abstract
Impaired habit-learning has been proposed to underlie the tic symptoms of Tourette syndrome (TS). However, accounts differ in terms of how habit-learning is altered in TS, with some authors proposing habit formation is impaired due to a deficient 'chunking' mechanism, and others proposing habit-learning is overactive and tics reflect hyperlearned behaviours. Attention-deficit/hyperactivity disorder (ADHD) frequently co-occurs with TS and is known to affect cognitive function in young people with co-occurring TS and ADHD (TS+ADHD). It is unclear, however, how co-occurring ADHD symptoms affect habit-learning in TS. In this study, we investigated whether young people with TS would show deficient or hyperactive habit-learning, and assessed the effects of co-occurring ADHD symptoms on habit-learning in TS. Participants aged 9-17years with TS (n=18), TS+ADHD (n=17), ADHD (n=13), and typical development (n=20) completed a motor sequence learning task to assess habit-learning. We used a 2 (TS-yes, TS-no)×2 (ADHD-yes, ADHD-no) factorial analysis to test the effects of TS, ADHD, and their interaction on accuracy and reaction time indices of sequence learning. TS was associated with intact sequence learning, but a tendency for difficulty transitioning from sequenced to non-sequenced performance was suggestive of hyper-learning. ADHD was associated with significantly poorer accuracy during acquisition of the sequence, indicative of impaired habit-learning. There were no interactions between the TS and ADHD factors, indicating young people with TS+ADHD showed both TS- and ADHD-related atypicalities in habit-learning.
Highlights
Tourette syndrome (TS) is a neurodevelopmental disorder characterised by chronic motor and phonic tics, i.e. involuntary and repetitive movements and sounds (American Psychiatric Association, 2013)
These effects were absent in adults with TS taking dopamine-blocking neuroleptic medication, supporting the view that unregulated dopamine levels are involved in atypical habit-learning and tics in TS (Delorme et al, 2015; Palminteri et al, 2009; 2011)
The 3 x 2 x 2 ANOVA assessing the effects of task block, TS, Attention-deficit/hyperactivity disorder (ADHD), and their interaction on reaction times (RTs) during the acquisition of the repeating sequence revealed a significant main effect of block (F(2, 114) = 6.72, p = .002, η2 = .105)
Summary
Tourette syndrome (TS) is a neurodevelopmental disorder characterised by chronic motor and phonic tics, i.e. involuntary and repetitive movements and sounds (American Psychiatric Association, 2013). Enhanced learning performance was positively associated with tic severity and with connectivity in motor CSTC circuitry (Delorme et al, 2015; Palminteri et al, 2009; 2011) These effects were absent in adults with TS taking dopamine-blocking neuroleptic medication, supporting the view that unregulated dopamine levels are involved in atypical habit-learning and tics in TS (Delorme et al, 2015; Palminteri et al, 2009; 2011). Drawing conclusions about the role of habit-learning in tics from studies conducted exclusively with adults with TS is problematic
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