Affective speech processing in patients with primary cervical dystonia

Primary cervical dystonia as a basal ganglia disorder mainly presents with dysfunction of the motor system. Up to now, insufficient research is carried out regarding the co-existence of eventual non-motor deficits. Recent studies (Rinnerthaler M. et al. 2006) have revealed that individuals with primary focal dystonia demonstrate impairment in recognizing emotional cues from facial expressions, indicating an alteration of emotional processing. The objective of our study was to find out if patients with primary focal dystonia have disturbances in affective speech perception. Moreover, we were interested in whether a potential deficit is due to an impaired processing of valence or arousal dimension of emotional prosody. By means of event related brain potentials (ERP) we investigated 16 patients with primary cervical dystonia (CD) and 19 healthy controls (HC). The stimulus material comprised various words with semantically neutral content, spoken by professional actors in four different emotional intonations (sad, relieved, happy and angry). Stimuli were presented in a modified oddball paradigm (80% probability of standard and 20% of deviant stimuli). The task was to determine the emotional tone of each word, according to its 'valence' or 'arousal', in two experimental conditions.

Analysis of behavioural data revealed a significantly poorer performance of dystonic patients (CD) in evaluating angry and happy emotional tone. ERP voltages elicited by the deviant stimuli showed a negative deflection with a maximum at 150–250ms and a positive deflection peaking at 250–350ms, and mean amplitudes that are smaller in CD as compared to HC. This difference was most prominent for angry and happy intonated words, and correlates with the behavioural data. Our preliminary findings imply that processing of emotional prosody in CD seems to be altered. It is possible that the recognition of angry (and to a lesser extent happy) emotional tone in patients with dystonia is disturbed. This assumption is in line with other studies indicating impaired processing of emotional prosody in basal ganglia disorders.