Emotion, Mood and Executive Function in Parkinson's Disease (PD)

Parkinson's disease (PD) is associated with a range of cognitive impairments, most notably deficits of higher order cognitive control mechanisms referred to as "executive dysfunction". These problems have consistently been related to dysfunction of fronto-striatal circuitry (summary see Stocchi \& Brusa, 2000). Executive function impairments may already be present in early stages of PD (Uekermann et al., 2004) and their severity may be exacerbated by affective changes such as depression (Uekermann et al., 2003). In addition to cognitive problems, PD patients frequently suffer from mood changes, in particular apathy (Kirsch-Darrow et al., 2006) and from affect processing impairments, relating to both the ability to decode the affective state of other people on the basis of facial expressions or prosody and to the ability to adequately express the patients' own emotions (e.g. Breitenstein et al., 1998; Zgaljardic et al., 2003, Pell \& Leonard, 2005). The capacity for emotion perception was found to be linked to the severity of executive dysfunction; affective and cognitive changes are thus not independent, at least in patients with moderate PD (Breitenstein et al., 2001). In a recent drug monitoring study by Lundbeck GmbH/TEVA Pharma GmbH based on a small group of PD patients (n=29), introduction of Azilect (Rasagiline) therapy was associated with a significant improvement of PD patients' emotional expressiveness (e.g. facial expression, gestures, voice intonation) over an 8 week observation period. Significant improvements were observed for self-ratings of emotional expressiveness as well as ratings by physicians and relatives. The lack of a placebo-control group, however, does not allow any firm conclusions with regard to the specificity of these effects. Intact affect recognition and an adequate ability to express emotions are of critical importance for social interaction. The therapeutic efficacy of drug treatment on non-motor symptoms in PD has so far only rarely been addressed. The documentation of a beneficial effect of Azilect on emotional processing would be of great relevance for the quality of life of PD patients and greatly enhance their ability to participate in social life. The addition of a placebo control group is critical for the assessment of the specificity of the expected beneficial effects of Azilect.