Background/objectives: Patients with Parkinson disease (PD) exhibit motor and frontal-executive dysfunction and often seem to be emotionally apathetic. We investigated whether PD patients have alterations in their emotional reactivity and how this might impact their proximal (avoidance) versus distal (approach) allocation of attention-intention.
Methods: Nine participants with PD and 9 normal controls were asked to judge the valence (pleasant-positive vs. unpleasant-negative) and arousal of 30 pictures from the International Affective Picture System. Participants were instructed to rate the pictures by marking 14-cm radial lines placed in front of them. On those lines where the subjects were going to rate emotional valence, the lines had a happy face at 1 end and a sad face at the other and when rating the arousal, they were presented with lines that had an "excited" and a "calm" face at opposite ends. For the emotional ratings, the dependent measures were the distances from the end of the line that had the "calm" or "sad" face to the participants' mark. For the approach-avoidance analysis, the dependent measure was the distance from the bottom of the line, regardless of the position of faces.
Results: The PD patients did not differ from controls when judging valence, but their judgments of arousal was lower than that of the controls. In addition, in contrast to the controls when judging neutral pictures and arousal, the PD patients, independent of the proximal or distal position of the sad/happy faces or excited/calm faces, demonstrated an overall proximal bias. When presented with emotional versus neutral stimuli, the control group reduced their extrapersonal spatial bias, whereas the subjects with PD did not change their spatial bias.
Conclusions: The judgments of valence made by the subjects with PD were the same as that of the controls. These judgments might be based on cognitive decisions and as our PD subjects were not demented they could accurately determine valence. In contrast, judgments of arousal were reduced in the PD participants, and this result might reflect these patients impaired arousal-activation systems. Although emotional, versus neutral stimuli, induced a proximal deviation in the responses of the control subjects, the subjects with PD did not change their spatial bias. This Parkinsonian "emotional akinesia" might be related to either a reduced capacity to experience emotions or to an inability of emotional experiences to influence intentional and attentional systems.