| Individuals with Parkinson's disease (PD) display impairments in facial emotion recognition (FER), but the sources of these impairments remain poorly understood. The present set of studies examined whether deficient FER arises exclusively from difficulties in emotional processing, or whether it may also result from PD-related abnormalities in cognitive and visual processing. In the first study, FER was examined in 20 non-demented PD and 23 healthy control (HC) participants relative to their performance on a control test of landscape categorization. PD participants' impairments were limited to emotion recognition, and were specific for anger, fear, and surprise. Hence, FER difficulties were not an artifact of general cognitive task requirements. The second study investigated whether visual scanning impairments contribute to FER deficits, as has been found in other disorders that, like PD, are associated with frontal-lobe and subcortical pathology. Eye movements were recorded in 16 PD and 20 HC participants during a task of FER. Compared to the HC group, PD participants fixated more in the right visual field for fearful expressions. Their greater time fixating in lower facial regions of sad expressions correlated with reduced recognition of this emotion. Several factors that could affect visual scanning and FER were assessed, including oculomotor (i.e., saccades), visual (e.g., acuity, contrast sensitivity), and frontally-mediated cognitive abilities (i.e., executive function). PD participants, especially those with left-sided motor-symptom onset, displayed abnormal voluntary saccades, but these abnormalities did not correlate with scanning patterns or FER Visual measures correlated with scanning patterns in PD participants only, but did not relate to FER. Reductions in executive function in PD participants correlated with greater fixation times in upper faces of angry, fearful, neutral, and surprised expressions, but were unrelated to FER. Taken together, these findings indicate that FER impairments in PD do not arise from abnormalities in cognitive and visual abilities. Instead, they likely result from changes in limbic networks important for emotion recognition, including the ventral striatum, amygdala, and prefrontal cortex. Finally, deficits in FER correlated with levels of interpersonal distress in PD participants, underscoring the need to better understand FER impairments in this disorder. |
