Faces of emotion in Parkinsons disease: Micro-expressivity and bradykinesia during voluntary facial expressions

Abstract

In humans, the neural circuitry underlying facial expressions differs, depending on whether facial expressions are spontaneously (i.e., limbic, subcortical) or voluntarily initiated (i.e., frontal cortex). Previous investigators have suggested that the "masked face" of Parkinson's disease involves spontaneous, but not intentional, facial expressions. In contrast, we hypothesized that intentional facial expressions may be slowed (bradykinetic) and involve less movement, in much the same way that other intentional movements are affected by Parkinson's disease. To test this hypothesis, we used sophisticated computer imaging techniques to quantify dynamic facial movement. Relative to controls, Parkinson patients had reduced facial movement (entropy) and were significantly slowed in reaching a peak expression (i.e., bradykinesia). These findings are consistent with the view that the basal ganglia play a role in affecting intentional facial movements. This possibly occurs because of diminished efficiency and/or activation of face representation areas in the frontal cortical regions (i.e., motor, premotor, and supplementary motor area) or because of movement-based suppression secondary to dopaminergic reduction in frontostriatal pathways. Taken together, the characterization of Parkinson's disease as a model system for the neuroanatomic dissociation between voluntary and spontaneous expressions may be unjustified.

The late positive potential, emotion and apathy in Parkinson’s disease

“…Whether emotional difficulties, particularly apathy, result from an affective disturbance or a behavioral deficit remains unclear (Brown & Pluck, 2000; Levy & Czernecki, 2006). For instance, PD patients report that emotion is experienced as intensely as healthy controls, but rate themselves as less emotionally expressive (Mikos et al, 2009), partially due to reduced emotional facial expressions (Bowers et al, 2006a). …”

“…According to this view, emotional reactions to environmental cues reflect activation in basic defensive and appetitive neural circuits, indexing the extent of both defensive and appetitive motivation. Pictures depicting threatening and appetitive natural scenes encountered by humans in the world are cues that reliably activate these circuits (Lang & Bradley, 2010); Bowers et al, 2006a, b; Miller, Okun, Marsiske, Fennell, & Bowers, 2009; Zahodne, 2012) have found that individuals with PD showed reduced potentiation of the startle eye blink response, a defensive reflex, when viewing unpleasant pictures, compared to healthy controls.…”

Emotion and ocular responses in Parkinson's disease

“…Parkinson’s patients experience high rates of apathy and depression and recent research suggests that apathy may be a core feature of Parkinson’s disease, with estimates of apathy in PD ranging from 38% to 51% across studies (Isella et al, 2002; Starkstein et al, 2002; Pluck & Brown 2002; Sockeel et al, 2006). A recent study that compared rates of depression, apathy, and combined apathy and depression in Parkinson’s disease and a comparative movement disorder population, dystonia, found that 29% of PD patients endorsed clinically significant apathy without depression, whereas no dystonic patients endorsed significant apathy in the absence of depression (Kirsch-Darrow, Fernandez, Marsiske, Okun, & Bowers, 2006). …”

Startle reflex hyporeactivity in Parkinson's disease: An emotion-specific or arousal-modulated deficit?

“…Some researchers have found that although PD patients are not as facially or prosodically expressive as their healthy counterparts, they typically report subjective feelings that are comparable in intensity when viewing emotion-eliciting pictures (Bowers et al, 2006a; Simons, Pasqualini, Reddy, & Wood, 2004; Smith et al, 1996). However, self-report ratings such as these are potentially unreliable because they are subject to demand characteristics, meaning that the participant may simply respond in the fashion that he believes is expected of him.…”