Emotional processing tied to facial recognition in Parkinson’s: Study
Moving faces harder to read than those with static, non-emotional expressions
Deficits in emotional processing, rather than impaired ability to simulate facial expressions, likely explain problems Parkinson’s disease patients encounter when trying to recognize emotions on human faces, a study suggests.
Researchers asked patients and healthy individuals to recognize different, non-emotional facial expressions on avatars, either static or moving. No differences were found between the two groups.
“We conclude that in [Parkinson’s disease] patients the observed impairment with emotional expressions is likely due to a specific deficit for emotions to a greater extent than for facial expressivity processing,” the scientists wrote in the study, “Facial expressions and identities recognition in Parkinson disease,” published in Heliyon.
Problems identifying and recognizing emotional facial expressions are among nonmotor symptoms experienced by people with Parkinson’s, possibly due to a dysfunction in emotional processing caused by neurodegeneration.
Parkinson’s patients often exhibit a lack of facial expressiveness due to motor impairments, a condition known as facial masking, or hypomimia. This condition, in turn, may impair emotional facial recognition, as the ability to recognize the emotions of others is partly based on facial mimicry.
Recognizing expressions on avatars
A team led by scientists at the University of Milan-Bicocca in Italy conducted two separate experiments to disentangle the factors underlying deficits in recognizing emotional facial expressions in Parkinson’s.
In the first experiment, 22 Parkinson’s patients and 24 healthy controls were asked to recognize non-emotional expressions on faces with different identities and expressions.
They created avatars — five male and five female, all without hair — with 10 static (non-moving) facial expressions for each of the 10 identities. Participants were administered the Benton Facial Recognition Test (BFRT) to evaluate their ability to recognize faces. Accuracy in expression and identity recognition was measured by the number of correct responses divided by the total number of responses.
Tests revealed that the expression task was significantly harder, on average, than the identity task. Still, no overall differences were found between Parkinson’s patients and controls in either task. Time since last medication or onset of symptoms had no effect, nor did hypomimia scores on the Unified Parkinson Disease Rating Scale (UPDRS).
The findings showed that “our patients do not show difficulties in recognizing facial expressions or identities compared to the control group,” the researchers wrote.
The second experiment aimed to discover whether Parkinson’s patients showed differences in processing dynamic (moving) faces.
Ten avatars — again, five of them male — were created to assume six non-emotional facial expressions. Twenty-five captures were taken, each with a different and growing intensity of expression. The faces were presented rapidly to induce perceived movement. The researchers also created 30 static, neutral identities, 15 of them males, to serve as distractors to filter out irrelevant information.
The 24 Parkinson’s patients and 25 controls in this experiment underwent BFRT testing as well as a cognitive evaluation using the Montreal Cognitive Assessment (MoCA). BFRT and MoCA raw scores significantly differed between patients and controls, and were applied to statistical adjustments.
A difference was noted between movement and neutral conditions, with moving faces recognized to a poorer extent than neutral faces. Again, there were no differences between Parkinson’s patients and controls. Likewise, UPDRS hypomimia scores were not related to the presentation of moving facial expressions.
“From these two studies, it emerged that Parkinson’s Disease patients do not show difficulties in recognizing static non-emotional facial expressions compared to Healthy Controls,” the scientists wrote. “Moreover, they do not show deficits in the recognition of identities of faces encoded through a dynamic non-emotional expression.”
The results, they said, “point into an explanation of the deficit reported for [Parkinson’s disease] in recognizing emotional expressions which is predominantly tied to emotion processing rather than to expression simulation.”
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