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ALS Patients Evaluate Facial Expressions Differently, Even Without Cognitive Impairment
Patients with amyotrophic lateral sclerosis (ALS) exhibit different gaze patterns when visually scanning human facial expressions compared to healthy controls, according to study findings recently published in the journal Neurology.
Up to 50% of ALS patients present problems with motor functions and cognitive abilities, including recognition of emotions displayed on human faces. Oculomotor function, though, generally remains preserved until late-stage ALS and has not been previously tied to motor impairment. Thus, study authors sought to examine whether motor processes responsible for visual scanning disrupt the evaluation of facial expressions.
The authors recruited 45 cognitively unimpaired ALS patients matched with 37 healthy control participants. Using video-based gaze tracking technology, the researchers tracked participants' eye movements as they viewed images of faces exhibiting various emotions, including neutral, disgusted, happy, fearful, and sad.
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The results showed that ALS patients, compared to controls, fixated significantly longer on non-emotional-relevant regions, such as the cheeks instead of the eyes and mouth, when faces expressed fear (Mann-Whitney-U-test (U)=544.0, P=0.007) and disgust (U=535.0, P=0.006). These differences in observation did not manifest when patients examined happy or neutral faces. The authors also did not find significant differences between ALS patients and healthy controls when they looked at sad faces.
Fixation duration in any facial region of interest was not associated with the patients' cognitive state or clinical symptoms of disease severity. The researchers speculated that the altered visual scanning patterns might reflect impaired top-down neural processes involving prefrontal cortical areas responsible for face and emotion recognition. Additionally, they suggested that these visuomotor abnormalities might contribute to the observed deficits in emotion recognition among ALS patients.
While the study did not directly assess the association between altered visual scanning and emotion recognition, the researchers acknowledged that such data could inform future testing protocols and provide insights into subclinical neuropsychological deficits in ALS patients. These findings lay the foundation for the development of test batteries to assess neuropsychological performance in severely affected ALS patients, including those who are physically impaired or "locked in."
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