Patients at a pre-symptomatic stage of Huntington’s disease have marked difficulties recognizing and understanding negative and neutral mental states of other individuals, regardless of gender, a study has found.
The results, “Effects of Stimulus-Related Variables on Mental States Recognition in Huntington’s Disease,” were published in the International Journal of Neuroscience.
Huntington’s disease is a genetic neurodegenerative disorder characterized by motor, psychiatric, and cognitive disturbances. One particular cognitive feature that may occur early in the course of the disease is patients’ difficulties to recognize and understand the emotions of others.
“[Previous studies have shown that patients with Huntington’s have] a specific and early impairment to negative emotions recognition (i.e., disgust, fear, anger) associated with [certain] brain alterations,” the researchers wrote.
“However, there is still a lot of discussion about the causes of this difficulty (i.e., related to general cognitive decline or to affective or motor impairment), the specificity of the inputs (i.e., related to a verbal, visual, auditory stimulus, or to inanimate objects or to body acting in a context, to faces, or to eyes only),” they added.
In this study, a group of Italian researchers set out to evaluate the impact of different factors, including patients’ and peers’ gender, type of mental state, and recognition difficulty of the mental states displayed, on patients’ abilities to perceive the emotions of others.
The study enrolled 60 patients with Huntington’s disease, including 20 at a pre-symptomatic stage of the disease, and 40 with symptoms. All were asked to complete the revised “Reading the Mind in the Eyes Test” (RMET-R), in which participants must determine the way others are feeling by looking at their eyes.
Each group of patients was compared directly to 40 age- and sex-matched healthy individuals (controls).
Results showed that, in general, the performance of patients with Huntington’s in the RMET-R was worse than that of matched controls. Difficulties in recognizing test subjects’ emotions were already apparent among asymptomatic patients and tended to worsen with disease progression.
As for the type of mental state displayed, investigators found that asymptomatic patients had more difficulties recognizing negative (58.3% of accuracy) and neutral (56.9% of accuracy) emotions, compared to positive emotions (68% of accuracy). Similar findings were obtained for symptomatic patients, whose overall performance was worse than that of asymptomatic patients.
As for recognition difficulty, researchers found that asymptomatic patients had more difficulties identifying mental states that had a moderate recognition difficulty, but not for mental states with high or low recognition difficulty, when compared to healthy controls.
Symptomatic patients had worse performance than controls in all tiers of recognition difficulty. However, their performance was similar to that of asymptomatic patients for mental states that were harder to identify.
Patients’ gender had no effect in their ability to correctly identify test subjects’ emotions. On the other hand, researchers found that patients’ accuracy on the test tended to improve when mental states were displayed by females instead of males (61.9% versus 58.0% of accuracy).
“[O]ur results unequivocally highlighted an early impairment in affective social cognition preceding manifest symptoms. This finding has the important clinical implication that the skills of detecting other people’s mental state show abnormalities many years before the onset of motor manifestations affording a help for an early diagnosis,” the investigators wrote.
“Our results, moreover, suggest that specific features of the stimulus (…) may [affect] (…) recognition skills in subjects at the pre-symptomatic stage of HD [Huntington’s disease]. Further studies on larger [groups] may try to analyze whether these abnormalities may also represent potential clinical markers of onset or progression in the first stages of HD,” they stated.