Perception of Emotional Facial Expressions in Amyotrophic Lateral Sclerosis (ALS) at Behavioural and Brain Metabolic Level

Abstract

Introduction: Amyotrophic lateral sclerosis (ALS) primarily impairs motor abilities but also affects cognition and emotional processing. We hypothesise that subjective ratings of emotional stimuli depicting social interactions and facial expressions is changed in ALS. It was found that recognition of negative emotions and ability to mentalize other's intentions is reduced.

Methods: Processing of emotions in faces was investigated. A behavioural test of Ekman faces expressing six basic emotions was presented to 30 ALS patients and 29 age-, gender and education matched healthy controls. Additionally, a subgroup of 15 ALS patients that were able to lie supine in the scanner and 14 matched healthy controls viewed the Ekman faces during functional magnetic resonance imaging (fMRI). Affective state and a number of daily social contacts were measured.

Results: ALS patients recognized disgust and fear less accurately than healthy controls. In fMRI, reduced brain activity was seen in areas involved in processing of negative emotions replicating our previous results. During processing of sad faces, increased brain activity was seen in areas associated with social emotions in right inferior frontal gyrus and reduced activity in hippocampus bilaterally. No differences in brain activity were seen for any of the other emotional expressions. Inferior frontal gyrus activity for sad faces was associated with increased amount of social contacts of ALS patients.

Conclusion: ALS patients showed decreased brain and behavioural responses in processing of disgust and fear and an altered brain response pattern for sadness. The negative consequences of neurodegenerative processes in the course of ALS might be counteracted by positive emotional activity and positive social interactions.

Fig 1. Example sequence of the event related fMRI paradigm of different intensities of emotions and meaningless and neutral stimuli.

In total three trials, each including 26 stimulation sequences was presented. A stimulation sequence consisted of a block of three stimuli of one second interleaved by rest epochs of one second. Each block was followed by a rest period of nine seconds. Stimulus blocks of different emotions (anger, disgust, fear, sadness, surprise and happiness; here only fear and happiness are displayed as examples) with different intensities and neutral and meaningless stimuli were presented in a randomized order. Reprinted from FEEST [23] under a CC BY license, with permission from Paul Ekman Group, LLC, original copyright 2002.

Fig 2. Number of correct categorizations of facial emotion expressions.

* indicates statistical significance with p<0.05 and ** indicates statistical significance with p<0.01 between patients (n = 30) and healthy controls (n = 29) in a two-sample t-test.

Fig 3. Increased activation of ALS patients compared to healthy controls when processing different emotional facial expressions.

Activation in a sub region of the right inferior frontal gyrus (MNI coordinates: x = 49mm y = 18mm z = 30mm; cluster size = 37 voxels; T = 3.53; p_uncorr = 0.001), right angular gyrus (MNI coordinates: x = 56mm y = -58mm z = 34mm; cluster size = 102 voxels; T = 4.40; p_uncorr<0.001) and right precuneus (MNI coordinates: x = 6mm y = -62mm z = 34mm; cluster size = 31 voxels; T = 3.42; p_uncorr = 0.001). Activations show areas with significant increase of activity in patients in average for all emotions.

Fig 4. Regression analysis of brain activity and social contacts during processing of emotional facial stimuli in ALS patients.

Activation in a subregion of right inferior frontal gyrus/Brodmann Area 44 and 45. MNI-coordinates: x = 44mm, y = 21mm, z = 30mm; cluster-size = 12 voxels; T = 3.36; p_uncorr = 0.003.