Anna Pohl

Neural correlates of impaired emotion processing in manifest Huntington’s disease

The complex phenotype of Huntingtons disease (HD) encompasses motor, psychiatric and cognitive dysfunctions, including early impairments in emotion recognition. In this first functional magnetic resonance imaging study, we investigated emotion-processing deficits in 14 manifest HD patients and matched controls. An emotion recognition task comprised short video clips displaying one of six basic facial expressions (sadness, happiness, disgust, fear, anger and neutral). Structural changes between patients and controls were assessed by means of voxel-based morphometry. Along with deficient recognition of negative emotions, patients exhibited predominantly lower neural response to stimuli of negative valences in the amygdala, hippocampus, striatum, insula, cingulate and prefrontal cortices, as well as in sensorimotor, temporal and visual areas. Most of the observed reduced activity patterns could not be explained merely by regional volume loss. Reduced activity in the thalamus during fear correlated with lower thalamic volumes. During the processing of sadness, patients exhibited enhanced amygdala and hippocampal activity along with reduced recruitment of the medial prefrontal cortex. Higher amygdala activity was related to more pronounced amygdala atrophy and disease burden. Overall, the observed emotion-related dysfunctions in the context of structural neurodegeneration suggest both disruptions of striatal-thalamo-cortical loops and potential compensation mechanism with greater disease severity in manifest HD.

Positive Facial Affect – An fMRI Study on the Involvement of Insula and Amygdala

Imitation of facial expressions engages the putative human mirror neuron system as well as the insula and the amygdala as part of the limbic system. The specific function of the latter two regions during emotional actions is still under debate. The current study investigated brain responses during imitation of positive in comparison to non-emotional facial expressions. Differences in brain activation of the amygdala and insula were additionally examined during observation and execution of facial expressions. Participants imitated, executed and observed happy and non-emotional facial expressions, as well as neutral faces. During imitation, higher right hemispheric activation emerged in the happy compared to the non-emotional condition in the right anterior insula and the right amygdala, in addition to the pre-supplementary motor area, middle temporal gyrus and the inferior frontal gyrus. Region-of-interest analyses revealed that the right insula was more strongly recruited by (i) imitation and execution than by observation of facial expressions, that (ii) the insula was significantly stronger activated by happy than by non-emotional facial expressions during observation and imitation and that (iii) the activation differences in the right amygdala between happy and non-emotional facial expressions were increased during imitation and execution, in comparison to sole observation. We suggest that the insula and the amygdala contribute specifically to the happy emotional connotation of the facial expressions depending on the task. The pattern of the insula activity might reflect increased bodily awareness during active execution compared to passive observation and during visual processing of the happy compared to non-emotional facial expressions. The activation specific for the happy facial expression of the amygdala during motor tasks, but not in the observation condition, might reflect increased autonomic activity or feedback from facial muscles to the amygdala.

Affect-specific activation of shared networks for perception and execution of facial expressions

Previous studies have shown overlapping neural activations for observation and execution or imitation of emotional facial expressions. These shared representations have been assumed to provide indirect evidence for a human mirror neuron system, which is suggested to be a prerequisite of action comprehension. We aimed at clarifying whether shared representations in and beyond human mirror areas are specifically activated by affective facial expressions or whether they are activated by facial expressions independent of the emotional meaning. During neuroimaging, participants observed and executed happy and non-emotional facial expressions. Shared representations were revealed for happy facial expressions in the pars opercularis, the precentral gyrus, in the superior temporal gyrus/medial temporal gyrus (MTG), in the pre-supplementary motor area and in the right amygdala. All areas showed less pronounced activation in the non-emotional condition. When directly compared, significant stronger neural responses emerged for happy facial expressions in the pre-supplementary motor area and in the MTG than for non-emotional stimuli. We assume that activation of shared representations depends on the affect and (social) relevance of the facial expression. The pre-supplementary motor area is a core-shared representation-structure supporting observation and execution of affective contagious facial expressions and might have a modulatory role during the preparation of executing happy facial expressions.

Impaired Emotional Mirroring in Parkinson’s Disease—A Study on Brain Activation during Processing of Facial Expressions

Background Affective dysfunctions are common in patients with Parkinson’s disease, but the underlying neurobiological deviations have rarely been examined. Parkinson’s disease is characterized by a loss of dopamine neurons in the substantia nigra resulting in impairment of motor and non-motor basal ganglia-cortical loops. Concerning emotional deficits, some studies provide evidence for altered brain processing in limbic- and lateral-orbitofrontal gating loops. In a second line of evidence, human premotor and inferior parietal homologs of mirror neuron areas were involved in processing and understanding of emotional facial expressions. We examined deviations in brain activation during processing of facial expressions in patients and related these to emotion recognition accuracy. Methods 13 patients and 13 healthy controls underwent an emotion recognition task and a functional magnetic resonance imaging (fMRI) measurement. In the Emotion Hexagon test, participants were presented with blends of two emotions and had to indicate which emotion best described the presented picture. Blended pictures with three levels of difficulty were included. During fMRI scanning, participants observed video clips depicting emotional, non-emotional, and neutral facial expressions or were asked to produce these facial expressions themselves. Results Patients performed slightly worse in the emotion recognition task, but only when judging the most ambiguous facial expressions. Both groups activated inferior frontal and anterior inferior parietal homologs of mirror neuron areas during observation and execution of the emotional facial expressions. During observation, responses in the pars opercularis of the right inferior frontal gyrus, in the bilateral inferior parietal lobule and in the bilateral supplementary motor cortex were decreased in patients. Furthermore, in patients, activation of the right anterior inferior parietal lobule was positively related to accuracy in the emotion recognition task. Conclusion Our data provide evidence for a contribution of human homologs of monkey mirror areas to the emotion recognition deficit in Parkinson’s disease.

Don't worry, be happy - Neural correlates of the influence of musically induced mood on self-evaluation

&NA; Self‐evaluation affects ones own mental state, social interactions and everyday life. Mood, in turn, has an impact on self‐evaluation. However, the influence of mood on self‐evaluation at the neural level has barely been examined. In this fMRI study, the interaction of mood and self‐perception was investigated in 20 healthy participants. Happy, sad and neutral music was presented while participants were instructed to immerse themselves in the mood of the music and to rate how well presented traits characterized themselves. In a lexical control condition, subjects had to count a specific letter in the word. Behavioral data reflected successful mood induction. While self‐ascription of positive traits was unaffected by mood, self‐ascription of negative characteristics was decreased by negative affect. A positive correlation was found between self‐worth scores and the difference in the amount of self‐ascribed positive versus negative traits during negative mood induction. At the neural level, amygdalo‐hippocampal, superior and middle temporal structures were differently involved in self‐evaluation (vs. lexical processing) depending on the mood. While activation of the amygdalo‐hippocampal complex was found during sad in comparison to both happy and neutral mood, superior/middle temporal gyrus (STG/MTG) activation was only found when contrasting sad vs. neutral mood. Further, a correlation analysis with self‐worth ratings revealed a positive relation to STG activation during self‐ascription of trait adjectives in sad compared to neutral mood. Our results underscore the importance of the current emotional state for self‐evaluation and identify some neural correlates of this effect. Our findings in healthy research participants suggest a compensatory mechanism during sad mood induction to maintain a positive self‐image, which is supported by activation of limbic and fronto‐temporal cortex. Studies in clinically depressed populations could reveal whether this compensatory mechanism is aberrant. HighlightsNew fMRI paradigm to investigate the influence of mood induction on self‐evaluation.Ascribing positive traits to oneself was unaffected by mood.Ascription of negative characteristics was decreased by negative mood induction.Higher self‐worth leads to a more positive self‐evaluation under sad mood induction.Self‐worth is related to STG activation during self‐evaluation in sad vs. neutral mood.

Training-related changes of brain activation for speech production in healthy speakers – a longitudinal fMRI study to mimic aphasia therapy

ABSTRACT Background: Re-learning of lexical entries is fundamental to rehabilitation of the common word finding deficits in language disorders after brain damage. Previous studies examined and compared neural correlates of speech production and word learning in aphasic and healthy speakers, but longitudinal control studies were rarely set out to mimic the lexical confusion and therapeutic remediation in aphasia. Aims: Thus, we aimed to examine functional brain organisation before (familiar word naming), during (learning phase) and after (consolidation phase) standardised training of speech production modulated by aphasia therapy. Methods & Procedures: During the first functional magnetic resonance imaging (fMRI) measurement, participants were asked to name pictures using familiar words; during learning and in the consolidation phase, they were asked to name pictures using newly acquired pseudowords. To examine differential involvement of brain areas dependent on learning and consolidation success, we followed up activations for finally correctly learned (CoL) items between fMRI measurements, and compared activation during naming of CoL versus finally not learned (NoL) items at each measurement. Outcomes & Results: Naming accuracy of participants improved significantly. Although performance increase until the second fMRI measurement was minor, brain activation was present for CoL in comparison to NoL items in right hemisphere homologues of fronto-temporal language-related areas in this phase. Comparing learning with consolidation phases for pseudowords, naming CoL items was accompanied by activation in areas related to monitoring and selection between multiple lexical competitors, and in the right posterior middle temporal gyrus. Conversely, activation specific to the consolidation phase, and also to CoL items in that phase, consisted of a widely distributed network involving areas associated with motor, language and consolidation processes. Activation in right supramarginal and left superior temporal gyrus was related to individual learning success. Conclusions: We were able to demonstrate phase- and performance-dependent activation differences in various areas of the speech production network, which were in part correlated with learning success. The observed similarities to therapy-induced activation changes in aphasia reveal that the novel paradigm is useful in mimicking therapy and may uncover compensatory mechanisms specific to aphasia.