Neural basis of emotional awareness

Abstract

Emotional awareness is the ability to recognize and describe emotion in oneself and others. A prominent theory postulates that emotional awareness depends on the cognitive skills developed for differentiation and integration of the schemata for processing emotional information. Nevertheless, emotional awareness might also depend on emotional experiences elicited at an earlier stage before emotional information are cognitively processed, especially the processing mechanisms involved in emotional attention and interoceptive awareness (sensing of bodily state).

In order to explore the neural bases of emotional awareness, this thesis studied people with relatively extreme characteristics of emotional awareness, namely alexithymia and mindfulness. Study One explored the neural correlates of alexithymia, a condition reflecting a reduced level of emotional awareness in oneself, in 22 female depressive patients and 21 matched nonclinical controls. Degree of alexithymia was found to be associated with reducing white-matter diffusivity at corpus callosum for the patients and at right superior longitudinal fasciculus for the controls, confirming our a priori hypothesis that alexithymia in these two groups may be associated with different neural mechanisms. Further analysis using resting-state functional connectivity showed that increasing alexithymia in depressive patients was associated with decreasing coupling of right precentral gyrus and several right brain regions associated with self-reference and emotion regulation, while increasing alexithymia in controls was associated with increasing coupling between the prefrontal site for evaluating stimuli significance and the occipital site for gathering of perceptual information. These functional connectivity changes at different remote brain regions were interpreted as associated with the microstructural changes of the different neural correlates of alexithymia for the two groups.

Study Two sought to substantiate the findings in Study One that alexithymia without depression would be associated with reduced detection of stimuli significance, by studying a non-depressive subject with lesions at the extrastriate cortex. The findings were interpreted as supportive of the proposal by attributing that the lesion might have impaired the colliculus-pulvinar-amygdala pathway for rapid evaluation of stimulus emotional significance.

Study Three investigated 22 male meditation practitioners on their mindfulness, a trait associated with heightened level of emotional awareness, and neurophysiological reactivity upon perception of emotional stimuli. The results showed that mindfulness would predict both the behavioral ratings of stimulus valence and amplitudes of P2 (an ERP component) for the contrast between positive and negative stimuli. Combining these findings with the existing theories on mindfulness, a mechanism for explaining how mindfulness trait might contribute to reduce negativity bias was proposed.

In summary, findings of the three studies described in this thesis would offer significant insights on how dynamic interactions of neural networks across both early and late stages of affective processing may have impacts on emotional awareness. In terms of clinical implications, firstly, our findings suggested that microstructural changes in corpus callosum might be specific to comorbid Type II alexithymia (high in cognitive characteristics only) in depressive patients. Secondly, mindfulness training might have implications on treatment of affective disorders that are associated with attentional bias, through its effect on negativity bias reduction.