Emotion processing and its interactions with memory: evidence from the dementias

Emotion processing is a pivotal component of everyday social interactions. It is necessary for emotion recognition in others, and also modulates other cognitive domains including memory. Emotion recognition and emotional memory are thought to depend on interactions between the frontal and temporal lobes, although the nature and mechanisms underlying these complex behaviours require further explication. This thesis examines emotion recognition and emotional memory using a combination of behavioural and neuroimaging approaches in two common neurodegenerative conditions characterised by atrophy in brain regions known to underlie emotion processing and memory: frontotemporal dementia (FTD) and Alzheimers disease (AD).The results from this thesis demonstrated that emotion recognition is impaired in the three main FTD subtypes: behavioural-variant FTD, semantic dementia and progressive nonfluent aphasia; however, the mechanisms underlying these deficits differ (Chapter 3). Neuroimaging analyses revealed that the deficits in emotion processing were due to atrophy in discrete brain regions across the frontal and temporal lobes. The results suggested that recognition of specific basic emotions, such as fear and disgust, is subserved by distinct brain regions (Chapter 4).Comparison of the FTD subtypes with AD patients, who show impaired memory in the context of relatively intact emotion processing, revealed that the impact of emotion on memory differed across these dementia syndromes. All three FTD groups showed an attenuation of emotional enhancement of memory, whereas in AD, emotional enhancement of memory was preserved, despite an overall reduction in memory ability (Chapter 5 and 6). Neuroimaging analyses revealed that, irrespective of emotional content, general memory was associated with the integrity of classic memory regions including the hippocampus, precuneus and posterior cingulate. In contrast, emotional memory was associated with integrity of frontal lobe regions, specifically the orbitofrontal cortex (Chapter 6).The results of this thesis reveal the utility of examining brain-behaviour relationships in neurodegenerative conditions, in order to test models of complex human behaviours. From a clinical perspective, these novel findings have important implications for the characterisation and management of FTD and AD patients