The cerebral blood flow correlates of emotional facial processing in mild Alzheimer's disease

Deficits in facial emotion processing are features of mild Alzheimer’s disease (AD). These impairments are often distressing for carers as well as patients. Such non-cognitive symptoms are often cited as a contributing reason for admission into institutionalised care. The ability to interpret emotional cues is crucial to healthy psychological function and relationships and impaired emotional facility may lead to antisocial behavior. Understanding the origins of the noncognitive aspects of AD may lead to an improvement in the management of sufferers and ease the carer burden. In a cross-sectional study we recorded patients’ facial processing abilities, (emotion and identity recognition), disease severity (ADAS-cog, Neuropsychiatic Inventory) and investigated the regional cerebral blood flow correlates of facial emotion processing deficits using 99Tcm HMPAO rCBF SPECT. Using statistical parametric mapping (SPM) we identified decreased blood flow in posterior frontal regions specifically associated with emotion perception deficits and independent of non-emotional facial processing abilities or/and disease severity. The posterior frontal lobe has been identified in previous studies in the absence of dementia as being important in emotion processing. The results suggest that the cognitive disease severity, in combination with the facial processing ability, do not completely explain facial emotion processing in AD patients and that the posterior frontal lobe mediates such behaviour.