Deficits in emotion processing in Alzheimer's disease: a systematic review

Emotional processing involves the ability of the individual to infer emotional information. There is no consensus about how Alzheimer's disease (AD) affects emotional processing. Objective: Our aim is to systematically review the impact of AD on emotion processing.

We conducted a search based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). The literature search was performed using the electronic databases MEDLINE (PubMed) and Science Citation Index (Institute for Scientific Information [ISI]). The following descriptors were used in the review process: emotion or emotional processing, cognition or cognitive functions, and Alzheimer disease or Alzheimer's disease. This systematic review was recorded in the International Prospective Register of Systematic Reviews (PROSPERO) under the number CRD42018115891.

We identified 425 articles, 19 of which met our criteria. Visual emotional stimuli were the most used among studies. Most studies used tasks of emotional naming, discrimination, identification, and correspondence. The results were contradictory. Many studies reported that individuals with AD were impaired on emotional perception tasks, while other results reported preserved skills. The relationship between emotional processing and cognition is also unclear. Some studies suggested that general cognitive performance affects performance in emotional perception tasks among people with AD, but other studies have shown deficits in recognizing emotion, regardless of cognitive performance.

Studies are scarce, present contradictory results, and report impairment in emotional processing in relation to cognition. Moreover, the analyses of the correlation between emotion processing and cognitive functioning failed to reveal clear relationships.