Implicit memory for emotional facial expressions (EFEs) was investigated in young adults, healthy old adults, and mild Alzheimer's disease (AD) patients. Implicit memory is revealed by the effect of experience on performance by studying previously encoded versus novel stimuli, a phenomenon referred to as perceptual priming. The aim was to assess the changes in the patterns of priming as a function of aging and dementia. Participants identified EFEs taken from the Facial Action Coding System and the stimuli used represented the emotions of happiness, sadness, surprise, fear, anger, and disgust. In the study phase, participants rated the pleasantness of 36 faces using a Likert-type scale. Subsequently, the response to the 36 previously studied and 36 novel EFEs was tested when they were randomly presented in a cued naming task. The results showed that implicit memory for EFEs is preserved in AD and aging, and no specific age-related effects on implicit memory for EFEs were observed. However, different priming patterns were evident in AD patients that may reflect pathological brain damage and the effect of stimulus complexity. These findings provide evidence of how progressive neuropathological changes in the temporal and frontal areas may affect emotional processing in more advanced stages of the disease.
The current study examined the hypothesis that old people have a selective deficit in the identification of emotional facial expressions (EFEs) when the task conditions require the mechanism of the central executive. We have used a Dual Task (DT) paradigm to assess the role of visuo-spatial interference of working memory when processing emotional faces under two conditions: DT at encoding and DT at retrieval. Previous studies have revealed a loss of the ability to identify specific emotional facial expressions (EFEs) in old age. This has been consistently associated with a decline of the ability to coordinate the performance of two tasks concurrently. Working memory is usually tested using DT paradigms. Regarding to aging, there is evidence that with DT performance during encoding the costs are substantial. In contrast, the introduction of a secondary task after the primary task (i.e. at retrieval), had less detrimental effects on primary task performance in either younger or older adults. Our results demonstrate that aging is associated with higher DT costs when EFEs are identified concurrently with a visuo-spatial task. In contrast, there was not a significant age-related decline when the two tasks were presented sequentially. This suggests a deficit of the central executive rather than visuo-spatial memory deficits. The current data provide further support for the hypothesis that emotional processing is "top-down" controlled, and suggest that the deficits in emotional processing of old people depend, above all, on specific cognitive impairment.
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