Executive Dysfunction in Alzheimer's Disease

Abstract

Executive functioning was examined in 20 patients with Alzheimer's disease (AD) and 20 normal elderly subjects. The results showed that AD patients present lower performance compared to control subjects in all executive tasks, confirming that some executive deficits may be present in the first stages of the disease. A factorial analysis suggested that these deficits can be related to two domains of the executive functions: the inhibition abilities and the capacity to co-ordinate simultaneously storage and processing of information. Moreover, the performance on these factors is correlated to different anterior and posterior cortical areas.

Specificity of inhibitory deficits in normal aging and Alzheimer's disease

“…Impaired performance on the Hayling task in normal aging had previously been described in the literature [6,13,14], and was also partly explained by an influence of processing speed [6]. With regard to the AD patients' performance, there were no differences in comparison to control subjects in terms of response speed, but they produced more responses related to the item to be inhibited (for similar results, see [23]). These results indicate that AD patients are able to correctly inhibit the target word but not to restrain the production of the first alternative responses that came in mind, these alternatives being or not semantically related to the target words.…”

“…Similarly, a less reliable or absent negative priming effect has been observed in these patients [3,96; see, however, 67]. With regard to semantic inhibition, Collette et al [23] observed a weaker ability to suppress semantically related but task-irrelevant responses on the Hayling task [17], 5 and Duchek et al [36] found that AD patients are disproportionately influenced by semantically related distracting information during a reading task. Finally, perseverations [41,42,91] and intrusion errors [2,12,19,69] are frequently produced by AD patients during list recall performance, indicating an impairment of the suppression processes associated with explicit memory tasks.…”

Sensitivity to Expectancy Violations in Healthy Aging and Mild Cognitive Impairment.

“…Ready, Ott, Grace, and Cahn-Weiner (2003) also reported impairments in executive function in those with MCI. Similar to the episodic memory deficits, the executive (working memory) dysfunction in MCI seems to subtly mirror the impairments observed in early AD (Collette, Van der Linden, & Salmon, 1999;Greene, Hodges, & Baddeley, 1995;Lafleche & Albert, 1995;R. G. Morris, 1994).…”

Two aspects of impaired consciousness in Alzheimer's disease

“…Moreover, recollection of episodic memories (controlled retrieval compared to simple familiarity for information) was related to activation in prefrontal, parietal, and posterior cingulate regions in normal subjects (Henson et al, 1999). In AD, performances at diverse executive tasks were related either to frontal activity for phonemic 290 fluency, or to posterior associative cortices for dual tasks (Collette et al, 1999c). From this perspective, two interpretations may be proposed to account for the controlled process deficits of AD patients: they could originate either from multiple neuropathological and metabolic changes in both anterior and posterior cerebral areas or from a (partial) disconnection between the anterior and posterior cortical areas, leading to a less efficient transfer of information between these regions.…”