Abstract
A difficulty in encoding spatial information in an egocentric (i.e., body-to-object) and especially allocentric (i.e., object-to-object) manner, and impairments in executive function (EF) are typical in amnestic mild cognitive impairment (aMCI) and Alzheimer’s disease (AD). Since executive functions are involved in spatial encodings, it is important to understand the extent of their reciprocal or selective impairment. To this end, AD patients, aMCI and healthy elderly people had to provide egocentric (What object was closest to you?) and allocentric (What object was closest to object X?) judgments about memorized objects. Participants’ frontal functions, attentional resources and visual-spatial memory were assessed with the Frontal Assessment Battery (FAB), the Trail Making Test (TMT) and the Corsi Block Tapping Test (forward/backward). Results showed that ADs performed worse than all others in all tasks but did not differ from aMCIs in allocentric judgments and Corsi forward. Regression analyses showed, although to different degrees in the three groups, a link between attentional resources, visuo-spatial memory and egocentric performance, and between frontal resources and allocentric performance. Therefore, visuo-spatial memory, especially when it involves allocentric frames and requires demanding active processing, should be carefully assessed to reveal early signs of conversion from aMCI to AD.
Highlights
We argue that the reason for these conflicting results across samples of Amnestic mild cognitive impairment (aMCI) may be due to the complexity of executive function (EF) and the concomitant involvement of visuo-spatial deficits
In the past few years, much evidence has suggested that reduced ability to encode, represent and retrieve visuo-spatial information from memory, especially according to an allocentric reference frame, could be one of the early behavioral markers of the conversion from aMCI to Alzheimer’s disease (AD) dementia [27,38,60,61]
AD patients were less accurate than both aMCI people and healthy participants in providing egocentric judgments
Summary
Amnestic mild cognitive impairment (aMCI) is a clinical condition characterized by alterations in memory domains and a high risk of neurodegenerative progression [1,2].Epidemiological studies have revealed that people with aMCI progress to Alzheimer’s disease (AD) dementia at a 4–10 times higher risk than healthy elderly people [1,3,4].Conversion from aMCI to AD implies impairments in cognitive domains that may appear within a decade, with deficits in episodic and semantic memory, executive function, visuospatial memory, spatial skills, attention, apraxia, perceptual speed and verbal recall, up to the involvement of all cognitive domains in overt AD [5,6,7].In the attempt to identify prodromal cognitive signs of AD onset, separate clinical observations have reported impairments of the executive function (EF) in aMCI and AD (forMCI: [8,9], for AD: [10,11,12]; for a review, see [13]). Amnestic mild cognitive impairment (aMCI) is a clinical condition characterized by alterations in memory domains and a high risk of neurodegenerative progression [1,2]. In the attempt to identify prodromal cognitive signs of AD onset, separate clinical observations have reported impairments of the executive function (EF) in aMCI and AD Zhang et al [16] reported that the aMCI group had difficulties compared with the healthy control group on tests of cognitive planning (e.g., Trail Making, verbal fluency tests) but not inhibition and control (Go/NoGo and Stroop tests). Gu et al [9] observed more severe alterations in updating operations of working memory (WM), detections of the target stimulus and conflict processes in multiple domain-aMCI, compared to singledomain-aMCI patients and healthy controls. Bisiacchi et al [17] showed preserved EF in aMCI patients compared to healthy elderly individuals
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