Topographical short‐term memory differentiates Alzheimer's disease from frontotemporal lobar degeneration

Abstract

We used a recently developed test of spatial memory--the Four Mountains Test--to investigate the core cognitive processes underpinning topographical disorientation in patients with amnestic mild cognitive impairment (a-MCI) and mild Alzheimer's disease (AD). Performance of these clinical groups was compared with age-matched controls, patients with frontotemporal lobar degeneration (FTLD), and patients with subjective memory impairments. We investigated the perception (concurrent match-to-sample) and short-term retention (2-s delayed match-to-sample) of the configuration of topographical features in computer-generated landscapes shown from different viewpoints. Thirty-one patients were tested (7 AD, 6 a-MCI, 7 temporal variant FTLD, 5 frontal variant FTLD, 6 subjective memory impairment) and 25 age- and gender-matched controls. Brain MRI was available for 27 patients; medial temporal lobe atrophy was assessed using a visual rating scale. Patients with a-MCI or mild AD were impaired on topographical short-term memory, but not perception. No other group differences were found on the topographical subtests. Notably, patients with temporal variants of FTLD performed normally, regardless of the laterality of damage. Subtests for the perception and retention of nonspatial aspects of the landscapes (weather conditions, seasonal and daily variations in lighting and color) were poor at differentiating the patient groups. These results indicate a core deficit in representing topographical layout, even for very short durations, within the context of more general long-term memory impairments found in AD, and suggest that this function is particularly sensitive to the earliest stages of the disease.

Temporal Order Memory Assessed during Spatiotemporal Navigation As a Behavioral Cognitive Marker for Differential Alzheimer's Disease Diagnosis

“…2 B). The form of learning impairment presented here is consistent with other studies' results showing intact topographical perception in AD (Bird et al, 2010) and partially preserved route learning capacities in virtual reality in early AD (Cushman et al, 2008).…”

“…This hippocampal locus of early AD pathology is consistent with spatiotemporal orientation impairments in everyday activities (Pai and Jacobs, 2004), such as difficulties in finding one's way in unfamiliar environments in both patients with prodromal AD-the symptomatic predementia phase (deIpolyi et al, 2007;Cushman et al, 2008)-and AD patients (Bird et al, 2010). Correspondingly, patients with mild AD are impaired for spatial memory (Kessels et al, 2005;Hort et al, 2007;Cushman et al, 2008) as well as for spatiotemporal memory (Cherrier et al, 2001;Kalová et al, 2005;deIpolyi et al, 2007).…”

The 4 Mountains Test: A Short Test of Spatial Memory with High Sensitivity for the Diagnosis of Pre-dementia Alzheimer's Disease

“…Correlations were not determined for other brain regions, reflecting the study hypothesis. In particular, correlations with frontal brain regions were not calculated since 4MT performance is not impaired in patients with frontotemporal dementia 18,19 . All study groups (MCI, AD, HC), and within the MCI biomarker subgroups, were matched in terms of demographics (age, gender, years of education) ( Table 1 20 .…”

“…There were significant differences between study groups in terms of performance on the 4MT test (p <0.001, 18,19 , 4MT scores differed significantly between groups of MCI patients with and without CSF biomarker evidence of AD, who were otherwise matched in terms of demographics, symptom duration, premorbid IQ and performance on general neuropsychometric testing. Of particular note, there was no significant difference between the 2 MCI groups in terms of Rey Auditory Verbal Learning Test (RAVLT) performance.…”

“…The aim of the viewpoint change is to encourage allocentric spatial strategies (exploiting spatial representations which are known to exist within the hippocampal formation, see Hartley et al, 2014 for a recent review , this test was applied to patients with dementia. Results from separate research groups showed that the 4MT could differentiate patients with ADrelated dementia, not only from age-matched control subjects but also from patients with other dementia-causing disorders 18,19 .…”