Short-term Memory Binding Task Research Articles

Associations between sex and lifestyle activities with cognitive reserve in mid-life adults with genetic risk for Alzheimer's disease.

Females have a higher age-adjusted incidence of Alzheimer's Disease (AD) than males, even when accounting for longer lifespan and, therefore, stand to benefit the most from dementia prevention efforts. As exposure to many modifiable risk factors for dementia begins in mid-life, interventions must be implemented from middle-age. Building cognitive reserve, particularly through stimulating avocational activities and occupational attainment presents a crucial, underexplored, dementia prevention approach for mid-life. It is currently unknown, however, whether modifiable lifestyle factors can protect against AD processes, from mid-life, differentially for females and males who carry inherited risk for late-life dementia. To address this gap, this study investigated the impact of biological sex and APOE4 carrier status on the relationship between stimulating activities, occupational attainment, and cognition in mid-life. We leveraged the PREVENT-Dementia program, the world's largest study investigating the origins and early diagnosis of dementia in mid-life at-risk individuals (N = 700; 40-59 years). Cognitive performance was measured using the Cognito Battery and the Visual Short Term Memory Binding task. Mid-life specific reserve contributors were assessed via the Lifetime of Experiences Questionnaire. Females had significantly better episodic and relational memory (p < 0.001), and lower occupational attainment than males (p < 0.001). Engagement in stimulating activities was positively associated with episodic and relational memory, regardless of sex and APOE4 status (β = 0.05, CI 0.03-0.07, p < 0.001). APOE4 carriers showed significant sex differences in the association between occupational attainment and episodic and relational memory (β = 0.38, CI 0.12-0.63, p = 0.003). APOE4 carrier females with higher occupational attainment showed better cognition (β = 0.16, CI -0.002-0.32, p = 0.053), whereas APOE4 carrier males showed the opposite effect (β = -0.20, CI -0.40 - -0.001, p = 0.049). Our findings suggest that occupational attainment in mid-life contributes to cognitive reserve against inherited risk of dementia in females, but not males. They highlight the need for high precision approaches that consider biological sex and APOE4 carrier status to inform Alzheimer's disease prevention strategies and clinical trials.

The development and validation of a digital biomarker for remote assessment of Alzheimer's diseases risk.

Digital cognitive assessment is becoming increasingly widespread in ageing research and care, especially since the COVID-19 pandemic. Remote online collection provides opportunities for ageing and dementia professionals to collect larger datasets, increase the diversity of research participants and patients and offer cost-effective screening and monitoring methods for clinical practice and trials. However, the reliability of self-administered at-home tests compared to their lab-based counterparts often goes unexamined, compromising the validity of adopting such measures. Our aim is to validate a self-administered web-based version of the visual short-term memory binding task (VSTMBT), a potential digital biomarker sensitive to Alzheimer's disease processes, suitable for use on personal devices. A final cross-sectional sample of 37 older-adult (51-77 years) participants without dementia completed our novel self-administered version of the VSTMBT, both at home on a personal device and in the lab, under researcher-controlled conditions. ANOVA and Bayesian t-test found no significant differences between the task when it was remotely self-administered by participants at home compared to when it was taken under controlled lab conditions. These results indicate the VSTMBT can provide reliable data when self-administered at-home using an online version of the task and on a personal device. This finding has important implications for remote screening and monitoring practices of older adults, as well as supporting clinical practices serving diverse patient communities. Future work will assess remote administration in older adults with cognitive impairment and diverse socio-economic and ethno-cultural backgrounds as well as a bench-to-bedside application.

Electrophysiological correlates of objective memory impairments in community‐dwelling older adults at risk of dementia

AbstractBackgroundThe electrophysiological correlates of Short‐Term Memory Binding (STMB) have been previously investigated in older adults at risk of dementia (i.e., Mild Cognitive Impairment ‐MCI). Pietto et al. (2016) reported reduced early electrophysiological activity (100‐250 ms) over fronto‐central (FC) and parieto‐occipital (PO) regions in MCI patients recruited from clinic. We investigated if such an electrophysiological pattern is also observed in a larger sample of community‐dwelling older adults with MCI who had not sought medical advice.MethodsA sample of 215 community‐dwelling older adults were recruited into the study. They were assessed with a battery of cognitive tests including CERAD (Aguirre‐Acevedo et al., 2016), the Addenbrooke’s Cognitive Examination (ACE‐R), the STMB Task, clinical, and functional scales. The STMB task assesses the ability to detect changes between two consecutive visual arrays of coloured shapes. Changes consisted of shapes swapping colours (the binding condition). Time‐locked EEG signals were collected while participants performed the STMB task. Monte Carlo tests and non‐parametric bootstrapping running 1000 permutations revealed electrodes and time windows of relevance.ResultsA group of 108 participants met classical criteria for MCI (Petersen, 2004; Winblad et al., 2004). They showed impaired STMB abilities. ERP analyses revealed significant Group x Time Windows interactions (p&lt;0.01). Early ERP showed reduced neural recruitment (MCI&lt;HC) on the left PO and right centro‐parietal (CP) (300‐500ms) regions during shape‐colour encoding, and on PO bilaterally and left FC during retrieval (150‐450ms). Late ERP showed increased neural recruitment (MCI&gt;HC) on right fronto‐central (FC) regions (900‐1200ms) during shape‐colour encoding, and on left FC and PO regions (872‐1200ms) during retrieval.ConclusionAltered spatio‐temporal dynamics underpinning STMB deficits in MCI patients followed a pattern similar to that described by Pietto et al. (2016). Of note, we observed hyper‐recruitment for late ERP linked to encoding and retrieval over anterior and posterior regions of the STMB network. Such hyper‐recruitment may reflect compensatory changes in the early stages of MCI. These results confirm the usefulness of EEG‐based cognitive biomarkers to screen community‐dwelling older adults at risk of dementia.Aguirre‐Acevedo et al. (2016). Int. Psychogeriatr, 28(3), 503‐510.Pietto et al. (2016). Journal of Alzheimer’s Disease, 53(4), 1325‐1340.

The "when" matters: Evidence from memory markers in the clinical continuum of Alzheimer's disease.

Cognitive assessment able to detect impairments in the early neuropathological stages of Alzheimer's disease (AD) is urgently needed. The visual short-term memory binding task (VSTMBT) and the Free and Cued Selective Reminding Test (FCSRT) have been recommended by the neurodegenerative disease working group as promising tests to aid in the early detection of AD. In this study, we investigated their complementary value across the clinical stages of the AD continuum. One hundred and seventeen older adults with subjective cognitive complaint (SCC), 79 with mild cognitive impairment (MCI), 31 patients with AD dementia (ADD), and 37 cognitively unimpaired (CU) subjects, underwent assessment with the VSTMBT and the picture version of the Spanish FCSRT. After controlling for multiple comparisons, significant differences were found across groups. The VSTMBT was the only test that "marginally" differentiated between CU and SCC (d = 0.47, p = .052). Moreover, whereas the FCSRT showed a gradient (CU = SCC) > MCI > ADD, the VSTMBT gradient was CU > SCC > (MCI = ADD) suggesting that conjunctive binding deficits assessed by the latter may be sensitive to the very early stages of the disease. Our results suggest that the VSTMBT and the FCSRT are sensitive to the clinical continuum of AD. Whereas the former detects changes in the early prodromal stages, the latter is more sensitive to the advanced prodromal stages of AD. These novel tests can aid in the early detection, monitor disease progression and response to treatment, and thus support drug development programs. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

A digital biomarker for remote self‐assessment of Alzheimer’s Diseases: development and validation

AbstractBackgroundOnline data‐collection provide an opportunity for Alzheimer’s Disease research to collect large datasets crucial for understanding important public health concerns. However, the reliability of online tasks as compared to those administered in the lab is poorly examined. Our goal is to validate an online version of the short‐term memory‐binding task (STMBT), a potential digital biomarker sensitive to Alzheimer’s Disease (Parra et al., 2010), to understand if data collected online in two environments, at‐home and in the lab, is comparable.MethodWe created an online version of the STMBT task using Psytoolkit (Stoet 2010; Stoet 2017). Development involved piloting, group and user discussions to explore how such a novel tool could be best presented for self‐assessment. Useful insights led to refinement of the online tool (i.e., instruction videos, images, and text). The validation stage involves test‐retest reliability assessment of cognitively fit participants (aged &gt;40 years) who complete the two conditions of this paradigm (i.e., shape only and binding). Task Environment (home and in the lab) and conditions (shape and binding) were fully counterbalanced. Measures of general cognitive abilities, anxiety and at‐home environment were also taken.ResultRecruitment is on‐going, but preliminary data (n = 10) has already proved informative. A repeated measures ANOVA looking at task‐accuracy with factors of Environment (home vs. lab) and Condition (shape vs. binding) revealed no significant effects of Environment: F(1, 9) = 0.308, p = .591; Condition: F(1, 9) = 2.202, p = .172); or Interaction: F(1, 9) = 0.308, p = .591). For the shape condition, all participants performed near ceiling regardless of testing environment. In the binding condition, we observed good‐to‐excellent test‐retest reliability between environments using single measures interclass correlation (ICC = 0.954, CI 0.83‐0.99, (F(9, 9) = 39.62, p &lt;.001).ConclusionThese preliminary results indicate the STMBT can provide reliable data when self‐administered using an online version of the task which has important implications for public health researchers. For our fully powered sample, we will provide summary of other measures.

A digital biomarker for remote self-assessment of Alzheimer's Diseases: development and validation.

Online data-collection provide an opportunity for Alzheimer's Disease research to collect large datasets crucial for understanding important public health concerns. However, the reliability of online tasks as compared to those administered in the lab is poorly examined. Our goal is to validate an online version of the short-term memory-binding task (STMBT), a potential digital biomarker sensitive to Alzheimer's Disease (Parra et al., 2010), to understand if data collected online in two environments, at-home and in the lab, is comparable. We created an online version of the STMBT task using Psytoolkit (Stoet 2010; Stoet 2017). Development involved piloting, group and user discussions to explore how such a novel tool could be best presented for self-assessment. Useful insights led to refinement of the online tool (i.e., instruction videos, images, and text). The validation stage involves test-retest reliability assessment of cognitively fit participants (aged >40 years) who complete the two conditions of this paradigm (i.e., shape only and binding). Task Environment (home and in the lab) and conditions (shape and binding) were fully counterbalanced. Measures of general cognitive abilities, anxiety and at-home environment were also taken. Recruitment is on-going, but preliminary data (n=10) has already proved informative. A repeated measures ANOVA looking at task-accuracy with factors of Environment (home vs. lab) and Condition (shape vs. binding) revealed no significant effects of Environment: F(1, 9) = 0.308, p = .591; Condition: F(1, 9) = 2.202, p = .172); or Interaction: F(1, 9) = 0.308, p = .591). For the shape condition, all participants performed near ceiling regardless of testing environment. In the binding condition, we observed good-to-excellent test-retest reliability between environments using single measures interclass correlation (ICC = 0.954, CI 0.83-0.99, (F(9, 9) = 39.62, p <.001). These preliminary results indicate the STMBT can provide reliable data when self-administered using an online version of the task which has important implications for public health researchers. For our fully powered sample, we will provide summary of other measures.

Short-Term Memory Binding Distinguishing Amnestic Mild Cognitive Impairment from Healthy Aging: A Machine Learning Study.

Amnestic mild cognitive impairment (aMCI) is the most common preclinical stage of Alzheimer's disease (AD). A strategy to reduce the impact of AD is the early aMCI diagnosis and clinical intervention. Neuroimaging, neurobiological, and genetic markers have proved to be sensitive and specific for the early diagnosis of AD. However, the high cost of these procedures is prohibitive in low-income and middle-income countries (LIMCs). The neuropsychological assessments currently aim to identify cognitive markers that could contribute to the early diagnosis of dementia. Compare machine learning (ML) architectures classifying and predicting aMCI and asset the contribution of cognitive measures including binding function in distinction and prediction of aMCI. We conducted a two-year follow-up assessment of a sample of 154 subjects with a comprehensive multidomain neuropsychological battery. Statistical analysis was proposed using complete ML architectures to compare subjects' performance to classify and predict aMCI. Additionally, permutation importance and Shapley additive explanations (SHAP) routines were implemented for feature importance selection. AdaBoost, gradient boosting, and XGBoost had the highest performance with over 80%success classifying aMCI, and decision tree and random forest had the highest performance with over 70%success predictive routines. Feature importance points, the auditory verbal learning test, short-term memory binding tasks, and verbal and category fluency tasks were used as variables with the first grade of importance to distinguish healthy cognition and aMCI. Although neuropsychological measures do not replace biomarkers' utility, it is a relatively sensitive and specific diagnostic tool for aMCI. Further studies with ML must identify cognitive performance that differentiates conversion from average MCI to the pathological MCI observed in AD.

Optimizing Subjective Cognitive Decline to Detect Early Cognitive Dysfunction.

The utility of subjective cognitive decline (SCD) as an indicator of preclinical AD is overshadowed by its inconsistent association with objective cognition. This study examines if manipulations of SCD measurement affect its association with early cognitive dysfunction characteristic of preclinical AD. Cognitively healthy older adults (n = 110) completed SCD questionnaires that elicited complaints in general, compared to 5 years ago (retrospective SCD) and compared to their peers (age-anchored SCD) in binary and Likert scales. Outcome cognitive tasks included an associative memory task (Face-Name Test), a visual short-term memory binding task (STMB test), and a clinical neuropsychological list learning test (Selective Reminder Test). SCD complaints, when compared to age-matched peers (age-anchored SCD) were endorsed less frequently than complaints compared to 5 years ago (retrospective SCD) (p < 0.01). In demographically adjusted regressions, age-anchored ordinal-rated SCD was associated with short term memory binding (β= -0.22, p = 0.040, CI = -0.45, -0.01), associative memory (β= -0.26, p = 0.018, CI = -0.45, -0.06), and list learning (β= -0.31, p = 0.002, CI = -0.51, -0.12). Retrospective and general ordinal-rated SCD was associated with associative memory (β= -0.25, p = 0.012, CI = -0.44, -0.06; β= -0.29, p = 0.003, CI = -0.47, -0.10) and list learning only (β= -0.25, p = 0.014, CI = -0.45, -0.05; β= -0.28, p = 0.004, CI = -0.48, -0.09). Ordinal age-anchored SCD appears better suited than other SCD measurements to detect early cognitive dysfunction characteristic of preclinical AD.

Translating Visual Short-Term Memory Binding Tasks to Clinical Practice: From Theory to Practice.

Translating Visual Short-Term Memory Binding Tasks to Clinical Practice: From Theory to Practice.

Neurocognitive mechanisms underlying working memory encoding and retrieval in Attention-Deficit/Hyperactivity Disorder

Working memory (WM) impairments in ADHD have been consistently reported along with deficits in attentional control. Yet, it is not clear which specific WM processes are affected in this condition. A deficient coupling between attention and WM has been reported. Nevertheless, most studies focus on the capacity to retain information rather than on the attention-dependent stages of encoding and retrieval. The current study uses a visual short-term memory binding task, measuring both behavioral and electrophysiological responses to characterize WM encoding, binding and retrieval comparing ADHD and non-ADHD matched adolescents. ADHD exhibited poorer accuracy and larger reaction times than non-ADHD on all conditions but especially when a change across encoding and test displays occurred. Binding manipulation affected equally both groups. Encoding P3 was larger in the non-ADHD group. Retrieval P3 discriminated change only in the non-ADHD group. Binding-dependent ERP modulations did not reveal group differences. Encoding and retrieval P3 were significantly correlated only in non-ADHD. These results suggest that while binding processes seem to be intact in ADHD, attention-related encoding and retrieval processes are compromised, resulting in a failure in the prioritization of relevant information. This new evidence can also inform recent theories of binding in visual WM.

P3‐013: PRELIMINARY EVIDENCE OF THE IMPACT OF INTRATHECAL CELL THERAPY WITH AUTOLOGOUS STROMAL CELLS ON SHORT‐TERM MEMORY BINDING IN EARLY ALZHEIMER'S DISEASE CASES

Background: A decrease in brain glucose metabolism in Alzheimer’s disease (AD) patients is considered a critical driver of cognitive impairment, and medications used in AD target this metabolic dysfunction. Recent evidence has shown a significant increase in glucose metabolism associated with neurocognitive improvement after intrathecal administration of bone marrow mesenchymal stromal cells (MSCs) in patients suffering from severe TBI or haemorrhagic stroke. We hypothesise that this cell therapy could also be useful in AD patients. Methods: We studied two AD patients with cerebral beta-amyloid neuritic plaques detected with 18FFDG-PET. The patients received every three months 100 million of autologous MSCs by intrathecal route, until a total dose of 300 million. None received any other medication for its disease at the time of receiving cell therapy. Clinical and neuroimaging studies were performed previous and after the therapy, including brain glucose metabolism by 18F-FDG-PET and assessment with the visual short-term memory binding task (VSTMBT). This task has been proposed as a preclinical marker of AD. It requires subjects to detect whether or not two combinations of shape and colour change across two sequential arrays. Results: A global increase in cerebral glucose metabolism was observed after each administration of cell therapy. Single case statistics revealed that treated and untreated patients did not differ on their pre-treatment VSTMBT scores and both were significantly impaired relative to controls. The chance that an untreated AD patient would show more impairment than treated patients was 39.25% (p= 0.785) for case 1, and 50.00% (p=1.0) for case 2. This chance increased post-treatment to 97.40% (p=0.05) and 99.74% (p=0.005) respectively. Conclusion: These preliminary findings suggest that intrathecal administration of autologous MSCs should be considered as a new therapeutic strategy for Alzheimer’s dementia and deserves further studies.

Network analysis through the use of joint-distribution entropy on EEG recordings of MCI patients during a visual short-term memory binding task.

The early diagnosis of Alzheimer's disease (AD) is particularly challenging. Mild cognitive impairment (MCI) has been linked to AD and electroencephalogram (EEG) recordings are able to measure brain activity directly with high temporal resolution. In this context, with appropriate processing, the EEG recordings can be used to construct a graph representative of brain functional connectivity. This work studies a functional network created from a non-linear measure of coupling of beta-filtered EEG recordings during a short-term memory binding task. It shows that the values of the small-world characteristic and eccentricity are, respectively, lower and higher in MCI patients than in controls. The results show how MCI leads to EEG functional connectivity changes. They expect that the network differences between MCIs and control subjects could be used to gain insight into the early stages of AD.

Visual Processing during Short-Term Memory Binding in Mild Alzheimer's Disease.

Patients with Alzheimer's disease (AD) typically present with attentional and oculomotor abnormalities that can have an impact on visual processing and associated cognitive functions. Over the last few years, we have witnessed a shift toward the analyses of eye movement behaviors as a means to further our understanding of the pathophysiology of common disorders such as AD. However, little work has been done to unveil the link between eye moment abnormalities and poor performance on cognitive tasks known to be markers for AD patients, such as the short-term memory-binding task. We analyzed eye movement fixation behaviors of thirteen healthy older adults (Controls) and thirteen patients with probable mild AD while they performed the visual short-term memory binding task. The short-term memory binding task asks participants to detect changes across two consecutive arrays of two bicolored object whose features (i.e., colors) have to be remembered separately (i.e., Unbound Colors), or combined within integrated objects (i.e., Bound Colors). Patients with mild AD showed the well-known pattern of selective memory binding impairments. This was accompanied by significant impairments in their eye movements only when they processed Bound Colors. Patients with mild AD remarkably decreased their mean gaze duration during the encoding of color-color bindings. These findings open new windows of research into the pathophysiological mechanisms of memory deficits in AD patients and the link between its phenotypic expressions (i.e., oculomotor and cognitive disorders). We discuss these findings considering current trends regarding clinical assessment, neural correlates, and potential avenues for robust biomarkers.

Locating Temporal Functional Dynamics of Visual Short-Term Memory Binding using Graph Modular Dirichlet Energy

Visual short-term memory binding tasks are a promising early marker for Alzheimer’s disease (AD). To uncover functional deficits of AD in these tasks it is meaningful to first study unimpaired brain function. Electroencephalogram recordings were obtained from encoding and maintenance periods of tasks performed by healthy young volunteers. We probe the task’s transient physiological underpinnings by contrasting shape only (Shape) and shape-colour binding (Bind) conditions, displayed in the left and right sides of the screen, separately. Particularly, we introduce and implement a novel technique named Modular Dirichlet Energy (MDE) which allows robust and flexible analysis of the functional network with unprecedented temporal precision. We find that connectivity in the Bind condition is less integrated with the global network than in the Shape condition in occipital and frontal modules during the encoding period of the right screen condition. Using MDE we are able to discern driving effects in the occipital module between 100–140 ms, coinciding with the P100 visually evoked potential, followed by a driving effect in the frontal module between 140–180 ms, suggesting that the differences found constitute an information processing difference between these modules. This provides temporally precise information over a heterogeneous population in promising tasks for the detection of AD.

Memory binding and white matter integrity in familial Alzheimer's disease.

Binding information in short-term and long-term memory are functions sensitive to Alzheimer's disease. They have been found to be affected in patients who meet criteria for familial Alzheimer's disease due to the mutation E280A of the PSEN1 gene. However, only short-term memory binding has been found to be affected in asymptomatic carriers of this mutation. The neural correlates of this dissociation are poorly understood. The present study used diffusion tensor magnetic resonance imaging to investigate whether the integrity of white matter structures could offer an account. A sample of 19 patients with familial Alzheimer's disease, 18 asymptomatic carriers and 21 non-carrier controls underwent diffusion tensor magnetic resonance imaging, neuropsychological and memory binding assessment. The short-term memory binding task required participants to detect changes across two consecutive screens displaying arrays of shapes, colours, or shape-colour bindings. The long-term memory binding task was a Paired Associates Learning Test. Performance on these tasks were entered into regression models. Relative to controls, patients with familial Alzheimer's disease performed poorly on both memory binding tasks. Asymptomatic carriers differed from controls only in the short-term memory binding task. White matter integrity explained poor memory binding performance only in patients with familial Alzheimer's disease. White matter water diffusion metrics from the frontal lobe accounted for poor performance on both memory binding tasks. Dissociations were found in the genu of corpus callosum which accounted for short-term memory binding impairments and in the hippocampal part of cingulum bundle which accounted for long-term memory binding deficits. The results indicate that white matter structures in the frontal and temporal lobes are vulnerable to the early stages of familial Alzheimer's disease and their damage is associated with impairments in two memory binding functions known to be markers for Alzheimer's disease.

Relational and conjunctive binding functions dissociate in short-term memory

Remembering complex events requires binding features within unified objects (conjunctions) and holding associations between objects (relations). Recent studies suggest that the two functions dissociate in long-term memory (LTM). Less is known about their functional organization in short-term memory (STM). The present study investigated this issue in patient AE affected by a stroke which caused damage to brain regions known to be relevant for relational functions both in LTM and in STM (i.e., the hippocampus). The assessment involved a battery of standard neuropsychological tasks and STM binding tasks. One STM binding task (Experiment 1) presented common objects and common colors forming either pairs (relations) or integrated objects (conjunctions). Free recall of relations or conjunctions was assessed. A second STM binding task used random polygons and non-primary colors instead (Experiment 2). Memory was assessed by selecting the features that made up the relations or the conjunctions from a set of single polygons and a set of single colors. The neuropsychological assessment revealed impaired delayed memory in AE. AE’s pronounced relational STM binding deficits contrasted with his completely preserved conjunctive binding functions in both Experiments 1 and 2. Only 2.35% and 1.14% of the population were expected to have a discrepancy more extreme than that presented by AE in Experiments 1 and 2, respectively. Processing relations and conjunctions of very elementary nonspatial features in STM led to dissociating performances in AE. These findings may inform current theories of memory decline such as those linked to cognitive aging.

Specific deficit of colour–colour short-term memory binding in sporadic and familial Alzheimer's disease

Short-term memory binding of visual features which are processed across different dimensions (shape–colour) is impaired in sporadic Alzheimer's disease, familial Alzheimer's disease, and in asymptomatic carriers of familial Alzheimer's disease. This study investigated whether Alzheimer's disease also impacts on within-dimension binding processes. The study specifically explored whether visual short-term memory binding of features of the same type (colour–colour) is sensitive to Alzheimer's disease. We used a neuropsychological battery and a short-term memory binding task to assess patients with sporadic Alzheimer's disease (Experiment 1), familial Alzheimer's disease (Experiment 2) due to the mutation E280A of the Presenilin-1 gene and asymptomatic carriers of the mutation. The binding task assessed change detection within arrays of unicoloured objects (Colour Only) or bicoloured objects the colours of which had to be remembered separately (Unbound Colours) or together (Bound Colours). Performance on the Bound Colours condition (1) explained the largest proportion of variance between patients (sporadic and familial Alzheimer's disease), (2) combined more sensitivity and specificity for the disease than other more traditional neuropsychological tasks, (3) identified asymptomatic carriers of the mutation even when traditional neuropsychological measures and other measures of short-term memory did not and, (4) contrary to shape–colour binding, correlated with measures of hippocampal functions. Colour–colour binding and shape–colour binding both appear to be sensitive to AD even though they seem to rely on different brain mechanisms.

Visual short-term memory binding in Alzheimer’s disease and depression

The differential diagnosis between Alzheimer's disease (AD) and major depression (MD) in the elderly can be problematic because the cognitive profile of the two conditions overlaps. Associative learning tasks seem to separate AD from MD. However, they are sensitive to the effects of normal ageing. Short-term memory-binding tasks have proved insensitive to the effects of normal ageing and highly sensitive to AD. However, they have not been used to differentiate AD from MD. The present study was aimed at investigating visual short-term memory binding in AD and MD. Fourteen AD patients, 14 patients with MD, and 14 healthy older adults were asked to perform a visual short-term memory binding task that investigated the retention of shapes, colors, or combinations of shapes and colors. Participants were to recognize changes occurring between two consecutive displays either in a single dimension (i.e., shape or color only) or in two dimensions (i.e., shape-color binding). Short-term memory performance for shape or color only was equivalent across groups. The only significant effect found was in short-term memory for shape-color binding and this was due to AD patients performing poorly in this condition only. The results extend previous findings in AD to visual short-term memory and suggest that the specific impairment in binding information in memory differentiates between the performance of AD and patients with MD.