Exploring the sociodemographic, clinical and neuropsychological factors associated with relational memory in schizophrenia

Episodic memory impairments in schizophrenia, including its relational memory component, are associated with significant clinical and functional variables, such as employment status, social and occupational functioning, and early and long-term remission. The Transverse Patterning (TP) task, a computer task designed to detect impairment in relational memory performance, has been used as a measure of relational binding deficit in this population. Individuals with schizophrenia often fail to learn TP with standard training and more than a quarter of patients fail the task even when extensive training is provided. TP failure may reflect multiple cognitive deficits (i.e. executive functions, working memory and visual memory). Identifying the neuropsychological factors, awareness distinctions, and strategy use differences between TP learners and non-learners can improve our understanding of underlying mechanisms required for successful performance in TP and, consequently, improve cognitive interventions that are targeted to ameliorate relational memory performance. The present study investigated the sociodemographic, clinical, neuropsychological and task-specific (i.e. task awareness and strategy use) factors associated with TP learning and impairment in schizophrenia. Sixty-nine participants with a diagnosis of schizophrenia or related psychosis were recruited for this study (66 completers). They completed two versions of the TP task (one semantically-rich and one relational-binding dependent) and answered a questionnaire to evaluate task awareness and strategy use in each condition and had sociodemographic and clinical data collected at screening. Twenty-six participants (38.8%) were unable to learn all the task rules after extensive training. In a subset of participants who underwent neurocognitive assessment (N = 29), learners had significantly superior verbal, visual and working memory, executive functions and overall cognitive functioning compared to non-learners. Group comparisons also suggested superior awareness of task rules and pairs relationships for learners compared to non-learners. Learners used cognitive strategies (such as memorizing how the objects interacted, naming the objects and qualifying their interactions with action verbs) more often than non-learners, and strategies seemed to be more elaborated for learners than for non-learners. This study confirmed previous findings that a subset of individuals with schizophrenia shows significant relational memory impairment assessed by the transverse-patterning paradigm which is not improved by stepwise TP training. It also brings new insight into factors associated with TP task performance, including neurocognitive markers that seem to contribute to TP learning. Finally, this study points to task awareness and strategy use components underlying successful TP learning. This knowledge could be useful for future interventions that are targeted to improve relational memory performance in schizophrenia when stepwise training is not sufficient.

Reliability and Feasibility of the Memory Associative Test TMA-93

Background: Memory tests focused on binding may be more sensitive to diagnose Alzheimer’s disease (AD) at an early phase. TMA-93 examines relational binding by images. Objective: Evaluate the reliability (internal consistency and inter-rater and test-retest reliability) and feasibility of the TMA-93 in a clinic setting with low-educated individuals and limited face-to-face time per patient. Methods: The study was undertaken in a neurology outpatient clinic of a hospital in Southern Spain. The internal consistency of the TMA-93 was estimated in 35 patients with amnestic mild cognitive impairment (aMCI) and 40 healthy controls (HCs). The inter-rater reliability (by two raters) and feasibility (by recording the percentage of participants who completed the test, and by timing the administration time) were evaluated in HCs (n = 16), aMCI patients (n = 18), and mild dementia patients (n = 15). The test-retest reliability for the TMA-93 total score was studied in 51 HCs tested by the same examiner 2–4 months apart. The internal consistency was estimated by Cronbach’s alpha. The inter-rater and test-retest reliability was quantified by the intraclass correlation coefficient (ICC). The administration time was compared by diagnosis. Results: The internal consistency was “optimal” (Cronbach’s alpha = 0.936). The test-retest reliability was “good” [ICC = 0.802 (CI 95% = 0.653–0.887)]. The inter-rater reliability was “optimal” [ICC = 0.999, (CI 95% = 0.999–1)]. All participants completed the test. The administration time ranged from less than 3 min in HCs to 6 min in aMCI patients, and 7 min in mild dementia patients. Conclusion: Good feasibility and reliability support using the TMA-93 for examining visual relational binding, particularly in the context of low-educational attainment and limited time per patient.

Relational binding and holistic retrieval in aging

Episodic memory binds together diverse elements of an event into a cohesive unit. This property enables the reconstruction of multidimensional experiences when triggered by a cue related to a past event via pattern completion processes. Such holistic retrieval is evident in young adults, as shown by dependency in the retrieval success for different associations from the same event (Horner & Burgess, 2013, 2014). Aspects of episodic memory capacity are vulnerable to aging processes, as shown by reduced abilities to form linkages within an event through relational binding (associative deficit hypothesis: Naveh-Benjamin, 2002). However, prior work has not examined whether this reduction affects holistic retrieval in typical aging. Here, we leveraged dependency analyses to examine whether older adults remember or forget events holistically, and whether the degree of holistic retrieval declines with old age. We found evidence for continued holistic retrieval, because accuracy for one aspect of an event predicted accuracy for other aspects of the same event. Younger and older adults did not differ in the degree of holistic recollection, despite robust age-related differences in relational binding. However, within the group of older adults, holistic recollection showed a significant decline with advancing age, controlling for pairwise relational binding performance, verbal IQ, and general cognitive status. These results suggest that a decline in holistic retrieval is an aspect of episodic memory decrements later in cognitive aging.

Building up and wearing down episodic memory: Mnemonic discrimination and relational binding

Our capacity to form and retrieve episodic memories improves over childhood but declines in old age. Understanding these changes requires decomposing episodic memory into its components: (1) mnemonic discrimination of similar people, objects and contexts, and (2) relational binding of these components. We designed novel memory tasks to assess these component processes involving animations that are appropriate across the lifespan (ages 4 - 80 in our sample). In Experiment 1, we assessed mnemonic discrimination of objects as well as relational binding in a common task format. Both components follow an inverted U-shaped curve across age but were positively correlated only in the aging group. In Experiment 2, we examined mnemonic discrimination of context and its effect on relational binding. Relational memory in low-similarity contexts showed robust gains between the ages of 4 and 6, and 6-year-olds performed similarly to adults. In contrast, relational memory in high-similarity contexts showed more protracted development, with 4- and 6-year-olds both performing worse than young adults and not differing from each other. Relational memory in both context conditions declined in aging. As in Experiment 1, performances in low- and high-similarity contexts were strongly related only in the older adults. This multi-process approach provides important theoretical insights into lifespan changes in episodic memory.