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.

S66. USING UNITIZATION TO CIRCUMVENT RELATIONAL MEMORY DEFICITS IN SCHIZOPHRENIA

Background Relational memory (RM) is disproportionately affected in schizophrenia. Unitization is a cognitive strategy that compensates for RM deficits by facilitating the combination of disparate pieces of information to form a single functional unit. Unitization has been effective in circumventing RM impairment in hippocampal amnesia and older adults with RM deficits when performing a Transverse Patterning (TP) task. We developed a brief intervention using unitization to circumvent RM impairment in individuals with schizophrenia when learning arbitrary item-relations in a TP task. We subsequently developed the Relational Trip Task (RTT), which uses pairs of real-life stimuli (faces, places, objects) and a narrative frame for encoding to investigate if unitization generalizes to a more relatable real-life context. Methods Twenty-two individuals with an RM deficit and a diagnosis of schizophrenia or related disorder were pseudo-randomized to either the unitization or control condition, from which 19 completed all TP tasks and 17 completed RTT. TP performance was measured at screening. TP and RTT task performances were measured pre-post learning unitization. During the RTT-unitized task, participants created their own unitizations, with assistance (50% of the task) and on their own. The control group received unitization training following study participation. The TP-unitized control group results were included in the analysis. Results TP task performance (percentage of correct trials) did not significantly differ between control (M = 49%, SD = 13%) and unitization groups (M= 60%, SD = 18%) at screening (t(17) = -1.506, p = 0.15). A 2-way mixed analysis of variance (ANOVA) did not reveal a group-task interaction for unitization and control group accuracy in the four TP versions (F(3,51) = 2.38, p = 0.08). A main effect of task (F(3, 51) = 9.43, p > 0.001) was decomposed using Tukey HSD pairwise post-hoc analyses and showed significantly higher TP task accuracy following unitization (M = 85%, SD = 19%) compared to the TP task at screening (M = 55%, SD = 16% p > 0.001), before unitization (M = 61%, SD = 19%, p = 0.001) and when prompting self-unitization (M = 68%, SD = 28%, p = 0.04). No other significant differences in task accuracies were revealed. Group accuracies in the RTT were compared using a 2-way mixed ANOVA, and yielded a significant interaction between group and task accuracy (F(1,15) = 4.93, p = 0.042). Simple main effect analysis showed that accuracy in the RTT post unitization training (M = 90%, SD = 9%) was higher than before training (M = 77%, SD = 14%, p = 0.046), but performance between the same versions of the RTT did not significantly differ in the control group (M1 = 73%, SD = 19%; M2 = 70%, SD = 23%; p = 0.26). Discussion TP performance improved when the unitization strategy was provided, but not when the self-generation of unitization was encouraged. Improved RTT performance was limited to the unitization group, suggesting that effects were unitization-specific rather than lead by practice. Logic follows that this strategy may be generalizable to more relatable, real-life contexts. Self-generation of unitization was effective in improving task performance when assistance was provided rather than merely encouraged, suggesting that patients may benefit from guidance generating their own unitizations rather than integrating this strategy on their own. These findings should be replicated in a larger sample, and strategies to provide effective self-generation of unitization should be explored. Moreover, the extent to which the RTT can detect differential relational memory impairment in individuals with schizophrenia when compared to healthy controls warrants further investigation.

Principles of Current Vertebrate Neuromorphology

Causal analysis of molecular patterning at neural plate and early neural tube stages has shown that the central nervous system (CNS) of vertebrates is essentially organized into transverse neural segments or neuromeres and longitudinal zones which follow the curved axis of the brain. The intersection of the longitudinal and transverse patterning processes in the embryonic brain leads to the formation of a checkerboard pattern of distinct progenitor domains called “fundamental morphological units” (FMUs). The topologically invariant pattern formed by the ventricular surfaces of the FMUs of a given taxon represents the “Bauplan” or “blueprint” of the brain of that taxon. The FMUs initially represent thin epithelial fields; during further development they are transformed into three-dimensional radial units, extending from the ventricular surface to the meningeal surface. It is of note that the boundaries of the neuromeres, longitudinal zones, and radial units all strictly adhere to a non-Cartesian coordinate system inherent to the CNS of all vertebrates. The major neural histogenetic processes, including cellular proliferation, radial migration, and differentiation, as well as the formation of grisea (cell masses, nuclei, and cortices), occur principally within the confines of the FMUs, although tangential migration may also take cells to distant sites. Hence, recognition and delimitation of these units is essential for the identification and interpretation of grisea. An outline of the procedure to be followed in these processes of identification and interpretation is presented, and a list of the pertinent homology criteria is provided.

Hippocampal Lateralization and Memory in Children and Adults

The neural organization of cognitive processes, particularly hemispheric lateralization, changes throughout childhood and adolescence. Differences in the neural basis of relational memory between children and adults are not well characterized. In this study we used magnetoencephalography to observe the lateralization differences of hippocampal activation in children and adults during performance of a relational memory task, transverse patterning (TP). The TP task was paired with an elemental control task, which does not depend upon the hippocampus. We contrasted two hypotheses; the compensation hypothesis would suggest that more bilateral activation in children would lead to better TP performance, whereas the maturation hypothesis would predict that a more adult-like right-lateralized pattern of hippocampal activation would lead to better performance. Mean-centered partial least squares analysis was used to determine unique patterns of brain activation specific to each task per group, while diminishing activation that is consistent across tasks. Our findings support the maturation hypothesis that a more adult-like pattern of increased right hippocampal lateralization in children leads to superior performance on the TP task. We also found dynamic changes of lateralization throughout the time course for all three groups, suggesting that caution is needed when interpreting conclusions about brain lateralization. (JINS, 2013, 19, 1–11)