Transverse Patterning Research Articles

Effects of extended practice and unitization on relational memory in older adults and neuropsychological lesion cases

ABSTRACT Unitization – the fusion of objects into a single unit through an action/consequence sequence – can mitigate relational memory impairments, but the circumstances under which unitization is effective are unclear. Using transverse patterning (TP), we compared unitization (and its component processes of fusion, motion, and action/consequence) with extended practice on relational learning and transfer in older adults and neuropsychological cases with lesions (to varying extents) in the medial prefrontal cortex (mPFC) or hippocampus/medial temporal lobe (HC/MTL). The latter included a person with bilateral HC lesions primarily within the dentate gyrus. For older adults, TP accuracy increased, and transfer benefits were observed, with extended practice and unitization. Broadly, the lesion cases did not benefit from either extended practice or unitization, suggesting the mPFC and dentate gyrus play important roles in relational memory and in unitization. The results suggest that personalized strategy interventions must align with the cognitive and neural profiles of the user.

Network connectivity underlying episodic memory in children: Application of a pediatric brain tumor survivor injury model.

Episodic memory involves personal experiences paired with their context. The Medial Temporal, Posterior Medial, Anterior Temporal, and Medial Prefrontal networks have been found to support the hippocampus in episodic memory in adults. However, there lacks a model that captures how the structural and functional connections of these networks interact to support episodic memory processing in children. Using diffusion-weighted imaging, magnetoencephalography, and memory tests, we quantified differences in white matter microstructure, neural communication, and episodic memory performance, respectively, of healthy children (n=23) and children with reduced memory performance. Pediatric brain tumor survivors (PBTS; n=24) were used as a model, as they exhibit reduced episodic memory and perturbations in white matter and neural communication. We observed that PBTS, compared to healthy controls, showed significantly (p<0.05) (1) disrupted white matter microstructure between these episodic memory networks through lower fractional anisotropy and higher mean and axial diffusivity, (2) perturbed theta band (4-7Hz) oscillatory synchronization in these same networks through higher weighted phase lag indices (wPLI), and (3) lower episodic memory performance in the Transverse Patterning and Children's Memory Scale (CMS) tasks. Using partial-least squares path modeling, we found that brain tumor treatment predicted network white matter damage, which predicted inter-network theta hypersynchrony and lower verbal learning (directly) and lower verbal recall (indirectly via theta hypersynchrony). Novel to the literature, our findings suggest that white matter modulates episodic memory through effect on oscillatory synchronization within relevant brain networks. RESEARCH HIGHLIGHTS: Investigates the relationship between structural and functional connectivity of episodic memory networks in healthy children and pediatric brain tumor survivors Pediatric brain tumor survivors demonstrate disrupted episodic memory, white matter microstructure and theta oscillatory synchronization compared to healthy children Findings suggest white matter microstructure modulates episodic memory through effects on oscillatory synchronization within relevant episodic memory networks.

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

ABSTRACT Introduction The Transverse Patterning (TP) task has been used to measure episodic relational memory (RM) deficits in clinical populations. Individuals with schizophrenia often fail to learn TP with standard, and sometimes extensive training. Identifying the differences between TP learners and non-learners can improve our understanding of successful TP performance and its underlying mechanisms, which may help improve interventions aimed at ameliorating RM performance. We investigated sociodemographic, clinical and neuropsychological factors associated with TP performance in schizophrenia. Methods Sixty-six participants with schizophrenia completed a semantically rich and a relational-binding dependent version of the TP task and reported on their task awareness and strategy use. Results Twenty-six participants failed to learn the task rules after extensive training. Learners had superior verbal, visual and working memory, executive functions and overall cognitive functioning compared to non-learners. Learners also had superior awareness of task rules and pairs relationships and used elaborated cognitive strategies more often. Conclusions Our results support previous findings that some individuals with schizophrenia show RM impairment even with extensive TP training. We shed light on neuropsychological and metacognitive factors associated with TP performance. This knowledge could enhance interventions targeted to improve relational memory in schizophrenia when extensive training fails.

Brain-behavior investigation of potential cognitive markers of Alzheimer's disease in middle age: a multi-modal imaging study.

Early detection of Alzheimer's disease remains a challenge, and the development and validation of novel cognitive markers of Alzheimer's disease is critical to earlier disease detection. The goal of the present study is to examine brain-behavior relationships of translational cognitive paradigms dependent on the medial temporal lobes and prefrontal cortices, regions that are first to undergo Alzheimer's-associated changes. We employed multi-modal structural and functional MRI to examine brain-behavior relationships in a healthy, middle-aged sample (N = 133; 40-60years). Participants completed two medial temporal lobe-dependent tasks (virtual Morris Water Task and Transverse Patterning Discriminations Task), and a prefrontal cortex-dependent task (Reversal Learning Task). No associations were found between various MRI measures of brain integrity and the Transverse Patterning or Reversal Learning tasks (p's > .05). We report associations between virtual Morris Water Task performance and medial temporal lobe volume, hippocampal microstructural organization, fornix integrity, and functional connectivity within the executive control and frontoparietal control resting state networks (all p's <0.05; did not survive correction for multiple comparisons). This study suggests that virtual Morris Water Task performance is associated with medial temporal lobe integrity in middle age, a critical window for detection and prevention of Alzheimer's disease, and may be useful as an early cognitive marker of Alzheimer's disease risk.

The Relational Trip Task, a novel ecological measure of relational memory: data from a schizophrenia sample

ABSTRACT Introduction Relational memory (RM) is severely impaired in schizophrenia. Unitisation can circumvent RM impairments in clinical populations as measured by the transverse-patterning (TP) task, a well-established measure of RM capacity. We compared memory performance on a new ecological RM measure, the Relational Trip Task (RTT), to that of TP at baseline and examined the effects of a unitisation intervention in RTT performance. RTT involves learning relational information of real-life stimuli, such as the relationship between people and places or objects. Methods TP and RTT performances were examined in 45 individuals with schizophrenia. TP-impaired participants (n = 22) were randomised to either the intervention or an active control group. TP and RTT were administered again after unitisation training. Task validity and reliability were assessed. Intervention group’s pre- and post-RTT accuracies were compared and contrasted to that in the control group. Results RTT and TP were moderately correlated. TP non-learners had inferior performance in RTT at baseline. Improvement in RTT performance after unitisation training was observed in the intervention group; no pre–post improvement was observed in the control group. Conclusion RTT has an acceptable criterion validity and excellent alternate-form reliability. Unitisation seemed to be successfully generalized to support associations of real-life stimuli.

A-223 Hopkins Verbal Learning Test-Revised (HVLT-R) and Brief Visuospatial Memory Test-Revised (BVMT-R) Embedded Performance Validity Analyses in a Healthy Non-Clinical Sample

Abstract Objective The Hopkins Verbal Learning Test–Revised (HVLT-R) and Brief Visuospatial Memory Test-Revised (BVMT-R) are memory tests with embedded measures of performance validity (Recognition Discrimination [RD] and Discrimination Index [DI], respectively). We evaluated whether cognitive ability and age influenced embedded measures of effort. Methods Participants included 30 young adults (YA) and 29 older adults (dichotomized into unimpaired [OAu] and impaired [OAi]). Participants completed a medication management ability assessment (MMAA), daily memory lapses survey (DM), digit span, and the Transverse Patterning (TP) and Reversal Learning (RL) computerized tests. Two Repeated-Measures MANOVAs were conducted to determine if Passing PVT and Age/Cognitive Ability influenced performance. An ROC analysis was conducted for HVLT-RD and BVMT-DI to determine pass/fail, and false positives/negatives on embedded measures. Results Those in the YA group who failed RDS (YA-fail), performed better than OAi-fail and OAi-pass groups on RT Errors (p &amp;lt; .0001). On TP Errors, the YA group differed from all four OA groups (p &amp;lt; .0001). On MMAA a significant difference was observed between OAi-fail and all other groups (p &amp;lt; .001). On RD, YA groups differed from both OAi groups (p = .0008). On DI, the YA groups differed from the OAi-fail group (p = .002). A logistic regression classified 43/57 participants successfully into the three cognitive groups using the six predictors (χ2 = 55.73, p &amp;lt; .0001, R2 = .468). RT Errors and TP were significant (Likelihood χ2 = 7.25, p = .027). Conclusion HVLT-RD failed to detect validity for OAi, as did BVMT-DI for YA and OAu. Instead, impairment effects are seen on HVLT-RD and BVMT-DI where YA groups differed from some combination of both/one of the OA groups.

S66. USING UNITIZATION TO CIRCUMVENT RELATIONAL MEMORY DEFICITS IN SCHIZOPHRENIA

BackgroundRelational 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.MethodsTwenty-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.ResultsTP 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).DiscussionTP 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.

Gradual learning and inflexible strategy use in amnesia: Evidence from case H.C.

The value of case studies in informing our understanding of dissociations and interactions in memory was recognized early on by Endel Tulving, whose comprehensive work with the amnesic case K.C. helped to confirm distinctions between episodic and semantic memory. Following in this tradition, we examined memory and the use of cognitive strategies in the developmental amnesic case H.C., a young woman with structural abnormalities in the extended hippocampal system (Rosenbaum et al., 2014). H.C. was tested on two tasks, transitivity and transverse patterning, that each required learning the relations among items, and for the former, also examined the ability to make inferences across sets of relations. H.C. was tested across multiple sessions and demonstrated two seemingly contradictory patterns of performance: evidence of gradual learning, yet an inability to flexibly switch to a cognitive strategy that may otherwise benefit performance. Specifically, on the transitivity task, H.C. showed gradual learning of novel relations that led to successful inferential performance. On transverse patterning, H.C. showed some gradual learning of the relations among the objects across sessions, and expressed knowledge that the task followed ‘rock-paper-scissors’ rules. However, H.C. did not benefit from a unitization strategy, which had shown previous success with other amnesic cases (D’Angelo et al., 2015; Ryan, Moses, Barense, & Rosenbaum, 2013). H.C.’s over-reliance on ‘rock-paper-scissors’ rules, even in the face of alternate strategies, is suggestive of an inability to enact cognitive flexibility. Poor performance thus may have resulted from interference from the experimentally presented strategy on her self-imposed strategy. The present findings echo work reported by Tulving in case K.C. (Tulving, Hayman, & Macdonald, 1991). Whereas neurologically intact individuals may rely on the functions of the hippocampal system to rapidly learn new information and resolve interference, some individuals with hippocampal amnesia may learn information gradually, but such learning is particularly prone to interference, resulting in an inability to flexibly adapt to changes in the learning conditions in order to optimize performance.

Exogenous Auxin Induces Transverse Microtubule Arrays Through TRANSPORT INHIBITOR RESPONSE1/AUXIN SIGNALING F-BOX Receptors.

Auxin plays a central role in controlling plant cell growth and morphogenesis. Application of auxin to light-grown seedlings elicits both axial growth and transverse patterning of the cortical microtubule cytoskeleton in hypocotyl cells. Microtubules respond to exogenous auxin within 5 min, although repatterning of the array does not initiate until 30 min after application and is complete by 2 h. To examine the requirements for auxin-induced microtubule array patterning, we used an Arabidopsis (Arabidopsis thaliana) double auxin f-box (afb) receptor mutant, afb4-8 afb5-5, that responds to conventional auxin (indole-3-acetic acid) but has a strongly diminished response to the auxin analog, picloram. We show that 5 µm picloram induces immediate changes to microtubule density and later transverse microtubule patterning in wild-type plants, but does not cause microtubule array reorganization in the afb4-8 afb5-5 mutant. Additionally, a dominant mutant (axr2-1) for the auxin coreceptor AUXIN RESPONSIVE2 (AXR2) was strongly suppressed for auxin-induced microtubule array reorganization, providing additional evidence that auxin functions through a transcriptional pathway for transverse patterning. We observed that brassinosteroid application mimicked the auxin response, showing both early and late microtubule array effects, and induced transverse patterning in the axr2-1 mutant. Application of auxin to the brassinosteroid synthesis mutant, diminuto1, induced transverse array patterning but did not produce significant axial growth. Thus, exogenous auxin induces transverse microtubule patterning through the TRANSPORT INHIBITOR 1/AUXIN F-BOX (TIR1/AFB) transcriptional pathway and can act independently of brassinosteroids.

A Cycloheximide-Sensitive Step in Transverse Microtubule Array Patterning.

The growth properties of individual cells within a tissue determine plant morphology, and the organization of the cytoskeleton, particularly the microtubule arrays, determines cellular growth properties. We investigated the mechanisms governing the formation of transverse microtubule array patterns in axially growing Arabidopsis (Arabidopsis thaliana) epidermal hypocotyl cells. Using quantitative imaging approaches, we mapped the transition of the cortical microtubule arrays into a transverse coaligned pattern after induction with auxin and gibberellic acid. Hormone induction led to an early loss of microtubule plus end density and a rotation toward oblique patterns. Beginning 30 min after induction, transverse microtubules appeared at the cell's midzone concurrently with the loss of longitudinal polymers, eventually progressing apically and basally to remodel the array pattern. Based on the timing and known hormone-signaling pathways, we tested the hypothesis that the later events require de novo gene expression and, thus, constitute a level of genetic control over transverse patterning. We found that the presence of the translation inhibitor cycloheximide (CHX) resulted in a selective and reversible loss of transverse patterns that were replaced with radial-like pinwheel arrays exhibiting a split bipolar architecture centered at the cell's midzone. Experiments using hormone induction and CHX revealed that pinwheel arrays occur when transverse microtubules increase at the midzone but longitudinal microtubules in the split bipolar architecture are not suppressed. We propose that a key regulatory mechanism for creating the transverse microtubule coalignment in axially growing hypocotyls involves the expression of a CHX-sensitive factor that acts to suppress the nucleation of the longitudinally oriented polymers.

Genetic Risk for Age-Related Cognitive Impairment Does Not Predict Cognitive Performance in Middle Age.

Alzheimer's disease (AD) is characterized by memory loss and executive dysfunction, which correspond to structural changes to the medial temporal lobes (MTL) and prefrontal cortex (PFC), respectively. Given the overlap in cognitive deficits between healthy aging and the earliest stages of AD, early detection of AD remains a challenge. The goal of the present study was to study MTL- and PFC-dependent cognitive functioning in middle-aged individuals at genetic risk for AD or cognitive impairment who do not currently manifest any clinical symptoms. Participants (N = 150; aged 40-60 years) underwent genotyping of 47 single nucleotide polymorphisms (SNPs) in six genes previously associated with memory or executive functioning: APOE, SORL1, BDNF, TOMM40, KIBRA, and COMT. They completed two MTL-dependent tasks, the virtual Morris Water Task (vMWT) and transverse patterning discriminations task (TPDT), and the PFC-dependent reversal learning task. Although age was associated with poorer performance on the vMWT and TPDT within this middle-aged sample, there were no genotype-associated differences in cognitive performance. Although the vMWT and TPDT may be sensitive to age-related changes in cognition, carriers of APOE, SORL1, BDNF, TOMM40, KIBRA, and COMT risk alleles do not exhibit alteration in MTL- and PFC-dependent functioning in middle age compared to non-carriers.

Multimodal Neuroimaging in Schizophrenia: Description and Dissemination

In this paper we describe an open-access collection of multimodal neuroimaging data in schizophrenia for release to the community. Data were acquired from approximately 100 patients with schizophrenia and 100 age-matched controls during rest as well as several task activation paradigms targeting a hierarchy of cognitive constructs. Neuroimaging data include structural MRI, functional MRI, diffusion MRI, MR spectroscopic imaging, and magnetoencephalography. For three of the hypothesis-driven projects, task activation paradigms were acquired on subsets of ~200 volunteers which examined a range of sensory and cognitive processes (e.g., auditory sensory gating, auditory/visual multisensory integration, visual transverse patterning). Neuropsychological data were also acquired and genetic material via saliva samples were collected from most of the participants and have been typed for both genome-wide polymorphism data as well as genome-wide methylation data. Some results are also presented from the individual studies as well as from our data-driven multimodal analyses (e.g., multimodal examinations of network structure and network dynamics and multitask fMRI data analysis across projects). All data will be released through the Mind Research Network’s collaborative informatics and neuroimaging suite (COINS).

Learning the rules of the rock–paper–scissors game: chimpanzees versus children

The present study aimed to investigate whether chimpanzees (Pan troglodytes) could learn a transverse pattern by being trained in the rules of the rock-paper-scissors game in which "paper" beats "rock," "rock" beats "scissors," and "scissors" beats "paper." Additionally, this study compared the learning processes between chimpanzees and children. Seven chimpanzees were tested using a computer-controlled task. They were trained to choose the stronger of two options according to the game rules. The chimpanzees first engaged in the paper-rock sessions until they reached the learning criterion. Subsequently, they engaged in the rock-scissors and scissors-paper sessions, before progressing to sessions with all three pairs mixed. Five of the seven chimpanzees completed training after a mean of 307 sessions, which indicates that they learned the circular pattern. The chimpanzees required more scissors-paper sessions (14.29±6.89), the third learnt pair, than paper-rock (1.71±0.18) and rock-scissors (3.14±0.70) sessions, suggesting they had difficulty finalizing the circularity. The chimpanzees then received generalization tests using new stimuli, which they learned quickly. A similar procedure was performed with children (35-71months, n=38) who needed the same number of trials for all three pairs during single-paired sessions. Their accuracy during the mixed-pair sessions improved with age and was better than chance from 50months of age, which indicates that the ability to solve the transverse patterning problem might develop at around 4 years of age. The present findings show that chimpanzees were able to learn the task but had difficulties with circularity, whereas children learned the task more easily and developed the relevant ability at approximately 4years of age. Furthermore, the chimpanzees' performance during the mixed-pair sessions was similar to that of 4-year-old children during the corresponding stage of training.

Structural learning difficulties implicate altered hippocampal functioning in adults with autism spectrum disorder.

Structural learning is fundamental to the formation of cognitive maps that are necessary for learning, memory, and spatial navigation. It also enables successful navigation of the social world, which is something that individuals with autism spectrum disorder (ASD) find particularly difficult. To master these situations, a person needs to bind pieces of information to one another and to consider the context in which experiences happen. Such binding is a capacity of the hippocampus. Although altered hippocampal function has for long been suspected to play a role in the etiology of ASD, the relevant evidence has remained inconclusive because few behavioral tests that are known to specifically necessitate preserved hippocampal function have been employed in studies of ASD. To address this gap in the literature, a total sample of 57 pairs of age and ability matched ASD and comparison participants was divided into 3 subsamples who were asked either to complete structural learning, or 1 of 2 configural learning control tasks (biconditional discrimination and transverse patterning) drawn from animal research. As predicted, ASD adults demonstrated specific difficulty with structural learning but not with other forms of configural learning. These differences were not attributable to decreased attentional shifting or increased perseveration, which would have indicated atypical frontal modulation of hippocampal processes. Instead, the observations implicate atypical hippocampal functioning as the source of structural learning difficulties in ASD. The data suggest that disturbances in domain-general cognitive processes such as structural learning, caused by altered hippocampal function, play a critical role in the etiology of ASD. (PsycINFO Database Record

Breaking down unitization: Is the whole greater than the sum of its parts?

Memory impairments are often observed in aging. Specifically, older adults have difficulty binding together disparate elements (relational memory). We have recently shown that a cognitive strategy known as unitization can mitigate impaired relational learning in the transverse patterning task (TP) in both amnesia and healthy aging. This strategy allows items to be fused together through an interaction such that one item acts upon another. In the context of TP, unitization is comprised of three component processes: (1) fusion, (2) motion, and (3) semantic comprehension of action/consequence sequences. Here, we examine which of these components are sufficient to mitigate age-related impairments. Four groups of older adults were given either the full unitization strategy or one of the three component strategies. Each group of older adults showed impairments in memory for the relations among items under standard training instructions relative to a threshold that marks learning of a winner-take-all rule (elemental threshold). However, participants who were given either the full unitization strategy or the action/consequence-only strategy showed improved performance, which was maintained following the 1-hour delay. Therefore, semantically rich action/consequence interactions are sufficient to mitigate age-related relational memory impairments.

Development of relational memory processes in monkeys

The present study tested whether relational memory processes, as measured by the transverse patterning problem, are late-developing in nonhuman primates as they are in humans. Eighteen macaques ranging from 3 to 36 months of age, were trained to solve a set of visual discriminations that formed the transverse patterning problem. Subjects were trained at 3, 4–6, 12, 15–24 or 36 months of age to solve three discriminations as follows: 1) A+ vs. B−; 2) B+ vs. C−; 3) C+ vs. A. When trained concurrently, subjects must adopt a relational strategy to perform accurately on all three problems. All 36 month old monkeys reached the criterion of 90% correct, but only one 24-month-old and one 15-month-old did, initially. Three-month-old infants performed at chance on all problems. Six and 12-month-olds performed at 75–80% correct but used a ‘linear’ or elemental solution (e.g. A>B>C), which only yields correct performance on two problems. Retraining the younger subjects at 12, 24 or 36 months yielded a quantitative improvement on speed of learning, and a qualitative improvement in 24–36 month old monkeys for learning strategy. The results suggest that nonspatial relational memory develops late in macaques (as in humans), maturing between 15 and 24 months of age.

Transverse patterning, aging, and neuropsychological correlates in humans.

Transverse patterning is a learning and memory adaptation of the 'rock/paper/scissors' problem that has been though to depend on the hippocampus, is sensitive to aging, and requires pattern separation to solve. Previous investigators dichotomized cognitively normal older adults who passed a cognitive screening into impaired and unimpaired subsets, and found that impaired older adults were disproportionately deficient in pattern separation abilities. However, this variability in pattern separation ability has not been examined using a transverse patterning task. Our aims, then, were two-fold: First, to determine if impaired older adults were inferior on transverse patterning compared to unimpaired older adults and young adults; second, to identify the neuropsychological correlates of transverse patterning. Our findings revealed that impaired older adults required more trials to criterion on the transverse patterning task than both young adults and unimpaired older adults. Unimpaired older adults also required more trials to criterion than young adults. A detailed analysis of the transverse patterning task confirmed that the aforementioned group differences were only observed in high interference conditions when pattern separation demands were at their peak. Finally, regression analyses showed that both memory and executive functioning neuropsychological composite scores were related to different indices of transverse patterning performance. Consistent with the pattern separation literature, and despite passing a cognitive screening, we found disproportionate transverse patterning deficits in impaired older adults. Forthcoming work should determine if transverse patterning performance is similar between impaired older adults and patients with Mild Cognitive Impairment. © 2016 Wiley Periodicals, Inc.

The effectiveness of unitization in mitigating age-related relational learning impairments depends on existing cognitive status

ABSTRACTBinding relations among items in the transverse patterning (TP) task is dependent on the integrity of the hippocampus and its extended network. Older adults have impaired TP learning, corresponding to age-related reductions in hippocampal volumes. Unitization is a training strategy that can mitigate TP impairments in amnesia by reducing reliance on hippocampal-dependent relational binding and increasing reliance on fused representations. Here we examined whether healthy older adults and those showing early signs of cognitive decline would also benefit from unitization. Although both groups of older adults had neuropsychological performance within the healthy range, their TP learning differed both under standard and unitized training conditions. Healthy older adults with impaired TP learning under standard training benefited from unitized training. Older adults who failed the Montreal Cognitive Assessment (MoCA) showed greater impairments under standard conditions, and showed no evidence of improvement with unitization. These individuals’ failures to benefit from unitization may be a consequence of early deficits not seen in older adults who pass the MoCA.

Unitization supports lasting performance and generalization on a relational memory task: Evidence from a previously undocumented developmental amnesic case

Recently, the amnesic case D.A. was shown to circumvent his relational memory impairments, as observed in the transverse patterning (TP) task, using a self-generated unitization strategy, and such performance benefits were maintained over extended delays (Ryan et al., 2013). “Unitization” encourages fusing of distinct items, through an action, into a single unit from which the relations among the items may then be derived. Here, we provide the first documentation of the developmental amnesic case, N.C., who presents with relatively circumscribed lesions to the extended hippocampal system, and with impaired episodic memory. Despite impairments on standard versions of TP, N.C. benefited from unitization, showed evidence of transfer to novel stimuli, and maintained his performance over extended delays. These findings suggest that self-generation is not a requirement for the successful implementation of unitization, and further provides the first evidence of rapid transfer and long-lasting success of a learning strategy in a human amnesic case.

Responses of monkey prefrontal neurons during the execution of transverse patterning

Recent functional imaging studies have suggested that the prefrontal cortex (PF) is engaged in the performance of transverse patterning (TP), which consists of 3 conflicting discriminations (A+/B−, B+/C−, C+/A−). However, the roles of PF in TP are still unclear. To address this issue, we examined the neuronal responses in 3 regions [the principal sulcus (PS), dorsal convexity (DC), and medial prefrontal cortex (MPF)] of the macaque PF during the performance of an oculomotor version of TP. A delayed matching-to-sample (DMS) task was used as a control task. The TP task-responsive neurons were most abundant in MPF. We analyzed the dependency of each neuronal response on the task type (TP or DMS), target shape (A, B, or C), and target location (left or right). Immediately after the choice cue presentation, many MPF neurons showed task dependency. Interestingly, some of them already exhibited differential activity between the 2 tasks before the choice cue presentation. Immediately before the saccade, the number of target location-dependent neurons increased in MPF and PS. Among them, many MPF neurons were also influenced by the task type, whereas PS neurons tended to show location dependency without task dependency. These results suggest that MPF and PS are involved in the execution of TP: MPF appears to be more important in the target selection based on the TP rule, whereas PS is apparently more related to the response preparation. In addition, some neurons showed a postsaccadic response, which may be related to the feedback mechanism.