The Towers of Hanoi (ToH) and London (ToL), historically held as isomorphic measures of problem solving, have had their equivalence questioned in recent years. Adult studies that equalized administration and task structure have found increased correlation between Towers, but insufficient evidence exists regarding whether the same results would be found in young children. This study examined 29 typically developing preschoolers. Both Towers, along with four measures of executive function, were administered in two sessions. The Towers were strongly correlated, but the strength of this relationship was impacted by discontinuation type (i.e., quit vs. standardized), and analyses revealed differences in sustained attention and Tower correlations for those who quit. Complex Tower items showed stronger correlations, and Tower performance and visuospatial WM were also highly correlated. Overall, these results suggest that the Towers, when equated in administrative and structural features, are interchangeable measures of problem solving in preschoolers. / Graduate / 0621 / 0620 / 0622 / jsheehan@uvic.ca

The primary objective of this research was to explore the impact of glucose ingestion on 2-back task performance (accuracy, discrimination, and reaction times (RT) to target), its relationship to neural activation, using functional magnetic resonance imaging, and potential modulation by insulin resistance (IR) and low density lipoprotein (LDL) in hypertensive but otherwise healthy older adults. While there was no effect of glucose ingestion on task performance or task-relevant neural activation patterns, this study uniquely observed that IR and LDL associated with all 3 measures of 2-back performance and task-relevant neural activation patterns. The left and right precuneus, left cingulate, and left insula were identified as task-associated regions according to our specific target minus nontarget contrast. Of particular importance was the task activation in the right precuneus as it both showed sensitivity to IR and predicted task RTs to targets, suggesting it plays a modulatory role linking IR to task performance.

The primary objective of this research was to explore the impact of glucose ingestion on 2-back task performance (accuracy, discrimination, and reaction times (RT) to target), its relationship to neural activation, using functional magnetic resonance imaging, and potential modulation by insulin resistance (IR) and low density lipoprotein (LDL) in hypertensive but otherwise healthy older adults. While there was no effect of glucose ingestion on task performance or task-relevant neural activation patterns, this study uniquely observed that IR and LDL associated with all 3 measures of 2-back performance and task-relevant neural activation patterns. The left and right precuneus, left cingulate, and left insula were identified as task-associated regions according to our specific target minus nontarget contrast. Of particular importance was the task activation in the right precuneus as it both showed sensitivity to IR and predicted task RTs to targets, suggesting it plays a modulatory role linking IR to task performance.

Prevention and treatment of type 2 diabetes mellitus (T2DM), relies heavily on self-care behaviours such as dietary modification, physical activity, and medication adherence. Ability to perform these self-care behaviours depends, at least in part, on executive function (EF). Recent evidence suggests a correlation between T2DM and impaired cognitive function, including EF. Given the importance of EF for regulation of behaviours, and the importance of self-care in diabetes management, attenuated EF would represent a potential barrier to proper disease management. Thus the objective of Study 1 was to examine the association between T2DM and EF through meta-analytic techniques. Medline, PsychoInfo, and Scopus, as well as article references, were used to identify studies comparing individuals with T2DM to a control population. Effect size was calculated using cohen’s d and random effects modeling, and the potential impact of moderators (age, sex, and T2DM duration) were examined. Review of 60 studies (59 articles), revealed a significant, small-to-moderate effect size (d=-0.249, p<0.001) such that those with T2DM have lower EF. This finding was consistent across all aspects of EF examined (verbal fluency, mental flexibility, inhibition, working memory, and attention), and the association was stronger for those with shorter disease duration. The findings of study 1 illustrate that although individuals with T2DM have a great need for EF, as evidenced by the reliance of self-care behaviours on EF, this population has lower EF upon which to draw to perform these behaviours. Thus, strategies that improve EF, such as aerobic exercise, may be particularly relevant to this population. Acute aerobic exercise has been shown to improve EF in young and older adults; however this effect had not yet been examined in individuals with T2DM. Thus the objective of Study 2 was to examine the effects of acute aerobic exercise on EF in adults with T2DM. A within-subject design was used to compare the change in EF task performance following moderate and minimal intensity aerobic exercise, using Stroop and GNG to measure EF. Analysis revealed a significant effect of moderate exercise in women (but not men) and recently active (but not inactive) individuals, such that moderate exercise mitigated the self-regulatory fatigue effect observed following exercise. This study provides preliminary evidence of a significant beneficial effect of moderate aerobic exercise on EF in female and recently active adults with T2DM.

The purpose of this study was to examine the development of the ability to multitask in children along with other executive control processes that likely underlie goal-directed behavior in novel situations. 35 children, ages 7-11, completed an experimental multitasking paradigm, the Children’s Multiple Activities Game (CMAG), and an existing measure, the Six Parts Test (SPT) as well as two working memory and inhibition tasks and a prospective memory task. Results indicated that multitasking ability improves across this age range and is related to a number of executive abilities. Performance on the CMAG was related to a number of executive abilities, while the SPT was unrelated to these measures. To our knowledge, this is the first study to investigate the development of this ability in children. Findings will be discussed in terms of how this ability develops in relation to cognitive processes that are crucial and account for its variation.

An emerging topic in cognitive development is whether being bilingual constitutes an advantage in children’s performance on executive function (EF) tasks. The purpose of this study was to compare the performance of EF tasks in English monolingual children and German-English bilingual children aged 3 to 6 years old. Fifty-six children completed tasks of short-term memory, working memory, inhibition, cognitive flexibility, and verbal ability. No significant difference was found between the performance of bilingual and monolingual children in EF tasks, even when level of language proficiency was taken into account. Monolingual children performed better on measures of English verbal ability than bilingual children. Limitation to the study and avenues for future research are presented.

Mild Traumatic Brain Injury (mTBI), often called concussion, has become a growing public health concern, prevalent in both athletic and military settings. In response, many researchers have explored cognitive outcomes post-mTBI, with a plethora of meta-analyses summarizing these findings; however, these meta-analyses examine solely mean performances on cognitive tasks, ignoring intra-individual variability (IIV) in cognitive performance that may elucidate neuropsychological impairment following mTBI. The current thesis involved two studies, responding to both the growing meta-analytic research and limited IIV findings. Study 1: Many meta-analyses have amalgamated individual study results on post-mTBI neuropsychological outcomes. With the abundance of meta-analyses, a systematic review of meta-analyses stands as the next logical step. Method: A systematic literature search yielded 11 meta-analyses meeting inclusion criteria (i.e., English-language systematic reviews/meta-analyses covering post-mTBI observational cognitive research on late adolescents/adults), with their findings qualitatively synthesized based on moderator variables (i.e., cognitive domain, time since injury, past head injury, participant characteristics, comparison group, assessment technique, and persistent symptoms). Results: The overall effect sizes ranged for both general (range: .07-.61) and sports-related mTBI (range: .40-.81) and differed both between and within cognitive domains, with executive functions appearing most sensitive to multiple mTBI. Cognitive domains varied in recovery rates, but overall recovery occurred by 90 days post-injury for most individuals and by seven days post-injury for athletes. Greater age/education and male gender produced smaller effects sizes, while high school athletes suffered the largest deficits post-mTBI. Control-group comparisons yielded larger effects than within-person designs, while assessment techniques had limited moderating effects. Conclusions: Overall, meta-analytic review quality remained low with few studies assessing publication or study quality bias. Meta-analyses consistently identified adverse acute mTBI-related effects and fairly rapid symptom resolution. Study 2: The long-term outcomes of executive functions and IIV following mTBI are unclear due to inconsistent and limited research, respectively. Further, the relationship between physical activity (PA) and cognitive performance at young adulthood remains almost fully unexplored. In turn, the current study aimed to (a) assess the diagnostic utility of both executive functions and IIV at predicting mTBI history and (b) evaluate the interaction between PA levels and mTBI on both of these cognitive metrics. Method: Altogether 138 self-identified athletes (Mage = 19.9 ± 1.91 years, 60.8% female, 19.6% 1 mTBI, 18.1% 2+ mTBIs) completed three executive-related cognitive tasks (i.e., N-Back, Go/No-go, Local-Global). Ordinal logistic regression analyses examined the joint effect of person-mean and IIV as predictors of mTBI status. Multi-level models examined mTBI and PA levels as predictors of trial-to-trial changes in performance. Results: Only mean response time (RT) for the Local-Global task predicted mTBI status, while no IIV variables reached unique significance. PA levels predicted subtle within-task decreases in RT across Local-Global trials. Conclusions: IIV research on mTBI remains limited; however, the preliminary results do not indicate any additional predictive value of IIV indices above mean performances. For executive functions, shifting appeared most affected, with past researchers identifying post-mTBI impairment in attentional processing. Higher PA levels minutely benefited within-task shifting and mean inhibitory performance, although these finding require cautious interpretation. / Graduate / 0622 / jkarr@uvic.ca

Children with autism spectrum disorder show imaginative and representational drawing deficits, despite reports of a “visual thinking style”. I examined whether these two drawing characteristics could be explained by the unique cognitive style of children with autism (specifically, executive dysfunction and a local processing bias). I administered a cognitive/drawing task battery to a group of 24 school-age children with autism and 29 mental age-matched neurotypically developing controls. I expected that better executive function ability would be associated with better imaginative and representational drawing, and that a local processing bias (weak central coherence) would be associated with better representational drawing but worse imaginative drawing. In children with autism, better executive function was associated with better imaginative drawing. Greater central coherence was associated with better representational drawing, but executive function was associated with worse representational drawing. Underlying cognitive components of imaginative and representational drawing were different for the neurotypically developing children. Overall, findings were unexpected, leading to novel theoretical suggestions for the field of autism cognition and drawing research. / Graduate / 0620 / 0623 / kd.teneycke@gmail.com

This study investigated executive function and sustained attention in preterm and full-term infants at 8 months after expected date of delivery and at 10-11 months chronological age. Executive function and sustained attention emerge in infancy and continues to develop throughout childhood. Executive function and sustained attention is believed to underlie some learning problems in children at school age. Although numerous studies have reported that the overall development of preterm infants is comparable to that of full-term infants at the same corrected age, it is unclear to what extent the development of specific cognitive abilities is affected by prematurity and/or other factors such as medical complications. As preterm infants have a high rate of learning difficulties, it is possible that factors associated with prematurity specifically affect the development of some regions of the brain associated with the regulation of executive function and sustained attention. Thirty-seven preterm infants without identified disabilities, and 74 due date and gender matched healthy bull-term infants, participated in the present study. The preterm infants were all less that 32 weeks gestation and less that 1500 grams birth weight. The current study aimed to examine the effects of maturation and length of exposure to extrauterine environmental stimuli on the development of executive function and sustained attention, by comparing the development of preterm infants with that of full-term infants at both the same corrected age and the same chronological age. All infants were therefore assessed on executive function and sustained attention tasks at 8 months after the expected date of delivery (when preterm infants were actually 10-11 months chronological age). The full-term infants in the study were then reassessed at an age equivalent to the chronological age of their matched preterm infants at the time of the first assessment. The findings of the study showed that preterm infants performed significantly more poorly than full-term infants at both 8 months after the expected date of delivery and 10-11 months chronological age on all measures of executive function and sustained attention. However the difference between preterm and full-term infants at 8 months after expected date of delivery was much less that at 10-11 months chronological age. The results suggested that the effects of maturation are greater that the effects of exposure to extrauterine environmental stimuli on the development of executive function and sustained attention. However, as the performance of the preterm infants was below that of the term infants at the same corrected age, it was necessary to consider whether other factors associated with preterm birth were contributing to this difference. Confounding factors including cognitive abilities and psychomotor skills on the Bayley Scales of Infant Development, infant temperament, maternal education, family socioeconomic status and maternal psychological wellbeing were examined. Statistical analysis of the effects of these factors on the difference between preterm ad full-term infants found that only psychomotor sills significantly affected the differences between preterm and full-term infants of the same corrected age on executive function measures, although not on sustained attention measures. The differences between preterm and full-term infants of the same corrected age remained even when psychomotor skills were taken into consideration; therefore psychomotor skills were not sufficient to fully explain the differences between preterm and full-term infants in the performance of executive function. Consequently, the preterm infants were divided into two subgroups on the basis of (a) low or high medical risk factors, (b) birth weight of less that 1000g versus 1000-1500g, and (c) gestation age of less that 28 weeks versus 28-32 weeks, in order to assess the effects of these variables on the performance of executive function and sustained attention. Medical risk, lower birth weight and lower gestation age were all found to adversely affect performance on executive function, but did not affect the performance on sustained attention tasks. It is argued that these factors may influence the development of specific areas of the brain which govern executive function, and that as the prefrontal regions are particularly immature they may be especially vulnerable to damage or disruption. The fact that these perinatal factors did not contribute to the difference between preterm and full-term infants' performance on sustained attention tasks. This suggests that the deficits of sustained attention in preterm infants may be associated with birth prematurity per se, and that additional complications may not have any further detrimental effect. The three components of executive function (i.e., working memory, inhibition, and planning) did not correlate with each other when only infants with Bayley psychomotor ability scores greater that 85 were included, suggesting that the components of executive function may be discrete abilities which are governed by different parts of the prefrontal cortex. Sustained attention correlated with planning, supporting the suggestion that it may be a cognitive dimension which overlaps with executive function, depending upon the task requirement. Neither executive functio nor sustained attention correlated with the Bayley mental ability and Bayley psychomotor ability scores when infants with scores of less than 85 were excluded. This suggests that executive function and sustained attention measures are independent of general development.

Impairments in both theory of mind (ToM; the ability to attribute mental states to oneself and others) and executive function (EF; a group of high-level cognitive functions which help guide and control goal-directed behaviour) have been demonstrated in individuals with autism spectrum disorders (ASDs). Both deficits have been proposed by different groups of researchers as being the single primary cognitive deficit of autism, which can subsume the other deficit as secondary or artefactual. However, few studies have examined the nature of the relationship between ToM and EF in ASDs or conducted a systematic investigation of their relative primacy. This research principally sought to establish the primacy and independence of impairments in ToM and EF in ASDs and thereby evaluate the validity of single versus multiple primary deficit models of autism. These aims were addressed in two studies, both broad in scope. The first study was an investigation of the profile, primacy, and independence of ToM and EF impairments in individuals with ASDs. The sample included 46 participants with ASDs and 48 control participants matched on age and non-verbal ability. The profile of impairments was examined by measuring ToM and a range of EF components using tasks employing, wherever possible, process-pure indices of performance. Primacy was measured by focussing on i) whether or not the deficits observed were universal among individuals with ASDs; ii) whether the deficits were able to discriminate individuals with ASDs from matched controls (i.e., predict group membership); and iii) the ability of ToM and EF deficits to explain the full range of autistic symptomatology, as measured by correlating cognitive performances with behavioural indices. The relationship between ToM and EF impairments was investigated by conducting correlations between ToM and EF variables as well as analysing the incidence of dissociations between impairments in the two domains. The ASD group was found to demonstrate significant impairments in ToM and several components of EF including planning, verbal inhibition, working memory (in a context where inhibitory control was required), and both verbal and non-verbal generativity. However, neither ToM nor EF impairments were able to meet all of the criteria for a primary deficit in ASDs. EF deficits were found to be more primary, but could not account for ToM as a secondary deficit, as ToM and EF were found to be independent (i.e., uncorrelated and dissociable) deficits in the ASD group. This pattern of results suggested that a multiple deficits model involving at least two independent impairments appeared to best characterise ASDs, but the data were compatible with several variants of such a model (e.g., involving distinct subtypes versus a multidimensional spectrum). The second study was an investigation of ToM and EF impairments in siblings of individuals with ASDs, who have previously been found to demonstrate a subclinical “broad autism phenotype”. The main aims of this study were i) to identify whether ToM or EF deficits could meet criteria for an “endophenotype” or vulnerability marker for the autism genotype in unaffected relatives, which would have further implications about the primacy of ToM and EF in ASDs; and ii) to further investigate the validity of various multiple deficits models of ASDs by examining the pattern of ToM and EF performance in those showing the broad phenotype. Participants were 108 siblings of individuals with ASDs and 67 siblings of controls, tested on the same ToM and EF tasks used in the first study. Confirming the superior primacy of EF deficits found in Study One, there was no significant difference in ToM performance between ASD and control siblings, but ASD siblings showed weaknesses on two measures of EF. Furthermore, there appeared to be different subgroups of siblings demonstrating different cognitive profiles, consistent with the heterogeneity evident in the first study. This research indicated that ASDs cannot be explained by a single primary cognitive deficit. These findings hold important theoretical and empirical implications and highlight further questions about which type of multiple deficits model might best explain ASDs.