This study investigated the important question of whether pupils' executive functions (EF) predict early academic achievement. Current conceptualizations suggest that developmental trends in EF can be measured in young children and that EF may play an important role in predicting academic achievement and school readiness. To date, however, there is little empirical support for this assertion. This study explored EF skills of 3- to 5 year-olds using the Dimensional Change Card Sort Task (DCCS). The first objective was to determine if EF indeed predicts math, reading, and writing achievement in 3- to 5-year-olds. The second objective was to determine if EF's prediction of academics occurs independent of the contribution made by general ability (e.g., Battelle motor and language subdomains). The third objective was to determine if the contribution of EF remains uniform across the age span. Consequently, existing data from 969 participants between 54 to 71 months was used. This consisted of scores on the DCCS as well as the Phonological Awareness Literacy Screening (PALS) to measure early reading and writing skills, the Test of Early Math Ability -Third Edition (TEMA-3) to measure early math skills, and sections of the Battelle Developmental Inventory 2nd Edition (BDI- 2) to measure general development. A positive relationship between EF and early math, reading, and writing skills was found. Also EF, as measured by the DCCS, contributed a significant portion of variance in early math, reading, and writing skills after accounting for general development, age, and socioeconomic status. Finally, the contribution of EF to early reading and writing skills remained stable between 3 and 5 years old. In contrast, EF was a stronger predictor of early math skills among 3-year-olds when compared to 5- year-olds.

Children at a certain age often have difficulty in flexibly shifting attention between different representational schemes. One example of such cognitive inflexibility occurs in the Dimensional Change Card Sorting (DCCS) task in which 3-year-old children have difficulty switching between sorting dimensions. For instance, after initially sorting the cards by one dimension (e.g., colour) they are unable to sort the cards by a second dimension (e.g., shape). This finding has been primarily associated with problems in attention or inhibition. The present study investigated the role of perceptual information on children’s dimensional shift abilities by manipulating the perceptual characteristics of both task-relevant (the colour or shape of the images on the cards) and task-irrelevant (the background colour or shape of the actual cards themselves) aspects of the task materials between the pre- and post-switch experimental phases. Across three experiments better performance was observed when either task-relevant or task-irrelevant information was changed, with this improved performance occurring when these changes were salient enough to induce a stimulus novelty effect. Experiment 4 investigated yet another perceptual feature of the task; the degree of stimulus realism (abstractness) on children’s cognitive flexibility. Children successfully sorted the cards when three-dimensional stimuli were used but perseverated when using two-dimensional cards, providing evidence for the role of representational status of the stimuli in influencing children’s dimensional switching. Manipulations made to increase the salience of the task material as well as those resulting in reduction of similarity between the two phases of the tasks (or increased novelty) were used to enhance children’s cognitive flexibility. Overall, these findings highlight the critical role played by the perceptual information of the overall experimental context, and have important implications for theories of cognitive flexibility.

Psychopharmacological studies have implicated the mesolimbic dopamine (DA) system in the mediation of cost/benefit evaluations about effort-related costs associated with larger rewards. However, the role of DA in risk-based decision making remains relatively unexplored. The present study investigated how systemic manipulations of DA transmission affect risky choice assessed with a probabilistic discounting task. Over discrete trials, rats between two levers; a press on the “small/certain” lever always delivered one reward pellet, whereas a press on the other, “large/risky” lever delivered four pellets, but the probability of receiving reward decreased across the four trial blocks (100%, 50%, 25%, 12.5%). In separate groups of well-trained rats we assessed the effects of the DA releaser amphetamine, as well as receptor selective agonists and antagonists. Amphetamine consistently increased preference for the large/risky lever; an effect that was blocked or attenuated by co-administration of either D₁ (SCH23390) or D₂ (eticlopride) receptors antagonists. Blockade of either of these receptors alone induced risk aversion. Conversely, stimulation of D₁ (SKF81297) or D₂ (bromocriptine) receptors also increased risky choice. In contrast, activation of D₃ receptors with PD128,907 induced risk aversion. Likewise, D₃ antagonism with nafadotride potentiated the amphetamine-induced increase in risky choice. Blockade or stimulation of D₄ receptors did not reliably alter patterns of choice. These findings indicate that DA plays a critical role in mediating risk-based decision making, where increased activation of D₁ and D₂ receptors biases choice towards larger, probabilistic rewards, whereas D₃ receptors appear to exert opposing effects on this form of decision making.

Children at a certain age often have difficulty in flexibly shifting attention between different representational schemes. One example of such cognitive inflexibility occurs in the Dimensional Change Card Sorting (DCCS) task in which 3-year-old children have difficulty switching between sorting dimensions. For instance, after initially sorting the cards by one dimension (e.g., colour) they are unable to sort the cards by a second dimension (e.g., shape). This finding has been primarily associated with problems in attention or inhibition. The present study investigated the role of perceptual information on children’s dimensional shift abilities by manipulating the perceptual characteristics of both task-relevant (the colour or shape of the images on the cards) and task-irrelevant (the background colour or shape of the actual cards themselves) aspects of the task materials between the pre- and post-switch experimental phases. Across three experiments better performance was observed when either task-relevant or task-irrelevant information was changed, with this improved performance occurring when these changes were salient enough to induce a stimulus novelty effect. Experiment 4 investigated yet another perceptual feature of the task; the degree of stimulus realism (abstractness) on children’s cognitive flexibility. Children successfully sorted the cards when three-dimensional stimuli were used but perseverated when using two-dimensional cards, providing evidence for the role of representational status of the stimuli in influencing children’s dimensional switching. Manipulations made to increase the salience of the task material as well as those resulting in reduction of similarity between the two phases of the tasks (or increased novelty) were used to enhance children’s cognitive flexibility. Overall, these findings highlight the critical role played by the perceptual information of the overall experimental context, and have important implications for theories of cognitive flexibility.

Children born very preterm (VPT) are known to be at high risk of under-achievement in mathematics. However the nature of these difficulties is poorly understood. In this study, a regionally representative cohort of 102 children born VPT and a comparison group of 108 children born full term (FT) during 1998-2000 were followed from birth to nine years. At age nine, children were tested using the Woodcock-Johnson III maths fluency subtest, and teacher reports of mathematical achievement and curriculum-based (numeracy project) achievement data were collected. The data was analysed using group comparisons and multiple regression. Parent and teacher ratings of executive function at age six were included as predictors. Findings indicated that children born VPT had elevated rates of mathematical difficulties across all measures including the standardised and curriculum-based measures, and teacher ratings. They also had higher rates of mathematical learning disability. With the exception of curriculum-based measures, these results remained significant even after controlling for socioeconomic status and severe neurodevelopmental impairment. Children born VPT showed particular difficulty using operational strategies, rather than with factual knowledge, and this effect was most marked for addition and multiplication. As well as difficulties in mathematics, children born VPT also showed more difficulty than children born FT in almost all areas of executive function. Difficulties with working memory at age six were significantly associated with poor performance in aspects of curriculum-based measures at age nine.

The Integrative Neuropsychological Theory of Executive-Related Abilities and Component Transactions (INTERACT; Garcia-Barrera, 2011) is a novel perspective on executive function(s), and the functional interactions among those neural systems thought to underlie them. INTERACT was examined in this validation study using structural equation modeling. A novel battery of computerized tasks was implemented in a sample of 218 healthy, adult, university students. Each of the derived indicator variables represented a specific aspect of performance, and corresponded with one of the five distinct executive components of INTERACT. After eliminating tasks that demonstrated poor psychometric properties, overall model fit was excellent, χ2 = 36.38, df = 44, p = .786; CFI = 1.00; RMSEA = .000. Further, INTERACT was superior to six alternative measurement models, which were theoretically-based. Although the structural model of INTERACT was too complex to be tested here, a novel analysis of the data was introduced to test the interactions among INTERACT’s components. This analysis demonstrated the significant utility of INTERACT’s fundamental theoretical predictions. Given the outcome of this initial validation study, the predictive power of INTERACT should continue to be exploited in future studies of executive function(s), and should be extended to explore executive systems in unique populations. / Graduate

Based on classic and contemporary theories of cognitive development by Vygotsky, Luria, and Zelazo and colleagues, the main objective of the present study was to systematically evaluate the association between different aspects of language, namely semantic and syntactic knowledge, and specific executive functioning (EF) abilities (working memory, inhibition, and flexibility) in preschoolers. Sixty-seven children age 3-5 years were administered a battery of EF and language measures. A latent variable approach was used to estimate performance on EF tasks. A two-factor model consisting of working memory/inhibition (WM/INH) and flexibility provided the best fit for the data. The results showed that syntactic ability uniquely explained a significant amount of variance in both WM/INH and flexibility over and above age and semantic ability. Furthermore, children’s complex syntax scores predicted their performance on complex blocks of flexibility tasks. These findings provide preliminary evidence for the association between children’s understanding of the structure of language and EF. / Graduate / 0620 / eyeung@uvic.ca

This study examined whether cortical changes underlying treatment for children with aggressive behaviour problems are related to changes in executive function (EF) performance. Fifty-five 8- to 12-year-old clinically-referred children were tested before and after a 14-week treatment intervention. Performance on four EF tasks varying in affective relevance was assessed at each session. EEG was also used to record peak amplitudes for the “inhibitory” N2, an event-related potential, while the children completed an emotion-induction Go/Nogo task. Results showed that changes in N2 amplitudes significantly predicted changes in performance only for the Iowa Gambling Task (IGT) – an affectively relevant task. Subsequent analysis revealed that only children who improved with treatment displayed significant decreases in N2 amplitudes and significant improvement in IGT performance from pre- to post-treatment. These findings suggest that cortical changes underlying successful treatment for children’s aggressive behaviour problems tap improvement in executive functions recruited for emotionally demanding events.

This study examined whether cortical changes underlying treatment for children with aggressive behaviour problems are related to changes in executive function (EF) performance. Fifty-five 8- to 12-year-old clinically-referred children were tested before and after a 14-week treatment intervention. Performance on four EF tasks varying in affective relevance was assessed at each session. EEG was also used to record peak amplitudes for the “inhibitory” N2, an event-related potential, while the children completed an emotion-induction Go/Nogo task. Results showed that changes in N2 amplitudes significantly predicted changes in performance only for the Iowa Gambling Task (IGT) – an affectively relevant task. Subsequent analysis revealed that only children who improved with treatment displayed significant decreases in N2 amplitudes and significant improvement in IGT performance from pre- to post-treatment. These findings suggest that cortical changes underlying successful treatment for children’s aggressive behaviour problems tap improvement in executive functions recruited for emotionally demanding events.

Psychopharmacological studies have implicated the mesolimbic dopamine (DA) system in the mediation of cost/benefit evaluations about effort-related costs associated with larger rewards. However, the role of DA in risk-based decision making remains relatively unexplored. The present study investigated how systemic manipulations of DA transmission affect risky choice assessed with a probabilistic discounting task. Over discrete trials, rats between two levers; a press on the “small/certain” lever always delivered one reward pellet, whereas a press on the other, “large/risky” lever delivered four pellets, but the probability of receiving reward decreased across the four trial blocks (100%, 50%, 25%, 12.5%). In separate groups of well-trained rats we assessed the effects of the DA releaser amphetamine, as well as receptor selective agonists and antagonists. Amphetamine consistently increased preference for the large/risky lever; an effect that was blocked or attenuated by co-administration of either D₁ (SCH23390) or D₂ (eticlopride) receptors antagonists. Blockade of either of these receptors alone induced risk aversion. Conversely, stimulation of D₁ (SKF81297) or D₂ (bromocriptine) receptors also increased risky choice. In contrast, activation of D₃ receptors with PD128,907 induced risk aversion. Likewise, D₃ antagonism with nafadotride potentiated the amphetamine-induced increase in risky choice. Blockade or stimulation of D₄ receptors did not reliably alter patterns of choice. These findings indicate that DA plays a critical role in mediating risk-based decision making, where increased activation of D₁ and D₂ receptors biases choice towards larger, probabilistic rewards, whereas D₃ receptors appear to exert opposing effects on this form of decision making.