Dana L. Byrd

The Tower of London spatial problem-solving task: enhancing clinical and research implementation.

Since its development in 1982, The Tower of London (TOL; Shallice, 1982) spatial problem-solving task has been increasingly employed in test batteries of executive functions. This task has served as a rich source of information on preparation, planning and processing, but a number of issues remain unaddressed in the literature: (1) the problem structure, or problem space of the task, (2) the impact of modifications from the original, Shallice TOL, and (3) the variety of performance measures that can be derived from the TOL. We present here an overview of these issues in the hope that it may lead to a more effective and reasoned use of the TOL task by clinical and nonclinical investigators, alike.

Newborn infants learn during sleep

Newborn infants must rapidly adjust their physiology and behavior to the specific demands of the novel postnatal environment. This adaptation depends, at least in part, on the infants ability to learn from experiences. We report here that infants exhibit learning even while asleep. Bioelectrical activity from face and scalp electrodes was recorded from neonates during an eye movement conditioning procedure in which a tone was followed by a puff of air to the eye. Sleeping newborns rapidly learned the predictive relationship between the tone and the puff. Additionally, in the latter part of training, these infants exhibited a frontally maximum positive EEG slow wave possibly reflecting memory updating. As newborns spend most of their time sleeping, the ability to learn about external stimuli in the postnatal environment during nonawake states may be crucial for rapid adaptation and infant survival. Furthermore, because eyelid conditioning reflects functional cerebellar circuitry, this method potentially offers a unique approach for early identification of infants at risk for a range of developmental disorders including autism and dyslexia.

Talking through transitions: Microgenetic changes in preschoolers’ private speech and executive functioning:

In this study we explored the relation between private speech and task mastery by using the microgenetic method to examine the language and performance of 13 children aged 4 and 5 as they gained expertise with a spatial, multi-step planning task across 6 sessions. Seven of the 13 children’s performances across these sessions were characterized by a sharp change in performance between two consecutive sessions. Detailed microgenetic examinations of individual children suggested that abrupt improvements in performance were associated with a higher use of on-task private speech. More variability was noted in the problem-solving and private speech patterns of children who did not experience abrupt shifts in performance. Implications regarding the role of individual differences in the use of private speech during problem-solving are discussed.

Age differences in high frequency phasic heart rate variability and performance response to increased executive function load in three executive function tasks.

The current study examines similarity or disparity of a frontally mediated physiological response of mental effort among multiple executive functioning tasks between children and adults. Task performance and phasic heart rate variability (HRV) were recorded in children (6 to 10 years old) and adults in an examination of age differences in executive functioning skills during periods of increased demand. Executive load levels were varied by increasing the difficulty levels of three executive functioning tasks: inhibition (IN), working memory (WM), and planning/problem solving (PL). Behavioral performance decreased in all tasks with increased executive demand in both children and adults. Adults’ phasic high frequency HRV was suppressed during the management of increased IN and WM load. Children’s phasic HRV was suppressed during the management of moderate WM load. HRV was not suppressed during either children’s or adults’ increasing load during the PL task. High frequency phasic HRV may be most sensitive to executive function tasks that have a time-response pressure, and simply requiring performance on a self-paced task requiring frontal lobe activation may not be enough to generate HRV responsitivity to increasing demand.

Developmental differences in the preparatory heart rate response: childhood through adulthood

The present article examines developmental differences across childhood, adolescence, and adulthood in the triphasic anticipatory heart rate response and the impact of age on the relationship between anticipatory deceleration (D2) and reaction time (RT). Heart rate and RT were recorded from participants ages 5-25 during a fixed, 6 s anticipatory paradigm. The triphasic anticipatory heart rate response was larger in children, with the children displaying a delayed acceleratory component. Across this wide age range sample, D2 significantly predicted RT, but a model that included Age and D2 predicted significantly more of the RT variance. When comparing across ages on the triphasic response components or the relationship between D2 and RT, researchers should account for developmental effects.

Executive functioning in attention-deficit/hyperactivity disorder: questioning the notion of planning deficits with heart rate reactivity

Abstract This study employed a paired stimulus paradigm to compare phasic changes in heart rate among children (age categories 6–8, 9–10, and 11–12) and adults (age categories 18–19 and 20–22) with attention-deficit/hyperactivity disorder (ADHD) and age-matched controls. A sample of 95 participants (19 ADHD-diagnosed children, 34 controls, 20 ADHD-diagnosed adults, and 22 controls) solved a planning task, the Tower of London, through 4 levels of difficulty. It was hypothesized that groups with ADHD would show greater heart rate acceleration and less final deceleration than would controls, and that these heart rate responses would change with age and difficulty level as well. Though heart rate differences were found among age categories and difficulty levels, none were found between participants with ADHD and controls. The lack of ADHD differences are not consistent with the behavioral evidence that planning by itself is one of the marked executive function deficits in ADHD. Because ADHD differences were not evident, the effects either were not present or were smaller than that of difficulty level and age. Possible explanations for this lack of difference and future directions are discussed.