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

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.

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.

One-month-old human infants learn about the social world while they sleep.

Although infants display preferences for social stimuli early in their lives, we know relatively little about the mechanisms of infant learning about the social world. In the current set of studies, 1-month-old infants underwent an adapted eyeblink conditioning paradigm to examine learning to both 'social' and non-social cues. While infants were asleep, they were presented with either a 'social' stimulus (a female voice) or one of two non-social stimuli (tone or backward voice) followed by an airpuff presented to the eyelid. Infants in the experimental groups displayed increased learning across trials, regardless of stimulus type. However, infants conditioned to the 'social' stimulus showed increased learning compared to infants conditioned to either of the non-social stimuli. These results suggest a mechanism by which learning about the social world occurs early in life and the power of ecologically valid cues in facilitating that learning.

Planning: fixed-foreperiod event-related potentials during the Tower of London task.

Slow wave ERPs were recorded from 28 young adults as they generated plans for various difficulty levels of a fixed-foreperiod version of the Tower of London task. The resulting waveform included three segments: (1) a left-lateralized negative early-interval wave, which was frontally maximal but not sensitive to difficulty, (2) a right-lateralized frontally maximal mid-interval wave, which was more positive for more difficult problems, and (3) a left lateralized centrally maximal negative-ramping contingent negative variation (CNV) late wave, which was more negative for more difficult problems. The current study adds to the current literature in that it finds that the frontal and central neural utilization with difficulty changes across plan generation. This suggests that plan generation should be considered in terms of when component processes of planning are differentially utilized as plan generation unfolds.

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 infant's 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.

Deconstructing the tower: parameters and predictors of problem difficulty on the Tower of London task.

The Tower of London (TOL) task has been widely used in both clinical and research realms. In the current study, 104 healthy participants attempted all possible moderate- to high-difficulty TOL problems in order to determine: (1) optimal measures of problem solving performance, (2) problem characteristics, other than the minimum moves necessary to solve the problem, that determine participants' difficulty in solving problems successfully, quickly, and efficiently, and (3) effects of increased task experience on which problem characteristics determine problem difficulty. A factor analysis of six performance measures found that, regardless of task experience, problem difficulty could be captured well either by a single factor corresponding to general quality of solution or possibly by three subordinate factors corresponding to solution efficiency, solution speed, and initial planning speed. Regression analyses predicting these performance factors revealed that in addition to a problem's minimum moves three problem parameters were critical in determining the problem difficulty: goal position hierarchy, start position hierarchy, and number of solution paths available. The relative contributions of each of the characteristics strongly depended on which performance factor defined performance. We conclude that TOL problem performance is multifaceted, and that classifying problem difficulty using only the minimum moves necessary to solve the problem is inadequate.

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.