Episodic memory and future thinking during early childhood: Linking the past and future.

Despite extensive examination of episodic memory and future thinking development, little is known about the concurrent emergence of these capacities during early childhood. In Experiment 1, 3-year-olds participated in an episodic memory hiding task ("what, when, where" [WWW] components) with an episodic future thinking component. In Experiment 2, a group of 4-year-olds (including children from Experiment 1) participated in the same task (different objects and locations), providing the first longitudinal investigation of episodic memory and future thinking. Although children exhibited age-related improvements in recall, recognition, and binding of the WWW episodic memory components, there were no age-related changes in episodic future thinking. At both ages, WWW episodic memory performance was higher than future thinking performance, and episodic future thinking and WWW memory components were unrelated. These findings suggest that the WWW components of episodic memory are potentially less fragile than the future components when assessed in a cognitively demanding task.

What's mom got to do with it? Contributions of maternal executive function and caregiving to the development of executive function across early childhood.

Executive functions (EFs; e.g. working memory, inhibitory control) are mediated by the prefrontal cortex and associated with optimal cognitive and socio-emotional development. This study provides the first concurrent analysis of the relative contributions of maternal EF and caregiving to child EF. A group of children and their mothers (n = 62) completed age-appropriate interaction (10, 24, 36 months) and EF tasks (child: 24, 36, and 48 months). Regression analyses revealed that by 36 months of age, maternal EF and negative caregiving behaviors accounted for unique variance in child EF, above and beyond maternal education and child verbal ability. These findings were confirmed when using an early child EF composite-our most reliable measure of EF - and a similar pattern was found when controlling for stability in child EF. Furthermore, there was evidence that maternal EF had significant indirect effects on changes in child EF through maternal caregiving. At 24 months, EF was associated with maternal EF, but not negative caregiving behaviors. Taken together, these findings suggest that links between negative caregiving and child EF are increasingly manifested during early childhood. Although maternal EF and negative caregiving are related, they provide unique information about the development of child EF. A video abstract of this article can be viewed at http://www.youtube.com/watch?v=NPKXFbbrkps.

Self-regulation of negative affect at 5 and 10 months.

One hundred six infants participated in a longitudinal study of cognition-emotion integration exploring the effects of attentional control on regulation of negative affect across infancy. At both 5 and 10 months, attentional control was measured behaviorally (looking time to neutral stimulus), physiologically (cardiac reactivity), and with temperament-based parental ratings of orienting/regulation. Looking and cardiac measures were examined both before and after a mild stressor. At 5 months, post-distress negative affect was related only to distress-related increases in heart rate. At 10 months, however, behavioral, cardiac, and parent-report aspects of attentional control explained unique variance in post-distress negative affect. Attentional control measures at 5 months did not predict negative affect at 10 months. This pattern of results is discussed with respect to the development of frontally mediated regulatory mechanisms from infancy into early childhood.

The role of inhibitory control in behavioral and physiological expressions of toddler executive function.

A total of 81 toddlers (24-27months of age) participated in a biobehavioral investigation of inhibitory control. Maternal report measures of inhibitory control were related to laboratory tasks assessing inhibitory abilities under conditions of conflict, delay, and compliance challenge as well as toddler verbal ability. In addition, unique variance in inhibitory control was explained by task-related changes in brain electrical activity at lateral frontal scalp sites as well as concurrent inhibitory task performance. Implications regarding neural correlates of executive function during early development and a central organizing role of inhibitory processing during toddlerhood are discussed.

Persistent deficits in heart rate response habituation following neonatal binge ethanol exposure.

BACKGROUND: We have previously shown that the rate of habituation of the heart rate orienting response to a novel odor in rats is negatively affected by neonatal ethanol exposure. Thus far, however, only young rats (16 days of age) have been tested. Given the persistence of attention and memory problems evident in humans exposed to ethanol in utero, the purpose of this experiment was to examine the longer-term consequences of ethanol exposure on response habituation. METHODS: Ethanol (5.25 g/kg/d) was administered intragastrically to male and female Sprague-Dawley rats on postnatal days (PD) 4 to 9, and controls were given sham intubations. Animals were tested for heart rate orienting and response habituation to a novel olfactory stimulus (amyl acetate) on PD 16, 23, or 30. RESULTS: Animals tested on PD 16 or 23 showed normal heart rate deceleration to the novel odor, a measure of the orienting response. However, ethanol-treated subjects showed impaired response habituation compared with sham controls. While controls exhibited complete habituation within 4 to 5 trials, ethanol-treated animals continued to respond throughout the testing session, with little decrement in heart rate response magnitude across 10 stimulus presentations. A different pattern of responding was observed in animals tested during adolescence (PD 30). Control animals failed to show the typical heart rate decrease indicative of orienting, and instead showed a tendency toward tachycardia. In contrast, ethanol-treated animals tested on PD 30 showed orienting bradycardia that persisted for several trials. CONCLUSIONS: These data suggest that there are relatively long-term consequences of neonatal ethanol exposure on nonassociative memory. This impairment in habituation may be relevant to the distractibility and poor focused attention that is pervasive among humans diagnosed with fetal alcohol spectrum disorders.

Patterns of brain-electrical activity during declarative memory performance in 10-month-old infants.

This study of infant declarative memory concurrently examined brain-electrical activity and deferred imitation performance in 10-month-old infants. Continuous electroencephalogram (EEG) measures were collected throughout the activity-matched baseline, encoding (modeling) and retrieval (delayed test) phases of a within-subjects deferred imitation task. Infants were divided into two memory performance groups based on the exhibition of ordered-recall after a 24-h delay. Whereas no group differences were found in EEG collected during encoding, performance-group differences in EEG were present during retrieval. Infants who successfully displayed ordered-recall showed a pattern of increasing EEG from baseline to task at anterior temporal scalp locations, whereas infants showing no ordered-recall displayed no changes in EEG from baseline to task. These findings are discussed with respect to the biobehavioral developments underlying declarative memory abilities.

Physiological and neurobehavioral effects of cholinesterase inhibition in healthy adults.

INTRODUCTION: Based on common pharmacodynamic mechanisms, recent efforts to develop second generation alternatives for organophosphate (OP) prophylaxis have expanded to include cholinesterase (ChE) inhibiting compounds traditionally approved for use in the treatment of Alzheimer's disease (AD). The primary purpose of this study was to determine the extent to which low-dose huperzine A, galantamine, or donepezil selectively inhibited acetylcholinesterase (AChE) versus butyrylcholinesterase (BChE) activity in healthy adults and whether such inhibition impacted neurobehavioral performance. METHODS: In addition to hourly red blood cell cholinesterase sampling, neurobehavioral function was assessed before and after a single oral dose of huperzine A (100 or 200 µg), galantamine (4 or 8 mg), donepezil (2.5 or 5mg), or placebo (n=12 subjects per drug/dose). RESULTS: Compared to placebo, both dosages of huperzine A and galantamine inhibited circulating AChE but not BChE. With the exception of huperzine A (200 µg), which maintained declarative recall performance across sessions, compounds did not improve neurobehavioral performance. Some aspects of neurobehavioral performance correlated with AChE activity, although associations may have reflected time of day effects. DISCUSSION: Although huperzine A and galantamine significantly inhibited AChE (and likely increased central acetylcholine levels), neither compound improved neurobehavioral performance. The latter was likely due to ceiling effects in this young, healthy test population. Under conditions of reduced cholinergic activity (e.g., Alzheimer's disease), AChE inhibition (and corresponding maintenance of cholinergic tone) could potentially maintain/augment some aspects of neurobehavioral function.

Modality-specific impairments in response habituation following postnatal binge ethanol.

The rate of habituation of the heart rate orienting response (OR) to both olfactory and auditory cues was examined in subjects neonatally exposed to ethanol. Subjects were administered 5.25 g/kg/day ethanol in a binge-like manner on either postnatal days (PDs) 4-9 or 10-15. Controls were given sham intubations. Ethanol exposure had no effect on the form or magnitude of the heart rate OR; all subjects exhibited a monophasic bradycardia to the olfactory and auditory cues. However, ethanol treatment severely affected the rate of response habituation to an olfactory cue, regardless of the timing of that exposure. Ethanol treatment on either PDs 4-9 or 10-15 resulted in a failure of animals to show complete heart rate response habituation. For the auditory cue, rate of response habituation was unaffected by ethanol treatment. These results indicate that response habituation deficits in a postnatal model of human fetal-alcohol exposure are modality specific. The response habituation paradigm may be useful for studying mechanisms of short-term recognition memory deficits following early alcohol exposure, although modality of the test stimulus needs to be taken into account. The results suggest that central nervous system structures affected by ethanol may be specific to those involved in olfactory processing, such as the olfactory bulb or hippocampus.

A longitudinal intergenerational analysis of executive functions during early childhood.

Despite the importance of executive function (EF) in both clinical and educational contexts, the aetiology of individual differences in early childhood EF remains poorly understood. This study provides the first longitudinal intergenerational analysis of mother-child EF associations during early childhood. A group of children and their mothers (n = 62) completed age-appropriate EF tasks. Mother and child EFs were modestly correlated by 24 months of age, and this association was stable through 48 months. Importantly, maternal-child EF associations were still robust after controlling for verbal ability (potential indicator of verbal/crystallized intelligence) and maternal education (correlate of socio-economic status and verbal intelligence). Potential implications of these findings as well as underlying mechanisms of the maternal-child EF association (gene-environment interplay) are discussed.