Kimberly Cuevas

Multiple memory systems are unnecessary to account for infant memory development: An ecological model

How the memory of adults evolves from the memory abilities of infants is a central problem in cognitive development. The popular solution holds that the multiple memory systems of adults mature at different rates during infancy. The early-maturing system (implicit or nondeclarative memory) functions automatically from birth, whereas the late-maturing system (explicit or declarative memory) functions intentionally, with awareness, from late in the first year. Data are presented from research on deferred imitation, sensory preconditioning, potentiation, and context for which this solution cannot account and present an alternative model that eschews the need for multiple memory systems. The ecological model of infant memory development (N. E. Spear, 1984) holds that members of all species are perfectly adapted to their niche at each point in ontogeny and exhibit effective, evolutionarily selected solutions to whatever challenges each new niche poses. Because adults and infants occupy different niches, what they perceive, learn, and remember about the same event differs, but their raw capacity to learn and remember does not.

Infant attention and early childhood executive function.

Individual differences in infant attention are theorized to reflect the speed of information processing and are related to later cognitive abilities (i.e., memory, language, and intelligence). This study provides the first systematic longitudinal analysis of infant attention and early childhood executive function (EF; e.g., working memory, inhibitory control, cognitive flexibility). A group of 5-month-olds (n = 201) were classified as short or long lookers. At 24, 36, and 48 months of age, children completed age-appropriate EF tasks. Infant short lookers (i.e., more efficient information processors) exhibited higher EF throughout early childhood as compared to infant long lookers, even after controlling for verbal ability (a potential indicator of intelligence). These findings are discussed in relation to the emergence of executive attention.

Infants Form Associations Between Memory Representations of Stimuli That Are Absent

Traditional models of learning assume that an association can be formed only between cues that are physically present. Here, we report that when two objects that had never appeared together were simultaneously activated in memory, young human infants associated the representations of those objects. Neither object was physically present at the time the association was formed. The association remained latent for up to 2 weeks, when the infants used it to perform a deferred imitation task. These findings reveal that what infants merely see “brings to mind” what they saw before and combines it in new ways. In addition to challenging a fundamental tenet of classic learning models, these findings have major theoretical and practical implications for early cognitive development. Every day, in the same manner, young infants probably form numerous associations between activated memories of objects that are physically absent, creating a potential knowledge base of untold dimensions.

EEG and ECG from 5 to 10 Months of Age: Developmental Changes in Baseline Activation and Cognitive Processing During a Working Memory Task

We recorded electroencephalogram (EEG) and electrocardiogram (ECG) from 20 infants monthly between 5 and 10 months of age during baseline and during performance on the looking A-not-B task of infant working memory. Analyses of baseline data showed age-related increases in EEG power (medial frontal, central, temporal, medial parietal, lateral parietal, and occipital electrode sites) and coherence (frontal pole-medial frontal, medial frontal-lateral frontal, medial frontal-medial parietal, and medial frontal-occipital electrode pairs), and decreases in heart rate (HR). Patterns of age-related change were similar for EEG power, EEG coherence, and HR. Analyses of task data relative to baseline revealed task-related increases in EEG power (all electrode sites), but no task-related changes in EEG coherence (medial frontal pairings) and HR. There was some evidence of localized task-related changes in EEG power by 10 months of age. These data highlight age-related changes in EEG and ECG, as well as the functional significance of these psychophysiological measures during baseline and during cognitive processing in the first year.

Using EEG to Study Cognitive Development: Issues and Practices

Developmental research is enhanced by use of multiple methodologies for examining psychological processes. The electroencephalogram (EEG) is an efficient and relatively inexpensive method for the study of developmental changes in brain–behavior relations. In this review, we highlight some of the challenges for using EEG in cognitive development research. We also list best practices for incorporating this methodology into the study of early cognitive processes. Consideration of these issues is critical for making an informed decision regarding implementation of EEG methodology.

Early Childhood Predictors of Post-Kindergarten Executive Function: Behavior, Parent Report, and Psychophysiology

Research Findings: This study examined whether childrens executive functions before kindergarten would predict variance in executive functions after kindergarten. We obtained behavioral (working memory task performance), parent-reported (temperament-based inhibitory control), and psychophysiological (working memory–related changes in heart rate and brain electrical activity) measures of executive functions from a group of preschool-age children. After children finished kindergarten, approximately 2 years later, parents were asked to complete an assessment of childrens executive function skills. A regression analysis revealed that pre-kindergarten behavioral, parent-reported, and psychophysiological measures accounted for variance in post-kindergarten executive functions. Specifically, working memory task performance, temperament-based inhibitory control, and working memory–related changes in brain electrical activity accounted for unique variance in post-kindergarten executive functions. These data provide a unique contribution to the executive function literature: No other study has examined whether behavioral, psychophysiological, and parent-reported executive function measures can account for unique variance in future executive function. Practice or Policy: These findings are discussed in relation to childrens transition to school and executive function training programs.

The Contribution of Executive Function to Source Memory Development in Early Childhood

Age-related differences in episodic memory judgments assessing recall of fact information and the source of this information were examined. The role of executive function (EF) in supporting early episodic memory ability was also explored. Four- and 6-year-old children were taught 10 novel facts from two different sources (experimenter or puppet), and memory for both fact and source information was later tested. Measures of working memory, inhibitory control, and set shifting were obtained to produce an indicator of childrens EF. Six-year-olds recalled more fact and source information than did 4-year-olds. Regression analyses revealed that age, language ability, and EF accounted for unique variance in childrens fact recall and source recall performance. These findings suggest a link between episodic memory and EF, and we propose that developmental investigations should further explore this association.

Electroencephalogram and Heart Rate Measures of Working Memory at 5 and 10 Months of Age

We recorded electroencephalogram (EEG; 6-9 Hz) and heart rate (HR) from infants at 5 and 10 months of age during baseline and performance on the looking A-not-B task of infant working memory (WM). Longitudinal baseline-to-task comparisons revealed WM-related increases in EEG power (all electrodes) and EEG coherence (medial frontal-occipital electrode pairs) at both ages. WM-related decreases in HR were only present at 5 months, and WM-related increases in EEG coherence became more localized by 10 months. Regression analyses revealed that baseline-to-task changes in psychophysiology accounted for variability in WM performance at 10 but not 5 months. HR and EEG power (medial frontal and lateral frontal electrodes) were unique predictors of variability in 10-month WM performance. These findings are discussed in relation to frontal lobe development and represent the first comprehensive longitudinal analysis of age-related changes in the behavioral and psychophysiological correlates of WM.

Functional connectivity and infant spatial working memory: A frequency band analysis

The limited research on the functional meaning of infant EEG frequency bands has used measures of EEG power. The purpose of this study was to examine task-related changes in frontal EEG coherence measures for three infant EEG frequency bands (2-5 Hz, 6-9 Hz, 10-13 Hz) during a spatial working memory task. Eight-month-olds exhibited baseline-to-task changes in frontal EEG coherence for all infant frequency bands. Both the 2-5 Hz and the 10-13 Hz bands differentiated frontal functional connectivity during the distinct processing stages, but each band provided unique information. The 10-13 Hz band, however, was the only frequency band to distinguish frontal EEG coherence values during correct and incorrect responses. These data reveal valuable information concerning frontal functional connectivity and the functional meaning of three different infant EEG frequency bands during working memory processing.

Measures of frontal functioning and the emergence of inhibitory control processes at 10 months of age

During the first year, infants begin to exhibit initial evidence of working memory and inhibitory control in conjunction with substantial maturation of the frontal cortex and corresponding neural circuitry. Currently, relatively little is known about the neural and autonomic resources that are recruited in response to increased executive demands during the first year of development. To this end, we recorded electroencephalogram (EEG; 6-9 Hz) and electrocardiogram from 10-month-olds during a working memory and inhibitory control task (looking A-not-B). Analyses compared measures of frontal functioning (EEG power, EEG coherence, heart rate) during nonreversal (working memory) and reversal (working memory+inhibitory control) trials. The increased cognitive demand of inhibitory control processing was associated with increases in heart rate and frontal coherence (medial frontal-lateral frontal, medial frontal-temporal, medial frontal-medial parietal, and medial frontal-occipital electrode pairs). Thus, synchronized activity across distributed cortical regions appeared to be essential to inhibitory control processes during infancy. The addition of inhibitory control processes, however, was not associated with any changes in neuronal activity (EEG power). These findings are discussed in relation to other neuroscience findings and provide insight into the development of integrated frontal functioning in infancy.