Angela F. Lukowski

Iron deficiency in infancy and neurocognitive functioning at 19 years: evidence of long-term deficits in executive function and recognition memory

Abstract Iron deficiency in infancy negatively impacts a variety of neurodevelopmental processes at the time of nutrient insufficiency, with persistent central nervous system alterations and deficits in behavioral functioning, despite iron therapy. In rodent models, early iron deficiency impairs the hippocampus and the dopamine system. We examined the possibility that young adults who had experienced chronic, severe, iron deficiency as infants would exhibit deficits on neurocognitive tests with documented frontostriatal (Trail Making Test, Intra-/Extra-dimensional Shift, Stockings of Cambridge, Spatial Working Memory, Rapid Visual Information Processing) and hippocampal specificity (Pattern Recognition Memory, Spatial Recognition Memory). Participants with chronic, severe iron deficiency in infancy performed less well on frontostriatal-mediated executive functions, including inhibitory control, set-shifting, and planning. Participants also exhibited impairment on a hippocampus-based recognition memory task. We suggest that these deficits may result from the long-term effects of early iron deficiency on the dopamine system, the hippocampus, and their interaction.

Electrophysiological indexes of encoding and behavioral indexes of recall: examining relations and developmental change late in the first year of life.

Long-term memory undergoes pronounced development in the latter part of the 1st year. This reasearch combines electrophysiological (event-related potential [ERP]) and behavioral (deferred imitation) measures of encoding and recall, respectively, in an examination of age-related changes in and relations between encoding and recall during this time. In a short-term longitudinal study, infants were exposed to different multistep sequences at 9 and at 10 months. In both phases, they were tested for immediate recognition of the events via ERPs (as an index of encoding), and for recall of them 1 month later. At both ages, infants encoded the events; encoding was more robust at 10 months than at 9 months. After the 1-month delay, infants failed to recall the events experienced at 9 months, but evidenced recall of the events experienced at 10 months. In spite of developmental differences in encoding and recall over this period, indexes of encoding at 9 months were correlated with measures of recall of events experienced at 10 months and tested 1 month later.

The memory is in the details: Relations between memory for the specific features of events and long-term recall during infancy

The second year of life is marked by pronounced changes in the length of time over which events are remembered. We tested whether the age-related differences are related to differences in memory for the specific features of events. In our study, 16- and 20-month-olds were tested for immediate and long-term recall of individual actions and temporal order of actions of three-step sequences in an elicited imitation paradigm as well as for forced-choice recognition of the specific feature of the props used to produce the sequences. Memory for the props was related to long-term recall of the events only for the 20-month-olds. It accounted for unique variance above and beyond the variance explained by immediate recall of the individual actions and the temporal order of actions of the sequences. The different pattern of relations in the older and younger infants seemingly reflects a developmental difference in the determinants of long-term recall over the second year of life.

Sleeping like a baby: Examining relations between habitual infant sleep, recall memory, and generalization across cues at 10 months.

Previous research suggests that sleep is related to cognitive functioning in infants and adults. In the present study, we examined whether individual differences in infant sleep habits over the seven days prior to elicited imitation testing were associated with variability in (a) the encoding of 2-step event sequences and (b) memory for the presented information and generalization across cues after a 2-h delay in 10-month-olds. Significant correlations indicated that both daytime napping and nighttime sleep were related to encoding and generalization across cues after the 2-h delay; significant findings were not found in relation to baseline or delayed recall performance. We suggest that individual differences in infant sleep habits may be one mechanism underlying the observed variability in recall memory and generalization as these abilities are coming online late in the first year of life.

Sequence imitation and reaching measures of executive control: a longitudinal examination in the second year of life.

Despite increasing interest in the early development of executive control, few assessment tools are available for use in the second year of life. At 15 and 20 months, children completed a task battery that included reaching and sequence imitation tasks expected to require executive control. With age, children showed reduced perseveration and increased ability to resist interference across trials and from distractors. At each age, A-not-B with invisible displacement was correlated with one of the sequence imitation tasks modified to increase executive control demands. Correlations between child performance on individual tasks at 15 and 20 months were generally low.

Theory of Mind in Children with Autism Spectrum Disorder: Do Siblings Matter?

Research indicates a positive relation between the sibling constellation and theory of mind (ToM) development in typically developing (TD) children. Less is known about this association in children with autism spectrum disorder (ASD). The current study examined the association among the presence and number of siblings, birth order, and false belief (FB) understanding in children with ASD and a TD comparison group. Two FB tasks (change of contents and change of location) and the Peabody Picture Vocabulary Test were administered to 57 children with ASD and 28 TD children during a home visit. One parent of each child reported on demographics and the sibling constellation. Separate hierarchical regressions controlled for age, receptive language ability, and scores on the Social Communication Questionnaire. In children with ASD, no association was observed between presence or number of siblings and ToM. However, the presence of older (but not younger) siblings was found to be positively associated with ToM. Children with ASD who had at least one older sibling performed similarly to the TD group, whereas children with ASD who had no older siblings performed significantly worse than the TD group. These findings indicate an advantage for FB performance in children with ASD who have an older sibling. They may bear on decisions to include older siblings or peers in intervention programs and may also contribute to a more complete understanding of the origins of individual differences in ToM ability in children with ASD. Autism Res 2013, ●●: ●●–●●.

Memory for events and locations obtained in the context of elicited imitation: Evidence for differential retention in the second year of life

Previous research has suggested that infants may have more robust memory for past experiences relative to memory for locations that have been encountered previously. This assertion, however, primarily results from the comparison of data that were collected using different experimental procedures. In the present study, we examined memory for events and memory for locations in the context of elicited imitation. Specifically, 13-, 16-, and 20-month-old infants were tested for long-term memory for events and locations after between-subjects delays of 1, 3, 6, 9, and 12 months. The results indicated that the event memory was retained over lengthier delays relative to the location memory, despite superior encoding of location information. The possible adaptive significance of long-term memory for events ontogenetically preceding long-term memory for locations is discussed.

Going beyond the specifics: generalization of single actions, but not temporal order, at 9 months.

We examined generalization in 9-month-old infants after a 24-h delay using deferred imitation. Infants flexibly applied their knowledge of sequence actions across changes in props even though they had no opportunity for immediate imitation.

Sleep problems and temperament in young children with Down syndrome and typically developing controls.

BACKGROUND Although group differences have been found between children with Down syndrome (DS) and typically developing (TD) children when considering sleep problems and temperament independently, none of the research conducted to date has examined sleep-temperament associations in children with DS. The present research was conducted to determine (1) whether the sleep problems experienced by children with DS are associated with temperament or (2) if the demonstrated relations between sleep and temperament differ from those that are observed in TD children. METHOD The present study included examination of relations between parent-reported sleep problems and temperament in 19 children with DS and 20 TD controls matched on developmental age. RESULTS The results revealed group differences in temperament and sleep problems. Mediation models indicated that temperament (effortful control and inhibitory control) mediated the association between group and sleep problems; sleep problems also mediated the association between group and temperament (effortful and inhibitory control). CONCLUSION Findings indicated that sleep problems may serve as both cause and consequence of variability in effortful and inhibitory control and provide insight as to future experimental studies that should be conducted to better elucidate these relations.

Recall Memory in Children with Down Syndrome and Typically Developing Peers Matched on Developmental Age.

BACKGROUND Whereas research has indicated that children with Down syndrome (DS) imitate demonstrated actions over short delays, it is presently unknown whether children with DS recall information over lengthy delays at levels comparable with typically developing (TD) children matched on developmental age. METHOD In the present research, 10 children with DS and 10 TD children participated in a two-session study to examine basic processes associated with hippocampus-dependent recall memory. At the first session, the researcher demonstrated how to complete a three-step action sequence with novel stimuli; immediate imitation was permitted as an index of encoding. At the second session, recall memory was assessed for previously modelled sequences; children were also presented with two novel three-step control sequences. RESULTS The results indicated that group differences were not apparent in the encoding of the events or the forgetting of information over time. Group differences were also not observed when considering the recall of individual target actions at the 1-month delay, although TD children produced more target actions overall at the second session relative to children with DS. Group differences were found when considering memory for temporal order information, such that TD children evidenced recall relative to novel control sequences, whereas children with DS did not. CONCLUSIONS These findings suggest that children with DS may have difficulty with mnemonic processes associated with consolidation/storage and/or retrieval processes relative to TD children.