Eyeblink Conditioning in Infants and Adults

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DESCRIPTION (provided by applicant): The ability to recall changes dramatically in the 2nd half of the 1st year of life. During this period there is great variability in performance: some infants recall after long delays, whereas others do not. One factor underlying individual differences may be variability in the developmental status of the neural substrate, specifically components of the hippocampus. Although there are no direct measures of hippocampal functioning for use with typically developing human infants, a promising indirect measure is trace eyeblink conditioning, which is known to be hippocampally dependent, making performance on the task an excellent candidate as a marker for hippocampal development in human infants. In spite of this potential, there have been no studies of changes in trace eyeblink conditioning across the 1st year of life, a period of substantial & significant hippocampal development. The proposed research is the first such study & also is the first in what will be a series of investigations of relations between hippocampal development (as measured by age-related changes in trace eyeblink conditioning) & long-term memory assessed via recognition (measured using event- related potentials: ERPs) & recall (measured by elicited & deferred imitation). The first aim of the proposal is to examine changes in performance on delay (standard & long) & trace eyeblink conditioning tasks across the latter half of the first year. Due to differential development of the neural structures implicated in the tasks (cerebellum & hippocampus, respectively), delay conditioning performance is expected to change more rapidly than trace conditioning performance. The second specific aim is to compare infants' performance on delay & trace conditioning tasks with that of adults' to determine relative functional maturity of behavior. Because trace eyeblink conditioning can be tested across the lifespan & across species (more typically, different populations must be tested on different tasks), it can be used to examine continuities & discontinuities in memory development. Because the task can be used across species, it has enormous potential to "diagnose" the specific source of memory impairment in special populations of human infants known to experience memory deficits (e.g., infants of diabetic mothers; infants born prior to term but otherwise healthy). Development of trace eyeblink conditioning as a marker for hippocampal development thus holds significant promise for basic as well as translational research. The ability to recall changes dramatically in the 2nd half of the 1st year of life. At this early age, impairments in memory are apparent in the behavior of at-risk groups, including infants of diabetic mothers and infants born prior to term but otherwise healthy. One factor implicated in both normative development and behavioral deficits is the integrity of the hippocampus. The proposed research is to test trace eyeblink conditioning as a possible marker or probe of the integrity of the hippocampus, thereby establishing the task for use in early diagnosis and treatment.