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Neurite density of the hippocampus is associated with trace eyeblink conditioning latency in 4- to 6-year-olds
Vanessa Vieites1, Yvonne Ralph2, Bethany Reeb-Sutherland3
1Department of Psychology, Rutgers, The State University of New Jersey, New Brunswick, New Jersey, USA.
Insights
Trace eyeblink conditioning (EBC) in children shows a link between left hippocampal neurite density and conditioned response timing. This suggests EBC may help assess hippocampal development in young children.
Area of Science:
- Neuroscience
- Developmental Psychology
- Pediatric Imaging
Background:
- Assessing hippocampal function in young children is challenging.
- Trace eyeblink conditioning (EBC) is known to depend on hippocampal function.
- Investigating EBC's link to hippocampal structure could offer a developmental indicator.
Purpose of the Study:
- To explore associations between hippocampal structure (volume, neurite density) and trace EBC performance in children.
- To determine if trace EBC can serve as a measure of hippocampal development.
Main Methods:
- Participants: 30 typically developing children (4-6 years old).
- Procedures: T1-weighted and diffusion-weighted MRI scans, followed by a 15-minute trace EBC task.
- Measures: Conditioned response (CR) onset latency and percentage of CRs (% CR).
Main Results:
- Higher left hippocampal neurite density correlated with delayed CR onset latency.
- Increased left hippocampal neurite density was associated with more precise CR timing (blinking closer to unconditioned stimulus onset).
- No significant associations found for hippocampal volume, cerebellum measures, or white matter connectivity with EBC outcomes.
Conclusions:
- Trace EBC performance is linked to specific aspects of hippocampal microstructure in young children.
- This suggests trace EBC is a promising, non-invasive tool for evaluating hippocampal development.
- Potential applications include studying neurodevelopmental disorders and typical development trajectories.
Abstract:
Limited options exist to evaluate the development of hippocampal function in young children. Research has established that trace eyeblink conditioning (EBC) relies on a functional hippocampus. Hence, we set out to investigate whether trace EBC is linked to hippocampal structure, potentially serving as a valuable indicator of hippocampal development. Our study explored potential associations between individual differences in hippocampal volume and neurite density with trace EBC performance in young children. We used onset latency of conditioned responses (CR) and percentage of conditioned responses (% CR) as measures of hippocampal-dependent associative learning. Using a sample of typically developing children aged 4 to 6 years (N = 30; 14 girls; M = 5.70 years), participants underwent T1- and diffusion-weighted MRI scans and completed a 15-min trace eyeblink conditioning task conducted outside the MRI. % CR and CR onset latency were calculated based on all trials involving tone-puff presentations and tone-alone trials. Findings revealed a connection between greater left hippocampal neurite density and delayed CR onset latency. Children with higher neurite density in the left hippocampus tended to blink closer to the onset of the unconditioned stimulus, indicating that structural variations in the hippocampus were associated with more precise timing of conditioned responses. No other relationships were observed between hippocampal volume, cerebellum volume or neurite density, hippocampal white matter connectivity and any EBC measures. Preliminary results suggest that trace EBC may serve as a straightforward yet innovative approach for studying hippocampal development in young children and populations with atypical development.
