Neurite density of the hippocampus is associated with trace eyeblink conditioning latency in 4‐ to 6‐year‐olds

• Published in: The European journal of neuroscience Vol. 59; no. 3; pp. 358 - 369
• Main Authors: Vieites, Vanessa, Ralph, Yvonne, Reeb‐Sutherland, Bethany, Dick, Anthony Steven, Mattfeld, Aaron T., Pruden, Shannon M.
• Format: Journal Article
• Language: English
• Published: France Wiley Subscription Services, Inc 01.02.2024
• Subjects: Associative learning; Blinking; Cerebellum; Cerebellum - diagnostic imaging; Child; Child, Preschool; Children; Conditioning, Classical - physiology; Conditioning, Eyelid - physiology; development; diffusion‐weighted MRI; Eyelid conditioning; Female; Hippocampus; Hippocampus - diagnostic imaging; Hippocampus - physiology; Humans; Latency; Magnetic resonance imaging; Neurites; structural MRI; Substantia alba; trace eyeblink conditioning; Unconditioned stimulus; development; structural MRI; hippocampus; trace eyeblink conditioning; diffusion-weighted MRI
• ISSN: 0953-816X; 1460-9568
• DOI: 10.1111/ejn.16217

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. This study explored associations between hippocampal volume and neurite density with trace eyeblink conditioning (EBC) performance in 4‐ to 6‐year‐olds. Children with higher neurite density in the left hippocampus blink closer to onset of unconditioned stimulus indicating structural variations in the hippocampus were associated with more precise timing of conditioned responses. Trace EBC may serve as a non‐invasive and innovative approach for studying hippocampal development in young children.