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Nonverbal Episodic Memory in Preschoolers: Behavioral Relations to Receptive Vocabulary and Neural Correlates of Encoding
Poster Session D, Thursday, October 1, 4:30 - 6:30 pm, Wangari Maathai
This poster is part of the Sandbox Series.
Jiayi Lu1, Jueyao Lin1, Xiaocong Chen1, Zhengqin Liu1, Lu Li1, Changsheng Li1, Michael Ullman2, Han Zhang3, Caicai Zhang1; 1The Hong Kong Polytechnic University, 2Georgetown University, 3ShanghaiTech University
INTRODUCTION The Declarative/Procedural (DP) Model (Ullman, 2016) posits that the declarative memory system is foundational for lexical acquisition. Declarative memory is typically operationalized with episodic memory paradigms. While episodic memory predicts L2 vocabulary (Morgan-Short et al., 2022), its L1 contribution remains underexplored – existing evidence links only verbal episodic memory to lexical ability (Lum et al., 2012). Nonverbal episodic memory, which eliminates shared verbalness confounds, remains unexamined. Moreover, studies rarely distinguish initial recognition and overnight retention phases or differentiate receptive from expressive vocabulary. Developmental fMRI studies of memory encoding have focused on school-aged children, revealing protracted prefrontal cortex (PFC) maturation for strategic encoding, complex developmental trajectories of the medial temporal lobe (MTL), and a shift away from a childhood over-reliance on posterior perceptual systems for detailed visual representation (Ofen et al., 2012). However, the encoding architecture remains uncharacterized in preschoolers. The present study addresses these gaps in Cantonese-speaking 4-year-olds. METHODS Data from 47 4-year-olds (54.21±2.91 months) were retained for behavioral analysis (excluding chance performers), with 19 (53.84±3.18 months, ≤30% motion) retained for fMRI analysis. A block-design fMRI encoding task (maximizing signal-to-noise ratio and preschooler compliance) interleaved five Novel blocks (8 unique scene photographs per block) and five Repeated baseline blocks (2 alternating photographs per block). Episodic memory was indexed behaviorally via separate old/new recognition sets across initial recognition d′ (30-min delay) and overnight retention d′ (24-h delay) phases. Receptive vocabulary was assessed using a Cantonese adaptation of the Peabody Picture Vocabulary Test (PPVT). Expressive vocabulary was assessed using the Hong Kong Test of Preschool Oral Language. Hierarchical regressions assessed how initial recognition and overnight retention predicted receptive and expressive vocabulary separately, controlling for age, gender, and nonverbal IQ. AFNI-processed fMRI data were registered to the Haskins Pediatric Nonlinear Atlas. The Novel>Repeated encoding contrast was thresholded at voxel-wise p<.001, cluster-level α<.01. RESULTS After controlling for covariates and initial recognition d′, overnight retention d′ accounted for significant additional variance in receptive vocabulary (ΔR2adj=0.176, p=.002) and was a positive predictor in the final model (b=3.46, t=3.30; p=.002; final R2adj=0.253, p=.004). No significant episodic memory predictors emerged for expressive vocabulary. Whole-brain fMRI encoding contrast (Novel > Repeated) identified bilateral occipito-temporal activation, yielding four significant clusters: right fusiform gyrus, right lingual gyrus, left fusiform gyrus, and left pericalcarine/lateral occipital. DISCUSSION Behaviorally, overnight retention, but not initial recognition, predicted receptive vocabulary, supporting the DP model while eliminating verbal confounds. The null effect on expressive vocabulary may reflect additional speech production demands. Neurally, group-level results showed robust occipito-temporal activation for novel scenes, reflecting posterior perceptual system engagement in processing visual details. This pattern matches prior evidence of a perceptual-to-frontal shift in episodic encoding across childhood, with later-emerging PFC and parietal contributions reflecting strategic encoding and greater cognitive control (Ofen et al., 2012). The absence of MTL activation aligns with the complex developmental trajectories and subregional differences characterizing early MTL development (Ofen et al., 2012). Planned ROI analyses targeting a priori (PFC, MTL) and empirical occipito-temporal peaks will further examine sub-threshold regional contributions to memory and vocabulary outcomes.
Topic Areas: Language Development/Acquisition, Meaning: Lexical Semantics