Neural Markers of Incidental Auditory Learning in Preverbal Infants Index and Predict Developmental Outcomes

• In Event: Infant learning and brain development

Abstract

Background: Auditory learning and memory are fundamental building blocks in the development of communicative functioning and cognition. Objective evaluation of these processes in preverbal infants can be challenging due to the limited range and reliability of overt behavioral responses. Measures of brain activity, such as event-related potentials (ERPs) may offer additional insights into early learning abilities and serve as predictors of developmental outcomes (Weibe et al., 2006; Cantiani et al., 2016). The study tested the hypothesis that stronger auditory incidental memory for novel spoken stimuli in preverbal infants will be reflected in more positive parietal ERP amplitudes within 200-500 ms after stimulus onset and associated with better communicative skills (both concurrently and predictively).
Method: Data were collected in 34 infants (16 females) tested at least twice between the ages of 6-17 months using an accelerated longitudinal design. At each visit, the infants completed the auditory incidental memory paradigm examining ERP markers of pseudoword repetition detection during passive listening (Key et al., 2018). The 6-minute paradigm included 51 novel single-syllable pseudowords (M duration=694.50 ms, SD=127.78 ms), one of which was randomly selected to be repeated 50 times (repeated condition), the remaining 50 stimuli were presented once (single condition). The use of pseudowords equated novelty of the stimuli and made the task suitable for non-English speakers. All stimuli were presented in sound field at 75 dB SPL with varied interstimulus interval between 1300-1600 ms. ERPs were recorded using 128-channel array (EGI, Inc), with 250 Hz sampling rate, 0.1-30 Hz filters, and average reference. The dependent measure was mean parietal amplitude within 200-500ms after stimulus onset for the repeated and single condition. Behavioral measures included standard scores on direct assessments (Mullen Scales of Early Learning) and caregiver reports (Vineland Adaptive Behavior Scales) of communicative, cognitive, and adaptive functioning.
Results: Infants as young as 8 months spontaneously attended to spoken pseudowords during passive exposure and detected stimulus repetition reflected by the parietal ERP response. The direction of significant condition differences varied based on familiarity vs. novelty preference: the more positive parietal amplitudes for the repeated than single stimuli reflected attention to the familiarized items, while more negative amplitudes to the repeated stimuli indexed habituation and reduced interest. Prior to 12 months of age, larger parietal ERP responses to repeated than single stimuli were associated with higher scores on behavioral measures of expressive communication. After 12 months of age, more positive parietal ERP amplitudes to the single stimuli were related to better language performance. The absence of a shift from familiarity to novelty preference around 12 months of age was associated with lower cognitive performance at 18-24 months.
Conclusion: Auditory ERPs during passive listening can assess real-time learning and memory ability in infants, capture developmental transitions in familiarity vs. novelty detection previously seen in behavioral paradigms (e.g., Reynolds & Romano, 2016), and inform about language and cognitive functioning. Repeated administration can reveal developmental trajectories that are informative about future outcomes.

Authors

• Alexandra Key, Vanderbilt University Medical Center
  Presenting Author

• Sydney Roth, Vanderbilt University

• Vivian R Nguyen, Vanderbilt University