Tracing trajectories of audio‐visual learning in the infant brain

Abstract

Although infants begin learning about their environment before they are born, little is known about how the infant brain changes during learning. Here, we take the initial steps in documenting how the neural responses in the brain change as infants learn to associate audio and visual stimuli. Using functional near-infrared spectroscopy (fNRIS) to record hemodynamic responses in the infant cortex (temporal, occipital, and frontal cortex), we find that across the infant brain, learning is characterized by an increase in activation followed by a decrease. We take this U-shaped response as evidence of repetition enhancement during early stages of learning and repetition suppression during later stages, a result that mirrors the Hunter and Ames model of infant visual preference. Furthermore, we find that the neural response to violations of the learned associations can be predicted by the shape of the learning curve in temporal and occipital cortex. These data provide the first look at the shape of the neural response during audio-visual associative learning in infancy establishing that diverse regions of the infant brain exhibit systematic changes across the time-course of learning.

Comparing statistical learning across perceptual modalities in infancy: An investigation of underlying learning mechanism(s)

“…For example, functional near-infrared spectroscopy (fNIRS) has been used to investigate learning trajectories (Kersey & Emberson, 2017) and responses to novelty or violations (Emberson, Richards, & Aslin, 2015;Lloyd-Fox et al, 2019;Nakano, Watanabe, Homae, & Taga, 2009 Orena & Polka, 2017). For example, functional near-infrared spectroscopy (fNIRS) has been used to investigate learning trajectories (Kersey & Emberson, 2017) and responses to novelty or violations (Emberson, Richards, & Aslin, 2015;Lloyd-Fox et al, 2019;Nakano, Watanabe, Homae, & Taga, 2009 Orena & Polka, 2017).…”

The emergence of top‐down, sensory prediction during learning in infancy: A comparison of full‐term and preterm infants

“…We are looking to uncover the same inverted u‐shaped neural changes that were observed in Kersey and Emberson () for this type of learning and contrast these trajectories across the two populations of infants. In addition to contrasting trajectories, we conduct an individual differences analysis (as in Kersey & Emberson, ) to investigate how variations in an infant's ability to generate top‐down prediction relates to their individual learning trajectories. We expect to find a positive correspondence between the emergence of top‐down predictions and the strength of U‐shape neural trajectories during learning.…”

“…There is already some evidence that the emergency of top‐down predictions are playing some role in neural learning trajectories. Kersey and Emberson () found that full‐term infants exhibit an inverted u‐shaped learning trajectory (i.e., repetition enhancement followed by repetition suppression) during the audiovisual learning that supports the generation of top‐down predictions. In exploratory analyses, Kersey and Emberson () found that the shape of an individual infant's learning trajectory can predict an infant's individual top‐down prediction abilities (i.e., their occipital lobe response during an unexpected visual omission).…”

“…Kersey and Emberson () found that full‐term infants exhibit an inverted u‐shaped learning trajectory (i.e., repetition enhancement followed by repetition suppression) during the audiovisual learning that supports the generation of top‐down predictions. In exploratory analyses, Kersey and Emberson () found that the shape of an individual infant's learning trajectory can predict an infant's individual top‐down prediction abilities (i.e., their occipital lobe response during an unexpected visual omission). In other words, how much an infant's occipital lobe was modulated during learning, in this inverted u‐shaped pattern, predicted how strongly an infant responded during unexpected omission trials which are designed to probe their top‐down predictions.…”

“…In the combined analysis, we included effects related to birth status (premature or full‐term) to examine the role that prematurity plays in the formation of these learning trajectories. Finally, we employed a method of analysis initially reported in Kersey and Emberson () to examine the relationship between individual infant's learning trajectories and infants’ signature of top‐down prediction (occipital responses to unexpected visual omission trials). Because each infant watched a different number of trials, we recognize the possibility that some of the results of the analyses described may be affected by these differences.…”