The Secret Life of Babies: an fMRI Approach to Infant Perception and Memory
Date of Award
Fall 2023
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Psychology
First Advisor
Turk-Browne, Nicholas
Abstract
Every human being begins life as an infant, yet the contents of infants' mental lives remain somewhat mysterious. Difficulty in deciphering the infant mind stems in part from limitations in infant behavior, such as their inability to speak, understand instructions, or perform complex actions. Thus, one approach to understanding infant cognition is to supplement (or even bypass) behavior and go directly to the source of the mind: the brain. In this thesis, I argue that functional magnetic resonance imaging (fMRI) with awake human infants shows promise for understanding aspects of the infant mind that may be inaccessible to other behavioral or neuroimaging methods. Across three case studies, I show how awake infant fMRI can give new insights into how infants perceive, remember, and are shaped by their worlds. First, I ask whether and how infants segment continuous sensory input into discrete events --- in other words, how they organize their perceptual experiences. Using naturalistic movies, I find reliable neural event segmentation in both early sensory and later associative regions of the infant brain, with neural events across regions persisting over longer timescales in infants compared to adults. Second, I investigate how the infant brain encodes new memories, with the goal of better understanding why memories from infancy are lost over time. I find that, despite its structural immaturity, the hippocampus is more active during the encoding of remembered versus forgotten items, but only after the first year of life. Third, I examine the role of experience in how infants perceive faces, making use of a serendipitous experiment that spanned the COVID-19 pandemic, which brought changes to infants' environments. Infants showed distinct neural patterns to novel versus repeat human faces depending on whether they were tested before or after the COVID-19 pandemic lockdowns, with pre-lockdown infants showing greater activity to novel faces, and post-lockdown infants showing greater activity to repeat faces. Together, these case studies demonstrate how awake infant fMRI can reveal cognitive representations (e.g., event timescales) and mechanisms (e.g., repetition suppression versus enhancement) that may otherwise be hidden. They also highlight how the infant brain is not just a smaller version of the adult brain, and instead helps to support cognitive capacities that may be adaptive for developing in a complex world. Finally, I consider the broader utility of awake infant fMRI for developmental science. Given the difficulty of this approach, many researchers have opted to study the sleeping infant brain, which has revealed organized functional brain networks early in life. However, it is unclear whether and how sleep/wake states influence infant functional brain networks, which has important implications for cognitive development. Here, I find that infant sleep/wake states can be decoded by functional brain network activity and meaningfully impact which functional brain networks appear more adultlike. Thus, in addition to answering fundamental questions in infant cognition, awake infant fMRI may be an important complement to developmental neuroscience research that primarily studies infant brain networks during the sleep state. Altogether, this thesis demonstrates the value of awake infant fMRI for understanding how infants represent their worlds.
Recommended Citation
Yates, Tristan Skye, "The Secret Life of Babies: an fMRI Approach to Infant Perception and Memory" (2023). Yale Graduate School of Arts and Sciences Dissertations. 1158.
https://elischolar.library.yale.edu/gsas_dissertations/1158
