Understanding what infants understand about objects and words that they encounter in the world has been an important goal in developmental science, but the field understands relatively little about how infants perform either of these two tasks. Several neuroimaging methods have been used to determine how adult brains recognize familiar objects and words, but most of these methods are not suitable for use with infants. The goal of this research project is to deploy two neuroimaging methods that are amenable for use with infants, as a novel way to gain insights into the fundamental brain mechanisms that enable object recognition and word understanding in 3- to 12-month-old infants. One technique, electroencephalography (EEG) involves measuring electrical activity generated by the brain from sensors on the scalp. The other, functional near-infrared spectroscopy (fNIRS), shines near-infrared light through the skull and measures how it is absorbed by the brain at each location as an index of how active that part of the brain is. Recording both these measures while infants watch and listen to stimuli will provide important insights into how the infant brain processes this information.
EEG has been in use with infants for many years, whereas functional near-infrared spectroscopy (fNIRS) is a relatively newer non-invasive neuroimaging technique ideally suited for use with infants. fNIRS, like fMRI, provides a signature of metabolic activity in localized regions of the brain but is more suitable for infants because it delivers light to the scalp via a tight-fitting cap. In this project, EEG and fNIRS will be used to measure electrical and metabolic activity in the brain as infants watch objects of various categories such as vehicles or furniture, or listen to words that they know or do not know (or nonsense words). The key analysis tool is a suite of machine-learning algorithms from the field of computer science that take the EEG or fNIRS signals to determine which components of these signals best predict, on a trial by trial basis, what the infant was seeing or hearing.
The outcome of the proposed research will localize in the brain where encoding of visual objects and spoken words takes place and over what time period after stimulus onset that processing occurs. These are fundamental aspects of object and language processing have eluded study in the human infant because of methodological challenges. Establishing protocols for analyzing data generated by these two methods will contribute to analytic techniques available for future infant brain research. Identifying normative properties of these processing mechanisms in the infant brain will set the stage for future research investigating how the developing brain is affected by variations in early experience, by compensation after injury, and by a variety of genetic anomalies.
