Language development following cochlear implantation
Cochlear implants improve the ability of profoundly deaf children to understand speech by allowing a way for sound to be transmitted to the auditory system, despite the lack of a working conduction system in the inner ear. It is of clinical and scientific importance to determine how cochlear implants facilitate the development of spoken language skills and where they fail. Together with a pediatric cochlear implant team based at Stanford University, Dr. Bortfeld is applying NIRS to track changes in cortical hemodynamics in young children following implantation and how that relates to language development outcomes.
Integration of audio and visual speech in early infancy
In addition to the auditory information that is fundamental to language development, infants also use visual speech cues to learn language. Recent behavioral research has revealed that infants rely on both the auditory and visual cues to speech in a manner equal to that observed in adults. This highlights the important role visual speech plays in supporting preverbal speech processing and subsequent language development. Research in the Bortfeld Lab applies both neurophysiological and behavioral techniques to establish how infants integrate multiple sources of perceptual information to make sense of the world around them.
Functional neuroimaging of the infant brain using near-infrared spectroscopy
Sensitivity to spoken language is an integral part of infants’ formative development yet relatively little is known about the neural mechanisms that underlie the emerging ability to perceive and process speech. This is in large part because there are a limited number of non-invasive techniques available to measure brain functioning in human infants. Since 2002, Dr. Bortfeld has been employing a hemodynamic-based measurement, near-infrared spectroscopy (NIRS), to assess the relation between speech processing and brain function in human infants. NIRS is an optical method that images cerebral hemodynamics non-invasively, particularly the total hemoglobin and oxygen saturation changes that are the result of brain activation. NIRS is completely safe and relatively robust to motion, making it ideal for use in research on how awake, behaving infants perceive the world around them.