Assessing infants' cortical response to speech using near-infrared spectroscopy

Abstract

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. Near-infrared spectroscopy (NIRS), an optical imaging technique that estimates changes in neuronal activity by measuring changes in total hemoglobin concentration and oxygenation, may be a viable procedure for assessing the relation between speech processing and brain function in human infants. While auditory processing data have been gathered from newborn and preterm infants using NIRS, such data have not been collected from older infants. Many behavioral measures used to establish linguistic sensitivity in this population are accompanied by visual stimuli; however, it is unclear how coupling of auditory and visual stimuli influences neural processing. Here we studied cortical activity in infants aged 6-9 months, as measured by NIRS, during exposure to linguistic stimuli paired with visual stimuli and compared this to the activity observed in the same regions during exposure to visual stimuli alone. Results dissociate infants' hemodynamic responses to multimodal and unimodal stimuli, demonstrating the utility of NIRS for studying perceptual development in infants. In particular, these findings support the utility of NIRS for studying the neurobiology of language development in older infants, a task that is difficult to accomplish without the use of attention-getting visual stimuli.Infants' ability to perceive speech begins in the womb, and progresses dramatically during the first year of life (DeCasper and Fifer, 1980;Werker and Tees, 1984). Research indicates that during the last trimester in-utero (Mehler et al., 1988), and in the first twelve months of life post-natally (Jusczyk, 1997), infants become aware of and adjust to regularities in their native language. By using various cues found in adult speech, infants gradually come to understand and use their native language. For example, between 6 and 9 months of age, infants become sensitive to patterns within their native language, such as prosodic cues (Cutler, 1990;Morgan, 1996), phonotactic cues (Hohne and Jusczyk, 1994;Jusczyk et al., 1994), and allophonic variation (Hohne and Jusczyk, 1994). Investigating and understanding the mechanisms of the trajectory of such advances is a difficult task, and researchers have advanced the study of infant speech perception largely based on clever behavioral paradigms (e.g., Eimas et al., 1971;Trehub, 1973;Jusczyk et al., 1993;Saffran et al., 1996).The behavioral methods used to understand language development across infants' first year are typically chosen based on the specific age group being studied and the particular question being asked. For example, with infants four months of age and younger, a useful method employs a pacifier to record changes in infant su...

The hemodynamic response to acoustically modified syllables in premature and full term newborn infants acquired by near infrared spectroscopy.

“…However, the hemodynamic response in infants does not always present the same characteristics of adults. Some research has found increase in both [oxyHb] and [deoxyHb] (Bortfeld, Wruck, & Boas, 2007;Sakatani, Chenb, Lichtyc, & Zuoa, 2009). …”

Using functional near-infrared spectroscopy (fNIRS) to detect the prefrontal cortical responses to deception under different motivations

“…This fNIRS system contains three wavelengths (780nm, 805nm, and 830nm) [1,30]. The concentration changes of oxygenated hemoglobin (HBO), deoxygenated hemoglobin (HB) and total hemoglobin (HbT) were measured.…”

“…The concentration changes of oxygenated hemoglobin (HBO), deoxygenated hemoglobin (HB) and total hemoglobin (HbT) were measured. The parameters were determined with the modified Beer-Lambert law [1,30]. The international 10-10 system [31] was used to localize the whole prefrontal cortex (PFC).…”

“…Functional near-infrared spectroscopy (fNIRS), which can assess the relative changes of oxy hemoglobin (HbO), deoxy hemoglobin (Hb) and total hemoglobin (HbT) in the cortical regions of the brain [1,2], is an emerging brain-imaging technique [3]. fNIRS has excellent time resolution and acceptable spatial resolution [4].…”

Long-term deficits of preterm birth: Evidence for arousal and attentional disturbances

“…These monitors are used clinically in Japan in rehabilitation/orthopedic settings, in neonatal intensive care units (continuous brain blood flow measured over the fontanelle), and emergency medicine applications. They are approved for research in the U.S. and are used, for example, to assess sensory and motor performance (Bortfeld et al 2007;Hatakenaka et al 2007;Otsuka et al 2007). Sampling occurred every 10sec over a 5 min baseline period, then every 10sec during the 10 min PVT test and during recording of each P50 potential ISI.…”