PubMed · 907541
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R Khurana. 1977. Brain stem auditory-evoked responses.. https://doi.org/10.1001/archneur.1977.00500220084020
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Rapid progress in effective methods to image brain functions has revolutionized neuroscience. It is now possible to study noninvasively in humans neural processes that were previously only accessible in experimental animals and in brain-injured patients. In this endeavor, positron emission tomography has been the leader, but the superconducting quantum interference device-based magnetoencephalography (MEG) is gaining a firm role, too. With the advent of instruments covering the whole scalp, MEG, typically with 5-mm spatial and 1-ms temporal resolution, allows neuroscientists to track cortical functions accurately in time and space. We present five representative examples of recent MEG studies in our laboratory that demonstrate the usefulness of whole-head magnetoencephalography in investigations of spatiotemporal dynamics of cortical signal processing.
Functional asymmetries were examined in 59 newborns by recording headturns from midline to binaurally equivalent sounds. Results showed that robust, asymmetric pattern of headturning occurred in most newborns' responses to binaurally presented unfiltered female speech sounds, with increased rightward orientation demonstrated in five replications. Female speech that was modified by attenuation of frequencies above 500 Hz, as well as speech attenuated below 1500 Hz and above 3000 Hz, resulted in a significant rightward bias in headturning. In contrast, female speech attenuated below 3500 Hz, and continuous, repetitive stimuli such as heartbeat sounds and phrases of speech repeated at the rate of heartbeat (termed heartspeech), failed to generate the rightward orientation bias. These results suggest that female speech sounds, particularly low-frequency sounds related to the naturally occurring prosodic characteristics of speech, are a salient class of stimuli for the organization of lateral biases in orienting in newborns.