Noise affects speech-signal processing differently in the cerebral hemispheres

THIS study explored the effects of acoustic noise on the cerebral asymmetry of speech perception. We measured magnetic fields of the brain elicited by consonant-vowel syllables in silence and white noise. Background noise aff ected brain responses to these stimuli differently in the left and right au ditory cortices. Its depressive effect on cortical responses was found main ly in the left hemisphere, whereas the right hemisphere was unaffected or e xhibited increased activity in noise. Locations of the P1, N1, and P2 activ ity sources in noise were different from those in silence in the right but not in the left hemisphere. These results suggest an increased right hemisp here role in speech sound processing in noisy conditions, involving the rec ruitment of additional right auditory cortex structures. NeuroReport 10:218 9-2192 (C) 1999 Lippincott Williams & Wilkins.