“Sound representation in higher language areas during language generation”

How language is encoded by neural activity in thehigher level language areas of humans is still largely unknown.We investigated if the electrophysiological activity of Broca's areacorrelates with the sound of the utterances produced. Duringspeech perception the electric cortical activity of the auditoryareas correlates with the sound-envelope of the utterances. Inour experiment we compared the electrocorticogram recordedduring awake neurosurgical operations in Broca's area and in thedominant temporal lobe with the sound-envelope of single wordsvs. sentences read aloud or mentally by the patients. Our resultsindicate that the electrocorticogram correlates with the soundenvelopeof the utterances starting before any sound is producedand even in the absence of speech when the patient is readingmentally. No correlations were found when the electrocorticogramwas recorded in the superior parietal gyrus an area not directly involvedin language generation or in Broca's area when the subjectswere executing a repetitive motor task without any linguistic contentwith their dominant hand. The distribution of supra-thresholdcorrelations across frequencies of cortical activities varied whetherthe sound-envelope derived from words or sentences. Our resultssuggest that the activity of language areas is organized by soundwhen language is generated before any utterance is produced andheard.