Neuronal activity in the human lateral temporal lobe

Abstract

We have recorded neuronal responses in the lateral temporal lobe of man to overt speech during open brain surgery for epilepsy. Tests included overt naming of objects and reading words or short sentences shown on a projector screen, repetition of tape recorded words or sentences presented over a loudspeaker, and free conversation. Neuronal activity in the dominant and non-dominant temporal lobe were about equally affected by overt speech. As during listening to language (see Creutzfeldt et al. 1989), responses differed between recordings from sites in the superior and the middle or inferior temporal gyrus. In the superior temporal gyrus all neurons responded clearly and each in a characteristic manner. Activation could be related to phonemic aspects, to segmentation or to the length of spoken words or sentences. However, neurons were mostly differently affected by listening to words and language as compared to overt speaking. In neuronal populations recorded simultaneously with one or two microelectrodes, some neurons responded predominantly to one or the other type of speech. Excitatory responses during overt speaking were always auditory. In the middle temporal gyrus more neurons (about 2/3) responded to overt speaking than to listening alone. Activations elicited during overt speech were seen in about 1/3 of our sample, but they were more sluggish than those recorded in the superior gyrus. A prominent feature was suppression of on-going activity, which we found in about 1/3 of middle and in some superior temporal gyrus neurons. This suppression could precede vocalization by up to a few hundred ms, and could outlast it by up to 1 s. Evoked ECoG-potentials to words heard or spoken were different, and those to overt speech were more widespread.

Decoding spectrotemporal features of overt and covert speech from the human cortex

“…In this study, we analyzed auditory stimuli from self-generated speech as opposed to external auditory stimulation. During self-produced speech, neural activity in human auditory cortex is reported to be suppressed (Creutzfeldt et al, 1989; Flinker et al, 2010) which has been attributed to the effect of efference copy or corollary discharge sent from the motor cortex onto sensory areas (Jeannerod, 2003). Despite this effect, we observed that high gamma activity in the superior temporal gyrus, pre- and post-central gyrus during vocalization was sufficient to reliably reconstruct continuous spectrotemporal auditory features of speech.…”

Subnormal sensory attenuation to self-generated speech in schizotypy: Electrophysiological evidence for a ‘continuum of psychosis’

“…N1-suppression – particularly to willed vocalizations – has been interpreted as being caused by an efference copy/corollary discharge mechanism that predicts and suppresses the sensory consequences of self-generated actions. Recordings of neuronal activity in the temporal cortex during neurosurgery found that neuronal firing was suppressed during overt speech compared to passive listening (Creutzfeldt et al, 1989), and this suppression appeared to be highly localized to circumscribed areas within the auditory cortex (Chen et al, 2011; Greenlee et al, 2011). …”

Assessing corollary discharge in humans using noninvasive neurophysiological methods

“…Support for this mechanism comes from studies by Creutzfeldt and colleagues in which recordings were made from human patients during pre-surgical planning from the exposed surface of the right and left temporal cortices while they talked and listened to others talking; suppression of activity in auditory cortex was noted during talking compared to listening 7 . Similarly, Eliades and Wang 8, 9 recorded from primary auditory cortex single units in marmoset monkeys during vocalization, and they reported vocalization-induced suppression beginning before vocalization, with excitation of different units beginning after vocal onset 9 .…”