Temporal envelope processing in the human auditory cortex: Response and interconnections of auditory cortical areas

Abstract

Temporal envelope processing in the human auditory cortex has an important role in language analysis. In this paper, depth recordings of local field potentials in response to amplitude modulated white noises were used to design maps of activation in primary, secondary and associative auditory areas and to study the propagation of the cortical activity between them. The comparison of activations between auditory areas was based on a signal-to-noise ratio associated with the response to amplitude modulation (AM). The functional connectivity between cortical areas was quantified by the directed coherence (DCOH) applied to auditory evoked potentials. This study shows the following reproducible results on twenty subjects: (1) the primary auditory cortex (PAC), the secondary cortices (secondary auditory cortex (SAC) and planum temporale (PT)), the insular gyrus, the Brodmann area (BA) 22 and the posterior part of T1 gyrus (T1Post) respond to AM in both hemispheres. (2) A stronger response to AM was observed in SAC and T1Post of the left hemisphere independent of the modulation frequency (MF), and in the left BA22 for MFs 8 and 16Hz, compared to those in the right. (3) The activation and propagation features emphasized at least four different types of temporal processing. (4) A sequential activation of PAC, SAC and BA22 areas was clearly visible at all MFs, while other auditory areas may be more involved in parallel processing upon a stream originating from primary auditory area, which thus acts as a distribution hub. These results suggest that different psychological information is carried by the temporal envelope of sounds relative to the rate of amplitude modulation.

Maximum decoding abilities of temporal patterns and synchronized firings: application to auditory neurons responding to click trains and amplitude modulated white noise

“…One should note that the time scale of such phenomena is still controversial since von der Malsburg argued that synchronous firing should occur on a time scale of <5 ms (von der Malsburg 1981;von der Malsburg 1985), while 66% of neuron pair correlograms in cat primary auditory cortex had peak widths >10 ms (Eggermont and Smith 1996). Our recent study (Gourévitch and Eggermont 2007) bolsters the hypothesis of long-term integration of activity across neurons by showing that, in the auditory cortex of the cat, up to 15 ms in the past of a spike train could have a noticeable influence on the future activity of another spike train even during spontaneous activity. Synfire chains may involve transmission times around 1-3 ms for a chain lasting about 1 s in total (Bienenstock 1995;Herrmann et al 1995).…”

“…Indeed, anesthesia is known to reduce the temporal resolution (Goldstein et al 1959;Eggermont 1994).…”

Multiple subregions in superior temporal cortex are differentially sensitive to vocal expressions: A quantitative meta-analysis

“…The primary AC might specifically decode diverse acoustic features of vocal expressions, such as pitch, which is mainly based on the f0 (Bendor and Wang, 2005). The primary AC is also sensitive to the (temporal) amplitude (Giraud et al, 2000;Gourevitch et al, 2008) and the harmonicsto-noise ratio (Lewis et al, 2009). These important features (Banse and Scherer, 1996;Patel et al, 2011) might help to classify and discriminate vocal expressions (Banse and Scherer, 1996).…”

Perception and coding of envelopes in weakly electric fishes

“…We now know that most natural auditory (Heil, 2003;Zeng et al, 2005), visual (Derrington and Cox, 1998;Baker, 1999) and somatosensory (Lundstrom et al, 2010) stimuli contain salient slow time-varying envelopes. These envelopes are critical for perception and are used during a variety of tasks such as second-order visual processing (Grosof et al, 1993;Mareschal and Baker, 1998), stereopsis (Langley et al, 1999;Tanaka and Ohzawa, 2006), speech perception (Calhoun and Schreiner, 1998;Smith et al, 2002;Zeng et al, 2005;Gourévitch et al, 2008;Nourski et al, 2009) and sound localization (Lohuis and Fuzessery, 2000).…”