Abstract
We used population-based cortical-surface analysis of functional magnetic imaging data to characterize the processing of consonant–vowel–consonant syllables (CVCs) and spectrally matched amplitude-modulated noise bursts (AMNBs) in human auditory cortex as subjects attended to auditory or visual stimuli in an intermodal selective attention paradigm. Average auditory cortical field (ACF) locations were defined using tonotopic mapping in a previous study. Activations in auditory cortex were defined by two stimulus-preference gradients: (1) Medial belt ACFs preferred AMNBs and lateral belt and parabelt fields preferred CVCs. This preference extended into core ACFs with medial regions of primary auditory cortex (A1) and the rostral field preferring AMNBs and lateral regions preferring CVCs. (2) Anterior ACFs showed smaller activations but more clearly defined stimulus preferences than did posterior ACFs. Stimulus preference gradients were unaffected by auditory attention suggesting that ACF preferences reflect the automatic processing of different spectrotemporal sound features.
Highlights
Introduction there is an increasing consensus that lateral regions of human auditory cortex play a central role in the analysis of speech sounds (Blumstein et al, 2005; Desai et al, 2005, 2008; Liebenthal et al, 2005; Rimol et al, 2005; Obleser et al, 2006, 2007; Sabri et al, 2008; Leff et al, 2009; Flinker et al, 2011; Leaver and Rauschecker, 2010; Turkeltaub and Coslett, 2010; Zheng et al, 2010) there is little information about how speech sounds are processed in human auditory cortical fields (ACFs)
In a recent study using tonotopic mapping of functional magnetic resonance imaging activations on the cortical surface analysis (Woods et al, 2010c), we found that the tuning properties of population-defined ACFs were similar to those observed in macaques (Petkov et al, 2006) and conformed to the Kaas et al (1999) model
Performance in the auditory conditions was further examined in 3-way ANOVAs with Stimulus-type (CVCs or amplitude-modulated noise bursts (AMNBs)), Condition and Ear of delivery as factors
Summary
There is an increasing consensus that lateral regions of human auditory cortex play a central role in the analysis of speech sounds (Blumstein et al, 2005; Desai et al, 2005, 2008; Liebenthal et al, 2005; Rimol et al, 2005; Obleser et al, 2006, 2007; Sabri et al, 2008; Leff et al, 2009; Flinker et al, 2011; Leaver and Rauschecker, 2010; Turkeltaub and Coslett, 2010; Zheng et al, 2010) there is little information about how speech sounds are processed in human auditory cortical fields (ACFs).Human auditory cortex shares a common anatomical structure with the auditory cortex of other primate species (Hackett et al, 2001; Morsan et al, 2005; Fullerton and Pandya, 2007; Hackett, 2008). Based on the results of anatomical (Galaburda and Pandya, 1983; Pandya, 1995; Kaas et al, 1999; Kaas and Hackett, 2000) and functional (Rauschecker, 1998; Recanzone and Sutter, 2008; Kusmierek and Rauschecker, 2009) studies in the macaque, Kaas and Hackett (2000) developed a influential model of primate ACFs with three tonotopically organized core ACFs receiving direct thalamocortical inputs from the ventral nucleus of the medial geniculate body, surrounded by eight belt ACFs that receive inputs from the core and that process more complex sound features (Rauschecker and Scott, 2009). In the current study we utilized the average ACF coordinates defined in this previous study to characterize the roles of human ACFs in processing more complex stimuli: consonant–vowel–consonant (CVC) syllables and spectrally matched amplitude-modulated noise bursts (AMNBs)
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