Abstract
There is not only evidence for behavioral differences in voice perception between female and male listeners, but also recent suggestions for differences in neural correlates between genders. The fMRI functional voice localizer (comprising a univariate analysis contrasting stimulation with vocal vs. non-vocal sounds) is known to give robust estimates of the temporal voice areas (TVAs). However, there is growing interest in employing multivariate analysis approaches to fMRI data (e.g., multivariate pattern analysis; MVPA). The aim of the current study was to localize voice-related areas in both female and male listeners and to investigate whether brain maps may differ depending on the gender of the listener. After a univariate analysis, a random effects analysis was performed on female (n = 149) and male (n = 123) listeners and contrasts between them were computed. In addition, MVPA with a whole-brain searchlight approach was implemented and classification maps were entered into a second-level permutation based random effects models using statistical non-parametric mapping (SnPM; Nichols and Holmes, 2002). Gender differences were found only in the MVPA. Identified regions were located in the middle part of the middle temporal gyrus (bilateral) and the middle superior temporal gyrus (right hemisphere). Our results suggest differences in classifier performance between genders in response to the voice localizer with higher classification accuracy from local BOLD signal patterns in several temporal-lobe regions in female listeners.
Highlights
Prior functional magnetic resonance imaging findings suggest a robust brain response to vocal vs. non-vocal sounds in many regions of the human auditory cortex in particular in the superior temporal gyrus (STG)
Vocal sounds, including but not restricted to speech sounds, evoke a greater response than non-vocal sounds with bilateral activation foci located near the anterior part of the STG extending to anterior parts of the superior temporal sulcus (STS) and posterior foci located in the middle STS (Binder et al, 2000; Belin et al, 2000, 2002)
The univariate analysis comparing activation to vocal and nonvocal sounds showed extended areas of greater response to vocal sounds in the typical regions of the temporal voice areas (TVA), highly similar for male and female subjects (Figure 1A). These regions were located bilaterally in the temporal lobes extending from posterior parts of the STS along the STG to anterior parts of the STS and including several parts of the superior and middle temporal gyrus (STG, MTG)
Summary
Prior functional magnetic resonance imaging (fMRI) findings suggest a robust brain response to vocal vs. non-vocal sounds in many regions of the human auditory cortex in particular in the superior temporal gyrus (STG). The conventional way of identifying voice sensitive regions is by applying univariate statistics, implemented using a Generalized-Linear Model (GLM), to fMRI data assuming independence among voxels. Instead of modeling individual voxels independently (univariate analysis), MVPA considers the information of distributed pattern in several voxels (e.g., Norman et al, 2006; Mur et al, 2009). Several studies used multivariate approaches to decode information reflected in brain activity patterns related to specific experimental conditions (Cox and Savoy, 2003; Haynes and Rees, 2005, 2006; Kotz et al, 2013). A multivariate approach has never been employed to investigate whether it may yield a different pattern of voice-specific (voice/nonvoice classification) brain regions compared to the univariate analysis
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