Musical Expertise Modulates Functional Connectivity of Limbic Regions during Continuous Music Listening

Music is known to be an important facet of all human cultures (Merriam, 1964). Listening to music in order to influence moods, evoke strong emotions, and derive pleasure is becoming increasingly common, especially in this day and age when access to music is easy and quick. In recent years, exploring the neural correlates of musical emotions has attracted the attention of neuroscientists (Brattico & Pearce, 2013; Koelsch, Fritz, v. Cramon, Muller, & Friederici, 2006). However, the majority of these studies have not accounted for the effect of musical expertise, despite increasing evidence of structural and functional differences between musicians and nonmusicians, particularly in the regions of the cerebrum associated with motor, auditory, and visuospatial processing (Amunts et al., 1997; Angulo-Perkins et al., 2014; Baumann et al., 2007; Fauvel et al., 2014; Gaser & Schlaug, 2003; Herdener et al., 2010; Hutchinson, Lee, Gaab, & Schlaug, 2003; Hyde et al., 2009; Lee, Chen, & Schlaug, 2003; Pantev & Herholz, 2011; Schlaug, Jancke, Huang, Staiger, & Steinmetz, 1995; Schlaug, Jancke, Huang, & Steinmetz, 1995; Sluming, Taylor, Keller, Cezayirli, & Roberts, 2003; Wong, Skoe, Russo, Dees, & Kraus, 2007). In addition, musicians were found to have greater amounts of white matter in the anterior corpus callosum than nonmusicians (for a review, see Moore, Schaefer, Bastin, Roberts, & Overy, 2014). Furthermore, higher cerebellar volume is associated with male musicians than nonmusicians (Hutchinson et al., 2003; Sluming et al., 2003), particularly concerning the regions involved in representing movement (Gaser & Schlaug, 2003). In addition, musicians have been found to have greater sensitivity in processing and discriminating sounds in the auditory cortex (Musacchia, Strait, & Kraus, 2008; Pantev et al., 1998; Strait et al., 2009; Tervaniemi et al., 2001; Wong et al., 2007). In sum, long-term musical practice causes structural and functional changes in the brain, with subsequent enhanced representation of sounds and music (see Kraus & Chandrasekaran, 2010; Reybrouck & Brattico, 2015 for an overview).The neuroscientific studies on musical emotions have predominantly utilized the classical controlled paradigm wherein the condition of interest is interspersed with other tasks or baseline, thereby not providing the entire picture of emotional networks in the brain. Recent times have seen an increase in fMRI studies that employ the continuous listening paradigm, in which participants listen to music continuously, typically lasting the entire span of the piece, and without any intermittent task, for investigating neural processing of music (Abrams et al., 2013; Alluri et al., 2012, 2013; Burunat, Alluri, Toiviainen, Numminen, & Brattico, 2014; Toiviainen, Alluri, Brattico, Wallentin, & Vuust, 2014; Trost, Ethofer, Zentner, & Vuilleumier, 2012). However, those studies examined whole brain regional activations, not focusing on limbic system structures or on the modulation of neural activity and connectivity by musical expertise. A single fMRI study (Koelsch et al., 2013) has used full pieces of music to investigate the dynamics of emotion processing in the limbic system, albeit with participants without musical training.On the contrary, resting-state-based fMRI studies have dealt with investigating functional networks that emerge during prolonged periods of rest without any stimulus (Lee, Smyser, & Shimony, 2013). There is abundant literature examining restingstate connectivity and connectivity in the visual domain, especially in terms of decoding. However, there has been a scarcity of studies investigating functional connectivity in the auditory domain as a function of musical expertise. The first resting-state study investigating connectivity differences between musicians and nonmusicians in resting state was conducted by Luo et al. (2012). Their functional connectivity analysis was limited to five seed regions representing the right primary motor, left primary auditory, left primary somatosensory cortices, and the left primary visual and left V2 areas. …