The Role of the Right Hemisphere in Processing Phonetic Variability Between Talkers

Abstract

Neurobiological models of speech perception posit that both left and right posterior temporal brain regions are involved in the early auditory analysis of speech sounds. However, frank deficits in speech perception are not readily observed in individuals with right hemisphere damage. Instead, damage to the right hemisphere is often associated with impairments in vocal identity processing. Herein lies an apparent paradox: The mapping between acoustics and speech sound categories can vary substantially across talkers, so why might right hemisphere damage selectively impair vocal identity processing without obvious effects on speech perception? In this review, I attempt to clarify the role of the right hemisphere in speech perception through a careful consideration of its role in processing vocal identity. I review evidence showing that right posterior superior temporal, right anterior superior temporal and right inferior / middle frontal regions all play distinct roles in vocal identity processing. In considering the implications of these findings for neurobiological accounts of speech perception, I argue that the recruitment of right posterior superior temporal cortex during speech perception may specifically reflect the process of conditioning phonetic identity on talker information. I suggest that the relative lack of involvement of other right hemisphere regions in speech perception may be because speech perception does not necessarily place a high burden on talker processing systems, and I argue that the extant literature hints at potential subclinical impairments in the speech perception abilities of individuals with right hemisphere damage.

Neural representations of naturalistic person identities while watching a feature film

“…Our findings reveal representations of person identity in three distinct brain areas. These include clusters in superior temporal areas that align with areas previously associated with voice identity processing (Belin et al, 2004;Schall et al, 2014;von Kriegstein & Giraud, 2004;von Kriegstein et al, 2003;Luthra, 2021;Maguinness et al, 2018;Tsantani et al, 2019;von Kriegstein et al, 2010), as well as right posterior STS (rpSTS), which has in previous work shown selectivity for both faces and voices as well as cross-modal identity integration between both modalities (Tsantani et al, 2019). We further found evidence for representations of person identity in the lateral occipital cortex, in areas overlapping with regions defined by Tsantani et al (2019) as the OFA.…”

“…The analysis also revealed widespread sensitivity to identity within the right inferior occipital and fusiform gyri, which overlapped with a small inferior region of the right inferior occipital gyrus identified in the previous analysis. As previously outlined, posterior areas within bilateral STS have been associated with phonological processing and analysis of sensory voice features (Luthra, 2021;Maguinness et al, 2018), and also with modality-general person identities (Tsantani et al, 2019). Both right occipital and fusiform gyri are widely established as regions that demonstrate sensitivity to face information (Anzellotti et al, 2014;Guntupalli et al, 2017;Rossion et al, 2003;Tsantani et al, 2019).…”

“…A large body of past research has identified brain regions that robustly and reliably respond to face and voice stimuli, and provides converging evidence for the processes proposed by theoretical models. Neuroimaging studies have localised distinct face-and voice-processing networks (see Pitcher et al, 2011;Rossion et al, 2012 for faces; see Luthra, 2021;Maguinness et al, 2018 for voices), in which different areas appear to engage in various hierarchical stages of low-level structural analysis and higher-order identity processing. Face-selective regions include regions within the lateral occipital cortex and right fusiform gyrus, referred to as the occipital face area (OFA) and fusiform face area (FFA) respectively (Kanwisher et al, 1997;Pitcher et al, 2011).…”

“…Voice-selective regions, often called the temporal voice areas, have been localised to bilateral superior temporal cortices (STG/S, Belin et al, 2004). Within these temporal voice areas, both posterior and anterior regions in STS and STG have been associated with voice identity processing (Andics et al, 2010;Belin & Zatorre, 2003;Schall et al, 2014;von Kriegstein & Giraud, 2004;von Kriegstein et al, 2003;Luthra, 2021;Maguinness et al, 2018;von Kriegstein et al, 2010;Zäske et al, 2017). Although face-and voice-sensitive regions have been defined independently from one another, these regions are structurally and functionally connected (Blank et al, 2011(Blank et al, , 2015.…”

A preliminary fMRI study of relative clause in comprehension among native and non-native Malay language speakers

“…In L2, the activation that lateralised to the brain's right hemisphere was noticed, indicating that the right hemisphere is equally important as the left hemisphere in SRC and ORC comprehension. In sentence processing, the right hemisphere is liable for assigning the meaning and context of the words (Federmeier et al, 2008;Luthra, 2021;Riès et al, 2016). Therefore, the intense activation at L2 has presumed that it was related to processing unpredicted semantic relation (Federmeier et al, 2008) of non-canonical SRC and ORC.…”