How may the basal ganglia contribute to auditory categorization and speech perception?

Abstract

Listeners must accomplish two complementary perceptual feats in extracting a message from speech. They must discriminate linguistically-relevant acoustic variability and generalize across irrelevant variability. Said another way, they must categorize speech. Since the mapping of acoustic variability is language-specific, these categories must be learned from experience. Thus, understanding how, in general, the auditory system acquires and represents categories can inform us about the toolbox of mechanisms available to speech perception. This perspective invites consideration of findings from cognitive neuroscience literatures outside of the speech domain as a means of constraining models of speech perception. Although neurobiological models of speech perception have mainly focused on cerebral cortex, research outside the speech domain is consistent with the possibility of significant subcortical contributions in category learning. Here, we review the functional role of one such structure, the basal ganglia. We examine research from animal electrophysiology, human neuroimaging, and behavior to consider characteristics of basal ganglia processing that may be advantageous for speech category learning. We also present emerging evidence for a direct role for basal ganglia in learning auditory categories in a complex, naturalistic task intended to model the incidental manner in which speech categories are acquired. To conclude, we highlight new research questions that arise in incorporating the broader neuroscience research literature in modeling speech perception, and suggest how understanding contributions of the basal ganglia can inform attempts to optimize training protocols for learning non-native speech categories in adulthood.

Statistical learning of language: Theory, validity, and predictions of a statistical learning account of language acquisition

“…Thus, much uncertainty remains regarding the neural systems underlying the various tasks that have been termed statistical learning. It is also entirely possible that these tasks do not recruit the same mechanisms (e.g., notably, as mentioned previously the Serial Reaction Time Task differs from statistical word segmentation and Artificial Grammar Learning tasks insofar as it uses a motor response which may provide participants with a source of implicit feedback, which is known to influence learning; e.g., Lim et al, 2014). Further work will be needed to disentangle the computational and neural mechanisms that support performance in these tasks.…”

“…To the extent that these regions are implicated in statistical learning, and influenced by individual differences in dopaminergic functions, a logical conclusion is that individual differences in language acquisition linked to differences in dopamine may be driven, in part, by individual differences in statistical learning. Given the number of neural learning systems that may play a role in language learning (e.g., striatal regions; Karuza et al, 2013;Lim, Fiez, & Holt, 2014;Tricomi, Delgado, McCandliss, McClelland, & Fiez, 2006), this kind of individual variation may have a wide variety of underlying causes, and potentially different effects on statistical learning processes and outcomes. An investigation of stable genetic differences and language proficiency will likely prove valuable to our understanding of individual variability in language learning abilities.…”

Individual Differences in Statistical Learning: Conceptual and Measurement Issues

“…Finally, although one of the hallmarks of traditional SL tasks is the absence of explicit feedback, a consequence of the response format used in the SRT task is that the motor response may provide the participant with an incidental source of feedback that may influence the learning systems that are engaged. As evidence of this, Lim, Fiez, and Holt [38] report that the basal ganglia are recruited by incidental feedback of the sort that is often found in these tasks.…”

Flexible and adaptive processes in speech perception

“…In Guediche et al (2014), we likened the proposal that cerebellar involvement in speech perception contributes to a domain-general supervised learning mechanism to the proposal that basal ganglia involvement in speech perception contributes to a domain-general reinforcement learning mechanism; just as sensory prediction errors mediate supervised learning, reward prediction errors mediate reinforcement learning (Doya, 2000). Indeed, previous studies confirm the involvement of the basal ganglia in reinforcement learning during speech perception (Tricomi et al, 2006;Lim, Fiez & Holt, 2014). However, more research that considers the role of subcortical Brought to you by | New York University Authenticated Download Date | 4/23/17 2:56 AM structures (also see Erb et al, 2013) in speech perception and bridges established learning mechanisms in other domains with adaptive processes in speech perception is needed.…”