Maps and streams in the auditory cortex: Nonhuman primates illuminate human speech processing. Nature Neuroscience, 12(6), 718-724

Laboratory of Integrative Neuroscience and Cognition, Georgetown University Medical Center, Washington, DC, USA.
Nature Neuroscience (Impact Factor: 16.1). 06/2009; 12(6):718-24. DOI: 10.1038/nn.2331
Source: PubMed


Speech and language are considered uniquely human abilities: animals have communication systems, but they do not match human linguistic skills in terms of recursive structure and combinatorial power. Yet, in evolution, spoken language must have emerged from neural mechanisms at least partially available in animals. In this paper, we will demonstrate how our understanding of speech perception, one important facet of language, has profited from findings and theory in nonhuman primate studies. Chief among these are physiological and anatomical studies showing that primate auditory cortex, across species, shows patterns of hierarchical structure, topographic mapping and streams of functional processing. We will identify roles for different cortical areas in the perceptual processing of speech and review functional imaging work in humans that bears on our understanding of how the brain decodes and monitors speech. A new model connects structures in the temporal, frontal and parietal lobes linking speech perception and production.

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    • "In contrast , the " what " pathway was proposed to origi - nate from anterior lateral belt areas and to project toward the temporal pole . Human functional imaging studies support the " where " part of the hypothesis in that auditory spatial tasks tend to activate parietal and pre - frontal areas that also are activated during visual spatial tasks ( Rauschecker and Scott , 2009 ; Recanzone and Cohen , 2010 "
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    ABSTRACT: The auditory system derives locations of sound sources from spatial cues provided by the interaction of sound with the head and external ears. Those cues are analyzed in specific brainstem pathways and then integrated as cortical representation of locations. The principal cues for horizontal localization are interaural time differences (ITDs) and interaural differences in sound level (ILDs). Vertical and front/back localization rely on spectral-shape cues derived from direction-dependent filtering properties of the external ears. The likely first sites of analysis of these cues are the medial superior olive (MSO) for ITDs, lateral superior olive (LSO) for ILDs, and dorsal cochlear nucleus (DCN) for spectral-shape cues. Localization in distance is much less accurate than that in horizontal and vertical dimensions, and interpretation of the basic cues is influenced by additional factors, including acoustics of the surroundings and familiarity of source spectra and levels. Listeners are quite sensitive to sound motion, but it remains unclear whether that reflects specific motion detection mechanisms or simply detection of changes in static location. Intact auditory cortex is essential for normal sound localization. Cortical representation of sound locations is highly distributed, with no evidence for point-to-point topography. Spatial representation is strictly contralateral in laboratory animals that have been studied, whereas humans show a prominent right-hemisphere dominance. © 2015 Elsevier B.V. All rights reserved.
    Handbook of Clinical Neurology 12/2015; 129C:99-116. DOI:10.1016/B978-0-444-62630-1.00006-8
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    • "A key distinction will be the separation of auditory STM into two components: a sensory trace, which may be passively retained, and a phonological rehearsal mechanism, as would subserve active (or 'working') memory (Baddeley, 2003; Cowan, 1984, 2008). These components may be mapped roughly to the ventral and dorsal streams (Hickok and Poeppel, 2007; Rauschecker and Scott, 2009) of auditory cortex, respectively. We will propose that nonhuman primates offer a tractable model for the perceptual and mnemonic processes of the ventral stream, including the trace that underlies passive STM (pSTM). "
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    ABSTRACT: Sounds are fleeting, and assembling the sequence of inputs at the ear into a coherent percept requires auditory memory across various time scales. Auditory short-term memory comprises at least two components: an active'working memory' bolstered by rehearsal, and a sensory trace that may be passively retained. Working memory relies on representations recalled from long-term memory, and their rehearsal may require phonological mechanisms unique to humans. The sensory component, passive short-term memory (pSTM), is tractable to study in nonhuman primates, whose brain architecture and behavioral repertoire are comparable to our own. This review discusses recent advances in the behavioral and neurophysiological study of auditory memory with a focus on single-unit recordings from macaque monkeys performing delayed-match-to-sample (DMS) tasks. Monkeys appear to employ pSTM to solve these tasks, as evidenced by the impact of interfering stimuli on memory performance. In several regards, pSTM in monkeys resembles pitch memory in humans, and may engage similar neural mechanisms. Neural correlates of DMS performance have been observed throughout the auditory and prefrontal cortex, defining a network of areas supporting auditory STM with parallels to that supporting visual STM. These correlates include persistent neural firing, or a suppression of firing, during the delay period of the memory task, as well as suppression or (less commonly) enhancement of sensory responses when a sound is repeated as a'match' stimulus. Auditory STM is supported by a distributed temporo-frontal network in which sensitivity to stimulus history is an intrinsic feature of auditory processing.
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    • "This " graded convergence " may provide a mechanism both for " feature combination " and, in the limit, for maximally invariant amodal, and thus abstract, conceptual representations. The culmination of this graded convergence up the temporal lobe (Rauschecker and Scott, 2009; Stringer and Rolls, 2002) is a basal rostral region of ATL shown to have very limited extra-temporal connectivity and high intra-temporal connectivity (Binney et al., 2012). Such neuroanatomical sequestration is arguably a sine qua non for a region able to represent abstract, modality-invariant semantics. "
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