Speech production has been studied predominantly from within two traditions, psycholinguistics and motor control. These traditions have rarely interacted, and the resulting chasm between these ...approaches seems to reflect a level of analysis difference: whereas motor control is concerned with lower-level articulatory control, psycholinguistics focuses on higher-level linguistic processing. However, closer examination of both approaches reveals a substantial convergence of ideas. The goal of this article is to integrate psycholinguistic and motor control approaches to speech production. The result of this synthesis is a neuroanatomically grounded, hierarchical state feedback control model of speech production.
Abstract Speech recognition is an active process that involves some form of predictive coding. This statement is relatively uncontroversial. What is less clear is the source of the prediction. The ...dual-stream model of speech processing suggests that there are two possible sources of predictive coding in speech perception: the motor speech system and the lexical-conceptual system. Here I provide an overview of the dual-stream model of speech processing and then discuss evidence concerning the source of predictive coding during speech recognition. I conclude that, in contrast to recent theoretical trends, the dorsal sensory–motor stream is not a source of forward prediction that can facilitate speech recognition. Rather, it is forward prediction coming out of the ventral stream that serves this function. Learning outcomes: Readers will (1) be able to explain the dual route model of speech processing including the function of the dorsal and ventral streams in language processing, (2) describe how disruptions to certain components of the dorsal stream can cause conduction aphasia, (3) be able to explain the fundamental principles of state feedback control in motor behavior, and (4) identify the role of predictive coding in motor control and in perception and how predictive coding coming out of the two streams may have different functional consequences.
Speech production has been studied within a number of traditions including linguistics, psycholinguistics, motor control, neuropsychology and neuroscience. These traditions have had limited ...interaction, ostensibly because they target different levels of speech production or different dimensions such as representation, processing or implementation. However, closer examination of reveals a substantial convergence of ideas across the traditions and recent proposals have suggested that an integrated approach may help move the field forward. The present article reviews one such attempt at integration, the state feedback control (SFC) model and its descendent, the hierarchical SFC model. Also considered is how phoneme-level representations might fit in the context of the model.
The discovery of mirror neurons in macaque frontal cortex has sparked a resurgence of interest in motor/embodied theories of cognition. This critical review examines the evidence in support of one of ...these theories, namely, that mirror neurons provide the basis of action understanding. It is argued that there is no evidence from monkey data that directly tests this theory, and evidence from humans makes a strong case
the position.
Abstract
Syntax, the structure of sentences, enables humans to express an infinite range of meanings through finite means. The neurobiology of syntax has been intensely studied but with little ...consensus. Two main candidate regions have been identified: the posterior inferior frontal gyrus (pIFG) and the posterior middle temporal gyrus (pMTG). Integrating research in linguistics, psycholinguistics, and neuroscience, we propose a neuroanatomical framework for syntax that attributes distinct syntactic computations to these regions in a unified model. The key theoretical advances are adopting a modern lexicalized view of syntax in which the lexicon and syntactic rules are intertwined, and recognizing a computational asymmetry in the role of syntax during comprehension and production. Our model postulates a hierarchical lexical-syntactic function to the pMTG, which interconnects previously identified speech perception and conceptual-semantic systems in the temporal and inferior parietal lobes, crucial for both sentence production and comprehension. These relational hierarchies are transformed via the pIFG into morpho-syntactic sequences, primarily tied to production. We show how this architecture provides a better account of the full range of data and is consistent with recent proposals regarding the organization of phonological processes in the brain.
The development of voluntary laryngeal control has been argued to be a key innovation in the evolution of language. Part of the evidence for this hypothesis comes from neuroscience. For example, ...comparative research has shown that humans have direct cortical innervation of motor neurons controlling the larynx, whereas nonhuman primates do not. Research on cortical motor control circuits has shown that the frontal lobe cortical motor system does not work alone; it is dependent on sensory feedback control circuits. Thus, the human brain must have evolved not only the required efferent motor pathway but also the cortical circuit for controlling those efferent signals. To fill this gap, I propose a link between the evolution of laryngeal control and neuroscience research on the human dorsal auditory-motor speech stream. Specifically, I argue that the dorsal stream Spt (Sylvian parietal-temporal) circuit evolved in step with the direct cortico-laryngeal control pathway and together represented a key advance in the evolution of speech. I suggest that a cortical laryngeal control circuit may play an important role in language by providing a prosodic frame for speech planning.
Despite decades of research, the functional neuroanatomy of speech processing has been difficult to characterize. A major impediment to progress may have been the failure to consider task effects ...when mapping speech-related processing systems. We outline a dual-stream model of speech processing that remedies this situation. In this model, a ventral stream processes speech signals for comprehension, and a dorsal stream maps acoustic speech signals to frontal lobe articulatory networks. The model assumes that the ventral stream is largely bilaterally organized--although there are important computational differences between the left- and right-hemisphere systems--and that the dorsal stream is strongly left-hemisphere dominant.
Sensorimotor integration is an active domain of speech research and is characterized by two main ideas, that the auditory system is critically involved in speech production and that the motor system ...is critically involved in speech perception. Despite the complementarity of these ideas, there is little crosstalk between these literatures. We propose an integrative model of the speech-related “dorsal stream” in which sensorimotor interaction primarily supports speech production, in the form of a state feedback control architecture. A critical component of this control system is forward sensory prediction, which affords a natural mechanism for limited motor influence on perception, as recent perceptual research has suggested. Evidence shows that this influence is modulatory but not necessary for speech perception. The neuroanatomy of the proposed circuit is discussed as well as some probable clinical correlates including conduction aphasia, stuttering, and aspects of schizophrenia.
The role of Broca's area in sentence processing has been debated for the last 30 years. A central and still unresolved issue is whether Broca's area plays a specific role in some aspect of syntactic ...processing (e.g., syntactic movement, hierarchical structure building) or whether it serves a more general function on which sentence processing relies (e.g., working memory). This review examines the functional organization of Broca's area in regard to its contributions to sentence comprehension, verbal working memory, and other multimodal cognitive processes. We suggest that the data are consistent with the view that at least a portion of the contribution of Broca's area to sentence comprehension can be attributed to its role as a phonological short-term memory resource. Furthermore, our review leads us to conclude that there is no compelling evidence that there are sentence-specific processing regions within Broca's area.
Despite intensive work on language–brain relations, and a fairly impressive accumulation of knowledge over the last several decades, there has been little progress in developing large-scale models of ...the functional anatomy of language that integrate neuropsychological, neuroimaging, and psycholinguistic data. Drawing on relatively recent developments in the cortical organization of vision, and on data from a variety of sources, we propose a new framework for understanding aspects of the functional anatomy of language which moves towards remedying this situation. The framework posits that early cortical stages of speech perception involve auditory fields in the superior temporal gyrus bilaterally (although asymmetrically). This cortical processing system then diverges into two broad processing streams, a ventral stream, which is involved in mapping sound onto meaning, and a dorsal stream, which is involved in mapping sound onto articulatory-based representations. The ventral stream projects ventro-laterally toward inferior posterior temporal cortex (posterior middle temporal gyrus) which serves as an interface between sound-based representations of speech in the superior temporal gyrus (again bilaterally) and widely distributed conceptual representations. The dorsal stream projects dorso-posteriorly involving a region in the posterior Sylvian fissure at the parietal–temporal boundary (area Spt), and ultimately projecting to frontal regions. This network provides a mechanism for the development and maintenance of “parity” between auditory and motor representations of speech. Although the proposed dorsal stream represents a very tight connection between processes involved in speech perception and speech production, it does not appear to be a critical component of the speech perception process under normal (ecologically natural) listening conditions, that is, when speech input is mapped onto a conceptual representation. We also propose some degree of bi-directionality in both the dorsal and ventral pathways. We discuss some recent empirical tests of this framework that utilize a range of methods. We also show how damage to different components of this framework can account for the major symptom clusters of the fluent aphasias, and discuss some recent evidence concerning how sentence-level processing might be integrated into the framework.
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