The Adaptive Self-Organization of Serial Order in Behavior: Speech, Language, And Motor Control

A shared serial order system for verbal working memory and language production: evidence from aphasia

Many aspects of human performance require producing sequences of items in serial order. The current study takes a multiple-case approach to investigate whether the system responsible for serial order is shared across cognitive domains, focusing on working memory (WM) and word production. Serial order performance in three individuals with post-stroke language and verbal WM disorders (hereafter persons with aphasia, PWAs) were assessed using recognition and recall tasks for verbal and visuospatial WM, as well as error analyses in spoken and written production tasks to assess whether there was a tendency to produce the correct phonemes/letters in the wrong order. One PWA exhibited domain-specific serial order deficits in verbal and visuospatial WM. The PWA with verbal serial order WM deficit made more serial order errors than expected by chance in both repetition and writing-to-dictation tasks, whereas the other two PWAs showed no serial order deficits in verbal WM and production tasks. These findings suggest separable serial order systems for verbal and visuospatial WM and a shared system for serial order processing in verbal WM and word production. Implications for the domain-generality of WM, its connection to language production, and serial order processing across cognitive functionssc are discussed.

Internal speech is faster than external speech: Evidence for feedback-based temporal control

A recent model of temporal control in speech holds that speakers use sensory feedback to control speech rate and articulatory timing. An experiment was conducted to assess whether there is evidence in support of this hypothesis by comparing durations of phrases in external speech (with sensory feedback) and internal speech (without sensory feedback). Phrase lengths were varied by including one to three disyllabic nouns in a target phrase that was always surrounded by overt speech. An inferred duration method was used to estimate the durations of target phrases produced internally. The results showed that internal speech is faster than external speech, supporting the hypothesis. In addition, the results indicate that there is a slow-down associated with transitioning between internal and external modes of production.

An informal logic of feedback-based temporal control

A conceptual framework and mathematical model of the control of articulatory timing are presented, in which feedback systems play a fundamental role. The model applies both to relatively small timescales, such as within syllables, and to relatively large timescales, such as multi-phrase utterances. A crucial distinction is drawn between internal/predictive feedback and external/sensory feedback. It is argued that speakers modulate attention to feedback to speed up and slow down speech. A number of theoretical implications of the framework are discussed, including consequences for the understanding of syllable structure and prosodic phrase organization.

Motoric Mechanisms for the Emergence of Non-local Phonological Patterns

Non-local phonological patterns can be difficult to analyze in the context of speech production models. Some patterns - e.g., vowel harmonies, nasal harmonies - can be readily analyzed to arise from temporal extension of articulatory gestures (i.e., spreading); such patterns can be viewed as articulatorily local. However, there are other patterns - e.g., nasal consonant harmony, laryngeal feature harmony - which cannot be analyzed as spreading; instead these patterns appear to enforce agreement between features of similar segments without affecting intervening segments. Indeed, there are numerous typological differences between spreading harmonies and agreement harmonies, and this suggests that there is a mechanistic difference in the ways that spreading and agreement harmonies arise. This paper argues that in order to properly understand spreading and agreement patterns, the gestural framework of Articulatory Phonology must be enriched with respect to how targets of the vocal tract are controlled in planning and production. Specifically, it is proposed that production models should distinguish between excitatory and inhibitory articulatory gestures, and that gestures which are below a selection threshold can influence the state of the vocal tract, despite not being active. These ideas are motivated by several empirical phenomena, which include anticipatory posturing before production of a word form, and dissimilatory interactions in distractor-target response paradigms. Based on these ideas, a model is developed which provides two distinct mechanisms for the emergence of non-local phonological patterns.

A neurophysiological approach to tinnitus: clinical implications

This paper presents a neurophysiological approach to tinnitus and discusses its clinical implications. A hypothesis of discordant damage of inner and outer hair cells systems in tinnitus generation is outlined. A recent animal model has facilitated the investigation of the mechanisms of tinnitus and has been further refined to allow for the measurement of tinnitus pitch and loudness. The analysis of the processes involved in tinnitus detection postulates the involvement of an abnormal increase of gain within the auditory system. Moreover, it provides a basis for treating patients with hyperacusis, which we are considering to be a pre-tinnitus state. Analysis of the process of tinnitus perception allows for the possibility of facilitating the process of tinnitus habituation for the purpose of its alleviation. The combining of theoretical analysis with clinical findings has resulted in the creation of a multidisciplinary Tinnitus Centre. The foundation of the Centre focuses on two goals: the clinical goal is to remove tinnitus perception from the patient's consciousness, while directing research toward finding a mechanism-based method for the suppression of tinnitus generators and processes responsible for enhancement of tinnitus-related neuronal activity.