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Speech is one of the most unique features of human communication. Our ability to articulate our thoughts by means of speech production depends critically on the integrity of the motor cortex. Long thought to be a low-order brain region, exciting work in the past years is overturning this notion. Here, we highlight some of major experimental advances in speech motor control research and discuss the emerging findings about the complexity of speech motocortical organization and its large-scale networks. This review summarizes the talks presented at a symposium at the Annual Meeting of the Society of Neuroscience; it does not represent a comprehensive review of contemporary literature in the broader field of speech motor control.

Abstract Background Violent content in video games evokes many concerns but there is little research concerning its rewarding aspects. It was demonstrated that playing a video game leads to striatal dopamine release. It is unclear, however, which aspects of the game cause this reward system activation and if violent content contributes to it. We combined functional Magnetic Resonance Imaging (fMRI) with individual affect measures to address the neuronal correlates of violence in a video game. Results Thirteen male German volunteers played a first-person shooter game (Tactical Ops: Assault on Terror) during fMRI measurement. We defined success as eliminating opponents, and failure as being eliminated themselves. Affect was measured directly before and after game play using the Positive and Negative Affect Schedule (PANAS). Failure and success events evoked increased activity in visual cortex but only failure decreased activity in orbitofrontal cortex and caudate nucleus. A negative correlation between negative affect and responses to failure was evident in the right temporal pole (rTP). Conclusions The deactivation of the caudate nucleus during failure is in accordance with its role in reward-prediction error: it occurred whenever subject missed an expected reward (being eliminated rather than eliminating the opponent). We found no indication that violence events were directly rewarding for the players. We addressed subjective evaluations of affect change due to gameplay to study the reward system. Subjects reporting greater negative affect after playing the game had less rTP activity associated with failure. The rTP may therefore be involved in evaluating the failure events in a social context, to regulate the players' mood.

Blind people can learn to understand speech at ultra-high syllable rates (ca. 20 syllables/s), a capability associated with hemodynamic activation of the central-visual system. To further elucidate the neural mechanisms underlying this skill, magnetoencephalographic (MEG) measurements during listening to sentence utterances were cross-correlated with time courses derived from the speech signal (envelope, syllable onsets and pitch periodicity) to capture phase-locked MEG components (14 blind, 12 sighted subjects; speech rate = 8 or 16 syllables/s, pre-defined source regions: auditory and visual cortex, inferior frontal gyrus). Blind individuals showed stronger phase locking in auditory cortex than sighted controls, and right-hemisphere visual cortex activity correlated with syllable onsets in case of ultra-fast speech. Furthermore, inferior-frontal MEG components time-locked to pitch periodicity displayed opposite lateralization effects in sighted (towards right hemisphere) and blind subjects (left). Thus, ultra-fast speech comprehension in blind individuals appears associated with changes in early signal-related processing mechanisms both within and outside the central-auditory terrain. (Contains 4 tables and 6 figures.)

During speech communication, visual information may interact with the auditory system at various processing stages. Most noteworthy, recent magnetoencephalography (MEG) data provided first evidence for early and preattentive phonetic/phonological encoding of the visual data stream--prior to its fusion with auditory phonological features [Hertrich, I., Mathiak, K., Lutzenberger, W., & Ackermann, H. Time course of early audiovisual interactions during speech and non-speech central-auditory processing: An MEG study. "Journal of Cognitive Neuroscience, 21," 259-274, 2009]. Using functional magnetic resonance imaging, the present follow-up study aims to further elucidate the topographic distribution of visual-phonological operations and audiovisual (AV) interactions during speech perception. Ambiguous acoustic syllables--disambiguated to /pa/ or /ta/ by the visual channel (speaking face)--served as test materials, concomitant with various control conditions (nonspeech AV signals, visual-only and acoustic-only speech, and nonspeech stimuli). (i) Visual speech yielded an AV-subadditive activation of primary auditory cortex and the anterior superior temporal gyrus (STG), whereas the posterior STG responded both to speech and nonspeech motion. (ii) The inferior frontal and the fusiform gyrus of the right hemisphere showed a strong phonetic/phonological impact (differential effects of visual /pa/ vs. /ta/) upon hemodynamic activation during presentation of speaking faces. Taken together with the previous MEG data, these results point at a dual-pathway model of visual speech information processing: On the one hand, access to the auditory system via the anterior supratemporal "what" path may give rise to direct activation of "auditory objects." On the other hand, visual speech information seems to be represented in a right-hemisphere visual working memory, providing a potential basis for later interactions with auditory information such as the McGurk effect.

This study investigates the temporal resolution capacities of the central-auditory system in a subject (NP) suffering from repetition conduction aphasia. More specifically, the patient was asked to detect brief gaps between two stretches of broadband noise (gap detection task) and to evaluate the duration of two biphasic (WN-3) continuous noise elements, starting with white noise (WN) followed by 3 kHz bandpass-filtered noise (duration discrimination task). During the gap detection task, the two portions of each stimulus were either identical ("intra-channel condition") or differed ("inter-channel condition") in the spectral characteristics of the leading and trailing acoustic segments. NP did not exhibit any deficits in the intra-channel condition of the gap detection task, indicating intact auditory temporal resolution across intervals of 1-3 ms. By contrast, the inter-channel condition yielded increased threshold values. Based upon the "multiple-looks" model of central-auditory processing, this profile points at a defective integration window operating across a few tens of milliseconds--a temporal range associated with critical features of the acoustic speech signal such as voice onset time and formant transitions. Additionally, NP was found impaired during a duration discrimination task addressing longer integration windows (ca. 150 ms). Concerning speech, this latter time domain approximately corresponds to the duration of stationary segmental units such as fricatives and long vowels. On the basis of our results we suggest, that the patient's auditory timing deficits in non-speech tasks may account, at least partially, for his impairments in speech processing. (Contains 1 table and 4 figures.)

At the level of clinical speech/language evaluation, the repetition type of conduction aphasia is characterized by repetition difficulties concomitant with reduced short-term memory capacities, in the presence of fluent spontaneous speech as well as unimpaired naming and reading abilities. It is still unsettled which dysfunctions of the pre-lexical processing stage of spoken word recognition contribute to this syndrome and whether there is any relevant top-down impact of the mental lexicon upon the phonetic/phonological level of speech perception. In order to further specify the underlying pathomechanisms, a comprehensive battery of psycholinguistic tests was applied to a patient suffering from repetition conduction aphasia. The obtained results point at a pre-lexical disorder in this subject. To further specify the assumed pre-lexical dysfunction, computer simulations of single-word processing, based upon an interactive activation model (IAM), were conducted. An attenuation of the features-to-phonemes inhibition value was found to simulate the observed profile of psycholinguistic deficits. Conceivably, these pre-lexical disorders interfere with the task-dependent adjustment of the temporal windows of signal analysis, giving rise to compromised sequencing of auditory-verbal information. (Contains 6 tables and 5 figures.)

Based on clinical and functional imaging data, the left anterior insula has been assumed to support prearticulatory functions of speech motor control such as the ''programming'' of vocal tract gestures. In order to further elucidate this model, a recent functional magnetic resonance imaging (fMRI) study of our group (Riecker, Ackermann, Wildgruber, Dogil, & Grodd, 2000) investigated both overt (aloud) and covert (silent) production of highly overlearned word strings (''automatic speech''), based on the suggestion that ''inner speech'' might provide a ''window'' into preparatory motor activities (Jeannerod, 1994). As a control condition, subjects were asked to reproduce a nonlyrical tune. In contrast to hemodynamic responses within motor cortex and cerebellum, activation of the intrasylvian cortex turned out to be bound to overt task performance. Rather than prearticulatory processes, these findings suggest the left insula to contribute to the actual coordination of the up to 100 muscles engaged in articulation and phonation. Conceivably, the association of speech production with intrasylvian cortex might have evolved within the framework of phylogenetically older connections between the insula and limbic structures, on the one hand, and nonspeech functions of the upper midline musculature such as swallowing, on the other. Whereas (overt) speech tasks predominantly elicit activation within left anterior insula, reproduction of a nonlyrical tune yielded an opposite response pattern. Conceivably, the opposite distributional pattern of speaking and singing at the level of intrasylvian cortex reflects operation of the two hemispheres across different time domains (''double filtering by frequency theory'': left HEMISPHERE=segmental information, right HEMISPHERE=intonation contours of verbal utterances and musical melodies; Ivry & Robertson, 1998). In line with this suggestion, a further study of our group (Ackermann et al., 2001) provided first evidence that differential hemispheric filtering might be bound to insular cortex.