Grzegorz Dogil

Opposite hemispheric lateralization effects during speaking and singing at motor cortex, insula and cerebellum.

Aside from spoken language, singing represents a second mode of acoustic (auditory-vocal) communication in humans. As a new aspect of brain lateralization, functional magnetic resonance imaging (fMRI) revealed two complementary cerebral networks subserving singing and speaking. Reproduction of a non-lyrical tune elicited activation predominantly in the right motor cortex, the right anterior insula, and the left cerebellum whereas the opposite response pattern emerged during a speech task. In contrast to the hemodynamic responses within motor cortex and cerebellum, activation of the intrasylvian cortex turned out to be bound to overt task performance. These findings corroborate the assumption that the left insula supports the coordination of speech articulation. Similarly, the right insula might mediate temporo-spatial control of vocal tract musculature during overt singing. Both speech and melody production require the integration of sound structure or tonal patterns, respectively, with a speakers emotions and attitudes. Considering the widespread interconnections with premotor cortex and limbic structures, the insula is especially suited for this task.

Self-Regulation of Regional Cortical Activity Using Real-Time fMRI: The Right Inferior Frontal Gyrus and Linguistic Processing

Neurofeedback of functional magnetic resonance imaging (fMRI) can be used to acquire selective control over activation in circumscribed brain areas, potentially inducing behavioral changes, depending on the functional role of the targeted cortical sites. In the present study, we used fMRI‐neurofeedback to train subjects to enhance regional activation in the right inferior frontal gyrus (IFG) to influence speech processing and to modulate language‐related performance. Seven subjects underwent real‐time fMRI‐neurofeedback training and succeeded in achieving voluntary regulation of their right Brodmanns area (BA) 45. To examine short‐term behavioral impact, two linguistic tasks were carried out immediately before and after the training. A significant improvement of accuracy was observed for the identification of emotional prosodic intonations but not for syntactic processing. This evidence supports a role for the right IFG in the processing of emotional information and evaluation of affective salience. The present study confirms the efficacy of fMRI‐biofeedback for noninvasive self‐regulation of circumscribed brain activity. Hum Brain Mapp 2009.

Hemispheric lateralization effects of rhythm implementation during syllable repetitions: an fMRI study.

Rhythm in terms of the modulation of syllable durations represents an information-bearing feature of verbal utterances contributing both to the meaning of a sentence (linguistic prosody) as well as a speakers emotional expression (affective prosody). In order to delineate the neural structures subserving rhythmic shaping of speech production, functional magnetic resonance imaging (fMRI) was performed during (a) isochronous syllable repetitions and (b) production of syllable triplets with lengthening either of the initial or final unit. A cognitive subtraction approach (rhythmic versus isochronous iterations) revealed activation of right-sided perisylvian areas (superior temporal gyrus, Broca analogue and adjacent premotor cortex) as well as contralateral subcortical structures (putamen and thalamus). Presumably, these responses reflect a right-hemisphere rehearsal mechanism of rhythmic patterns and left-hemisphere monitoring of verbal output.

The speaking brain: a tutorial introduction to fMRI experiments in the production of speech, prosody and syntax

Abstract In this study we will give an overview of the experimental work on the neuroanatomical correlates of language and speech production that we have done in recent years. First we will introduce the methodology of event-related functional magnetic neuro-imaging and the experimental paradigm that we employed. Then we will present and discuss the results of our experiments on (1) speech motor control, (2) articulatory complexity, (3) the neuroanatomical correlates of prosody, and (4) the neurocognitive substrates of syntactic processing. Experiments (1) and (2) show that the expected large motor speech network consisting of SMA, motor cortex and cerebellum is only active in planning and execution of simple articulatory movements. Increased articulatory complexity leads to more focused activation. Furthermore, we can show that only the execution of speech movements recruits the left anterior insula, while articulatory planning does not. The results of experiment (3) indicate that it is not the function of prosody (linguistic vs affective) that controls lateralization of prosodic processing, but that more general characteristics of the processing units like the size of the prosodic frame are responsible for the activation of different cortical regions. Finally, in experiment (4) we present first results on syntactic processing in speech production. Besides the expected activation of Brocas area we found activations in Wernickes area and in the cerebellum. We have also found evidence for activations in other cortical areas, which are less often implicated in clinical studies on brain language correlations. The cognitive relevance of these areas and networks is still to be elucidated.

Reorganization of Functional and Effective Connectivity during Real-Time fMRI-BCI Modulation of Prosody Processing.

Mechanisms of cortical reorganization underlying the enhancement of speech processing have been poorly investigated. In the present study, we addressed changes in functional and effective connectivity induced in subjects who learned to deliberately increase activation in the right inferior frontal gyrus (rIFG), and improved their ability to identify emotional intonations by using a real-time fMRI Brain-Computer Interface. At the beginning of their training process, we observed a massive connectivity of the rIFG to a widespread network of frontal and temporal areas, which decreased and lateralized to the right hemisphere with practice. Volitional control of activation strengthened connectivity of this brain region to the right prefrontal cortex, whereas training increased its connectivity to bilateral precentral gyri. These findings suggest that changes of connectivity in a functionally specific manner play an important role in the enhancement of speech processing. Also, these findings support previous accounts suggesting that motor circuits play a role in the comprehension of speech.

Selective phonological impairment: a case of apraxia of speech

The present study proposes a new interpretation of the underlying distortion in APRAXIA OF SPEECH . Apraxia of speech, in its pure form, is the only neurolinguistic syndrome for which it can be argued that phonological structure is selectively distorted. Apraxia of speech is a nosological entity in its own right which co-occurs with aphasia only occasionally. This…conviction rests on detailed descriptions of patients who have a severe and lasting disorder of speech production in the absence of any significant impairment of speech comprehension, reading or writing as well as of any significant paralysis or weakness of the speech musculature. (Lebrun 1990: 380) Based on the experimental investigation of poorly coarticulated speech of patients from two divergent languages (German and Xhosa) it is argued that apraxia of speech has to be seen as a defective implementation of phonological representations at the phonology–phonetics interface. We contend that phonological structure exhibits neither a homogeneously auditory pattern nor a motor pattern, but a complex encoding of sequences of speech sounds. Specifically, it is maintained that speech is encoded in the brain as a sequence of distinctive feature configurations. These configurations are specified with differing degrees of detail depending on the role the speech segments they underlie play in the phonological structure of a language. The transfer between phonological and phonetic representation encodes speech sounds as a sequence of vocal tract configurations. Like the distinctive feature representation, these configurations may be more or less specified. We argue that the severe and lasting disorders in speech production observed in apraxia of speech are caused by the distortion of this transfer between phonological and phonetic representation. The characteristic production deficits of apraxic patients are explained in terms of overspecification of phonetic representations.

Language talent and brain activity

This book describes and assesses pronunciation talent in its various dimensions, such as production and perception or the segmental and suprasegmental levels of speech. Special focus is put on the psychological and neural correlates of phonetic performance. Behavioral influences such as empathy or motivation are investigated. The resulting classification of proficiency and talent level is used to select subjects for neuroimaging studies in which differences in brain activity between talented and untalented individuals are observed. Key features indispensible contribution to research in the neurolinguistic analysis of pronunciation talent interesting case studies in language learning suitable reading for students of linguistics andforeign languages

Processing of inconsistent emotional information: an fMRI study

Previous studies investigating the anterior cingulate cortex (ACC) have relied on a number of tasks which involved cognitive control and attentional demands. In this fMRI study, we tested the model that ACC functions as an attentional network in the processing of language. We employed a paradigm that requires the processing of concurrent linguistic information predicting that the cognitive costs imposed by competing trials would engender the activation of ACC. Subjects were confronted with sentences where the semantic content conflicted with the prosodic intonation (CONF condition) randomly interspaced with sentences which conveyed coherent discourse components (NOCONF condition). We observed the activation of the rostral ACC and the middle frontal gyrus when the NOCONF condition was subtracted from the CONF condition. Our findings provide evidence for the involvement of the rostral ACC in the processing of complex competing linguistic stimuli, supporting theories that claim its relevance as a part of the cortical attentional circuit. The processing of emotional prosody involved a bilateral network encompassing the superior and medial temporal cortices. This evidence confirms previous research investigating the neuronal network that supports the processing of emotional information.

Where and how does grammatically geared processing take place: and why is Broca's area often involved. A coordinated fMRI/ERBP study of language processing

We address the possibility of combining the results from hemodynamic and electrophysiological methods for the study of cognitive processing of language. The hemodynamic method we use is Event-Related fMRI, and the electrophysiological method measures Event-Related Band Power (ERBP) of the EEG signal. The experimental technique allows us to approach the relation between cortical structure and cognitive function in a sophisticated way. In particular, we can formulate original working hypotheses about the language-induced changes in the ongoing brain dynamics. We show, on the basis of electrophysiological data collected in an experiment on language production, that synchronized cortical networks code cognitive processes induced by language in form of power modulations of specific frequency bands. The hemodynamic (fMRI) data collected in the same task point to the existence of a central processor for the phrase structure assignment. We conceptualize such a central processor as a frequency scanner, a cortical device designed to pick up synchronized brain activity over a specific range of frequencies. We discuss the experimental designs which result from this set of hypotheses and show their relevance for the models of language processing.

Multimodal Speech Synthesis

Speech output generation in the SmartKom system is realized by a corpus-based unit selection strategy that preserves many properties of the human voice. When the system’s avatar “Smartakus” is present on the screen, the synthetic speech signal is temporally synchronized with Smartakus visible speech gestures and prosodically adjusted to his pointing gestures to enhance multimodal communication. The unit selection voice was formally evaluated and found to be very well accepted and reasonably intelligible in SmartKom- specific scenarios.