Auditory temporal processing deficits in patients with insular stroke

Paving the way for speech: voice-training-induced plasticity in chronic aphasia and apraxia of speech--three single cases

Difficulties with temporal coordination or sequencing of speech movements are frequently reported in aphasia patients with concomitant apraxia of speech (AOS). Our major objective was to investigate the effects of specific rhythmic-melodic voice training on brain activation of those patients. Three patients with severe chronic nonfluent aphasia and AOS were included in this study. Before and after therapy, patients underwent the same fMRI procedure as 30 healthy control subjects in our prestudy, which investigated the neural substrates of sung vowel changes in untrained rhythm sequences. A main finding was that post-minus pretreatment imaging data yielded significant perilesional activations in all patients for example, in the left superior temporal gyrus, whereas the reverse subtraction revealed either no significant activation or right hemisphere activation. Likewise, pre- and posttreatment assessments of patients' vocal rhythm production, language, and speech motor performance yielded significant improvements for all patients. Our results suggest that changes in brain activation due to the applied training might indicate specific processes of reorganization, for example, improved temporal sequencing of sublexical speech components. In this context, a training that focuses on rhythmic singing with differently demanding complexity levels as concerns motor and cognitive capabilities seems to support paving the way for speech.

Auditory temporal processing deficits and language disorders in patients with neurofibromatosis type 1

Previous findings from a case report led to the argument of whether other patients with neurofibromatosis type 1 (NF1) may have abnormal central auditory function, particularly auditory temporal processing. We hypothesized that it is associated with language and learning disabilities in this population. The aim of this study was to measure central auditory temporal function in NF1 patients and correlate it with the results of language evaluation tests. A descriptive/comparative study including 25 NF1 individuals and 22 healthy controls compared their performances on audiometric evaluation and auditory behavioral testing (Sequential Verbal Memory, Sequential Non-Verbal Memory, Frequency Pattern, Duration Pattern, and Gaps in Noise Tests). To assess language performance, two tests (phonological and syntactic awareness) were also conducted. The study showed that all participants had normal peripheral acoustic hearing. Differences were found between the NF1 and control groups in the temporal auditory processing tests [Sequential Verbal Memory (P=0.009), Sequential Non-Verbal Memory (P=0.028), Frequency Patterns (P=0.001), Duration Patterns (P=0.000), and Gaps in Noise (P=0.000)] and in language tests. The results of Pearson correlation analysis demonstrated the presence of positive correlations between the phonological awareness test and Frequency Patterns humming (r=0.560, P=0.001), Frequency Patterns labeling (r=0.415, P=0.022) and Duration Pattern humming (r=0.569, P=0.001). These results suggest that the neurofibromin deficiency found in NF1 patients is associated with auditory temporal processing deficits, which may contribute to the cognitive impairment, learning disabilities, and attention deficits that are common in this disorder.

LEARNING OUTCOMES

The reader will be able to: (1) describe the auditory temporal processing in patients with neurofibromatosis type 1; and (2) describe the impact of the auditory temporal deficits in language in this population.

Is Central Auditory Processing Disorder Present in Psychosis?

Purpose

The scope of this study was to trace central auditory processing issues in patients with first-episode psychosis using a psychoacoustic test battery approach.

Method

Patients ( n = 17) and volunteer control subjects ( n = 17) with no personal or family history of schizophrenia were included in the study on the basis of normal hearing sensitivity. The authors implemented a central auditory processing battery consisting of monaural and binaural tests with verbal and nonverbal stimuli.

Results

Perceptual deficits in both nonverbal and verbal auditory stimuli are reported in this study, with temporal central auditory processing deficits and a mean left-ear advantage documented in the patient group.

Conclusion

This study points to the possibility of the existence of central auditory processing deficits in first-episode psychosis leading to schizophrenia. Audiologists should be aware of the psychiatric research pointing to enhanced verbal memory as a result of auditory training, linking bottom-up remediation with top-down improvement.

Insular ischemic stroke: clinical presentation and outcome

Background

The insula is a small but complex structure located in the depth of the sylvian fissure, covered by the frontal, parietal and temporal operculum. Ischemic strokes limited to the insula are rare and have not been well studied. Our objective is to better define the clinical presentation and outcome of insular ischemic strokes (IIS).

Methods

We reviewed the institutional prospective, consecutive stroke database from two centers to identify patients with IIS seen between 2008 and 2010. We also searched the Medline database using the keywords insula(r), infarction and stroke to identify previously published IIS cases confirmed by MRI. Minimal extension to an adjacent operculum or subinsular area was accepted. Clinicoradiological correlation was performed by distinguishing IIS involving the anterior (AIC) or posterior insular cortex (PIC). We collected clinical, demographic and radiological data. The outcome was determined using the modified Rankin Scale (mRS).

Results

We identified 7 patients from our institutions and 16 previously published cases of IIS. Infarcts were limited to the AIC (n = 4) or the PIC (n = 12) or affected both (n = 7). The five most frequent symptoms were somatosensory deficits (n = 10), aphasia (n = 10), dysarthria (n = 10), a vestibular-like syndrome (n = 8) and motor deficits (n = 6). A significant correlation was found between involvement of the PIC and somatosensory manifestations (p = 0.04). No other statistically significant associations were found. IIS presentation resembled a partial anterior circulation infarct (n = 9), a lacunar infarct (n = 2) or a posterior circulation infarct (n = 2). However, most cases presented findings that did not fit with these classical patterns (n = 10). At the 6 month follow up, mRS was 0 in 8/23 (35%) patients, 1–2 in 7/23 (30%) and unknown in 8/23 (35%).

Conclusions

IIS presentation is variable. Due to the confluence of functions in a restricted region, it results in multimodal deficits. It should be suspected when vestibular-like or motor but especially somatosensory, speech or language disturbances are combined in the same patient. The outcome of IIS is often favorable. Larger prospective studies are needed to better define the clinical presentation and outcome of IIS.

The dual loop model: its relation to language and other modalities

The current neurobiological consensus of a general dual loop system scaffolding human and primate brains gives evidence that the dorsal and ventral connections subserve similar functions, independent of the modality and species. However, most current commentators agree that although bees dance and chimpanzees grunt, these systems of communication differ qualitatively from human language. So why is language unique to humans? We discuss anatomical differences between humans and other animals, the meaning of lesion studies in patients, the role of inner speech, and compare functional imaging studies in language with other modalities in respect to the dual loop model. These aspects might be helpful for understanding what kind of biological system the language faculty is, and how it relates to other systems in our own species and others.

Patient-reported speech in noise difficulties and hyperacusis symptoms and correlation with test results

OBJECTIVES/HYPOTHESIS

To compare self-reported symptoms of difficulty hearing speech in noise and hyperacusis in adults with auditory processing disorders (APDs) and normal controls; and to compare self-reported symptoms to objective test results (speech in babble test, transient evoked otoacoustic emission [TEOAE] suppression test using contralateral noise).

STUDY DESIGN

A prospective case-control pilot study.

METHODS

Twenty-two participants were recruited in the study: 10 patients with reported hearing difficulty, normal audiometry, and a clinical diagnosis of APD; and 12 normal age-matched controls with no reported hearing difficulty. All participants completed the validated Amsterdam Inventory for Auditory Disability questionnaire, a hyperacusis questionnaire, a speech in babble test, and a TEOAE suppression test using contralateral noise.

RESULTS

Patients had significantly worse scores than controls in all domains of the Amsterdam Inventory questionnaire (with the exception of sound detection) and the hyperacusis questionnaire (P < .005). Patients also had worse TEOAE suppression test results in both ears than controls; however, this result was not significant after Bonferroni correction. Strong correlations were observed between self-reported symptoms of difficulty hearing speech in noise and speech in babble test results in the right ear (ρ = 0.624, P = .002), and between self-reported symptoms of hyperacusis and TEOAE suppression test results in the right ear (ρ = -0.597 P = .003).

CONCLUSIONS

There was no significant correlation between the two tests. A strong correlation was observed between right ear speech in babble and patient-reported intelligibility of speech in noise, and right ear TEOAE suppression by contralateral noise and hyperacusis questionnaire.

Temporal resolution deficits in patients with refractory complex partial seizures and mesial temporal sclerosis (MTS)

We studied the temporal resolution ability in patients with refractory complex partial seizures and mesial temporal sclerosis (MTS) using Gaps-In-Noise (GIN) test in a prospective cross-sectional study. Thirteen patients with right MTS (age: 31±7.67 years; M:F=8:5) and 13 patients with left MTS (age: 25.76±8.26 years; M:F=9:4) having normal hearing and mini-mental state examination (MMSE) score of >23/30 were recruited. Fifty healthy volunteers (26.3±5.17 years; M:F=28:22) formed the control group. Gaps-In-Noise test demonstrated impaired temporal resolution: 69.2% of patients with right MTS (RMTS) and 76.9% of patients with left MTS (LMTS) had abnormal scores in the right ear for gap detection threshold (GDT) measure. Similarly, 53.8% of patients in the RMTS group and 76.9% of patients in the LMTS group had abnormal scores in the left ear. In percentage of correct identification (PCI), 46.1% of patients with RMTS and 69.2% of patients with LMTS had poorer scores in the right ear, whereas 46.1% of patients with RMTS and 61.5% of patients with LMTS had poorer scores in the left ear. Both patient groups, viz., RMTS and LMTS, demonstrated bilateral temporal resolution deficits.

The variation of function across the human insula mirrors its patterns of structural connectivity: evidence from in vivo probabilistic tractography

The human insula is a functionally complex yet poorly understood region of the cortex, implicated in a wide range of cognitive, motor, emotion and somatosensory activity. To elucidate the functional role of the insula, the current study used in vivo probabilistic tractography to map the structural connectivity of seven anatomically-defined insular subregions. The connectivity patterns identified reveal two complementary insular networks connected via a dual route architecture, and provide key insights about the neural basis of the numerous functions ascribed to this area. Specifically, anterior-most insular regions were associated with a ventrally-based network involving orbital/inferior frontal and anterior/polar temporal regions, forming part of a key emotional salience and cognitive control network associated with the implementation of goal-directed behavior. The posterior and dorsal-middle insular regions were associated with a network focused on posterior and (to a lesser extent) anterior temporal regions via both dorsal and ventral pathways. This is consistent with the involvement of the insula in sound-to-speech transformations, with an implicated role in the temporal resolution, sequencing, and feedback processes crucial for auditory and motor processing, and the monitoring and adjustment of expressive performance.

Auditory discrimination as a condition for E-learning based Speech Therapy: a proposal for an auditory discrimination test (ADT) for adult dysarthric speakers

BACKGROUND

Web based speech training for dysarthric speakers, such as E-learning based Speech Therapy (EST), puts considerable demands on auditory discrimination abilities.

AIMS

To discuss the development and the evaluation of an auditory discrimination test (ADT) for the assessment of auditory speech discrimination skills in Dutch adult dysarthric speakers as a prelude to EST.

METHOD

Five ADT subtests were developed, each addressing a vital speech dimension in speech therapy: articulation (segmental elements), intensity, overall pitch, speech rate and intonation. A healthy control group of 36 participants performed a 'same-different task' in each subtest. ADT items yielding scores of at least 80% but below 100% correctly responding healthy controls were considered sensitive to diminished auditory discrimination. Subsequently, the ADT was carried out by 14 neurological patients with dysarthric speech and 14 matched healthy controls. Score percentages, sensitivity indices and reaction times (ms) on only sensitive items were compared.

RESULTS

The majority of the ADT items met the 'minimal 80% to below 100% criterion' in the healthy control group. The neurological participants performed lower on all outcome measures across all subtests than the healthy controls, although not all of these differences achieved statistical significance.

CONCLUSIONS

The results of the healthy control group show that the majority of the ADT items meet our criterion for sensitivity to diminished auditory discrimination. The poorer performance of dysarthric patients across all subtests supports the sensitivity of the ADT. However, further research involving larger and more homogeneous groups of neurological patients is required.

LEARNING OUTCOMES

Readers will be encouraged to (1) identify potential factors that may hinder web based speech training and (2) estimate the value of assessing auditory discrimination skills as a vital condition for (web based) speech training in dysarthric patients.

Polarity-dependent transcranial direct current stimulation effects on central auditory processing

Given the polarity dependent effects of transcranial direct current stimulation (tDCS) in facilitating or inhibiting neuronal processing, and tDCS effects on pitch perception, we tested the effects of tDCS on temporal aspects of auditory processing. We aimed to change baseline activity of the auditory cortex using tDCS as to modulate temporal aspects of auditory processing in healthy subjects without hearing impairment. Eleven subjects received 2mA bilateral anodal, cathodal and sham tDCS over auditory cortex in a randomized and counterbalanced order. Subjects were evaluated by the Random Gap Detection Test (RGDT), a test measuring temporal processing abilities in the auditory domain, before and during the stimulation. Statistical analysis revealed a significant interaction effect of time vs. tDCS condition for 4000 Hz and for clicks. Post-hoc tests showed significant differences according to stimulation polarity on RGDT performance: anodal improved 22.5% and cathodal decreased 54.5% subjects' performance, as compared to baseline. For clicks, anodal also increased performance in 29.4% when compared to baseline. tDCS presented polarity-dependent effects on the activity of the auditory cortex, which results in a positive or negative impact in a temporal resolution task performance. These results encourage further studies exploring tDCS in central auditory processing disorders.

[Central auditory processes evaluated with psychoacoustic tests in normal children]

OBJECTIVE

To identify the natural tendencies of hits and calculate the cutoff for a test group of central auditory processes (CAP): binaural fusion, filtered words, dichotic digits, frequency patterns and duration patterns and ambient sounds in normal 5-, 7-, 9- and 11-year-old children.

MATERIAL AND METHODS

We studied 369 children (738 ears) who attend public schools in Puebla City, administering 6 CAP tests (two binaural and four monaural); we used an audiometer at 50dB SL re-threshold at 1 kHz, from a CD recorded at the CCECADET-UNAM-INR (Centre for Applied Science and Technological Development at the National Autonomous University of Mexico and the National Institute for Rehabilitation).

RESULTS

We determined the cutoff points for the six tests.

CONCLUSION

This information represents an advance in the normative standards in the field of psychoacoustic tests for CAP in Spanish and in the socio-educational context prevalent in Mexico. It is important to evaluate these results against CAP disorders.

How the ventral pathway got lost: and what its recovery might mean

Textbooks dealing with the anatomical representation of language in the human brain display two language-related zones, Broca's area and Wernicke's area, connected by a single dorsal fiber tract, the arcuate fascicle. This classical model is incomplete. Modern imaging techniques have identified a second long association tract between the temporal and prefrontal language zones, taking a ventral course along the extreme capsule. This newly identified ventral tract connects brain regions needed for language comprehension, while the well-known arcuate fascicle is used for "sensorimotor mapping" during speech production. More than 130 years ago, Carl Wernicke already described a ventral connection for language, almost identical to the present results, but during scientific debate in the following decades either its function or its existence were rejected. This article tells the story of how this knowledge was lost and how the ventral connection, and in consequence the dual system, fits into current hypotheses and how language relates to other systems.

Temporal processing in schizophrenia: effects of task-difficulty on behavioral discrimination and neuronal responses

Deficits in temporal judgment in schizophrenia have been observed in behavioral and electrophysiological studies for years. The functional neuroanatomy of temporal judgment in schizophrenia is, however, poorly understood. Recent neurophysiological research suggests that timing deficits in this population may not be widespread across all timing tasks, but specifically associated with high levels of difficulty. We evaluated differences between individuals with schizophrenia (N=16) and healthy subjects (N=18) during a temporal discrimination task at two levels of difficulty. Subjects were studied with functional magnetic resonance imaging (fMRI) at 3T while discriminating tone durations. Behaviorally, the schizophrenia group performed worse than the control group at both levels of difficulty. Similarly, group differences in patterns of brain activation were observed across both difficulty conditions. In the easy condition, individuals with schizophrenia showed less activation in the supplementary motor area and insula/opercula, regions known to be involved in temporal processing. These group differences increased in the difficult condition. In addition, the striatum was less active in individuals with schizophrenia in the difficult condition. Comparing the difficult to easy conditions revealed robust differences in the bilateral striatum and the insula/opercula, suggesting that the striatum plays a key role in temporal processing deficits in schizophrenia, especially under difficult conditions. These observations suggest that temporal judgment deficits reflect widespread neuroanatomical network involvement in schizophrenia, some of which are not directly related to task difficulty. These findings shed light on disparate findings in the timing literature regarding the role of task difficulty in temporal judgment deficits in schizophrenia.

Hemispheric asymmetry: contributions from brain imaging

A series of studies using functional and structural magnetic resonance imaging, including diffusion tensor imaging measures also, to elucidate the aspects of hemispheric asymmetry are reviewed. It is suggested that laterality evolved as a response to the demands of language and the need for air-based communication which may have necessitated a division of labor between the hemispheres in order to avoid having duplicate copies in both the hemispheres that would increase processing redundancy. This would have put pressure on brain structures related to the evolution of language and speech, such as the left peri-Sylvian region. MRI data are provided showing structural and functional asymmetry in this region of the brain and how fibers connecting the right and left peri-Sylvian regions pass through the corpus callosum. It is further suggested that the so-called Yakelovian-torque, i.e., the twisting of the brain along the longitudinal axis, with the right frontal and left occipital poles protruding beyond the corresponding left and right sides, was necessary for the expansion of the left peri-Sylvian region and the right occipito-parietal regions subserving the processing of spatial relations. Functional magnetic resonance imaging data related to sex differences for visuo-spatial processing are presented showing enhanced right-sided activation in posterior parts of the brain in both sexes, and frontal activation including Broca's area in the female group only, suggesting that males and females use different strategies when solving a cognitive task. The paper ends with a discussion of the role of the corpus callosum in laterality and the role played by structural asymmetry in understanding corresponding functional asymmetry. WIREs Cogni Sci 2011 2 461-478 DOI: 10.1002/wcs.122 For further resources related to this article, please visit the WIREs website.

Endogenous neuromagnetic activity for mental hierarchy of timing

The frontal-striatal circuits, the cerebellum, and motor cortices play crucial roles in processing timing information on second to millisecond scales. However, little is known about the physiological mechanism underlying human's preference to robustly encode a sequence of time intervals into a mental hierarchy of temporal units called meter. This is especially salient in music: temporal patterns are typically interpreted as integer multiples of a basic unit (i.e., the beat) and accommodated into a global context such as march or waltz. With magnetoencephalography and spatial-filtering source analysis, we demonstrated that the time courses of neural activities index a subjectively induced meter context. Auditory evoked responses from hippocampus, basal ganglia, and auditory and association cortices showed a significant contrast between march and waltz metric conditions during listening to identical click stimuli. Specifically, the right hippocampus was activated differentially at 80 ms to the march downbeat (the count one) and approximately 250 ms to the waltz downbeat. In contrast, basal ganglia showed a larger 80 ms peak for march downbeat than waltz. The metric contrast was also expressed in long-latency responses in the right temporal lobe. These findings suggest that anticipatory processes in the hippocampal memory system and temporal computation mechanism in the basal ganglia circuits facilitate endogenous activities in auditory and association cortices through feedback loops. The close interaction of auditory, motor, and limbic systems suggests a distributed network for metric organization in temporal processing and its relevance for musical behavior.

Potencial Cognitivo P300 em pacientes com lesão isquêmica do hemisfério direito

TEMA: avaliação do potencial cognitivo P300 em indivíduos com lesão de hemisfério direito provocada por acidente vascular cerebral isquêmico. OBJETIVO: caracterizar os achados do potencial cognitivo P300 em indivíduos destros com lesão isquêmica do hemisfério cerebral direito, bem como comparar seus resultados aos obtidos em indivíduos normais. MÉTODO: foram realizadas anamnese, avaliação audiológica convencional e potencial cognitivo (P300), em 17 indivíduos com lesão do hemisfério direito (grupo pesquisa) e 25 normais (grupo controle), com idades entre 20 e 70 anos. RESULTADOS: na análise dos dados qualitativos do P300, não houve diferença estatisticamente significante entre os grupos para o resultado normal. Para a análise dos dados quantitativos, ocorreu diferença estatisticamente significante entre os grupos com relação à latência da onda P300, sendo que o grupo pesquisa apresentou latência maior. Além disso, houve uma tendência estatisticamente significante entre as orelhas direita e esquerda dentro do grupo pesquisa, mostrando aumento de latência da onda P300 na orelha direita. CONCLUSÃO: Indivíduos destros com lesão de hemisfério direito e limiares auditivos normais, apresentaram resultados eletrofisiológicos da audição indicativos de déficit no sistema nervoso auditivo central. Foram observados comprometimentos nas regiões geradoras deste potencial (áreas subcorticais e corticais). Dificuldades auditivas não foram percebidas pelos indivíduos, sugerindo que, provavelmente tal sinal possa estar relacionado à uma heminegligência auditiva. Tornam-se necessários mais estudos que avaliem a via auditiva central destes indivíduos para uma melhor caracterização dos achados eletrofisiológicos.

Multisensory integration of sounds and vibrotactile stimuli in processing streams for "what" and "where"

The segregation between cortical pathways for the identification and localization of objects is thought of as a general organizational principle in the brain. Yet, little is known about the unimodal versus multimodal nature of these processing streams. The main purpose of the present study was to test whether the auditory and tactile dual pathways converged into specialized multisensory brain areas. We used functional magnetic resonance imaging (fMRI) to compare directly in the same subjects the brain activation related to localization and identification of comparable auditory and vibrotactile stimuli. Results indicate that the right inferior frontal gyrus (IFG) and both left and right insula were more activated during identification conditions than during localization in both touch and audition. The reverse dissociation was found for the left and right inferior parietal lobules (IPL), the left superior parietal lobule (SPL) and the right precuneus-SPL, which were all more activated during localization conditions in the two modalities. We propose that specialized areas in the right IFG and the left and right insula are multisensory operators for the processing of stimulus identity whereas parts of the left and right IPL and SPL are specialized for the processing of spatial attributes independently of sensory modality.

Neural encoding of sound duration persists in older adults

Speech perception depends strongly on precise encoding of the temporal structure of sound. Although behavioural studies suggest that communication problems experienced by older adults may entail deficits in temporal acuity, much is unknown about the effects of age on the neural mechanisms underlying the encoding of sound duration. In this study, we measured neuromagnetic auditory evoked responses in young, middle-aged and older healthy participants listening to sounds of various durations. The time courses of cortical activity from bilateral sources in superior temporal planes showed specific differences related to the sound offsets indicating the neural representation of onset and offset markers as one dimension of the neural code for sound duration. Model free MEG source analysis identified brain areas specifically responding with an increase in activity to increases in sound duration in the left anterior insula, right inferior frontal, right middle temporal, and right post-central gyri in addition to bilateral supra-temporal gyri. Sound duration-related changes in cortical responses were comparable in all three age groups despite age-related changes in absolute response magnitudes. The results demonstrated that early cortical encoding of the temporal structure of sound presented in silence is little or not affected by normal aging.

Functional organization of the human anterior insular cortex

The human insular cortex is involved in a wide range of functions including motor control, language, and homeostatic regulation. Little is known, however, how these functions are topographically organized in the insular cortex and how they are functionally related to the amygdala, which is anatomically connected to the insular cortex. We have investigated these questions by conducting an activation likelihood estimate (ALE) meta-analysis of previously published neuroimaging studies reporting insula effects. We find auditory and language tasks to preferentially activate an area in the dorsal part of the anterior insular cortex (AIC). Motor tasks involving both the upper and lower extremity reproducibly activated a posterior AIC region, adjacent to the sulcus centralis insulae (SCI). Significant co-activation with the probabilistically defined amygdala was located in the ventral AIC where also responses related to peripheral physiological changes were repeatedly reported. These findings show that the human AIC is a functionally differentiated brain region. The dorsal region of the AIC may be involved in auditory-motor integration, while the ventral part of the AIC may interface the amygdala with insular regions involved in the regulation of physiological changes related to emotional states. Thus, the present findings provide insights into the organization of human AIC and a methodological approach that may be further used to refine the emerging functional map of the insular cortex.

Use of auditory learning to manage listening problems in children

This paper reviews recent studies that have used adaptive auditory training to address communication problems experienced by some children in their everyday life. It considers the auditory contribution to developmental listening and language problems and the underlying principles of auditory learning that may drive further refinement of auditory learning applications. Following strong claims that language and listening skills in children could be improved by auditory learning, researchers have debated what aspect of training contributed to the improvement and even whether the claimed improvements reflect primarily a retest effect on the skill measures. Key to understanding this research have been more circumscribed studies of the transfer of learning and the use of multiple control groups to examine auditory and non-auditory contributions to the learning. Significant auditory learning can occur during relatively brief periods of training. As children mature, their ability to train improves, but the relation between the duration of training, amount of learning and benefit remains unclear. Individual differences in initial performance and amount of subsequent learning advocate tailoring training to individual learners. The mechanisms of learning remain obscure, especially in children, but it appears that the development of cognitive skills is of at least equal importance to the refinement of sensory processing. Promotion of retention and transfer of learning are major goals for further research.

Silent and continuous fMRI scanning differentially modulate activation in an auditory language comprehension task

Sparse temporal acquisition schemes have been adopted to investigate the neural correlates of human audition using blood-oxygen-level dependent (BOLD) based functional magnetic resonance imaging (fMRI) devoid of ambient confounding acoustic scanner noise. These schemes have previously been extended to clustered-sparse temporal acquisition designs which record several subsequent BOLD contrast images in rapid succession in order to enhance temporal sampling efficiency. In the present study we demonstrate that an event-related task design can effectively be combined with a clustered temporal acquisition technique in an auditory language comprehension task. The same fifteen volunteers performed two separate auditory runs which either applied customary fMRI acquisition (CA) composed of continuous scanner noise or "silent" fMRI built on a clustered temporal acquisition (CTA) protocol. In accord with our hypothesis, the CTA scheme relative to the CA protocol is accompanied by significantly stronger functional responses along the entire superior temporal plane. By contrast, the bilateral insulae engage more strongly during continuous scanning. A post-hoc region-of-interest analysis reveals cortical activation in subportions of the supratemporal plane which varies as a function of acquisition protocol. The middle part of the supratemporal plane shows a rightward asymmetry only for the CTA scheme while the posterior supratemporal plane exposes a significantly stronger leftward asymmetry during the CTA. Our findings implicate that silent fMRI is advantageous when it comes to the exploration of auditory and speech functions residing in the supratemporal plane.

The Neural Correlate of Speech Rhythm as Evidenced by Metrical Speech Processing

The present study investigates the neural correlates of rhythm processing in speech perception. German pseudosentences spoken with an exaggerated (isochronous) or a conversational (nonisochronous) rhythm were compared in an auditory functional magnetic resonance imaging experiment. The subjects had to perform either a rhythm task (explicit rhythm processing) or a prosody task (implicit rhythm processing). The study revealed bilateral activation in the supplementary motor area (SMA), extending into the cingulate gyrus, and in the insulae, extending into the right basal ganglia (neostriatum), as well as activity in the right inferior frontal gyrus (IFG) related to the performance of the rhythm task. A direct contrast between isochronous and nonisochronous sentences revealed differences in lateralization of activation for isochronous processing as a function of the explicit and implicit tasks. Explicit processing revealed activation in the right posterior superior temporal gyrus (pSTG), the right supramarginal gyrus, and the right parietal operculum. Implicit processing showed activation in the left supramarginal gyrus, the left pSTG, and the left parietal operculum. The present results indicate a function of the SMA and the insula beyond motor timing and speak for a role of these brain areas in the perception of acoustically temporal intervals. Secondly, the data speak for a specific task-related function of the right IFG in the processing of accent patterns. Finally, the data sustain the assumption that the right secondary auditory cortex is involved in the explicit perception of auditory suprasegmental cues and, moreover, that activity in the right secondary auditory cortex can be modulated by top-down processing mechanisms.

Hemodynamic responses in human multisensory and auditory association cortex to purely visual stimulation

Background

Recent findings of a tight coupling between visual and auditory association cortices during multisensory perception in monkeys and humans raise the question whether consistent paired presentation of simple visual and auditory stimuli prompts conditioned responses in unimodal auditory regions or multimodal association cortex once visual stimuli are presented in isolation in a post-conditioning run. To address this issue fifteen healthy participants partook in a "silent" sparse temporal event-related fMRI study. In the first (visual control) habituation phase they were presented with briefly red flashing visual stimuli. In the second (auditory control) habituation phase they heard brief telephone ringing. In the third (conditioning) phase we coincidently presented the visual stimulus (CS) paired with the auditory stimulus (UCS). In the fourth phase participants either viewed flashes paired with the auditory stimulus (maintenance, CS-) or viewed the visual stimulus in isolation (extinction, CS+) according to a 5:10 partial reinforcement schedule. The participants had no other task than attending to the stimuli and indicating the end of each trial by pressing a button.

Results

During unpaired visual presentations (preceding and following the paired presentation) we observed significant brain responses beyond primary visual cortex in the bilateral posterior auditory association cortex (planum temporale, planum parietale) and in the right superior temporal sulcus whereas the primary auditory regions were not involved. By contrast, the activity in auditory core regions was markedly larger when participants were presented with auditory stimuli.

Conclusion

These results demonstrate involvement of multisensory and auditory association areas in perception of unimodal visual stimulation which may reflect the instantaneous forming of multisensory associations and cannot be attributed to sensation of an auditory event. More importantly, we are able to show that brain responses in multisensory cortices do not necessarily emerge from associative learning but even occur spontaneously to simple visual stimulation.