Blog Archives

A supramodal brain substrate of word form processing – an fMRI study on homonym finding with auditory and visual input

Homonym processing in German is of theoretical interest as homonyms specifically involve word form information. In a previous study (Weis et al., 2001), we found inferior parietal activation as a correlate of successfully finding a homonym from written stimuli. The present study tries to clarify the underlying mechanism and to examine to what extend the previous homonym effect is dependent on visual in contrast to auditory input modality.

from Brain Research

Advertisements

Functional magnetic resonance imaging exploration of combined hand and speech movements in Parkinson’s disease

Among the repertoire of motor functions, although hand movement and speech production tasks have been investigated widely by functional neuroimaging, paradigms combining both movements have been studied less so. Such paradigms are of particular interest in Parkinson’s disease, in which patients have specific difficulties performing two movements simultaneously. In 9 unmedicated patients with Parkinson’s disease and 15 healthy control subjects, externally cued tasks (i.e., hand movement, speech production, and combined hand movement and speech production) were performed twice in a random order and functional magnetic resonance imaging detected cerebral activations, compared to the rest. F-statistics tested within-group (significant activations at P values < 0.05, familywise error corrected), between-group, and between-task comparisons (regional activations significant at P values 10 voxels). For control subjects, the combined task activations comprised the sum of those obtained during hand movement and speech production performed separately, reflecting the neural correlates of performing movements sharing similar programming modalities. In patients with Parkinson’s disease, only activations underlying hand movement were observed during the combined task. We interpreted this phenomenon as patients’ potential inability to recruit facilitatory activations while performing two movements simultaneously. This lost capacity could be related to a functional prioritization of one movement (i.e., hand movement), in comparison with the other (i.e., speech production). Our observation could also reflect the inability of patients with Parkinson’s disease to intrinsically engage the motor coordination necessary to perform a combined task. © 2011 Movement Disorder Society

from Movement Disorders

Activation in left primary visual cortex representing parafoveal visual field during reading Japanese texts

Conclusions
The activation modulation during reading Japanese texts occurs in the parafoveal V1 of the left hemisphere. The attentional modulation did not change with the distance to the next goal of saccade but was fixed on the area representing about 4.5° of eccentricity.

from Brain Research

The contribution of functional near-infrared spectroscopy (fNIRS) to the presurgical assessment of language function in children

Before performing neurosurgery, an exhaustive presurgical assessment is required, usually including an investigation of language cerebral lateralization. Among the available procedures, the intracarotid amobarbital test (IAT) was formerly the most widely used. However, this procedure has many limitations: it is invasive and potentially traumatic, especially for children. To overcome these limitations, neuroimaging techniques such as functional magnetic resonance imaging (fMRI) have been used. Again, these methods are difficult to use with children, who must remain motionless during data acquisition. Functional near-infrared spectroscopy (fNIRS) is a noninvasive functional imaging technique that is easily applied to pediatric and cognitively limited patients. It has been used recently in epileptic children for presurgical assessment of expressive and receptive language brain lateralization. The aim of this review is to present the contribution of fNIRS to the presurgical assessment of language function in children with neurological diseases.

from Brain and Language

Neural correlates of rhyming vs. lexical and semantic fluency

Rhyming words, as in songs or poems, is a universal feature of human language across all ages. In the present fMRI study a novel overt rhyming task was applied to determine the neural correlates of rhyme production.

Fifteen right-handed healthy male volunteers participated in this verbal fluency study. Participants were instructed to overtly articulate as many words as possible either to a given initial letter (LVF) or to a semantic category (SVF). During the rhyming verbal fluency task (RVF), participants had to generate words that rhymed with pseudoword stimuli. On-line overt verbal responses were audiotaped in order to correct the imaging results for the number of generated words.

Fewer words were generated in the rhyming compared to both the lexical and the semantic condition. On a neural level, all language tasks activated a language network encompassing the left inferior frontal gyrus, the middle and superior temporal gyri as well as the contralateral right cerebellum. Rhyming verbal fluency compared to both, lexical and semantic verbal fluency, demonstrated significantly stronger activation of left inferior parietal region.

Generating novel rhyme words seems to be mainly mediated by the left inferior parietal lobe, a region previously found to be associated with meta-phonological as well as sub-lexical linguistic processes.

from Brain Research

Unification of sentence processing via ear and eye: An fMRI study

We present new evidence based on fMRI for the existence and neural architecture of an abstract supramodal language system that can integrate linguistic inputs arising from different modalities such that speech and print each activate a common code. Working with sentence material, our aim was to find out where the putative supramodal system is located and how it responds to comprehension challenges. To probe these questions we examined BOLD activity in experienced readers while they performed a semantic categorization task with matched written or spoken sentences that were either well-formed or contained anomalies of syntactic form or pragmatic content. On whole-brain scans, both anomalies increased net activity over non-anomalous baseline sentences, chiefly at left frontal and temporal regions of heteromodal cortex. The anomaly-sensitive sites correspond approximately to those that previous studies () have found to be sensitive to other differences in sentence complexity (object relative minus subject relative). Regions of interest (ROIs) were defined by peak response to anomaly averaging over modality conditions. Each anomaly-sensitive ROI showed the same pattern of response across sentence types in each modality. Voxel-by-voxel exploration over the whole brain based on a cosine similarity measure of common function confirmed the specificity of supramodal zones.

from Cortex

Atypical processing of auditory temporal complexity in autistics

Autistics exhibit a contrasting combination of auditory behavior, with enhanced pitch processing abilities often coexisting with reduced orienting towards complex speech sounds. Based on an analogous dissociation observed in vision, we expected that autistics’ auditory behavior with respect to complex sound processing may result from atypical activity in non-primary auditory cortex. We employed fMRI to explore the neural basis of complex non-social sound processing in 15 autistic and 13 non-autistics, using a factorial design in which auditory stimuli varied in spectral and temporal complexity. Spectral complexity was modulated by varying the harmonic content, whereas temporal complexity was modulated by varying frequency modulation depth. The detection task was performed similarly by autistics and non-autistics. In both groups, increasing spectral or temporal complexity was associated with activity increases in primary (Heschl’s gyrus) and non-primary (anterolateral and posterior superior temporal gyrus) auditory cortex Activity was right-lateralized for spectral and left-lateralized for temporal complexity. Increasing temporal complexity was associated with greater activity in anterolateral superior temporal gyrus in non-autistics and greater effects in Heschl’s gyrus in autistics. While we observed similar hierarchical functional organization for auditory processing in both groups, autistics exhibited diminished activity in non-primary auditory cortex and increased activity in primary auditory cortex in response to the presentation of temporally, but not of spectrally complex sounds. Greater temporal complexity effects in regions sensitive to acoustic features and reduced temporal complexity effects in regions sensitive to more abstract sound features could represent a greater focus towards perceptual aspects of speech sounds in autism.

from Neuropsychologia

Right parietal hypoactivation in a cocaine-dependent group during a verbal working memory task

It has been suggested that cocaine addiction affects the engagement of the frontoparietal networks in executive functions, such as attention and working memory. Thus, our objective was to investigate brain differences between cocaine-dependent subjects and healthy controls during the performance of a verbal working memory task. Nineteen comparison men and nineteen cocaine-dependent men performed a 2-back task. Data was acquired on a 1.5 T Siemens Avanto. Image processing and statistical analyses were carried out using SPM5; Biological Parametric Mapping (BPM) was used for further morphometric and correlation analyses. No performance differences were found between groups. However, the dorsal part of the right inferior parietal cortex (BA 40) was less activated in the cocaine-dependent group. Cocaine patients did not overactive any brain area when compared with controls. Our results show reduced activation in the brain areas related to the attention system in cocaine-dependent men while performing a verbal working memory task. Chronic cocaine use may affect the attentional system in the right parietal lobe, making patients more prone to attentional deficits.

from Brain Research

Language lateralization in left-handed patients with schizophrenia

We evaluated hemispheric lateralization of language production in non-right-handed (NRH) patients with schizophrenia compared with matched right-handed (RH) patients, NRH control, and RH control subjects. First, the ability to generate verbs during overt training trials was checked in 78 subjects. They were then evaluated with functional magnetic resonance imaging (fMRI) while performing a covert verb generation task. No significant interactions between illness and handedness and no illness effect were observed in functional asymmetry. There was significantly less leftward asymmetry of the inferior frontal, precentral, and supramarginal gyri as well as the intra-parietal sulcus in non-right-handers compared to right-handers taking into account the task performances. Our findings suggested that decreased lateralization for language production was more closely related to handedness than to schizophrenia.

from Neuropsychologia

Visual phonetic processing localized using speech and nonspeech face gestures in video and point-light displays

The talking face affords multiple types of information. To isolate cortical sites with responsibility for integrating linguistically relevant visual speech cues, speech and nonspeech face gestures were presented in natural video and point-light displays during fMRI scanning at 3.0T. Participants with normal hearing viewed the stimuli and also viewed localizers for the fusiform face area (FFA), the lateral occipital complex (LOC), and the visual motion (V5/MT) regions of interest (ROIs). The FFA, the LOC, and V5/MT were significantly less activated for speech relative to nonspeech and control stimuli. Distinct activation of the posterior superior temporal sulcus and the adjacent middle temporal gyrus to speech, independent of media, was obtained in group analyses. Individual analyses showed that speech and nonspeech stimuli were associated with adjacent but different activations, with the speech activations more anterior. We suggest that the speech activation area is the temporal visual speech area (TVSA), and that it can be localized with the combination of stimuli used in this study. Hum Brain Mapp, 2010. © 2010 Wiley-Liss, Inc.<p><p>from <a href=”http://onlinelibrary.wiley.com/doi/10.1002/hbm.21139/abstract;jsessionid=BFA721E0D247F9478322CBB6F0EE62EA.d03t01″><em>Human Brain Mapping</em></a></p>

Cortical Activation during Clock Reading as a Quadratic Function of Dementia State

In patients with Alzheimer’s disease (AD), neuroimaging studies have demonstrated decreased brain activation, while increased activation was detected in patients with mild cognitive impairment (MCI). It can be hypothesized that increased cerebral activity seen in patients with MCI reflects neural compensation at the beginning of neurodegenerative processes. Later, as patients develop AD, neural integrity is increasingly impaired. This is accompanied by decreased neural activation. In this study we examined cognitive performance and functional magnetic resonance imaging activation on a Clock Reading task (CRT) and a Spatial Control task (SCT) in healthy controls, patients with MCI, and patients with early AD. Correlations between neural-functional activation and cognitive state, measured by the Mini Mental Status Examination, were determined using rank, linear and quadratic correlation models. It could be shown that CRT, in comparison to SCT, specifically activates brain regions in the ventral visual stream and precuneus known to be involved in conceptual processing and spatial imagery. The correlation between brain activity and cognitive state followed a quadratic rather than a linear pattern in several brain regions, including the lingual gyrus, cuneus, and precuneus. The strongest brain activity was found in patients with MCI and less severely impaired early AD subjects. These findings support the hypothesis that patients in early stages of dementia compensate for neuronal loss by the recruitment of additional neural resources reflected by increased neural activation, as measured by the blood oxygen level-dependent signal.

from the Journal of Alzheimer’s Disease

The right posterior inferior frontal gyrus contributes to phonological word decisions in the healthy brain: evidence from dual-site TMS

There is consensus that the left hemisphere plays a dominant role in language processing, but functional imaging studies have shown that the right as well as the left posterior inferior frontal gyri (pIFG) are activated when healthy right-handed individuals make phonological word decisions. Here we used online transcranial magnetic stimulation (TMS) to examine the functional relevance of the right pIFG for auditory and visual phonological decisions. Healthy right-handed individuals made phonological or semantic word judgements on the same set of auditorily and visually presented words while they received stereotactically guided TMS over the left, right or bilateral pIFG (n= 14) or the anterior left, right or bilateral IFG (n= 14). TMS started 100 ms after word onset and consisted of four stimuli given at a rate of 10 Hz and intensity of 90% of active motor threshold. Compared to TMS of aIFG, TMS of pIFG impaired reaction times and accuracy of phonological but not semantic decisions for visually and auditorily presented words. TMS over left, right or bilateral pIFG disrupted phonological processing to a similar degree. In a follow-up experiment, the intensity threshold for delaying phonological judgements was identical for unilateral TMS of left and right pIFG. These findings indicate that an intact function of right pIFG is necessary for accurate and efficient phonological decisions in the healthy brain with no evidence that the left and right pIFG can compensate for one another during online TMS. Our findings motivate detailed studies of phonological processing in patients with acute and chronic damage of the right pIFG.

from Neuropsychologia

Reduced somatosensory activations in swallowing with age

Understanding the neural functional organization of swallowing in healthy elders is essential in diagnosing and treating older adults with swallowing difficulties. The primary aims of this investigation were to identify the neural activation sites of different components of deglutition in healthy elders using functional Magnetic Resonance Imaging (fMRI) and to investigate age differences in the neural control of swallowing. Ten young (age range 19-25 years of age) and nine older (age range 66-77 years of age) right-handed healthy individuals were scanned in a 3-Tesla MRI scanner. Subjects were visually cued for both a Swallow task and for component/control tasks ( Prepare to swallow, Tap your tongue, and Clear your throat). Behavioral interleaved gradient (BIG) methodology was used to address movement related artifacts. Between-group comparisons revealed statistically stronger activations in the primary somatosensory cortex of young adults during the motor tasks examined. Both groups showed activations in the major motor areas involved in the initiation and execution of movement; however, areas involved in sensory processing, sensorimotor integration and/or motor coordination and control, showed reduced or limited activity in the elderly. Potential implications of these findings for clinical practice are discussed. Hum Brain Mapp, 2010. © 2010 Wiley-Liss, Inc.

from Human Brain Mapping

Neural correlates of human somatosensory integration in tinnitus

Possible neural correlates of somatosensory modulation of tinnitus were assessed.Functional magnetic resonance imaging (fMRI) was used to investigate differences in neural activity between subjects that can modulate their tinnitus by jaw pro-trusion and normal hearing controls. We measured responses to bilateral sound and responses to jaw protrusion. Additionally we studied multimodal integration of somatosensory jaw protrusion and sound. The auditory system responded to both sound and jaw protrusion. Jaw responses were enhanced in the cochlear nu-cleus (CN) and the inferior colliculus (IC) in tinnitus patients. The responses of the auditory brain areas to jaw protrusion presumable account for the modulation of tinnitus as described by the patients. The somatosensory sys tem responded to jaw protrusion and not to sound. These responses occurred both in subjects with tinnitus and controls. Unexpectedly, the cerebellum responded to sound in normal hearing subjects, but not in tinnitus patients. Together, these results provide a neurophysiological basis for the effect of jaw protrusion on tinnitus

from Hearing Research

Localizing the Frequency X Regularity Word Reading Interaction in the Cerebral Cortex

The aim of this work is to combine behavioural and functional magnetic resonance imaging (fMRI) data to advance our knowledge of where the Frequency X Regularity interaction on word naming is located in the cerebral cortex. Participants named high and low frequency, regular and exception words in a behavioural lab (Experiment 1) and during an fMRI study (Experiment 2). We used the Additive Factors Method (AFM) to localize the expected overadditive Frequency X Regularity interaction both temporally, through word naming reaction times (whereby low frequency exceptions produce the longest reaction times), and spatially on the cortex, through hemodynamic response measures from fMRI (whereby low frequency exceptions produce the highest activation intensities). Activation maps revealed significant activation for low frequency exception words in the supplementary motor association cortex (SMA). We interpret the SMA activation as increased articulatory preparation, given previous demonstrations of the SMA’s involvement in motor programming. Hemodynamic time courses were extracted from four regions of interest: the middle temporal gyri, SMA, insula and the inferior frontal gyri. Importantly, hemodynamic intensities within the SMA displayed an overadditive interaction pattern parallel to that found with naming reaction times. Thus, we provide an application of the AFM to fMRI intensity measures and evidence that the SMA is a potential cortical source of the Frequency X Regularity interaction during a basic naming paradigm. While the AFM has traditionally been used to localize factors in time we provide evidence that the AFM is useful in understanding how variables influence one another in the brain.

from Neuropsychologia