Frontal Operculum Cortex Research Articles

Investigating language processing of syntax and prosody via dynamic causal modelling (DCM) on MEG data

Event Abstract Back to Event Investigating language processing of syntax and prosody via dynamic causal modelling (DCM) on MEG data Burkhard Maess1*, Olivier David2, Korinna Eckstein1 and Angela D. Friederici1 1 Max Planck Institute for Human Cognitive and Brain Sciences, Germany 2 INSERM U836, Grenoble Institut des Neuroscience, France Our study investigated the interplay of syntactic and prosodic information processing during language comprehension. For this purpose, we conducted a MEG-study using spoken sentences which were either correct, syntactically incorrect, prosodically incorrect or both [1]. Averaged MEG data were subjected to DCM analysis. DCM priors for the activity centres were taken from previous functional imaging studies. We included six cortical regions in the analysis: Heschl’s gyrus (HG), the (anterior part of the) superior temporal cortex (STG) and the frontal opercular cortex (FOP) of both hemispheres. Recent studies have indicated the importance of the basal ganglia and the thalamus for language processing. Therefore, we also tested the influence of such a deep but magnetically silent source. According to current knowledge on the structural connectivity between these regions, we defined the following functional connections in all models: Within each hemisphere, HG connects to STG and STG to FOP. Fifteen different models, which differed with respect to their connections between the hemispheres and their connections to the thalamus, were tested. Model comparison supported most models which had connections to the thalamus from all six cortical regions and temporal as well as interhemispheric connections via the corpsus callosum between STG and FOP. Hence DCM modelling stresses the role of the thalamo-cortical loop as a modulator of the STG and FOP crosstalks within as well as between the hemispheres. For syntactic violations, a significant increase in connectivity strength was observed mostly for the left hemispheric connections to the thalamus. Prosodic incongruencies strengthened STG-Thalamus connections while also weakening the direct interhemispheric connection. In conclusion, using DCM, we were able to model the spatio-temporal evolution of brain activity during language processing. Furthermore, the crucial role of the thalamus within the language network was demonstrated.

The effect of handedness on cortical motor activation during simple bilateral movements

The neuronal correlates of handedness are still poorly understood. Here we used event-related functional magnetic resonance imaging to investigate the impact of handedness on neuronal activation of the primary sensorimotor cortex, supplementary motor area and dorsal premotor cortex during simple unilateral and bilateral finger movements. In 16 right-handed and 16 left-handed individuals, we mapped changes in regional neuronal activity while participants responded to four symbolic cues presented in a pseudorandom order. According to pre-specified cues, they pressed a button with their right, left or both index fingers or withheld a response. For unilateral right index finger button presses, reaction times, motor and premotor activity were the same for both right- and left-handers. Compared with right-handers, left-handers had shorter reaction times with unilateral left index finger button presses, along with greater activation of the supplementary motor area and right frontal opercular cortex. Simultaneous bilateral compared with unilateral button presses led to a relative increase of activity in the right and left dorsal premotor cortex and the right primary sensorimotor cortex in right but not left-handers. Neither right nor left-handers showed any tendency during bilateral button presses towards faster responses with the dominant hand and the reaction times were equal in the two groups. Therefore, we conclude that the relative increase of activity in dorsal premotor and right primary sensorimotor cortices in right-handers represents a genuine difference in bimanual motor control related to handedness.

Acoustic Communication of Emotions: Processing of Emotional Prosody. An Investigation on Single Word Level using fMRI

Perception of emotional prosody plays an important role in every day social life. However, the underlying neuronal circuits are far from being identified. The objective of our study was to find out more about the neuronal networks involved in the processing of emotional speech on the single word level by means of fMRI. 13 young healthy subjects were tested in an auditory oddball paradigm where frequent standard words (“Anna“, p=0.7) and infrequent target words (“Anni“, p=0.1) were presented via headphones. The subjects had to press a button each time they heard the target word “Anni“. Both words, standard and the target, were spoken in a neutral tone. Additionally, infrequent words “Anna“ spoken in a happy (p=0.1) or sad (p=0.1) tone were presented as emotional oddballs. Functional MR images were acquired for each stimulus and then statistical parametrical maps (SPMs) were calculated for each subject and for a one-sample t-test. The contrasts “happy vs. neutral condition“ and “sad vs. neutral condition“ revealed activations in the middle gyrus of the temporal lobe and in the frontal opercular cortex bilaterally but with the main focus on the right side, suggesting a lateralization of emotional prosody processing to the right hemisphere already on the single word level. The results are discussed with respect to the relevant literature, the ecological validity and the limits of the experiment.

Interval and ordinal properties of sequences are associated with distinct premotor areas.

Lesion and imaging studies have suggested that the premotor cortex (PMC) is a crucial component in the neural network underlying the processing of sequential information. However, whether different aspects of sequential information like interval and ordinal properties are supported by different anatomical regions, and whether the representation of sequential information within the PMC is necessarily related to motor requirements, remain open questions. Brain activations were investigated during a sequence encoding paradigm in 12 healthy subjects using functional magnetic resonance imaging. Subjects had to attend either to the interval or to the ordinal information of a sequence of visually presented stimuli and had to encode the relevant information either before motor reproduction or before perceptual monitoring. Although interval and ordinal information led to activations within the same neural network, direct comparisons revealed significant differences. The pre-supplementary motor area (preSMA), the lateral PMC, the frontal opercular cortex as well as basal ganglia and the left lateral cerebellar cortex (CE) were activated significantly more strongly by interval information, whereas the SMA, the frontal eye field, the primary motor cortex (MI), the primary somatosensory cortex, the cuneus as well as the medial CE and the thalamus were activated more strongly by ordinal information. In addition, serial encoding before reproduction led to higher activations than serial encoding before monitoring in the preSMA, SMA, MI and medial CE. Our findings suggest overlapping but different kinds of sequential representation, depending on both the ordinal and interval aspects as well as motor requirements.

Functional organization of the lateral premotor cortex: fMRI reveals different regions activated by anticipation of object properties, location and speed

Previous studies have provided evidence that the lateral premotor cortex (PMC) is involved in representations triggered by attended sensory events. However, while the functional specificity of subregions of this large cortical structure has been intensively investigated in the monkey, little is known about functional differences within human lateral premotor areas. In the present study, functional magnetic resonance imaging was used to investigate if attending to object-specific (O), spatial (S), or temporal (T) properties of the same sensory event, i.e. moving objects, involves different premotor areas. We found a frontoparietal ‘prehension network’ comprising the pre-supplementary motor area (preSMA), the ventral PMC, and the left anterior intraparietal sulcus (aIPS) to be activated independently of the attended stimulus property, but most intensively during object-related attention. Moreover, several areas were exclusively activated according to the attended stimulus property. Particularly, different PMC regions responded to the Object (O) task (left superior ventrolateral PMC), the Spatial (S) task (dorsolateral PMC), and the Timing (T) task (frontal opercular cortex (FOP)). These results indicate that the representation of different stimulus dimensions engage distinct premotor areas and, therefore, that there is a functional specificity of lateral premotor subregions.

Phonological agraphia following a focal anterior insulo-opercular infarction

Following a unique infarction, restricted to the left anterior insula and the adjacent part of the intrasylvian frontal opercular cortex, an 83-year-old right-handed patient acutely developed a severe speech disorder that evolved into mere mutism within a few hours. After rapid recovery from mutism, oral language was characterized by severe apraxia of speech. In-depth language investigations further disclosed an isolated, highly selective disturbance of the spelling system (phonological agraphia) which resolved rapidly. One year after onset of neurological symptoms, the apraxia of speech had almost completely receded. The anatomoclinical findings in this first representative of pure and nearly isolated phonological agraphia complement previous neuroanatomical and neurolinguistic accounts of phonological agraphia. The data not only seem to enrich current insights in the anatomical locus for phonological agraphia, they also seem to contribute to a further delineation of the insular role in phonologically mediated aphasic manifestations.

Cortical activation during human volitional swallowing: an event-related fMRI study.

Functional magnetic resonance imaging (fMRI) provides a safe, noninvasive method for studying task-related cortical neuronal activity. Because the cerebral cortex is strongly implicated in the control of human swallowing, we sought to identify its functional neuroanatomy using fMRI. In 10 healthy volunteers, a swallow event-related paradigm was performed by injecting 5 ml water bolus into the oral cavity every 30 s. Whole brain functional magnetic susceptibility -weighted spiral imaging data were simultaneously acquired over 600 s on a 1.5-T magnetic resonance scanner, utilizing the blood oxygenation level-dependent technique, and correlation maps were generated using both >99% percentile rank and spatial extent thresholding. We observed areas of increased signal change consistently in caudal sensorimotor cortex, anterior insula, premotor cortex, frontal operculum, anterior cingulate and prefrontal cortex, anterolateral and posterior parietal cortex, and precuneus and superiomedial temporal cortex. Less consistent activations were also seen in posterior cingulate cortex and putamen and caudate nuclei. Activations were bilateral, but almost every region, particularly the premotor, insular, and frontal opercular cortices, displayed lateralization to one or the other hemisphere. Swallow-related cortical activity is multidimensional, recruiting brain areas implicated in processing motor, sensory, and attention/affective aspects of the task.

Perisylvian dysgenesis. Clinical, EEG, MRI and glucose metabolism features in 10 patients.

We studied 10 patients who had neurological disorders with a MRI-based diagnosis of perisylvian dysgenesis based on the fact that the parasagittal and centrifugal extremity of the sylvian fissure was abnormally mesial. This abnormality was bilateral in seven cases; in the other three patients, the contralateral sylvian fissure appeared either normal (two cases) or enlarged (open operculum). The perisylvian cortex had a polymicrogyric appearance in most patients. Potential aetiopathogenic factors were determined in four patients. In two of them, ischaemia at mid-gestation was ascribed to death of a co-twin in a context of monozygotic twinning. In the other two patients, who were siblings, genetic factors were suspected. Pseudobulbar palsy was found in eight patients and epilepsy in five patients. We used PET with [18F]fluorodeoxyglucose to test the hypothesis that, despite this clinical and MRI heterogeneity, regional cerebral glucose distribution could have common features in these patients. The analysis of PET data was performed by visual inspection in two cases and by using statistical parametric mapping (SPM) in eight patients compared with a control group. Segmented grey matter MRIs of seven out these patients were also analysed using SPM. We found that the abnormal perisylvian cortex had normal grey matter activity in eight patients and in the other two there was a heterogeneous pattern with areas of preserved metabolism and of decreased metabolism. Metabolic changes were also detected outside the polymicrogyric-like cortex; three patients had hypometabolic areas in cortical regions where the MRI appeared normal and had a normal intensity. When polymicrogyria extended into the white matter, this ectopic dysgenetic cortex was associated with a grey matter pattern within the white matter territory, and was detected by SPM as areas of PET hypermetabolism and MRI hyperintensity. In order to detect possible metabolic changes undetected by the individual analyses, the group of patients was compared with the control group. This comparison revealed bilateral hypometabolism in the frontal opercular cortex. We propose that these PET data be considered in light of the presumed cyto-architectonic pattern of perisylvian dysgenesis, i.e. polymicrogyria. In this malformation, two dense cell layers are separated by a necrotic sparse cell layer. We speculate that the amount of synaptic activity preserved in these dense cell layers depends on the importance and timing of the necrotic process; this hypothesis accounts for the large range of metabolic patterns found, from profoundly decreased glucose metabolism to nearly normal activity.

Intrauterine supraventricular tachyarrhythmias and transplacental digitalisation.

Six newborn infants with intrauterine supraventricular tachyarrhythmias (five cases of atrial flutter and one of supraventricular tachycardia) are described. Transplacental digitalisation was attempted in three cases. Supraventricular tachycardia associated with hydrops fetalis, detected in a fetus at a gestation of 31 weeks, was successfully converted to normal sinus rhythm eight days after the mother began treatment with digoxin. The serum concentration of digoxin in cord blood almost equalled the maternal concentration in three cases. In the remaining three cases treatment with digitalis was effective in converting tachyarrhythmias to sinus rhythm after delivery. With maintenance digoxin therapy, the prognosis of fetal tachyarrhythmias seems to be good, once conversion to sinus rhythm has been accomplished.

Gustatory responses in the frontal opercular cortex of the alert cynomolgus monkey.

The responses of 165 single taste neurons in the anterior operculum of the alert cynomolgus monkey were analyzed. Chemicals were deionized water, blackcurrant juice, and the four basic taste stimuli: glucose, NaCl, HCl, and quinine HCl. Taste-evoked responses could be recorded from an opercular region that measured approximately 4.0 mm in its anteroposterior extent, 2.0 mm mediolaterally, and 3.0 mm dorsoventrally. Within this area, taste-responsive neurons were sparsely distributed such that multiunit activity was rarely encountered and neuronal isolation was readily achieved. Intensity-response functions were determined for nine cells. In each case, the lowest concentration of the dynamic response range conformed well to human electrophysiological and psychophysical thresholds for the basic taste stimuli. There was some evidence of chemotopic organization. Cells that responded best to glucose tended to be distributed toward the anterior operculum, whereas most acid-sensitive neurons were located more posteriorly. The proportion of cells responding best to NaCl peaked in the middle of the area, whereas quinine sensitivity was rather evenly distributed throughout. Opercular neurons in the monkey showed moderate breadth of sensitivity compared with taste cells of other species and at other synaptic levels. A breadth-of-tuning coefficient was calculated for each neuron. This is a metric that can range from 0.0 for a cell that responds specifically to only one of the four basic stimuli to 1.0 for one that responds equally to all four stimuli. The mean coefficient for 165 cells in the operculum was 0.67 (range = 0.12-0.99). Efforts were made to determine whether neurons could be divided into a discrete number of types, as defined by their responsiveness to the stimulus array used here. It was concluded that most taste cells may be assigned to a small number of groups, each of which is statistically independent of the others, but within which the constituent neurons are not identical. An analysis of taste quality indicated that the sweet and salty stimuli evoked patterns of activity that were significantly intercorrelated. Similarly, patterns representing HCl, quinine HCl, and water were related.