Siegfried Bien

Speech processing activates visual cortex in congenitally blind humans

Neurophysiological recordings and neuroimaging data in blind and deaf animals and humans suggest that perceptual functions may be organized differently after sensory deprivation. It has been argued that neural plasticity contributes to compensatory performance in blind humans, such as faster speech processing. The present study employed functional magnetic resonance imaging (fMRI) to map language‐related brain activity in congenitally blind adults. Participants listened to sentences, with either an easy or a more difficult syntactic structure, which were either semantically meaningful or meaningless. Results show that blind adults not only activate classical left‐hemispheric perisylvian language areas during speech comprehension, as did a group of sighted adults, but that they additionally display an activation in the homologueous right‐hemispheric structures and in extrastriate and striate cortex. Both the perisylvian and occipital activity varied as a function of syntactic difficulty and semantic content. The results demonstrate that the cerebral organization of complex cognitive systems such as the language system is significantly shaped by the input available.

Brain Activation Modulated by the Comprehension of Normal and Pseudo-word Sentences of Different Processing Demands: A Functional Magnetic Resonance Imaging Study

Recent data from lesion and brain imaging studies have questioned the well-established assumption of a close functional-anatomic link between syntax and Brocas area and semantics and Wernickes area. In the present study we used functional magnetic resonance imaging (fMRI) to investigate the neuroanatomical correlates of semantic and syntactic functions and possible interdependencies between the related brain systems. In a completely crossed design we varied syntactic processing demands (easy vs difficult to process word order sequences) and the meaningfulness of sentences (real- vs pseudo-word sentences). In comparison to a backward speech condition we found an activation of the left perisylvian region, including the left inferior frontal cortex and the left superior and middle temporal gyri. Semantic in contrast to pseudo-word sentences elicited a stronger activation in both the anterior and the posterior perisylvian cortex. Syntactic difficulty had its strongest effect within the left inferior frontal region and this effect was more pronounced for semantic than nonsemantic speech. These results suggest that semantic and syntactic language functions are mediated by partly specialized brain systems but that there nevertheless exists a substantial functional overlap of the involved brain structures.

Current concepts in the classification, diagnosis and treatment of hemangiomas and vascular malformations of the head and neck

Abstract There are many different classifications of vascular anomalies. As the correct classification of the vascular lesion has a direct influence on therapy it is difficult to decide which treatment should be considered as the treatment of choice. Based on an extensive review of the literature and personal experience of the treatment of more than 200 patients with hemangiomas or vascular malformations of the head and neck, a clinical classification is described that allows vascular lesions to be categorized in order to plan purposeful treatment. In general, hemangiomas represent the main group of vascular lesions in infancy and childhood. They are usually apparent a few weeks after birth and are characterized by an initially rapid growth of epithelial cells, followed by spontaneous involution. Hemangiomas should be differentiated from vascular malformations that are present at birth but may not be evident clinically. Spontaneous involution of vascular malformations has never been reported, whereas laser therapy can induce involution of hemangiomas at an early stage in a majority of cases. In certain situations steroids or surgical removal may seem to be the appropriate therapy of choice. In contrast, vascular malformations have to be treated according to their histopathology and location, as well as their hemodynamic features as shown radiographically with angiography. The accurate diagnosis of vascular anomalies is essential for further treatment, as shown by clinical experience at the University of Marburg.

Language lateralization in patients with temporal lobe epilepsy: a comparison of functional transcranial Doppler sonography and the Wada test

This study prospectively investigates whether noninvasive functional transcranial Doppler sonography (fTCD) is a useful tool to determine hemispheric language lateralization in the presurgical evaluation of patients with medically intractable temporal lobe epilepsy (TLE). fTCD results were compared with the Wada test as the gold standard. Wada test and fTCD were performed in 13 patients suffering from TLE. fTCD continuously measured blood flow velocities in both middle cerebral arteries, while the patient was performing a cued word generation task. During the Wada test, spontaneous speech, comprehension, reading, naming, and repetition were investigated. A laterality index (LI) was obtained by both procedures. Due to a lack of an acoustic temporal bone window, fTCD could not be performed in two patients (15%). In 9 of the remaining 11 patients hemispheric language dominance was found on the left side, in 1 patient on the right side, and 1 patient showed bihemispheric language representation. In all patients fTCD and the Wada test were in good agreement regarding hemispheric language lateralization, and the LI of both techniques were highly correlated (r = 0.776, P = 0.005). fTCD gives predictions of hemispheric language dominance consistent with the Wada test results even in children, patients with low IQ, and nonnative speakers. It is an alternative to the Wada test in determining language lateralization in patients with temporal lobe epilepsy.

Treatment-induced neoangiogenesis in cerebral arteriovenous malformations.

We investigated the angiogenetic and proliferative activity of the endothelium of 30 consecutive surgical cases of AVM treated at our institution by immunohistochemical detection of the PCNA, MIB-1, Flk-1 and VEGF antibodies. Endothelial positive immunostaining was observed in 87% of the cases for PCNA, in 20% for MIB-1, and in 80% for Flk-1. Of 22 individuals treated with incomplete embolization prior to surgery, 17 showed an expression of VEGF (77%), but only two of the eight patients (25%) who were treated without prior embolization exhibited such an immunoreaction (P=0.0086). The proliferation and growth of cerebral AVMs is documented by endothelial expression of PCNA and MIB-1. The statistically significantly higher expression of VEGF in partially obliterated (embolized) AVMs is most likely caused by transient regional hypoxia within the AVM nidus that mediates neoangiogensis. It points out the clinical relevance of a complete occlusion in order to avoid neovascularization associated with subsequent morbidity and mortality.

The human dorsal action control system develops in the absence of vision.

The primate dorsal pathway has been proposed to compute vision for action. Although recent findings suggest that dorsal pathway structures contribute to somatosensory action control as well, it is yet not clear whether or not the development of dorsal pathway functions depends on early visual experience. Using functional magnetic resonance imaging, we investigated the pattern of cortical activation in congenitally blind and matched blindfolded sighted adults while performing kinesthetically guided hand movements. Congenitally blind adults activated similar dorsal pathway structures as sighted controls. Group-specific activations were found in the extrastriate cortex and the auditory cortex for congenitally blind humans and in the precuneus and the presupplementary motor area for sighted humans. Dorsal pathway activity was in addition observed for working memory maintenance of kinesthetic movement information in both groups. Thus, the results suggest that dorsal pathway functions develop in the absence of vision. This favors the idea of a general mechanism of movement control that operates regardless of the sensory input modality. Group differences in cortical activation patterns imply different movement control strategies as a function of visual experience.

Content-specific activation during associative long-term memory retrieval

We tested whether visual stimulus material that is assumed to be processed in different cortical networks during perception (i.e., faces and spatial positions) is also topographically dissociable during long-term memory recall. With an extensive overlearning procedure, 12 participants learned paired associates of words and faces and words and spatial positions. Each word was combined with either one or two positions or one or two faces. fMRI was recorded several days later during a cued recall test, in which two words were presented and the participants had to decide whether these were linked to each other via a common mediator, i.e., a face or a position. This paradigm enforces retrieval from long-term memory without confounding recall with perceptual processes. A network of cortical areas was found to be differently activated during recall of positions and faces, including regions along the dorsal and ventral visual pathways, such as the parietal and precentral cortex for positions and the left prefrontal, temporal (including fusiform gyrus) and posterior cingulate cortex for faces. In a subset of these areas, the BOLD response was found to increase monotonically with the number of the to-be-re-activated associations. These results show that material-specific cortical networks are systematically activated during long-term memory retrieval that overlap with areas also activated by positions and faces during perceptual and working memory tasks.

Hypoxia-inducible Factor and Vascular Endothelial Growth Factor Are Expressed More Frequently in Embolized than in Nonembolized Cerebral Arteriovenous Malformations

OBJECTIVE:In previous studies, we documented a marked neoangiogenesis and endothelial proliferation in cerebral arteriovenous malformations (AVMs) that were embolized before surgery compared with those that were not embolized. We hypothesized that embolization caused a local hypoxia that promotes neoangiogenesis as a possible pathomechanism. To support this hypothesis, we now examined the angiogenesis-related proteins in a larger cohort of patients. In addition, we investigated hypoxia-inducible factor-1&agr; as a possible protein operative during neoangiogenesis of cerebral AVMs. METHODS:Paraffin-embedded specimens of 56 AVMs obtained from surgical resection and 14 brain tissue controls were immunohistochemically stained with antibodies to proliferating cell nuclear antigen, MIB-1, vascular endothelial growth factor, Flk1, and hypoxia-inducible factor-1&agr; by standard protocols. RESULTS:In AVMs treated with embolization before surgery (n = 35, 63%), the expression of hypoxia-inducible factor-1&agr; (P = 0.0101) and vascular endothelial growth factor (P = 0.0007) was significantly higher (Fisher’s exact test) than in patients who did not have previous endovascular treatment. Differences in the expression of Flk-1 (P = 0.0798) and proliferating cell nuclear antigen (P = 0.0423) were in the same direction but were not significant when corrected for multiple testing. CONCLUSION:Our results provide circumstantial evidence that a partial occlusion of cerebral AVMs might induce local hypoxia-related neoangiogenesis. To support these data, future animal studies should be performed.

Digital volume tomography : Radiologic examinations of the temporal bone

OBJECTIVE We evaluated the clinical applicability and the value of digital volume tomography for visualization of the lateral skull base using temporal bone specimens. MATERIALS AND METHODS Twelve temporal bone specimens were used to evaluate digital volume tomography on the lateral skull base. Aside from the initial examination of the temporal bones, radiologic control examinations were performed after insertion of titanium, gold, and platinum middle-ear implants and a cochlear implant. RESULTS With high-resolution and almost artifact-free visualization of alloplastic middle-ear implants of titanium, gold, or platinum, it was possible to define the smallest bone structures or position of the prosthesis with high precision. Furthermore, the examination proved that digital volume tomography is useful in assessing the normal position of a cochlear implant. CONCLUSION Digital volume tomography expands the application of diagnostic possibilities in the lateral skull base. Therefore, we believe improved preoperative diagnosis can be achieved along with more accurate planning of the surgical procedure. Digital volume tomography delivers a small radiation dose and a high resolution coupled with a low purchase price for the equipment.

How moving objects become animated : The human mirror neuron system assimilates non-biological movement patterns

Abstract The so-called mirror neuron system (MNS) responds when humans observe actions performed by a member of their own species. This activity is understood as an internal motor representation of the observed movement pattern. By contrasting meaningless human hand movements with meaningless artificial movements of objects in space, we tested the claim that exclusively movements belonging to the human motor repertoire have direct access to the MNS. Eighteen participants observed video clips of moving hands and objects while the hemodynamic response was recorded with functional magnetic resonance imaging. Second-level analysis of the hemodynamic response revealed substantially overlapping activation patterns for both types of movements including relevant structures of the MNS (bilateral premotor and parietal areas, occipito-temporal junction, postcentral gyrus and the right superior temporal sulcus). This suggests that perceptual processing of moving hands and objects recruits similar and overlapping cortical networks. Direct comparison of the two movement types revealed stronger activations for hand movements mainly in structures of the MNS suggesting an “expertise effect”. Overall, our results provide evidence that observing movements not explicitly belonging to the human motor repertoire can activate the human MNS, most likely because an association with a biological movement is evoked.