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C Preibisch

Publications and source records attributed to C Preibisch.

10 recordsLinked to original sources
PubMed2005

Right hemispheric language dominance in a right-handed male with a right frontal tumor shown by functional transcranial Doppler sonography.

BACKGROUND: A 38-year-old, right-handed man with late-onset right frontal epilepsy due to a ganglioglioma and atypical right hemispheric language dominance is described. METHODS: Language dominance was investigated with functional transcranial Doppler sonography (fTCD), and language localization with functional magnetic resonance imaging (fMRI). RESULTS: During a word generation task, fTCD showed atypical right hemispheric language dominance, which was confirmed by fMRI using a semantic word comparison and a word stem completion task. This information helped to guide the resective procedure, which left the patient seizure-free and did not induce new deficits. CONCLUSION: Functional TCD appears to be a useful and reliable screening tool for determining hemispheric language dominance, even in patients with atypical language representation. Functional MRI may be used to confirm fTCD results and further localize eloquent cortex.

Adult↗
PubMed2004

Contributions of sensory input, auditory search and verbal comprehension to cortical activity during speech processing.

We studied eight normal subjects in an fMRI experiment where they listened to natural speech sentences and to matched simple or complex speech envelope noises. Neither of the noises (simple or complex) were understood initially, but after the corresponding natural speech sentences had been heard, comprehension was close to perfect for the complex but still absent for the simple speech envelope noises. This setting thus involved identical stimuli that were understood or not and permitted to identify (i) a neural substrate of speech comprehension unconfounded by stimulus acoustic properties (common to natural speech and complex noises), (ii) putative correlates of auditory search for phonetic cues in noisy stimuli (common to simple and complex noises once the matching natural speech had been heard) and (iii) the cortical regions where speech comprehension and auditory search interact. We found correlates of speech comprehension in bilateral medial (BA21) and inferior (BA38 and BA38/21) temporal regions, whereas acoustic feature processing occurred in more dorsal temporal regions. The left posterior superior temporal cortex (Wernicke's area) responded to the acoustic complexity of the stimuli but was additionally sensitive to auditory search and speech comprehension. Attention was associated with recruitment of the dorsal part of Broca's area (BA44) and interaction of auditory attention and comprehension occurred in bilateral insulae, the anterior cingulate and the right medial frontal cortex. In combination, these results delineate a neuroanatomical framework for the functional components at work during natural speech processing, i.e. when comprehension results from concurrent acoustic processing and effortful auditory search.

Acoustic Stimulation↗
PubMed2003

EEG-correlated fMRI of human alpha activity.

Electroencephalography-correlated functional magnetic resonance imaging (EEG/fMRI) can be used to identify blood oxygen level-dependent (BOLD) signal changes associated with both physiological and pathological EEG events. Here, we implemented continuous and simultaneous EEG/fMRI to identify BOLD signal changes related to spontaneous power fluctuations in the alpha rhythm (8-12 Hz), the dominant EEG pattern during relaxed wakefulness. Thirty-two channels of EEG were recorded in 10 subjects during eyes-closed rest inside a 1.5-T magnet resonance (MR) scanner using an MR-compatible EEG recording system. Functional scanning by echoplanar imaging covered almost the entire cerebrum every 4 s. Off-line MRI artifact subtraction software was applied to obtain continuous EEG data during fMRI acquisition. The average alpha power over 1-s epochs was derived at several electrode positions using a Fast Fourier Transform. The power time course was then convolved with a canonical hemodynamic response function, down-sampled, and used for statistical parametric mapping of associated signal changes in the image time series. At all electrode positions studied, a strong negative correlation of parietal and frontal cortical activity with alpha power was found. Conversely, only sparse and nonsystematic positive correlation was detected. The relevance of these findings is discussed in view of the current theories on the generation and significance of the alpha rhythm and the related functional neuroimaging findings.

Adult↗
PubMed2001

Perfusion imaging using spin-labeling methods: contrast-to-noise comparison in functional MRI applications.

In this study the performance of FLASH imaging with selective inversion preparation for functional perfusion studies was investigated. In addition to the absolute quantification of perfusion by measurement of the longitudinal relaxation times with global (T(1glob)) and selective (T(1sel)) inversion, the measurement of absolute (BASE) and relative (FAIR) perfusion increases by subtraction of appropriately weighted images was also considered. The subject averages of absolute perfusion obtained by the quantitative method were 70.7 +/- 4.0 ml/100g/min in gray matter, 10.2 +/- 3.4 ml/100g/min in white matter, and 89.0 +/- 3.1 ml/100g/min in visual cortex. These values, as well as the average increase of perfusion due to visual stimulation (44.4 +/- 3.7 ml/100g/min), agree well with respective data reported by PET and other MRI studies. However, for individual subjects the standard deviations over single ROIs inside the visual cortex lay around 100% which prevented the detection of significant activation. BASE and FAIR, on the other hand, were able to detect significant activation in single subjects. The measured average perfusion increases were 51.7 +/- 6.6 ml/100g/min and 56.5 +/- 13.8%, respectively. Magn Reson Med 46:172-182, 2001.

Adult↗
PubMed2001

Fast three-dimensional sodium imaging of human brain.

A three-dimensional sodium imaging technique with a minimum echo time of 0.9 ms is described in a 2.0 Tesla whole-body system. The relaxation behaviour in vivo of sodium was analysed: a fast T(2)(*) relaxation component between 1.2 and 1.6 ms and a slow T(2)(*) relaxation component between 7.1 ms and 8.4 ms were quantified in brain tissue of three volunteers. Three-dimensional sodium images of the human brain were acquired in 8.5 min with a resolution of 4.7 x 4.7 x 10 mm (0.2 cc voxel size) and a signal-to-noise ratio of 20 in brain tissue and 30 in cerebrospinal fluid.

Biophysics↗
PubMed2001

Cerebral activation patterns in patients with writer's cramp: a functional magnetic resonance imaging study.

Functional MRI (fMRI), visualizing changes in cerebral blood oxygenation, has to date not been performed either in patients with writer's cramp or in healthy subjects during writing. We compared the cerebral and cerebellar activation pattern of 12 patients with writer's cramp during writing with a group of 10 healthy subjects performing the same tasks over 30-s periods of rest or writing. Sixty echo planar imaging multislice datasets were analysed using SPM96 software. Data were analysed for each subject individually and groupwise for patients vs. controls. Healthy subjects showed a significant activation of the ipsilateral dentate nucleus, contralateral cerebellar hemisphere, contralateral primary sensorimotor cortex, and contralateral precentral gyrus during writing. Patients with writer's cramp showed significantly greater activation of the ipsilateral cerebellar hemisphere than controls. Also the activation in the primary sensorimotor cortex extended further caudally and anteriorly towards the premotor association area. Activation was observed in the thalamus during writing only among the patients. Our results indicate an increased basal ganglia output via the thalamus to the motor and premotor cortical areas in dystonia patients and support the notion of disinhibition of the motor cortex leading to cocontractions and dystonic postures.

Adult↗
PubMed2000

Cerebral activation pattern in primary writing tremor.

OBJECTIVE: To compare the cerebral activation pattern during writing of patients with writing tremor with healthy controls using functional MRI METHODS: Three patients with writing tremor and 10 healthy controls were examined using a 1.5 Tesla scanner. All subjects performed a paradigm of alternating 30 second periods of rest or writing. For functional imaging 60 EPI multislice data sets were acquired. All images were analyzed using SPM96 software. Data were analyzed for the group of patients with writing tremor and compared with those of the control group. RESULTS: Both patients with writing tremor and controls showed a significant activation of the contralateral primary sensorimotor cortex, SMA, and area 44. By contrast, motor cortex activation in writing tremor also included the contralateral premotor area (area 6) and ipsilateral prefrontal area (inferior frontal gyrus; areas 10, 44, and 47). Only patients with writing tremor showed a bilateral activation of the parietal lobule (area 40) with a more pronounced activation on the contralateral side. Furthermore, there was a bilateral activation of the cerebellum with a more pronounced area of activation on the ipsilateral side. CONCLUSIONS: Brain areas activated in writing tremor included activation patterns otherwise typical for both essential tremor and writer's cramp. Therefore a distinct category for writing tremor integrating hallmarks of essential tremor and writer's cramp is proposed.

Adult↗
PubMed1999

Functional MR imaging of the human brain using FLASH: influence of various imaging parameters.

In this study the influence of a large variety of imaging parameters on the signal increase (DeltaS) and the contrast-to-noise ratio (CNR) of functional magnetic resonance imaging experiments was determined using FLASH imaging at 2 T. During visual stimulation of the brain we detected significant variations of DeltaS as a function of the echo time (30 ms: 3.5 +/- 0.4%, 60 ms: 6.8 +/- 0.7%), slice thickness (2.5 mm: 6.8 +/- 0.7%, 10.0 mm: 3.3 +/- 0.3%), and pixel size (4.69 mm: 3.1 +/- 0.3%, 1.88 mm: 5.9 +/- 0.5%). Significant changes of DeltaS with flip angle occurred for TE = 20 ms (15 degrees : 2.1 +/- 0.2%, 60 degrees : 3.2 +/- 0.5%). At TE = 30 ms there still was a slight increase (15 degrees : 3.0 +/- 0.4%, 60 degrees : 3.8 +/- 0.5%), while at TE = 50 ms no changes of DeltaS could be detected with flip angle. Furthermore, DeltaS decreased with the use of first-order flow and motion compensation (off: 5.8 +/- 0.6%, on: 4.5 +/- 0.5%). The purpose of this study was to identify the optimal imaging parameters for blood oxygenation level dependent contrast using FLASH imaging at 2 T. Relying on a time normalized contrast-to-noise ratio (CNR(n)) we found the following parameters to be optimal: TE approximately 40-50 ms, a rather low spatial resolution (slice thickness approximately 5.0-7.5 mm, pixel size approximately 2.3-4.6 mm, matrix size 64 x 48), and flip angles lower than 30 degrees. Flow compensation should not be applied, and a rather low bandwidth of approximately 2.5 kHz is favorable, as it yields a superior signal-to-noise ratio.

Adult↗
PubMedDate not supplied

Noninvasive direct stimulation of the cochlear nerve for functional MR imaging of the auditory cortex.

We herein present our preliminary experience with functional MR imaging of the direct electrical stimulation of the cochlear nerve using an MR imaging-compatible electrode placed in the external auditory meatus of five patients with binaural sensorineural hearing loss. The stimulator was placed outside the imager's bore, and the electrode produced virtually no susceptibility artifacts. In three of five patients, it was possible to activate the superior temporal gyrus during functional MR imaging. No side effects were observed.

Auditory Cortex↗