Biomedical subjects

C Stippich

Publications and source records attributed to C Stippich.

25 records · Page 2Linked to original sources

PubMed2000

Fast temporal interactions in human auditory cortex.

The temporal resolution of the human primary auditory cortex (AC) was studied using middle-latency evoked fields. Paired sounds with either the same or different spectral characteristics were presented with gaps between the sounds of 1, 4, 8 and 14 ms. Spatio-temporal modelling showed (1) that the response to the second sound was recognizable with gaps of 1 ms and rapidly increased in amplitude with increasing gap durations, (2) an enhanced N40m amplitude at gaps > 4 ms, (3) delayed N19m-P30m latencies when the stimuli were different. The median psychoacoustical thresholds were 1.6 ms for the same stimuli and 2.5 ms for different stimuli, confirming the electrophysiological evidence for rapid pattern-specific temporal processing in human primary auditory cortex.

Acoustic Stimulation↗

PubMed2000

Time course of focal slow wave activity in transient ischemic attacks and transient global amnesia as measured by magnetoencephalography.

In this longitudinal study multichannel MEG was used to localize and to quantify focal pathological spontaneous neuromagnetic activity in six patients with transient ischemic attacks (TIA) and two patients with transient global amnesia (TGA). Slow (2-6 Hz) and beta (14-30 Hz) activity were monitored up to 10 weeks. Results were compared with normative data, and changes over time were statistically analyzed. MEG detected pathological activity that persisted clinical symptoms. Focal slow activity originating from sensorimotor (TIA) and mesiotemporal (TGA) cortices exceeded normal values up to 14 times during the first hours after the attack and recovered to normal within 11 days. Focal beta activity was not useful to monitor the time course of TIA or TGA.

Aged↗

PubMed2000

Magnetic source imaging of tactile input shows task-independent attention effects in SII.

We investigated whether attention to different stimulus attributes (location, intensity) has different effects on the activity of the secondary (SII) somatosensory cortex. Tactile stimuli were applied to the left index finger and somatosensory evoked fields (SEFs) were recorded using a whole-head magnetoencephalography (MEG) system. Two oddball paradigms with stimuli varying in location or intensity were performed in an ignore and an attend condition. Brain sources were estimated by magnetic source imaging. No attention effect was observed for the primary SI area. However, attention enhanced SII activity bilaterally from 55 to 130 ms by 52% in the spatial and 64% in the intensity discrimination task. SII attentional enhancement was very similar in both paradigms and occurred both for deviants and standards.

Adult↗

PubMed2000

Robust localization of the contralateral precentral gyrus in hemiparetic patients using the unimpaired ipsilateral hand: a clinical functional magnetic resonance imaging protocol.

Tumor related contralateral motor deficits complicate preoperative functional magnetic resonance imaging (fMRI). In plegic patients the localization of the sensorimotor cortex is often impossible. In this context we developed a clinical fMRI protocol dedicated to patients with motor deficits using the unaffected ipsilateral hand. Based on the hypothesis that selfpaced finger movements recruit more and larger neuronal populations with rising task complexity, different motor tasks were tested regarding ipsilateral localization in ten right handed volunteers. Complex finger opposition localized the ipsilateral premotor cortex (Brodman area 6) robustly and was introduced to preoperative fMRI in hemiparetic patients as functional landmark to identify the precentral gyrus on the tumors side. Additional contralateral automated tactile stimulation localized the primary somatosensory cortex and completed the protocol.

Adult↗

PubMed1999

Somatotopic mapping of the human primary somatosensory cortex by fully automated tactile stimulation using functional magnetic resonance imaging.

The clinical application of functional magnetic resonance imaging (fMRI) requires time-saving protocols insensitive to artifacts that provide robust localization and important information on brain function. A fully automated, pneumatically driven tactile stimulation is presented, that reproducibly localizes postcentral lip, finger and toe representations in contralateral primary somatosensory cortex (SI) with mean correlation coefficients (cc) and relative BOLD signal changes (dS) of cc approximately 0.59, dS approximately 1.95% (fingers); cc approximately 0.52, dS approximately 1.35% (lips); cc approximately 0.47, dS approximately 1.42% (toes). Bilateral somatotopic mapping requires 21 min of scanning time and has become a clinical routine fMRI application in patients with perirolandic tumors. Normative data may also be useful in monitoring cerebral plasticity and reorganization, e.g. in sensorimotor recovery after cerebral ischemia or in understanding mechanisms of supraspinal pain processing.

Adult↗

PubMed1999

Focal slow and beta brain activity in patients with multiple sclerosis revealed by magnetoencephalography.

In multiple sclerosis (MS) inflammatory infiltrations cause white matter lesions. Magnetoencephalography (MEG) offers the opportunity to localize abnormal electric activity of neurons with a high spatio-temporal resolution. In this study, we investigated patients with MS in order to find if abnormal cortical activity is associated with (subcortical) MS lesions using simultaneous bilateral recording of biomagnetic activity. Eight patients suffering from definite laboratory-supported MS with mainly somatosensory deficits and multiple bihemispheric plaques revealed by MRI were included in the study. To obtain normative data, 8 healthy volunteers were investigated following the same measuring protocol. Spontaneous magnetic brain activity was recorded using a 2x37-channel biomagnetic system (BTI, USA). Offline analysis included digital filtering (to separately investigate slow and beta wave activity), a Principle Component Analysis and the Dipole Density Plot. Localization results were inserted into MR images using our contour fit procedure. The dipole distribution in the brain was quantified and compared between the groups by statistical analysis. In all MS patients, the maximum of focal abnormal activity was localized in cortical areas adjacent to the fiber lesions. In the healthy subjects, no focal abnormal brain activity could be found. However, the standardized maximum concentrations of dipoles were significantly higher in the MS patients than in the healthy control group both in the slow and in the beta wave analysis. These results let assume that subcortical lesions can occur together with abnormal cortical neuronal activity. The results are discussed in respect to their impact on the interpretation of the analysis of spontaneous magnetic brain activity.

Adolescent↗

PubMed1998

Motor, somatosensory and auditory cortex localization by fMRI and MEG.

Functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG) were performed in six subjects during self-paced finger movement performance, tactile somatosensory stimulation and binaural auditory stimulation using identical stimulation paradigms. Both functional imaging modalities localized brain activity in adjacent areas of anatomically correct cortex. The mean distances measured between fMRI activity and the corresponding MEG dipoles were 10.1 mm (motor), 10.7 mm (somatosensory), 13.5 mm (auditory right hemisphere) and 14.3 mm (auditory left hemisphere). The distances found may reflect the correlation between electrophysiological and hemodynamic responses due to the different underlying substrates of neurophysiology measured by fMRI and MEG: BOLD contrast vs neuronal biomagnetic activity.

Adult↗