Classen. A temporally asymmetric Hebbian rule governing plasticity in the human motor cortex. J Neurophysiol 89: 2339 -2345, 2003. First published January 22, 2003 10.1152/jn.00900.2002 Synaptic plasticity is conspicuously dependent on the temporal order of the pre-and postsynaptic activity. Human motor cortical excitability can be increased by a paired associative stimulation (PAS) protocol. Here we show that it can also be decreased by minimally changing the interval between the two associative stimuli. Corticomotor excitability of the abductor pollicis brevis (APB) representation was tested before and after repetitively pairing of single right median nerve simulation with single pulse transcranial magnetic stimulation (TMS) delivered over the optimal site for activation of the contralateral APB. Following PAS, depression of TMS-evoked motor-evoked potentials (MEPs) was induced only when the median nerve stimulation preceded the TMS pulse by 10 ms, while enhancement of cortical excitability was induced using an interstimulus interval of 25 ms, suggesting an important role of the sequence of cortical events triggered by the two stimulation modalities. Experiments using F-wave studies and electrical brain stem stimulation indicated that the site of the plastic changes underlying the decrease of MEP amplitudes following PAS (10 ms) was within the motor cortex. MEP amplitudes remained depressed for approximately 90 min. The decrease of MEP amplitudes was blocked when PAS(10 ms) was performed under the influence of dextromethorphan, an N-methyl-D-aspartate-receptor antagonist, or nimodipine, an L-type voltage-gated calcium-channel antagonist. The physiological profile of the depression of human motor cortical excitability following PAS(10 ms) suggests long-term depression of synaptic efficacy to be involved. Together with earlier findings, this study suggests that strict temporal Hebbian rules govern the induction of long-term potentiation/long-term depression-like phenomena in vivo in the human primary motor cortex. I N T R O D U C T I O NActivity-dependent long-term modification of synaptic efficacy has been proposed to underlie information storage in neuronal populations. Hebb (1949) postulated that the strength of a synapse may be modulated by correlated activity of a (weak) input to a postsynaptic cell with activation of that cell, as a consequence of activity of another (strong) input to it. This principle, termed associativity, has been confirmed experimentally in numerous studies. Additionally, a stringent and surprisingly simple asymmetric temporal rule governing the direction of synaptic change has been revealed in many brain regions. With few notable exceptions (e.g., Bell et al. 1997; Egger et al. 1999; Holmgren and Zilberter 2001), it was found that associative long-term potentiation (LTP) was induced when an action potential of the postsynaptic neuron (induced by a strong input to the cell) followed the postsynaptic potential induced by a weak input. If the order of stimulation was reversed (i.e., ...

Monitoring of pH of the esophagus is a routine diagnostic procedure, whereas until now pH-monitoring of the hypopharynx has been used only for scientific research. In the present study a critical evaluation scale was used to record the results of 112 patients who underwent pH monitoring to determine possible reflux. Since high refluxes often remain unnoticed clinically, further study is required in certain cases. The extent of reflux in the esophagus may not represent pathological changes in the hypopharynx. In such cases 24-h pH monitoring of the hypopharynx can be a useful diagnostic procedure and may also help detect the pathogenesis of "gastric laryngitis".

Sarcoidosis should be considered in the differential diagnosis of inflammatory sinonasal disease, especially if the mucosa shows signs of granulation, but it should also be considered when an incidental finding of rhinosinusitis is recorded. Rhinosurgical intervention seems to be an appropriate therapy in terms of improving the symptoms of the disease, despite the prolonged period of postoperative healing and the necessity for individual treatment with medication. Following histological confirmation of the diagnosis, adequate medication and further appropriate diagnostic procedures drawing on internal medicine are essential.

We treated 64 patients with the diagnosis of laryngitis gastrica with Antra (Omeprazol) in doses of 10, 20, and 40 mg. To determine the success of the therapy, pH monitoring of the esophagus and hypopharynx, the voice status and measurement of vocal penetrating capacity were used. The results prove that a 20-mg dose of Antra is suitable for the therapy of laryngitis gastrica with a high rate of success. Problems which arose during the investigation, consequent changes of the original concept of the project as well as new aspects and questions which resulted from this are discussed with respect to further investigation.

Rupture of the round window membrane as a special cause of inner ear deafness is widely accepted after changing pressure levels, e.g. in diving. However, even without a barotrauma before, the spontaneous rupture of the round window membrane is suspected occasionally in patients with sudden hearing loss and/or vertigo and tinnitus. To carry through the tympanotomy is decided by ENT surgeons often in cases of progressive hearing loss despite infusion therapy. Perilymph fistulas have been detected relatively seldom, compared to the number of reported operations by several authors. However, covering the round niche with connective tissue leads to the improvement of symptoms sometimes even in cases without microscopical evidence of fistula. Within the last 3 years 14 patients suffering sudden hearing loss of one ear underwent tympanotomy in our department. Of these patients 8 reached restitution of the hearing ability. Especially 2 patients with sudden deafness caused by spontaneous rupture of the round window membrane are reported in the following article. Perilymph fistulas were detected in these cases by IV-application of fluorescein and fluorescence endoscopy of the middle ear. Both patients obtained a normal hearing curve within 1 week after surgical intervention and obliteration of the round niche.