Joseph Classen

Bio: Joseph Classen is an academic researcher from Leipzig University. The author has contributed to research in topics: Transcranial magnetic stimulation & Motor cortex. The author has an hindex of 59, co-authored 206 publications receiving 16737 citations. Previous affiliations of Joseph Classen include Max Planck Society & National Institutes of Health.

Depression of motor cortex excitability by low-frequency transcranial magnetic stimulation.

Abstract: We studied the effects of low-frequency transcranial magnetic stimulation (TMS) on motor cortex excitability in humans. TMS at 0.1 Hz for 1 hour did not change cortical excitability. Stimulation at 0.9 Hz for 15 minutes (810 pulses), similar to the parameters used to induce long-term depression (LTD) in cortical slice preparations and in vivo animal studies, led to a mean decrease in motor evoked potential (MEP) amplitude of 19.5%. The decrease in cortical excitability lasted for at least 15 minutes after the end of the 0.9 Hz stimulation. The mechanism underlying this decrease in excitability may be similar to LTD. TMS-induced reduction of cortical excitability has potential clinical applications in diseases such as epilepsy and myoclonus. Spread of excitation, which may be a warning sign for seizures, occurred in one subject and was not accompanied by increased MEP amplitude, suggesting that spread of excitation and amplitude changes are different phenomena and also indicating the need for adequate monitoring even with stimulations at low frequencies.

Induction of plasticity in the human motor cortex by paired associative stimulation.

Abstract: Current models of motor cortical plasticity, developed in studies on experimental animals, emphasize the importance of the conjoint activity of somatosensory afferents and intrinsic motor cortical circuits. The hypothesis that an enduring change in excitability in the cortical output circuitry can be induced in the human motor cortex by a paired-stimulation protocol was tested. Low-frequency median nerve stimulation was paired with transcranial magnetic stimulation (TMS) over the optimal cranial site for stimulating the abductor pollicis brevis muscle (APB). This protocol induced an increase in the amplitudes of the motor evoked potentials (MEPs) in the resting APB as well as a prolongation of the silent period measured in the precontracted APB following TMS; amplitudes of MEPs measured in voluntary contraction remained unchanged. Experiments testing the excitability of spinal motoneurons using F-wave studies and electrical stimulation of the brainstem suggested that the site of the plastic changes was within the motor cortex. The increases in resting amplitudes and silent period duration were conditionally dependent on the timing between the afferent and the magnetic stimulation in that they were present when events elicited by afferent and magnetic stimulation were synchronous at the level of the motor cortex. Plasticity induced by paired stimulation evolved rapidly (within 30 min), was persistent (minimum duration 30-60 min) yet reversible, and was topographically specific. This combination of features and the similarity to properties of induced enduring changes in synaptic efficacy, as elucidated in animal studies, leads us to propose that the induced plasticity may represent a signature of associative long-term potentiation of cortical synapses or closely related neuronal mechanisms in the human cortex.

Rapid Plasticity of Human Cortical Movement Representation Induced by Practice

Abstract: Classen, Joseph, Joachim Liepert, Steven P. Wise, Mark Hallett, and Leonardo G. Cohen. Rapid plasticity of human cortical movement representation induced by practice. J. Neurophysiol. 79: 1117–1123...

Differential effects on motorcortical inhibition induced by blockade of GABA uptake in humans

Abstract: 1Blockade of uptake carriers of γ-aminobutyric acid (GABA) has been shown to modulate inhibition in cortical slices of experimental animals, although little is known about this mechanism in vivo and, in particular, in humans. 2The effects of blockade of GABA uptake were studied using transcranial magnetic stimulation (TMS) in humans. In eight healthy volunteers several measures of cortical excitation and inhibition were obtained before and ≈2 h after ingestion of 5-15 mg of tiagabine (TGB). 3After TGB ingestion, the duration of the TMS-induced silent period observable in the electromyogram of the voluntarily contracted target muscle was prolonged. Similarly, paired-pulse inhibition of the motor-evoked potential (MEP), as tested by delivering two magnetic shocks of equal suprathreshold intensities at 160 ms interstimulus interval (ISI), was more pronounced. In apparent contradistinction, paired-pulse inhibition of the MEPs produced by a subthreshold conditioning stimulus delivered 3 ms prior to a suprathreshold stimulus was reduced. Paired-pulse facilitation elicited by the same double-shock protocol at an ISI of 10 ms was increased. 4The prolongation of the GABAB receptor-mediated component of the inhibitory postsynaptic potential observed with TGB in in vitro studies probably underlies the increase in cortical silent period duration. The reduction of the paired-pulse inhibition at 3 ms, in turn, probably reflects inhibition of GABAA receptor-mediated inhibition via presynaptic GABAB receptors. 5These data provide in vivo evidence of differential modulation of cortical inhibition by blockade of GABA uptake. Presynaptic GABA autoreceptors may be involved in modulating cortical inhibition in the human motor cortex.

Mechanisms of use-dependent plasticity in the human motor cortex

Abstract: Practicing movements results in improvement in performance and in plasticity of the motor cortex. To identify the underlying mechanisms, we studied use-dependent plasticity in human subjects premedicated with drugs that influence synaptic plasticity. Use-dependent plasticity was reduced substantially by dextromethorphan (an N-methyl-d-aspartate receptor blocker) and by lorazepam [a γ-aminobutyric acid (GABA) type A receptor-positive allosteric modulator]. These results identify N-methyl-d-aspartate receptor activation and GABAergic inhibition as mechanisms operating in use-dependent plasticity in intact human motor cortex and point to similarities in the mechanisms underlying this form of plasticity and long-term potentiation.

Principles of Neural Science

Abstract: I have developed "tennis elbow" from lugging this book around the past four weeks, but it is worth the pain, the effort, and the aspirin. It is also worth the (relatively speaking) bargain price. Including appendixes, this book contains 894 pages of text. The entire panorama of the neural sciences is surveyed and examined, and it is comprehensive in its scope, from genomes to social behaviors. The editors explicitly state that the book is designed as "an introductory text for students of biology, behavior, and medicine," but it is hard to imagine any audience, interested in any fragment of neuroscience at any level of sophistication, that would not enjoy this book. The editors have done a masterful job of weaving together the biologic, the behavioral, and the clinical sciences into a single tapestry in which everyone from the molecular biologist to the practicing psychiatrist can find and appreciate his or

The mirror-neuron system.

Abstract: A category of stimuli of great importance for primates, humans in particular, is that formed by actions done by other individuals. If we want to survive, we must understand the actions of others. Furthermore, without action understanding, social organization is impossible. In the case of humans, there is another faculty that depends on the observation of others' actions: imitation learning. Unlike most species, we are able to learn by imitation, and this faculty is at the basis of human culture. In this review we present data on a neurophysiological mechanism--the mirror-neuron mechanism--that appears to play a fundamental role in both action understanding and imitation. We describe first the functional properties of mirror neurons in monkeys. We review next the characteristics of the mirror-neuron system in humans. We stress, in particular, those properties specific to the human mirror-neuron system that might explain the human capacity to learn by imitation. We conclude by discussing the relationship between the mirror-neuron system and language.

2016 ESC Guidelines for the management of atrial fibrillation developed in collaboration with EACTS

Abstract: The Task Force for the management of atrial fibrillation of the European Society of Cardiology (ESC) Developed with the special contribution of the European Heart Rhythm Association (EHRA) of the ESC Endorsed by the European Stroke Organisation (ESO)