TY  - JOUR
A1  - Deane, Katrina E.
A1  - Brunk, Michael G. K.
A1  - Curran, Andrew W.
A1  - Zempeltzi, Marina M.
A1  - Ma, Jing
A1  - Lin, Xiao
A1  - Abela, Francesca
A1  - Aksit, Sümeyra
A1  - Deliano, Matthias
A1  - Ohl, Frank W.
A1  - Happel, Max F. K.
T1  - Ketamine anaesthesia induces gain enhancement via recurrent excitation in granular input layers of the auditory cortex
JF  - The Journal of Physiology
N2  - Ketamine is commonly used as an anaesthetic agent and has more recently gained attention as an antidepressant. It has been linked to increased stimulus‐locked excitability, inhibition of interneurons and modulation of intrinsic neuronal oscillations. However, the functional network mechanisms are still elusive. A better understanding of these anaesthetic network effects may improve upon previous interpretations of seminal studies conducted under anaesthesia and have widespread relevance for neuroscience with awake and anaesthetized subjects as well as in medicine. Here, we investigated the effects of anaesthetic doses of ketamine (15 mg kg\(^{-1}\) h\(^{-1}\)i.p.) on the network activity after pure‐tone stimulation within the auditory cortex of male Mongolian gerbils (Meriones unguiculatus). We used laminar current source density (CSD) analysis and subsequent layer‐specific continuous wavelet analysis to investigate spatiotemporal response dynamics on cortical columnar processing in awake and ketamine‐anaesthetized animals. We found thalamocortical input processing within granular layers III/IV to be significantly increased under ketamine. This layer‐dependent gain enhancement under ketamine was not due to changes in cross‐trial phase coherence but was rather attributed to a broadband increase in magnitude reflecting an increase in recurrent excitation. A time–frequency analysis was indicative of a prolonged period of stimulus‐induced excitation possibly due to a reduced coupling of excitation and inhibition in granular input circuits – in line with the common hypothesis of cortical disinhibition via suppression of GABAergic interneurons.
KW  - auditory cortex
KW  - continuous wavelet analysis
KW  - current source density
KW  - ketamine anaesthesia
KW  - laminar recording
KW  - mesoscopic
KW  - microcircuitry
KW  - population dynamics
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-216123
VL  - 598
IS  - 13
SP  - 2741
EP  - 2755
ER  - 
TY  - JOUR
A1  - Schecklmann, Martin
A1  - Giani, Anette
A1  - Tupak, Sara
A1  - Langguth, Berthold
A1  - Raab, Vincent
A1  - Polak, Thomas
A1  - Varallyay, Csanad
A1  - Harnisch, Wilma
A1  - Herrmann, Martin J.
A1  - Fallgatter, Andreas J.
T1  - Functional Near-Infrared Spectroscopy to Probe State- and Trait-Like Conditions in Chronic Tinnitus: A Proof-of-Principle Study
JF  - Neural Plasticity
N2  - Objective. Several neuroscience tools showed the involvement of auditory cortex in chronic tinnitus. In this proof-of-principle study we probed the capability of functional near-infrared spectroscopy (fNIRS) for the measurement of brain oxygenation in auditory cortex in dependence from chronic tinnitus and from intervention with transcranial magnetic stimulation. Methods. Twenty-three patients received continuous theta burst stimulation over the left primary auditory cortex in a randomized sham-controlled neuronavigated trial (verum = 12; placebo = 11). Before and after treatment, sound-evoked brain oxygenation in temporal areas was measured with fNIRS. Brain oxygenation was measured once in healthy controls (n = 12). Results. Sound-evoked activity in right temporal areas was increased in the patients in contrast to healthy controls. Left-sided temporal activity under the stimulated area changed over the course of the trial; high baseline oxygenation was reduced and vice versa. Conclusions. By demonstrating that rTMS interacts with auditory evoked brain activity, our results confirm earlier electrophysiological findings and indicate the sensitivity of fNIRS for detecting rTMS induced changes in brain activity. Moreover, our findings of trait-and state-related oxygenation changes indicate the potential of fNIRS for the investigation of tinnitus pathophysiology and treatment response.
KW  - transcranial magnetic stimulation
KW  - positron-emission-tomography
KW  - auditory cortex
KW  - FNIRS
KW  - RTMS
KW  - neural activity
KW  - FMRI
KW  - brain
KW  - activation
KW  - humans
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-117801
SN  - 1687-5443
IS  - 894203
ER  -