Desynchronizing effect of high-frequency stimulation in a generic cortical network model

Transcranial Electrical Stimulation (TCES) and Deep Brain Stimulation (DBS) are two different applications of electrical current to the brain used in different areas of medicine. Both have a similar frequency dependence of their efficiency, with the most pronounced effects around 100Hz. We apply superthreshold electrical stimulation, specifically depolarizing DC current, interrupted at different frequencies, to a simple model of a population of cortical neurons which uses phenomenological descriptions of neurons by Izhikevich and synaptic connections on a similar level of sophistication. With this model, we are able to reproduce the optimal desynchronization around 100Hz, as well as to predict the full frequency dependence of the efficiency of desynchronization, and thereby to give a possible explanation for the action mechanism of TCES.Comment: 9 pages, figs included. Accepted for publication in Cognitive Neurodynamic

Dynamic balance training with sensory electrical stimulation in chronic stroke patients

A case study investigating the impact of sensory electrical stimulation during perturbed stance in one chronic stroke patient is presented. A special apparatus called the BalanceTrainer was used. It allows the application of perturbations to neurologically impaired people during standing, while protecting the subject from falling. The subject underwent two different periods of perturbation training, each lasting ten days. During the first period the subject was perturbed in eight different directions. During the second period the subject was also perturbed, but was assisted by sensory electrical stimulation of the soleus, tibialis anterior, tensor fascia latae, and vastus muscles in the impaired leg. After each period of training an assessment was carried out to measure the forces the subject applied on the ground via two force plates. The subject improved his ability to balance throughout the training, with the largest improvements during the final period when electrical stimulation was used

In vitro functional properties of the rat bladder regenerated by the bladder acellular matrix graft.

PurposeTo assess the response of rat urinary bladder regenerated by the homologous bladder acellular matrix graft (BAMG) to in vitro electrical and pharmacologic stimuli.Materials and methodsIn Sprague-Dawley rats, partial cystectomy (>50%) was performed, followed by BAMG augmentation cystoplasty. After 4 months, organ bath studies of tissue strips in 10 were used to compare the contractility of the BAMG regenerates and the corresponding host detrusor smooth muscle.ResultsThe BAMG regenerates exhibited contractile activity to electrical field stimulation and a qualitatively identical pattern of response to muscarinic, purinergic, alpha- and beta-adrenergic drug administration and nitric oxide. At 4 months after surgery, the maximum forces of contraction of the BAMG regenerates to carbachol stimulation amounted to close to 80% of the host bladder response. With electrical field stimulation, they equaled 44% and 62% of the host bladder response after 2.5 and 4 months, respectively. Histological and immunohistochemical studies confirmed the presence of receptors for neurotransmitters that these functional in vitro studies implied.ConclusionsThe present study provides further evidence that augmentation cystoplasty with the BAMG leads to functional regeneration of the rat bladder detrusor smooth muscle

Does the midbrain dorsolateral periaqueductal grey have direct connections with the pontine A5 region? A neuropharmacologic and electrophysiological study

This study has been performed in spontaneously breathing anesthetised rats. We have analysed the possible interactions between the midbrain dorsolateral periaqueductal grey matter (dlPAG) and the pontine A5 region. Electrical stimulations of the dlPAG (1 ms pulses, 20-30 μA given at 100 Hz for 5s) were elicited and the evoked cardiorespiratory changes were analysed before and after ipsilateral blockade of the neurotransmission within the A5 region by means of microinjections of muscimol (50 nl, 0.25 nmol, 5s). Electrical stimulations evoked the classical “defence response” characterized by tachipnoea, hypertension and tachycardia. Tachipnoea consisted of an inspiratory facilitatory response [increase in respiratory rate (p<0.001) due to a decrease in expiratory time (p<0.01)] and was accompanied by a pressor (p<0.001) and tachycardic (p<0.001) response. Muscimol microinjected within the A5 region reduced pressor (p<0.05), tachycardic (p<0.001) and tachypnoeic (p<0.001) responses evoked to dlPAG electrical stimulations. Finally, in order to assess functional interactions between A5 and dlPAG, extracellular recordings of 40 putative A5 cells during dlPAG electrical stimulation were recorded. 16 cells were affected by dlPAG stimulation (40%). 3 cells showed orthodromic activation (14.2 ± 1.7 ms). 5 cells were excited (10.1 ± 1.6 ms). 7 cells decreased spontaneous activity to dlPAG stimulation. 24 cells were not modified by dlPAG stimulation (2 presented a respiratory pattern and 1 presented a cardiovascular pattern). These results contribute with new data on the role of the A5 region neurones in the modulation of the cardiorespiratory response evoked on dlPAG stimulation.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Effect of sensory deprivation and locus coeruleus phasic electrical stimulation following the deflection of adjacent whisker on response properties of principal whisker related-neurons in layer IV of rat barrel cortex

Background: Barrel cortex of rodents is responsible for sensory information processing via facial whiskers. Locus coeruleus (LC), main source of cortical norepinephrine (NE), influences tactile sensory processing. In this study, the effect of phasic electrical stimulation of LC and sensory deprivation following the deflection of adjacent whisker on response properties of principal whisker related-neurons in layer IV of rat barrel cortex was investigated. Materials and Methods: Response properties of 18 neurons in controls and 22 neurons in sensory deprivation group (P4) were evaluated using extracellular single unit recording following the controlled deflection of adjacent whisker or before a combined deflection of principal and adjacent whiskers. All whiskers on the left muzzle, except for D2, were plucked every other day for two mounts in P4 group. In both groups, LC was stimulated at 0, 50, 100, 200, 400 and 800 ms before adjacent whisker deflection and its effect on response latency, response magnitude and CTR (Condition Test Ratio) index was assessed. Results: The mechanical deflection of adjacent whisker with no electrical stimulation of LC in P4 group caused significant decrease and increase in neuronal response magnitude and CTR index, respectively. Almost in all times of LC stimulation and following combinations of whisker deflection, LC electrical stimulation before adjacent whisker deflection in P4 group caused a decrease in neuronal response magnitude and an increase in CTR index. Conclusion: LC electrical stimulation following sensory deprivation modulates neuronal response properties and changes the response patterns