Transcranial focal electrical stimulation via tripolar concentric ring electrodes does not modify the short- and long-term memory formation in rats evaluated in the novel object recognition test.

Noninvasive transcranial focal electrical stimulation (TFS) via tripolar concentric ring electrodes (TCREs) has been under development as an alternative/complementary therapy for seizure control. Transcranial focal electrical stimulation has shown efficacy in attenuating penicillin-, pilocarpine-, and pentylenetetrazole-induced acute seizures in rat models. This study evaluated the effects of TFS via TCREs on the memory formation of healthy rats as a safety test of TFS. Short- and long-term memory formation was tested after the application of TFS using the novel object recognition (NOR) test. The following independent groups were used: naïve, control (without TFS), and TFS (treated). The naïve, control, and stimulated groups spent more time investigating the new object than the familiar one during the test phase. Transcranial focal electrical stimulation via TCREs given once does not modify the short- and long-term memory formation in rats in the NOR test. Results provide an important step towards a better understanding for the safe usage of TFS via TCREs.

Fractionated premotor, motor, and ankle dorsiflexion reaction times in hemiplegia.

Ten hemiplegic subjects completed 20 rapid dorsiflexions of their afflicted and nonafflicted limbs. Electrodes were attached to the tibialis anterior and the gastrocnemius muscles and electromyograms were recorded for their premotor time, motor time, and simple reaction time during ankle dorsiflexion and plantar flexion of their lower limbs. The fractionated components of reaction time, namely, premotor time and motor time, of both legs were statistically compared. It was found that the premotor time of the subject's stroke-affected limb was significantly slower than the premotor time of the nonaffected limb (control), with no differences between their associated mean motor times. These results supported the hypothesis that a stroke has a deleterious affect upon the central, premotor time processing centers and has no disruptive influence upon the peripheral motor time. Comparing the fractionated components of reaction time (premotor time and motor time), with simple reaction time, the former provided a more sensitive and valid method to detect possible injurious side effects of a stroke upon the brain's neuromotor transmission centers and subcenters, and their peripheral, stimulus, response network.

Effects of transcranial focal electrical stimulation via tripolar concentric ring electrodes on pentylenetetrazole-induced seizures in rats.

PURPOSE: To study the effects of noninvasive transcranial focal electrical stimulation (TFS) via tripolar concentric ring electrodes (TCRE) on the electrographic and behavioral activity from pentylenetetrazole (PTZ)-induced seizures in rats. METHODS: The TCREs were attached to the rat scalp. PTZ was administered and, after the first myoclonic jerk was observed, TFS was applied to the TFS treated group. The electroencephalogram (EEG) and behavioral activity were recorded and studied. RESULTS: In the case of the TFS treated group, after TFS, there was a significant (p=0.001) decrease in power compared to the control group in delta, theta, and alpha frequency bands. The number of myoclonic jerks was significantly different (p=0.002) with median of 22 and 4.5 for the control group and the TFS treated groups, respectively. The duration of myoclonic activity was also significantly different (p=0.031) with median of 17.56 min for the control group versus 8.63 min for the TFS treated group. At the same time there was no significant difference in seizure onset latency and maximal behavioral seizure activity score between control and TFS treated groups. CONCLUSIONS: TFS via TCREs interrupted PTZ-induced seizures and electrographic activity was reduced toward the "baseline." The significantly reduced electrographic power, number of myoclonic jerks, and duration of myoclonic activity of PTZ-induced seizures suggests that TFS may have an anticonvulsant effect.

Ischemia-reperfusion impairs blood-brain barrier function and alters tight junction protein expression in the ovine fetus.

The blood-brain barrier is a restrictive interface between the brain parenchyma and the intravascular compartment. Tight junctions contribute to the integrity of the blood-brain barrier. Hypoxic-ischemic damage to the blood-brain barrier could be an important component of fetal brain injury. We hypothesized that increases in blood-brain barrier permeability after ischemia depend upon the duration of reperfusion and that decreases in tight junction proteins are associated with the ischemia-related impairment in blood-brain barrier function in the fetus. Blood-brain barrier function was quantified with the blood-to-brain transfer constant (K(i)) and tight junction proteins by Western immunoblot in fetal sheep at 127 days of gestation without ischemia, and 4, 24, or 48 h after ischemia. The largest increase in K(i) (P<0.05) was 4 h after ischemia. Occludin and claudin-5 expressions decreased at 4 h, but returned toward control levels 24 and 48 h after ischemia. Zonula occludens-1 and -2 decreased after ischemia. Inverse correlations between K(i) and tight junction proteins suggest that the decreases in tight junction proteins contribute to impaired blood-brain barrier function after ischemia. We conclude that impaired blood-brain barrier function is an important component of hypoxic-ischemic brain injury in the fetus, and that increases in quantitatively measured barrier permeability (K(i)) change as a function of the duration of reperfusion after ischemia. The largest increase in permeability occurs 4 h after ischemia and blood-brain barrier function improves early after injury because the blood-brain barrier is less permeable 24 and 48 than 4 h after ischemia. Changes in the tight junction molecular composition are associated with increases in blood-brain barrier permeability after ischemia.

Algorithm for automatic detection of pentylenetetrazole-induced seizures in rats.

Epilepsy affects approximately one percent of the world population. Antiepileptic drugs are ineffective in approximately 30% of patients and have side effects. We are developing a noninvasive, or minimally invasive, transcranial focal electrical stimulation (TFS) system through our novel concentric ring electrodes to control seizures. Here we report on the development of a seizure detecting algorithm to be used for automatic application of TFS. A cumulative sum (CUSUM) algorithm was evaluated that detected the electrographic seizure activity in all experiments well in advance of the behavioral seizure activity.

An optimal spatial filtering electrode for brain computer interface.

There are millions of people in the U.S. and many more worldwide who could benefit from a noninvasive-based electroencephalography (EEG) brain computer interface (BCI). A BCI is an alternative or augmentative communication method for people with severe motor disabilities. However, EEG suffers from poor spatial resolution and signal-to-noise ratio (SNR). To improve the spatial resolution and SNR many researchers have turned to implantable electrodes. We have previously reported on significant improvements in BCI recognition rates using tripolar concentric ring electrodes compared to disc electrodes. We now report on a optimal method for combining the outputs from the independent elements of the tripolar concentric ring electrodes to improve the spatial resolution further. We used minimum variance distortionless look (MVDL), a beamformer, on simulated data to compare the spatial sensitivity of the optimal combination to disc electrodes and the tripolar concentric ring electrode surface Laplacian. The optimal combination shows the highest spatial sensitivity with the Laplacian a close second and disc electrodes resulting in a distant third. Further analysis is necessary with a more realistic computer model and then real signals. however it appears that the optimal combination may improve the spatial resolution of EEG further which in turn can be utilized to improve noninvasive EEG-based BCIs.