Low-intensity Stimulation Research Articles

Does hearing in response to soft-tissue stimulation involve skull vibrations? A within-subject comparison between skull vibration magnitudes and hearing thresholds

Hearing can be elicited in response to bone as well as soft-tissue stimulation. However, the underlying mechanism of soft-tissue stimulation is under debate. It has been hypothesized that if skull vibrations were the underlying mechanism of hearing in response to soft-tissue stimulation, then skull vibrations would be associated with hearing thresholds. However, if skull vibrations were not associated with hearing thresholds, an alternative mechanism is involved. In the present study, both skull vibrations and hearing thresholds were assessed in the same participants in response to bone (mastoid) and soft-tissue (neck) stimulation. The experimental group included five hearing-impaired adults in whom a bone-anchored hearing aid was implanted due to conductive or mixed hearing loss. Because the implant is exposed above the skin and has become an integral part of the temporal bone, vibration of the implant represented skull vibrations. To ensure that middle-ear pathologies of the experimental group did not affect overall results, hearing thresholds were also obtained in 10 participants with normal hearing in response to stimulation at the same sites. We found that the magnitude of the bone vibrations initiated by the stimulation at the two sites (neck and mastoid) detected by the laser Doppler vibrometer on the bone-anchored implant were linearly related to stimulus intensity. It was therefore possible to extrapolate the vibration magnitudes at low-intensity stimulation, where poor signal-to-noise ratio limited actual recordings. It was found that the vibration magnitude differences (between soft-tissue and bone stimulation) were not different than the hearing threshold differences at the tested frequencies. Results of the present study suggest that bone vibration magnitude differences can adequately explain hearing threshold differences and are likely to be responsible for the hearing sensation. Thus, the present results support the idea that bone and soft-tissue conduction could share the same underlying mechanism, namely the induction of bone vibrations. Studies with the present methodology should be continued in future work in order to obtain further insight into the underlying mechanism of activation of the hearing system.

Ongoing brain rhythms shape I-wave properties in a computational model

BackgroundResponses to transcranial magnetic stimulation (TMS) are notoriously variable. Previous studies have observed a dependence of TMS-induced responses on ongoing brain activity, for instance sensorimotor rhythms. This suggests an opportunity for the development of more effective stimulation protocols through closed-loop TMS-EEG. However, it is not yet clear how features of ongoing activity affect the responses of cortical circuits to TMS. Objective/HypothesisHere we investigate the dependence of TMS-responses on power and phase of ongoing oscillatory activity in a computational model of TMS-induced I-waves. MethodsThe model comprises populations of cortical layer 2/3 (L2/3) neurons and a population of cortical layer 5 (L5) neurons and generates I-waves in response to TMS. Oscillatory input to the L2/3 neurons induces rhythmic fluctuations in activity of L5 neurons. TMS pulses are simulated at different phases and amplitudes of the ongoing rhythm. ResultsThe model shows a robust dependence of I-wave properties on phase and power of ongoing rhythms, with the strongest response occurring for TMS at maximal L5 depolarization. The amount of phase-modulation depends on stimulation intensity, with stronger modulation for lower intensity. ConclusionThe model predicts that responses to TMS are highly variable for low stimulation intensities if ongoing brain rhythms are not taken into account. Closed-loop TMS-EEG holds promise for obtaining more reliable TMS effects.

LOW-INTENSITY PULSED ULTRASOUND STIMULATION ON ATRIAL GANGLION PLEXUS PROTECTS THE HEART FROM ACUTE MYOCARDIAL ISCHEMIA/REPERFUSION IN A CANINE MODEL

Our previous study showed that atrial ganglion plexus electrical stimulation (GPES) protects the heart from acute ischemia/reperfusion injury (MIRI) canine model. Low-intensity pulsed ultrasound stimulation (LIPUS) has been demonstrated as a non-invasive strategy. In the present study, we aimed to

Modulation of the frontal-parietal network by low intensity anti-phase 20 Hz transcranial electrical stimulation boosts performance in the attentional blink task

Performance in the attentional blink task has been demonstrated to be directly influenced by alpha and beta neural oscillatory activity. In two experiments we stimulated the right parietal cortex and left frontal cortex with transcranial alternating current stimulation. For the first experiment we targeted only the right parietal cortex and found a non-significant increase in performance from 20 Hz stimulation. In the second experiment we applied two stimulators to the right parietal and left frontal cortex and found a significant increase in performance from 20 Hz tACS with a phase difference of 180°. Since low intensity stimulation has been shown to inhibit cortical excitability, and anti-phasic stimulation has been hypothesized to decrease presynaptic activation in one region and drive postsynaptic spikes in the other, we suggest that low intensity anti-phasic 20 Hz stimulation inhibited the parietal cortex, thereby disinhibiting the frontal cortex. This visual attention mechanism supposedly reduces processing of distractor stimuli and enhances processing of target stimuli. This study reveals that the frontal-parietal visual attention network may be modulated with low intensity 20 Hz anti-phase tACS.

Wide-pulse, high-frequency, low-intensity neuromuscular electrical stimulation has potential for targeted strengthening of an intrinsic foot muscle: a feasibility study

BackgroundStrengthening the intrinsic foot muscles is a poorly understood and largely overlooked area. In this study, we explore the feasibility of strengthening m. abductor hallucis (AH) with a specific paradigm of neuromuscular electrical stimulation; one which is low-intensity in nature and designed to interleave physiologically-relevant low frequency stimulation with high-frequencies to enhance effective current delivery to spinal motoneurones, and enable a proportion of force produced by the target muscle to be generated from a central origin. We use standard neurophysiological measurements to evaluate the acute (~ 30 min) peripheral and central adaptations in healthy individuals.MethodsThe AH in the dominant foot of nine healthy participants was stimulated with 24 × 15 s trains of square wave (1 ms), constant current (150% of motor threshold), alternating (20 Hz–100 Hz) neuromuscular electrical stimulation interspersed with 45 s rest. Prior to the intervention, peripheral variables were evoked from the AH compound muscle action potential (Mwave) and corresponding twitch force in response to supramaximal (130%) medial plantar nerve stimulation. Central variables were evoked from the motor evoked potential (MEP) in response to suprathreshold (150%) transcranial magnetic stimulation of the motor cortex corresponding to the AH pathway. Follow-up testing occurred immediately, and 30 min after the intervention. In addition, the force-time-integrals (FTI) from the 1st and 24th WPHF trains were analysed as an index of muscle fatigue. All variables except FTI (T-test) were entered for statistical analysis using a single factor repeated measures ANOVA with alpha set at 0.05.ResultsFTI was significantly lower at the end of the electrical intervention compared to that evoked by the first train (p < 0.01). Only significant peripheral nervous system adaptations were observed, consistent with the onset of low-frequency fatigue in the muscle. In most of these variables, the effects persisted for 30 min after the intervention.ConclusionsAn acute session of wide-pulse, high-frequency, low-intensity electrical stimulation delivered directly to abductor hallucis in healthy feet induces muscle fatigue via adaptations at the peripheral level of the neuromuscular system. Our findings would appear to represent the first step in muscle adaptation to training; therefore, there is potential for using WPHF for intrinsic foot muscle strengthening.

Transcutaneous nerve stimulation for pain relief during chest tube removal following cardiac surgery.

Background and Aims:In patients undergoing open heart surgery, chest tubes are removed postoperatively when patients are well awake and stable. Pain during chest tube removal can be moderate to severe and can be the worst experience of hospitalization. Various modalities of pain relief during chest tube removal have been tried with variable results. We sought to examine the effect of transcutaneous electrical nerve stimulation (TENS) as an intervention for pain relief during chest tube removal after cardiac surgery.Material and Methods:In a tertiary care center, fifty patients undergoing open heart surgery were randomized into two groups. Group TENS (n = 25) received TENS from 30 min before and continued up to 30 min after chest tube removal. Control Group (n = 25) did not receive TENS. In both the groups, additional analgesic medication was provided on demand, besides the standard analgesic regime which was injection ketorolac 30 mg intramuscularly every 8 h. Patients were studied for pain during chest drain removal and pain related nausea, vomiting, and sense of well-being.Results:Mean visual analog pain score assessed for chest tube removal was significantly less 4.1 ± 1.2 (P < 0.05) in TENS Group as compared to 6.1 ± 0.8 in Control Group. Significantly greater number of patients (n = 14) (P < 0.05) in Control Group demanded additional analgesia as compared to TENS Group (n = 5). Feeling of well-being, improvement in appetite, and sleep was better in TENS Group as compared to Control Group.Conclusion:We conclude that TENS might not replace the conventional analgesics but has definite adjuvant role in decreasing pain scores and improves sense of well-being during chest tube removal after cardiac surgery.

Bone-anabolic action of low-intensity vibratory stimulation and the involvement of bone microvascularity

Bone-anabolic action of low-intensity vibratory stimulation and the involvement of bone microvascularity

No Interaction between tDCS Current Strength and Baseline Performance: A Conceptual Replication.

Several recent studies have reported non-linear effects of transcranial direct current stimulation (tDCS), which has been attributed to an interaction between the stimulation parameters (e.g., current strength, duration) and the neural state of the cortex being stimulated (e.g., indexed by baseline performance ability, age) (see Fertonani and Miniussi, 2016). We have recently described one such non-linear interaction between current strength and baseline performance on a visuospatial attention (landmark) task (Benwell et al., 2015). In this previous study, we induced a small overall rightward shift of spatial attention across 38 participants using bi-hemispheric tDCS applied for 20 min (concurrent left posterior parietal (P5) anode and right posterior parietal (P6) cathode) relative to a sham protocol. Importantly, this shift in bias was driven by a state-dependent interaction between current intensity and the discrimination sensitivity of the participant at baseline (pre-stimulation) for the landmark task. Individuals with high discrimination sensitivity (HDS) shifted rightward in response to low- (1 mA) but not high-intensity (2 mA) tDCS, whereas individuals with low discrimination sensitivity (LDS) shifted rightward with high- but not low-intensity stimulation. However, in Benwell et al. (2015) current strength was applied as a between-groups factor, where half of the participants received 1 mA and half received 2 mA tDCS, thus we were unable to compare high and low-intensity tDCS directly within each individual. Here we aimed to replicate these findings using a within-group design. Thirty young adults received 15 min of 1 and 2 mA tDCS, and a sham protocol, each on different days, to test the concept of an interaction between baseline performance and current strength. We found no overall rightward shift of spatial attention with either current strength, and no interaction between performance and current strength. These results provide further evidence of low replicability of non-invasive brain stimulation protocols, and the need for further attempts to replicate the key experimental findings within this field.

Comparison of Active Stimulating Electrodes of Sacral Neuromodulation

The goal of this study was to compare the motor response to sacral neuromodulation (SNM) with different pairs of stimulating electrodes in anesthetized and awake sheep. Similar to SNM clinical use in humans, the InterStim® quadripolar tined lead was implanted adjacent to the S3 nerve root in sheep and bipolar stimulation was configured with one electrode negative and one electrode positive on the four contacts (0 most distal to device, 1, 2, and 3 most proximal). Electrode 3-cathode and electrode 0-anode (3-/0+) stimulation had the lowest visual response threshold (0.46 ± 0.14V, anesthetized, 0.56 ± 0.21V, conscious), representing the most sensitive stimulation. Stimulation on electrode 0 (0-/1+) had the highest response threshold among tested electrodes (2.70 ± 0.23V, anesthetized, 3.38 ± 0.96V, conscious). The order according to response threshold from low to high was 3 < 2 < 1 < 0. The triggered response by 3-/0+ stimulation solely occurred in the perineum, tail, or bellows. In contrast, the 0-/1+ stimulation frequently evoked response in gluteal and thigh regions. The electromyographic activities from the anus were sensitive to low intensities of stimulation on electrode 3 (e.g., 3-/0+, 3-/2+). Objective motor responses to SNM as a functional indicator for optimal lead placement may be used to demonstrate that the contact which is most proximal to the foramen (electrode 3) is an optimal electrode to trigger an "on-target" response to lower intensity stimulation. Data from this preclinical work suggest that there are several principles that may be referenced to simplify and expedite the programming process in clinical practice.

Exploration of Hand Grasp Patterns Elicitable Through Non-Invasive Proximal Nerve Stimulation

Various neurological conditions, such as stroke or spinal cord injury, result in an impaired control of the hand. One method of restoring this impairment is through functional electrical stimulation (FES). However, traditional FES techniques often lead to quick fatigue and unnatural ballistic movements. In this study, we sought to explore the capabilities of a non-invasive proximal nerve stimulation technique in eliciting various hand grasp patterns. The ulnar and median nerves proximal to the elbow joint were activated transcutanously using a programmable stimulator, and the resultant finger flexion joint angles were recorded using a motion capture system. The individual finger motions averaged across the three joints were analyzed using a cluster analysis, in order to classify the different hand grasp patterns. With low current intensity (<5 mA and 100 µs pulse width) stimulation, our results show that all of our subjects demonstrated a variety of consistent hand grasp patterns including single finger movement and coordinated multi-finger movements. This study provides initial evidence on the feasibility of a proximal nerve stimulation technique in controlling a variety of finger movements and grasp patterns. Our approach could also be developed into a rehabilitative/assistive tool that can result in flexible movements of the fingers.

Upregulation of Integrin-α6 and Integrin-β1 Gene Expressions in Mouse Spermatogonial Stem Cells after Continues and Pulsed Low Intensity Ultrasound Stimulation.

Objective low intensity ultrasound (continues and pulsed) is a form of energy. Spermatogonial stem cells (SSCs) are at the base of male fertility. This study investigated the effects of low intensity ultrasound stimulation (LIUS) and low intensity pulsed ultrasound stimulation (LIUPS) on the expression of germ cell-specific and pluripotency genes in SSCs in vitro. Materials and Methods In this experimental study, isolated SSCs from neonatal male mice were cultured in Dulbecco’s Modified Eagle’s Medium (DMEM) with 10% fetal bovine serum (FBS). In addition, to confirm identification of SSCs, PLZF protein was detected positively in SSCs derived colonies. SSCs were stimulated by LIUS and LIUPS for 5 days, followed by assessment of expression of integrin-α6 (Itga6) and β1 (Itgβ1), as two germ cell-specific genes, and Oct- 4, as a pluripotency gene, on day 21st by quantitive reverse transcriptase-polymerase chain reaction (qRT-PCR). To investigate the proliferation rate and colonization of SSCs in different groups, counting whole number of the cells and colonies as well as analysis of the respective diameters were performed on days 7th, 14th and 21st. Data was analyzed by ANOVA test. Results LIUS and LIUPS treatment of mouse SSCs increased expression of Itga6 and Itgβ1 genes in the experimental groups, compared to the control group (P<0.05), whereas there was no significant difference between the groups, regarding the expression of Oct-4 gene. These treatments maintained survival rate, while they increased proliferation rate and colonization of SSCs during the first week of culture. However, within the second week, proliferation rate and colonization were decreased in the experimental groups. ConclusionThese results suggested that LIUS and LIUPS treatment had good effect on SSCs proliferation and colonization, based on the gene-specific marker expression during 21 days culture in vitro.

Reduced Apparent Diffusion Coefficient in Various Brain Areas following Low-Intensity Transcranial Ultrasound Stimulation.

Diffusion of water molecules closely related to physiological and pathological information of brain tissue. Low-intensity transcranial ultrasound stimulation (TUS) has advantages of noninvasive, high spatial resolution and penetration depth. Previous studies have demonstrate that TUS can modulate neuronal activity and alter cortical hemodynamic. However, how TUS affect diffusion of water molecules remain unclear. In this paper, in order to evaluate the effect of low-intensity TUS on the diffusion of water molecules in brain tissue, diffusion-weighted magnetic resonance (MR) imaging was performed in 19 healthy Sprague-Dawley rats in sham surgery group (six rats) and TUS group (thirteen rats) Subsequently, rats were stimulated by low-intensity transcranial ultrasound for 5 min in TUS group. Finally, rats of sham surgery group and TUS group were imaged again by diffusion-weighted MR imaging. The apparent diffusion coefficient (ADC) was measured in caudate putamen region and middle brain motor-related region of each rat in sham surgery group and TUS group. Surgery-related and TUS-related changes were calculated using a statistical analysis. The mean ADC values of marked regions of six rats in sham surgery group were 0.743 ± 0.031 (pre-surgery) and 0.745 ± 0.029 (post-surgery). The mean ADC values of marked regions of 13 rats in TUS group were 0.749 ± 0.032 (pre-TUS) and 0.712 ± 0.033 (post-TUS) Compared to the pre-TUS values, the mean ADC values of the rats decreased 4.9% (*P < 0.05) post-TUS. These results of this study demonstrate that low-intensity TUS can restrict the diffusion of water molecules in brain tissue.

Level Specific CE-Chirp® BAEP's: A new faster technique in neuromonitoring cochlear nerve during cerebello-pontine angle tumor surgery

Abstract Background Level Specific (LS) CE-Chirp® Brainstem Auditory Evoked Potentials (BAEP's) are the most recent evolution of classical Click BAEP's, performed both in clinical studies and in intraoperative neuromonitoring (IONM) of acoustic pathways during several neurosurgical procedures. LS CE-Chirp® is a new group of acoustic stimuli, latter evolution of Broadband CE-Chirp®, designed by Claus Elberling to provide faster recording of larger amplitude BAEP's V waves in infants. While the original Broadband CE-Chirp® was conceived for optimal response amplitude of V wave at low and medium stimulation intensities, the LS CE-Chirp® provides clearer I–III–V waves at high intensities. Material and method We report a consecutive series of 31 cases in which the new LS CE-Chirp® BAEP's were performed during different skull base surgery procedures during the last 24 months: 25 vestibular schwannomas, 3 cerebello-pontine angle (CPA) meningiomas and 3 CPA epidermoid tumors. Results Using LS-CE-Chirp® BAEP's monitoring, neurosurgeon was alerted in 10–15 s about variation of conduction parameters of acoustic pathways. At the end of surgery, BAEP's were normal in 11 patients, showed deconstructed waves in 14, and elongated waves in 6. At a minimum clinical and BAEP's follow-up of 6 months, hearing function was preserved in 19 cases (61,3%). Conclusions We herein confirm that LS CE-Chirp® BAEP's provide a fast feedback to surgeons regarding acoustic pathways function, helping them during skull base tumor removal in the attempt to hearing preservation when it is socially useful in the preoperative evaluation.

A pilot treatment study for mild traumatic brain injury: Neuroimaging changes detected by MEG after low-intensity pulse-based transcranial electrical stimulation

ABSTRACTBackground: Mild traumatic brain injury (mTBI) is a leading cause of sustained impairments in military service members, Veterans, and civilians. However, few treatments are available for mTBI, partially because the mechanism of persistent mTBI deficits is not fully understood.Methods: We used magnetoencephalography (MEG) to investigate neuronal changes in individuals with mTBI following a passive neurofeedback-based treatment programme called IASIS. This programme involved applying low-intensity pulses using transcranial electrical stimulation (LIP-tES) with electroencephalography monitoring. Study participants included six individuals with mTBI and persistent post-concussive symptoms (PCS). MEG exams were performed at baseline and follow-up to evaluate the effect of IASIS on brain functioning.Results: At the baseline MEG exam, all participants had abnormal slow-waves. In the follow-up MEG exam, the participants showed significantly reduced abnormal slow-waves with an average reduction of 53.6 ± 24.6% in slow-wave total score. The participants also showed significant reduction of PCS scores after IASIS treatment, with an average reduction of 52.76 ± 26.4% in PCS total score.Conclusions: The present study demonstrates, for the first time, the neuroimaging-based documentation of the effect of LIP-tES treatment on brain functioning in mTBI. The mechanisms of LIP-tES treatment are discussed, with an emphasis on LIP-tES’s potentiation of the mTBI healing process.

Abstract P110: Low Intensity Stimulation of Aortic Baroreceptors as a Potential Therapeutic Alternative for Hypertension Treatment

Carotid baroreceptor stimulation has been clinically explored for antihypertensive benefits but aortic baroreceptor modulation remains untouched for clinical translation. Published studies use large current/voltage amplitudes (10V), longer pulse widths (2 ms) or ultra-high frequencies (70-100 Hz). These are energy inefficient neuromodulation methods. Our main goal was to identity optimal nerve stimulation parameters that would provide a sustained drop in mean arterial pressure (MAP) of ~30 mmHg. We stimulated aortic depressor nerve (ADN) in spontaneously hypertensive rats (SHR, n =4) at low ranges of frequencies, pulse amplitudes and pulse widths. Under urethane anesthesia, left ADN was stimulated for 20 seconds at varying frequencies (1, 2.5 and 5 Hz) and pulse amplitudes (0.2, 0.4 and 0.6 mA) at 0.1, 0.2 or 0.5 ms pulse width. A frequency-dependent depressor response was seen at all pulse amplitudes and widths used. Lower pulse amplitudes (0.2 mA) produced ~18 mmHg MAP drop at all pulse widths tested. Higher pulse amplitude (0.4 and 0.6 mA) produced similar drop in MAP of ~34 mmHg. The return to baseline values was relatively prolonged with higher charge injection with 32 seconds at 0.2 mA (0.1 or 0.2 ms at 5 Hz, maximum effect size: -18 mmHg) versus 42 seconds at 0.4 or 0.6 mA (0.1, 0.2 or 0.5 ms at 5 Hz, maximum effect size: -34 mmHg). There was no added benefit of pulse amplitudes beyond 0.4 mA. We conclude that low intensity stimulation is an effective alternate way to neuromodulation of the ADN. This will enable low energy consumption for neuromodulation. Future studies will study impact of these parameters in conscious SHR rats.

P300 Influence of rTMS with high and low frequency stimulation on motor and executive function in Parkinson’s disease. Follow-up study for half year

The non-invasive brain stimulation, like transcranial magnetic stimulation (rTMS) can influence on both cognitive and motor function of Parkinson’s disease (PD). However, a protocol for daily routine is not yet been known. Furthermore, there are not known the predictors of responders or not responders to rTMS treatment. Our main goal was to select the optimal frequency with low intensity for improving executive and motor function in PD. Furthermore, we clarified the importance of age. Three groups of patients with PD were compared with each other and healthy controls in the mental tests. The 1 Hz (N = 28), 5 Hz (N = 13) and 5 + 1 Hz (N = 19) frequency with low intensity was applied daily over both dorsolateral prefrontal cortices (DLPFC) and over the brain stem for 7 days. Patients were followed for six months after the treatment with rTMS. The participants were divided into two groups according to their age (⩽ 65 years and 65 years >). The patients were tested with UPDRS, walking for 6 min, 10 m walk, Trail Making Test, and dual tasks. Only the 1 Hz treatment with low intensity for 7 days had an effect on the motor scores. The rTMS with 1 Hz caused significant improvement in the motor symptoms assessed by UPDRS after one month (before trial (BF) ⩽ 65 UPDRS total score 32.0 ± 15.0 3, after 1 month: 18.1 ± 8.6 p 0.001 , >65 BF: 28.5 ± 15.8, after 1 month: 18.6 ± 10.3 p 0.05 and it was maintained for six months in the group with ⩽ 65 yrs (N = 10, 18.2 ± 8.8 p 0.001 ). However, in the group with >65 yrs (N = 16) the better outcome was observed only after one month (BF: 28.5 ± 15.8, 1 month later 18.6 ± 10.3 p 0.01 , after 6 months: UPDRS total score: 20.8 ± 12.7 p = 0.06). Although, the stimulation with 5 + 1 Hz decrease scores assessed by UPDRS, but neither the stimulation with 5 Hz nor with 5 + 1 Hz with low intensity caused significant changes in PD. Results of Trail Making Test and dual tests in PD ⩽ 65 yrs did not differ from controls (C) below 65 years. However, the executive function of patients over 65 yrs (N = 16) were significantly worse compared to controls (N = 15) (C: Trail B-A: 50.0 ± 25.1 s, PD: Trail B-A > 65 yrs: 76.0 ± 45.1 s p 0.01 ). Six months after treatment with rTMS with 1 Hz an improvement was observed in Trail Making Test compared to onset of treatment (PD: 48.70 ± 21.4 s p 0.05 ). The dual test was deteriorated in the group over 65 years compared to age match controls. The 1 Hz stimulation did not reverse their values. (C: counting back (CB) −3: 50.0 ± 25.9 s, >65 yrs PD CB −3: 57 ± 21, 1 month after rTMS CB −3: 69 ± 20, 6 months after rTMS: 60 ± 19 s; PD BF CB-7 100 ± 45 s, 1 month 102 ± 32 s, 6 months: 82 ± 23 s). Stimulation with rTMS in the group >65 yrs showed shorter effect in motor scores than in the younger age group. Patients over 65 years in PD caused a significant deterioration in the executive function compared with age matched healthy controls. It was influenced temporarily by 1 Hz low intensity stimulation. Both the low and high frequency stimulation with proper intensity may have good outcomes in neurological diseases. Patients over 65 yrs with PD may deteriorate in their executive function compared with age matched healthy controls and decreases in the therapeutic effect of rTMS on motor function.

Discrimination of a medial functional module within the temporal lobe using an effective connectivity model: A CCEP study

The temporal lobe is classically divided in two functional systems: the ventral visual pathway and the medial temporal memory system. However, their functional separation has been challenged by studies suggesting that the medial temporal lobe could be best understood as an extension of the hierarchically organized ventral visual pathway. Our purpose was to investigate (i) whether cerebral regions within the temporal lobe could be grouped into distinct functional assemblies, and (ii) which regions were central within these functional assemblies. We studied low intensity and low frequency electrical stimulations (0.5 mA, 1 Hz, 4 ms) performed during sixteen pre-surgical intracerebral EEG investigations in patients with medically intractable temporal or temporo-occipital lobe epilepsies. Eleven regions of interest were delineated per anatomical landmarks such as gyri and sulci. Effective connectivity based on electrophysiological feature (amplitude) of cortico-cortical evoked potentials (CCEPs) was evaluated and subjected to graph metrics. The amplitudes discriminated one medial module where the hippocampus could act as a signal amplifier. Mean amplitudes of CCEPs in regions of the temporal lobe showed a generalized Pareto distribution of probability suggesting neural synchronies to be self-organized critically. Our description of effective interactions within the temporal lobe provides a regional electrophysiological model of effective connectivity which is discussed in the context of the current hypothesis of pattern completion.

Modulation of Calcitonin, Parathyroid Hormone, and Thyroid Hormone Secretion by Electrical Stimulation of Sympathetic and Parasympathetic Nerves in Anesthetized Rats.

The thyroid and parathyroid glands are dually innervated by sympathetic (cervical sympathetic trunk [CST]) and parasympathetic (superior laryngeal nerve [SLN]) nerve fibers. We examined the effects of electrical stimulation of efferent or afferent nerve fibers innervating the thyroid and parathyroid glands on the secretion of immunoreactive calcitonin (iCT), parathyroid hormone (iPTH), 3,3′,5-triiodothyronine (iT3), and thyroxine (iT4) from the thyroid and parathyroid glands. In anesthetized and artificially ventilated rats, thyroid venous blood was collected. The rate of hormone secretion from the glands was calculated from plasma hormone levels, measured by ELISA, and the flow rate of thyroid venous plasma. SLNs or CSTs were stimulated bilaterally with rectangular pulses with a 0.5-ms width. To define the role of unmyelinated nerve fibers (typically efferent), the cut peripheral segments were stimulated at various frequencies (up to 40 Hz) with a supramaximal intensity to excite all nerve fibers. The secretion of iCT, iT3, and iT4 increased during SLN stimulation and decreased during CST stimulation. iPTH secretion increased during CST stimulation, but was not affected by SLN stimulation. To examine the effects of selective stimulation of myelinated nerve fibers (typically afferent) in the SLN, intact SLNs were stimulated with a subthreshold intensity for unmyelinated nerve fibers. iCT, iT3, and iT4 secretion increased during stimulation of intact SLNs at 40 Hz. These results suggest that excitation of myelinated afferents induced by low intensity and high frequency stimulation of intact SLNs promotes secretion of CT and thyroid hormones from the thyroid gland, potentially via reflex activation of parasympathetic efferent nerve fibers in the SLN.

The potential role of pain-related SSEPs in the early prognostication of long-term functional outcome in post-anoxic coma

Cardiac arrest (CA) is a common cause of disability. Multimodal evaluation has improved prognosis but precocious biomarkers are not appropriate in determining long-term functional outcome. To identify early prognostication markers of long-term functional outcome in post-anoxic coma. Retrospective assessment of outcomes. Individuals older than 18 years with post-anoxic coma hospitalized in intensive care units after cardiac arrest (CA) regardless of cause (cardiac or non-cardiac) and location of event (in or out-of-hospital). Clinical, biological and neurophysiological data were collected within 48 hours from CA. Clinical data included time of no and low flow, CA rhythm, pupillary reflex, Glasgow motor score at admission and hyperthermia. Biological marker was the highest creatinine level. Neurophysiological parameters included EEG pattern and reactivity, Somatosensory Evoked Potential (SSEP), and Middle-Latency (ML) SSEP evoked at low (10 mA) and high (50 mA) intensity stimulation. Level of Cognitive Functioning Scale (LCFS), Disability Rating Scale and recovery from coma (Revised coma Recovery Scale [CRS-R]) were collected at 12 months. A LASSO multiple regression analysis was fitted to data to investigate the best predictors of LCF, DRS and CRS-R. In-sample prediction was obtained to verify the quality of fitting, and accuracy indices (i.e., total error rate) produced. Presence of short and medium latency SSEPs with low and high stimulation intensity were identified as prognostic predictors of outcome for all the scales. Error rate was 4.5% for CRS and LCF, and 9.1% for DRS. Middle latency somatosensory evoked potentials associated with short latency somatosensory evoked potentials during the first 48 hours after a cardiac arrest are strong predictors of functional outcome at 12 months from the event. Replication on larger cohorts is needed to support their routine use as prognostic markers. These markers could inform more appropriate allocation of resources, provide a basis for realistic goal-setting, and help the family to adjust its expectations.

Low-Force Muscle Activity Regulates Energy Expenditure after Spinal Cord Injury.

This study aimed to determine the effects of low stimulation frequency (1 and 3 Hz) and stimulation intensity (50 and 100 mA) on energy expenditure in people with SCI. We also examined the relationship between body mass index and visceral adipose tissue on energy expenditure during low-frequency stimulation. Ten individuals with complete SCI underwent oxygen consumption monitoring during electrical activation of the quadriceps and hamstrings at 1 and 3 Hz and at 50 and 100 mA. We calculated the difference in energy expenditure between stimulation and rest and estimated the number of days that would be necessary to burn 1 lb of body fat (3500 kcal) for each stimulation protocol (1 vs 3 Hz). Both training frequencies induced a significant increase in oxygen consumption above a resting baseline level (P < 0.05). Energy expenditure positively correlated with stimulus intensity (muscle recruitment) and negatively correlated with adiposity (reflecting the insulating properties of adipose tissue). We estimated that 1 lb of body fat could be burned more quickly with 1 Hz training (58 d) as compared with 3 Hz training (87 d) if an identical number of pulses were delivered. Low-frequency stimulation increased energy expenditure per pulse and may be a feasible option to subsidize physical activity to improve metabolic status after SCI.