Msec Duration Research Articles

Home-based Functional Electrical Stimulation for long-term denervated human muscle: History, basics, results and perspectives of the Vienna Rehabilitation Strategy

We will here discuss the following points related to Home-based Functional Electrical Stimulation (h-b FES) as treatment for patients with permanently denervated muscles in their legs: 1. Upper (UMN) and lower motor neuron (LMN) damage to the lower spinal cord; 2. Muscle atrophy/hypertrophy versus processes of degeneration, regeneration, and recovery; 3. Recovery of twitch- and tetanic-contractility by h-b FES; 4. Clinical effects of h-b FES using the protocol of the “Vienna School”; 5. Limitations and perspectives. Arguments in favor of using the Vienna protocol include: 1. Increased muscle size in both legs; 2. Improved tetanic force production after 3-5 months of percutaneous stimulation using long stimulus pulses (> 100 msec) of high amplitude (> 80 mAmp), tolerated only in patients with no pain sensibility; 3. Histological and electron microscopic evidence that two years of h-b FES return muscle fibers to a state typical of two weeks denervated muscles with respect to atrophy, disrupted myofibrillar structure, and disorganized Excitation-Contraction Coupling (E-CC) structures; 4. The excitability never recovers to that typical of normal or reinnervated muscles where pulses less than 1 msec in duration and 25 mAmp in intensity excite axons and thereby muscle fibres. It is important to motivate these patients for chronic stimulation throughout life, preferably standing up against the load of the body weight rather than sitting. Only younger and low weight patients can expect to be able to stand-up and do some steps more or less independently. Some patients like to maintain the h-b FES training for decades. Limitations of the procedure are obvious, in part related to the use of multiple, large surface electrodes and the amount of time patients are willing to use for such muscle training.

Effect of Intermittent Phrenic Nerve Stimulation During Cardiothoracic Surgery on Mitochondrial Respiration in the Human Diaphragm*

Recent studies have shown that brief periods of mechanical ventilation in animals and humans can lead to ventilator-induced diaphragmatic dysfunction, which includes muscle atrophy, reduced force development, and impaired mitochondrial function. Studies in animal models have shown that short periods of increased diaphragm activity during mechanical ventilation support can attenuate ventilator-induced diaphragmatic dysfunction but corresponding human data are lacking. The purpose of this study was to examine the effect of intermittent diaphragm contractions during cardiothoracic surgery, including controlled mechanical ventilation, on mitochondrial respiration in the human diaphragm. Within subjects repeated measures study. Operating room in an academic health center. Five subjects undergoing elective cardiothoracic surgery. In patients (age 65.6 ± 6.3 yr) undergoing cardiothoracic surgery, one phrenic nerve was stimulated hourly (30 pulses/min, 1.5 msec duration, 17.0 ± 4.4 mA) during the surgery. Subjects received 3.4 ± 0.6 stimulation bouts during surgery. Thirty minutes following the last stimulation bout, samples of diaphragm muscle were obtained from the anterolateral costal regions of the stimulated and inactive hemidiaphragms. Mitochondrial respiration was measured in permeabilized muscle fibers with high-resolution respirometry. State III mitochondrial respiration rates (pmol O2/s/mg wet weight) were 15.05 ± 3.92 and 11.42 ± 2.66 for the stimulated and unstimulated samples, respectively (p < 0.05). State IV mitochondrial respiration rates were 3.59 ± 1.25 and 2.11 ± 0.97 in the stimulated samples and controls samples, respectively (p < 0.05). These are the first data examining the effect of intermittent contractions on mitochondrial respiration rates in the human diaphragm following surgery/mechanical ventilation. Our results indicate that very brief periods (duty cycle ~1.7%) of activity can improve mitochondrial function in the human diaphragm following surgery/mechanical ventilation.

Feedback-controlled electro-kinetic traps for single-molecule spectroscopy

A principal limitation of single-molecule spectroscopy in solution is the diffusion-limited residence time of a given molecule within the detection volume. A common solution to this problem is to immobilize molecules of interest on a passivated glass surface for extending the observation time to obtain reliable data statistics. However, surface tethering of molecules often introduces artifacts, particularly when studying the structural dynamics of biomolecules. To circumvent this limitation, we investigated alternative ways to extend single-molecule observation times in solution without surface immobilization. Among various possibilities, the so-called anti-Brownian electro-kinetic trap (or ABEL trap) seems best suited to achieve this goal. The essential part of that trap is a feedback-controlled electro-kinetic steering of a molecule’s position in reaction to its diffusive Brownian motion which is monitored by fluorescence, thus keeping the molecule within a sub-micron sized detection volume. Fluorescence trace recordings of over thousands of milliseconds duration on individual dye molecules within an ABEL trap have been reported. In this short review, we shall briefly discuss the principle and some results of ABEL trapping of individual molecules with possible extensions to future works.

034 Survival of mouse oocytes after cooling in lower cryoprotectant concentrations by ultra rapid warming using an IR laser pulse

Seki and Mazur have recently shown [PLoS One. 2012;7(4)] that about 90% of MII mouse oocytes survive vitrification in solutions of EAFS 10/10 that contain only half the usual concentration of solutes, provided that the warming rate is extremely high (117,000 °C/min). They reported that fewer than 10% survived if the concentration of EAFS were further reduced to 33% of normal. We are currently investigating whether high survivals could be obtained in 0.33× and 0.25× EAFS if the warming rates were still higher. For this purpose we have cooled MII oocytes in these media on Cryotops to −196 °C and warmed them 5 times more rapidly at ∼600,000 °C/min by subjecting them to a 13 joule pulse of 15 msec duration from a Nd:YAG laser. Kleinhans et al in a companion paper at this meeting discuss the physics attributes of the laser and the interactions of the pulse with the sample, as well as the jig he developed to permit the manipulation of the Cryotop before and during its exposure to the laser pulse. The osmotic/morphological survival of 31 samples suspended in 0.25× EAFS was 15.2 ± 22% (standard deviation). The survival of two samples in 0.33× EAFS was 30%. The total molality of these solutions is 1.27 and 1.72, respectively. These are in the range used in standard slow-freeze cryopreservation. For comparison, note that the total molality of full strength 1x EAFS is 7.37 molal, 5.8 and 4.3-fold higher. Although these preliminary results are encouraging, we have two caveats. One is that the variability of the former is high as evidenced by the large standard errors. The other is that the survival of controls subjected to the same cooling procedure but warmed at 117,000 °C/min (no laser) was close to the same (13.3% vs. 15.2%). Source of funding: NIH Grant 8R01 OD 011201, Peter Mazur, PI. Conflict of interest: None declared. pmazur@utk.edu

Gap detection measured with electrically evoked auditory event-related potentials and speech-perception abilities in children with auditory neuropathy spectrum disorder.

This study aimed (1) to investigate the feasibility of recording the electrically evoked auditory event-related potential (eERP), including the onset P1-N1-P2 complex and the electrically evoked auditory change complex (EACC) in response to temporal gaps, in children with auditory neuropathy spectrum disorder (ANSD); and (2) to evaluate the relationship between these measures and speech-perception abilities in these subjects. Fifteen ANSD children who are Cochlear Nucleus device users participated in this study. For each subject, the speech-processor microphone was bypassed and the eERPs were elicited by direct stimulation of one mid-array electrode (electrode 12). The stimulus was a train of biphasic current pulses 800 msec in duration. Two basic stimulation conditions were used to elicit the eERP. In the no-gap condition, the entire pulse train was delivered uninterrupted to electrode 12, and the onset P1-N1-P2 complex was measured relative to the stimulus onset. In the gapped condition, the stimulus consisted of two pulse train bursts, each being 400 msec in duration, presented sequentially on the same electrode and separated by one of five gaps (i.e., 5, 10, 20, 50, and 100 msec). Open-set speech-perception ability of these subjects with ANSD was assessed using the phonetically balanced kindergarten (PBK) word lists presented at 60 dB SPL, using monitored live voice in a sound booth. The eERPs were recorded from all subjects with ANSD who participated in this study. There were no significant differences in test-retest reliability, root mean square amplitude or P1 latency for the onset P1-N1-P2 complex between subjects with good (>70% correct on PBK words) and poorer speech-perception performance. In general, the EACC showed less mature morphological characteristics than the onset P1-N1-P2 response recorded from the same subject. There was a robust correlation between the PBK word scores and the EACC thresholds for gap detection. Subjects with poorer speech-perception performance showed larger EACC thresholds in this study. These results demonstrate the feasibility of recording eERPs from implanted children with ANSD, using direct electrical stimulation. Temporal-processing deficits, as demonstrated by large EACC thresholds for gap detection, might account in part for the poor speech-perception performances observed in a subgroup of implanted subjects with ANSD. This finding suggests that the EACC elicited by changes in temporal continuity (i.e., gap) holds promise as a predictor of speech-perception ability among implanted children with ANSD.

Two new species and a new subgenus of toothed Brachyhypopomus electric knifefishes (Gymnotiformes, Hypopomidae) from the central Amazon and considerations pertaining to the evolution of a monophasic electric organ discharge

We describe two new, closely related species of toothed Brachyhypopomus (Hypopomidae: Gymnotiformes: Teleostei) from the central Amazon basin and create a new subgenus for them. Odontohypopomus, new subgenus of Brachyhypopomus, is diagnosed by (1) small teeth present on premaxillae; (2) medialmost two branchiostegal rays thin with blades oriented more vertically than remaining three rays; (3) background color in life (and to lesser extent in preservation) distinctly yellowish with head and sides peppered with small, widely spaced, very dark brown stellate chromatophores that greatly contrast with light background coloration; (4) a dark blotch or bar of subcutaneous pigment below the eye; (5) electric organ discharge waveform of very long duration (head-positive phase approx. 2 milliseconds or longer, head-negative phase shorter or absent) and slow pulse repetition rate (3–16 Hz). The type species of the new subgenus, Brachyhypopomus (Odontohypopomus) walteri sp. n., is diagnosed by the following additional character states: (1) subcutaneous dark pigment at base of orbit particularly prominent, (2) body semi-translucent and nearly bright yellow background coloration in life, (3) a biphasic electric organ discharge (EOD) waveform of very long duration (between 3.5 and 4 milliseconds at 25° C) with head-positive first phase significantly longer than second head-negative phase in both sexes. Brachyhypopomus (Odontohypopomus) bennetti sp. n. is diagnosed by two character states in addition to those used to diagnose the subgenus Odontohypopomus: (1) a deep electric organ, visible as large semi-transparent area, occupying approximately 14–17% body depth directly posterior to the abdominal cavity in combination with a short, but deep, caudal filament, and (2) a monophasic, head-positive EOD waveform, approximately 2.1 milliseconds in duration in both sexes. These are the only described rhamphichthyoid gymnotiforms with oral teeth, and Brachyhypopomus bennetti is the first Brachyhypopomus reported to have a monophasic (head-positive) EOD waveform. Unlike biphasic species, the waveform of its EOD is largely unaffected by tail damage from predators. Such injuries are common among specimens in our collections. This species’ preference for floating meadow habitat along the major channels of the Amazon River basin may put it at particularly high risk of predation and “tail grazing.”

Immediate effect of neuromuscular electrical stimulation on vascular endothelial function in patients with acute myocardial infarction

Background: Neuromuscular electrical stimulation (NMES) is effective in preventing skeletal muscle mass loss and muscle weakness. Although a long-term NMES for thigh muscles has been shown to improve vascular endothelial function, the immediate effect of NMES on it is still unknown in patients with acute myocardial infarction (AMI). We investigated the immediate effect of NMES on vascular endothelial function in AMI patients. Methods: 35 male patients (63±11 years) were recruited for this study, who were admitted to Kitasato University hospital because of AMI and had clinically stable condition. The patients were divided into NMES and control groups. The NMES was performed for the quadriceps and gastrocnemius muscles with the cycle of 5-sec stimulation and 5-sec rest for 30 min, in which the 2.5 kHz alternating sinusoidal current was used at bursts of 50 Hz carrier frequency and 0.4 msec duration. The current was set at the highest tolerable intensity up to 100 mA in the NMES group and at the minimum intensity that did not lead to visible and palpable muscle contractions in the control group. Reactive hyperemia index (RHI), a noninvasive measure of vascular endothelial function, was measured before and after the NMES session, which was assessed as the ratio of the fingertip pulse wave amplitude measured after upper arm compression to that before compression using a finger plethysmograph. Transcutaneous oxygen tension (TcPO2) of foot was measured during the session using a transcutaneous O2/CO2 gas device as a parameter of peripheral circulation. Low-frequency component (LF) in blood pressure variability and high-frequency component (HF) in heart rate variability were also analyzed during the session, indicating sympathetic and parasympathetic activities, respectively. The Wilcoxon signed rank test and repeated measures analysis of variance (ANOVA) were used to assess the statistical differences in vascular endothelial function, and cardiovascular and autonomic responses before and after the session in the each group. Results: The RHI increased significantly from 1.50±0.4 before the session to 1.75±0.6 after the session (P<0.05) and TcPO2 increased from 48.5±12 to 60.5±11 mmHg (P<0.05) in the NMES group. They showed no significant changes before and after the session in the control group. No significant changes were observed in blood pressure, heart rate, LF and HF throughout the session in the two groups. Conclusion: A single session of NMES improves vascular endothelial function without an excessive elevation of sympathetic activity nor cardiovascular instability in AMI patients.

Adjustable Speed Drives Response to Voltage Sags

This paper presents a study to investigate response of adjustable speed drives due to voltage sags. A small ASD of 0.39 kW, 50/60 Hz, and 400-480 V was used for testing how drives will respond to voltage sag types; A, B, C and D. The drive response is influenced by sag magnitude, sag duration and phase angle shift. Behavior of the diodes rectifier for conducting is influenced by sag magnitude and phase angle shift represented by sag of types C and D. The diodes rectifiers are reverse biased when it was supplied by voltage sags. Even though there are no charging currents to dc bus capacitor during voltage sags, the drives did not directly trip to certain sag magnitude and sag duration. Sensitivity of the ASD to voltage sag types is presented in voltage tolerance curve. Sag of type A produces highest sensitivity on the ASD and it trips for sag magnitude of 62.5% and 250 milliseconds in duration.

Measured and simulated P waves in normal subjects reflect complex atrial anatomy

Introduction: The shape of the P wave can yield important information about the substrate of atrial fibrillation (AF). On the routine 12-lead ECG, P waves have a smooth appearance. Computer simulation studies with realistic atrial models have shown highly complex P-wave shapes with details that were linked to structural features of the atria. We assessed the true shape of the P wave in control subjects. Methods: We recorded 184-channel high-resolution ECGs in 6 healthy volunteers and averaged over 300 beats for each. Beats were aligned on their P waves. Alignment was based on a compound signal of all 184 channels to reduce the effect of noise on alignment. In addition, 12-lead ECGs were simulated using a single patient-tailored heart-torso model with detailed atrial anatomy. Results: Averaging reduced the noise level to less than 2 microvolt (uV) peak-to-peak. Signal features of a few uV amplitude and less than 5 milliseconds (ms) duration could be reliably distinguished. Measured P waves had 4 to 5 separate peaks that were reproducible between recordings. Simulated P waves demonstrated similar complexity, which was related to structural discontinuities in the computer model of the atria. Conclusions: The true shape of the P wave is very irregular and reflects the complex anatomy of the atria. High-resolution electrocardiography is necessary to reliably assess P-wave shape.

A new technique to investigate vestibulo-spinal reflexes.

Vestibulospinal reflexes can be elicited in humans by low amplitudes direct (galvanic) currents lasting tens of milliseconds and applied across the two mastoids bones, which can be delivered by particular stimulators. The stimulus induces a perception of body sway and a postural response appropriate to counteract the perceived sway. Both the direction of the perceived and induced body sway are modulated by the orientation of the head with respect to the body. This phenomenon is due to the fact that integration of vestibular and neck signals allows to correctly infer the direction of body sway from the labyrinthine input, which is instead related to direction of head motion. The modulation of stimulus-elicited body sway by neck rotation could be utilised for testing the effectiveness of neck proprioceptive signals in modifying the reference frame for labyrinthine signals from the head to the body. In the present experiments we showed that labyrinthine stimulation can be performed also by using train of pulses of 1 msec duration, which can be delivered by virtually all stimulators allowed for human use. Moreover, we developed a simple technique for visualising the time course of the changes in the direction of the postural response, based on the evaluation of the velocity vector of subject's centre of pressure. This method could be exploited in order to the test the efficacy of neck proprioceptive information in modifying the reference frame for processing vestibular signals in both physiological and pathological condition.

Non-Invasive Brain-to-Brain Interface (BBI): Establishing Functional Links between Two Brains

Transcranial focused ultrasound (FUS) is capable of modulating the neural activity of specific brain regions, with a potential role as a non-invasive computer-to-brain interface (CBI). In conjunction with the use of brain-to-computer interface (BCI) techniques that translate brain function to generate computer commands, we investigated the feasibility of using the FUS-based CBI to non-invasively establish a functional link between the brains of different species (i.e. human and Sprague-Dawley rat), thus creating a brain-to-brain interface (BBI). The implementation was aimed to non-invasively translate the human volunteer’s intention to stimulate a rat’s brain motor area that is responsible for the tail movement. The volunteer initiated the intention by looking at a strobe light flicker on a computer display, and the degree of synchronization in the electroencephalographic steady-state-visual-evoked-potentials (SSVEP) with respect to the strobe frequency was analyzed using a computer. Increased signal amplitude in the SSVEP, indicating the volunteer’s intention, triggered the delivery of a burst-mode FUS (350 kHz ultrasound frequency, tone burst duration of 0.5 ms, pulse repetition frequency of 1 kHz, given for 300 msec duration) to excite the motor area of an anesthetized rat transcranially. The successful excitation subsequently elicited the tail movement, which was detected by a motion sensor. The interface was achieved at 94.0±3.0% accuracy, with a time delay of 1.59±1.07 sec from the thought-initiation to the creation of the tail movement. Our results demonstrate the feasibility of a computer-mediated BBI that links central neural functions between two biological entities, which may confer unexplored opportunities in the study of neuroscience with potential implications for therapeutic applications.

OPTIMIZATION OF PARAMETERS OF THE OOCYTE ENUCLEATION AND FUSION WITH THE SOMATIC CELL DURING PRODUCTION OF MAMMALIAN CLONED EMBRYOS

Parameters of the oocyte enucleation and fusion with somatic cell for producing of cattle cloned cetohybrids were studied. It was established that the electrofusion efficiency depends on strength, duration and set number of electrical pulse. The optimal parameters for Multiporator (Eppendorf, Germany) were determined: two consistent pulses DC electrical field each of 30 V field strength and 15 msec duration followed by the pulse of AC electrical field of 5 V and 10 sec duration. It was found that the first polar body serving as a marker for the chromosome position at «blind» enuclea-tion must not deviate from the chromosome location by more than 10 degrees. Keywords: in vitro culture, oocyte, cattle nuclear transfer, electrofusion, enucleation.

Neuronavigated vs. Conventional Repetitive Transcranial Magnetic Stimulation Method for Virtual Lesioning on the Broca’s Area

This study was undertaken to test the hypothesis that repetitive transcranial magnetic stimulation (rTMS) using a neuronavigational TMS system (nTMS) to the Broca's area would elicit greater virtual aphasia than rTMS using the conventional TMS method (cTMS). Eighteen healthy subjects underwent a randomized crossover experiment to induce virtual aphasia by targeting the Brodmann area 44 and 45 for nTMS, and F3 of international 10-20 system for cTMS. Reaction time for a picture naming task and the reaction duration for a six-digit number naming task were measured before and after each session of stimulation, and compared between the cTMS and nTMS. The stability of the coil positioning on the target was measured by depicting the variability of talairach coordinates (x, y, z) of the sampled stimulation localizations. At baseline, outcome variables were comparable between cTMS and nTMS. nTMS induced significant delays in reaction time from 944.0 ± 203.4 msec to 1304.6 ± 215.7 msec (p < 0.001) and reaction duration from 1780.5 ± 286.8 msec to 1914.9 ± 295.6 msec (p < 0.001) compared with baseline, whereas cTMS showed no significant changes (p = 0.959 and p = 0.179, respectively). The mean talairach space coordinates of nTMS demonstrated greater consistency of localization of stimulation with the target, and the error range relative to the target was narrower for the nTMS compared with the cTMS (p < 0.001). nTMS leads to more robust neuromodulation of Broca's area, resulting in delayed verbal reaction time as well as more accurate targeting of the intended stimulation location, demonstrating superiority of nTMS over cTMS for therapeutic use of rTMS in neurorehabilitation.

A new technique to investigate vestibulospinal reflexes

800x600 Vestibulospinal reflexes can be elicited in humans by low amplitudes direct (galvanic) currents lasting tens of milliseconds and applied across the two mastoids bones, which can be delivered by particular stimulators. The stimulus induces a perception of body sway and a postural response appropriate to counteract the perceived sway. Both the direction of the perceived and induced body sway are modulated by the orientation of the head with respect to the body. This phenomenon is due to the fact that integration of vestibular and neck signals allows to correctly infer the direction of body sway from the labyrinthine input, which is instead related to direction of head motion. The modulation of stimulus-elicited body sway by neck rotation could be utilised for testing the effectiveness of neck proprioceptive signals in modifying the reference frame for labyrinthine signals from the head to the body. In the present experiments we showed that labyrinthine stimulation can be performed also by using train of pulses of 1 msec duration, which can be delivered by virtually all stimulators allowed for human use. Moreover, we developed a simple technique for visualising the time course of the changes in the direction of the postural response, based on the evaluation of the velocity vector of subject’s centre of pressure. This method could be exploited in order to the test the efficacy of neck proprioceptive information in modifying the reference frame for processing vestibular signals in both physiological and pathological condition. Normal 0 14 false false false IT X-NONE X-NONE MicrosoftInternetExplorer4

Disruptive communication: Stealth signaling in the toadfish

Male oyster toadfish, Opsanus tau, produce long duration (250 to 650 ms) sexual advertisement calls or 'boatwhistles' during the breeding season. When males are in close proximity, the fishes alternate the production of boatwhistles with other males to avoid call overlap. However, males can also produce a number of different sounds, including a single, short duration pulse or 'grunt' (~100 ms). The vocalizations of competing males were recorded in situ with multiple hydrophones to examine intraspecific interactions. These short grunts were emitted almost exclusively during the boatwhistle of a conspecific male. The fundamental frequency (or pulse repetition rate) of the boatwhistles were modified by this disruptive grunt, 'jamming' the signal and decreasing its frequency. The disruptive grunt specifically targeted the second stage or tonal portion of the boatwhistle, believed to be the primary acoustic attractant for females, and its brevity and precision may allow its emitter to remain undetectable. While the acoustic repertoire of teleost fishes may be less diverse compared with terrestrial species, the disruptive grunts indicate fish have the capacity for complex acoustic interactions.

Abstract 18522: Atrial Ganglionated Plexus Stimulation Prevents Myocardial Ischemia Reperfusion Arrhythmias by Preserving Connexin43 Protein

Atrial ganglionated plexus Stimulation Prevents Myocardial Ischemia Reperfusion Arrhythmias by Preserving Connexin43 Protein Background: Vagal nerve stimulation has been shown to provide protective effect against ischemia/reperfusion (I/R) arrhythmias. Since atrial epicardial ganglionated plexuses contain a large amount of parasympathetic elements, we hypothesize atrial epicardial ganglionated plexus stimulation (GP-S) may be an alternative to vagal nerve stimulation for preventing arrhythmias induced by myocardial I/R. Methods and Results: Twenty one dogs were randomly divided into GP stimulation (GP-S) group (N=11) and control group (N=10). Myocardial I/R was induced by first 2 hours of reperfusion in dogs subjected to 45 minutes of ischemia with occlusion of the left anterior descending coronary artery (LAD). A bipolar plaque electrode was sutured overlying the fad pad containing the superior left ganglionated plexus (SLGP), which located at the junction of left pulmonary artery and left superior pulmonary vein.The GP-S was performed by applying high frequency electrical stimulation (HFS: 20Hz, 0.1msec duration) to the SLGP. The lowest voltage level of GP-S that induced approximately 10% sinus rhythm slowing was chosen as the voltage for GP-S. Compared with control group, GP-S caused significant increases in ventricular ERP and vagal indice (HF nu), as well as an evident decrease in sympathetic tone (LF/HF), the numbers of PVCs, salvos, and VT runs were significantly reduced in GP-S group. And the incidences of salvo and VT in GP-S group were significantly lower. Immunoblotting revealed that the control group showed a marked reduction in the amount of phosphorylated connexin43 (Cx43), whereas the GP-S group showed only a slight reduction. Immunohistochemistry confirmed that the myocardial I/R-induced loss of Cx43 from intercellular junctions was prevented by GP-S. Conclusions: GP-S protects against ventricular arrhythmias resulting from brief myocardial I/R by modulating connexin43. GP-S may serve as a non-pharmacological clinical approach to improve acute myocardial I/R arrhythmias such as during coronary bypass surgery.

Does the ACC Have Potential as an Index of Early Speech Discrimination Ability? A Preliminary Study in 4-Month-Old Infants With Normal Hearing

The acoustic change complex (ACC), an auditory evoked potential (AEP) comprises overlapping slow cortical responses, which reflects discrimination capacity in the absence of attention, has not yet been recorded in infants. Because the ACC is a large response, it may be useful as an index of discrimination for infants at both the individual and group level. This is an advantage compared with mismatch negativity, another AEP that reflects discrimination of a change in stimulus, because mismatch negativity is based on difference waves and is most sensitive to group effects. The two objectives of this study were to determine whether: (1) the ACC can be elicited to a change in the English consonants /da/ and /ba/ in young infants and adults whose native language is English, and (2) the ACC can also be elicited to changes in Hindi consonant contrasts reflecting the predicted patterns of discrimination for young infants reported in previous studies. Participants were six adults and twenty-five 4-month-old infants whose native language was English, and were at low risk for hearing loss. Stimuli were concatenated consonant pairs comprised from a dental /da/, plus either /ba/, Hindi retroflex /Da/, a second /da/ or a silent period (i.e., /dada/, /daba/, /daDa/ and /da_/). It was predicted that adults would show the largest ACC to /daba/, similar responses to /dada/ and /daDa/, and no ACC to /da_/, whereas, it was predicted that infants would show a similar ACC to /daba/ and /daDa/, a smaller ACC to /dada/ and no ACC to /da_/. The stimuli were a total of 564 msec in duration and were presented at 86 dB peak SPL with an interstimulus interval of 2200 msec. At least 100 accepted trials for each participant were required in the final waveform to be included in the study. Individual peak amplitudes and latencies were measured for the P1, N1, P2, and N2 components of the response to the initial /da/ and the ACC. Grand mean waveforms were averaged for each stimulus condition. ACCs were elicited in adults to /dada/, /daba/, and /daDa/ with a trend toward a larger grand mean ACC for /daba/ compared with the other stimulus conditions. For infants, cortical responses to /da_/ resembled the adult P1-N1-P2 complex in morphology but had much longer latencies; /daba/ was the only stimulus that consistently elicited ACCs in infants. The ACC to /daba/ had a more distinct and less variable morphology compared with both /dada/ and /daDa/, which might reflect that the infants detected a greater change from /da/ to /ba/ than from /da/ to either /da/ or /Da/. It may also be the case that the ACC could not be detected for these other stimuli because the stimulus duration and interstimulus intervals used in this study were not optimal for eliciting ACCs for a range of stimuli. The pattern of speech discrimination, as reflected by the ACC, only loosely parallels the behavioral discrimination patterns reported in previous studies. These preliminary findings show that it is possible to record an ACC in young infants and provide a starting point for further investigation of the infant ACC and its utility as an index of discrimination.

Horizontal Plane Localization in Single-Sided Deaf Adults Fitted With a Bone-Anchored Hearing Aid (Baha)

: One purpose of this investigation was to evaluate the effect of a unilateral bone-anchored hearing aid (Baha) on horizontal plane localization performance in single-sided deaf adults who had either a conductive or sensorineural hearing loss in their impaired ear. The use of a 33-loudspeaker array allowed for a finer response measure than has previously been used to investigate localization in this population. In addition, a detailed analysis of error patterns allowed an evaluation of the contribution of random error and bias error to the total rms error computed in the various conditions studied. A second purpose was to investigate the effect of stimulus duration and head-turning on localization performance. : Two groups of single-sided deaf adults were tested in a localization task in which they had to identify the direction of a spoken phrase on each trial. One group had a sensorineural hearing loss (SNHL group; N = 7), and the other group had a conductive hearing loss (CHL group; N = 5). In addition, a control group of four normal-hearing adults was tested. The spoken phrase was either 1250 msec in duration (a male saying "Where am I coming from now?") or 341 msec in duration (the same male saying "Where?"). For the longer-duration phrase, subjects were tested in conditions in which they either were or were not allowed to move their heads before the termination of the phrase. The source came from one of nine positions in the front horizontal plane (from -79° to +79°). The response range included 33 choices (from -90° to +90°, separated by 5.6°). Subjects were tested in all stimulus conditions, both with and without the Baha device. Overall rms error was computed for each condition. Contributions of random error and bias error to the overall error were also computed. : There was considerable intersubject variability in all conditions. However, for the CHL group, the average overall error was significantly smaller when the Baha was on than when it was off. Further analysis of error patterns indicated that this improvement was primarily based on reduced response bias when the device was on; that is, the average response azimuth was nearer to the source azimuth when the device was on than when it was off. The SNHL group, on the other hand, had significantly greater overall error when the Baha was on than when it was off. Collapsed across listening conditions and groups, localization performance was significantly better with the 1250 msec stimulus than with the 341 msec stimulus. However, for the longer-duration stimulus, there was no significant beneficial effect of head-turning. Error scores in all conditions for both groups were considerably larger than those in the normal-hearing control group. : On average, single-sided deaf adults with CHL showed improved localization ability when using the Baha, whereas single-sided deaf adults with SNHL showed a decrement in performance when using the device. These results may have implications for clinical counseling for patients with unilateral hearing impairment.

Retrograde signaling does not mediate sodium excretion during dorsal column stimulation

Prior work found an increase in renal sodium excretion in male spontaneously hypertensive rats (SHR) following dorsal spinal column stimulation (DCS) at the spinal segment of the left renal sensory nerves (T12–T13). General sympathetic tone, and renal blood flow were unaltered by DCS. The effects of dorsal rhizotomy on the DCS‐induced renal sodium excretion was investigated in male SHR. SHR were randomly assigned to one of the following groups: no‐stimulation (NS), stimulation (S), no stimulation + Rhizotomy (NS+R), and Stimulation + Rhizotomy (S+R). Stimulated rats received DCS during the 2nd of five 15‐min. collection periods. Blood pressure was measured via a carotid artery cannula, and urine was collected via a bladder cannula. A standard stimulation parameter of 66% of the motor threshold (0.2 msec duration and 50 Hz) was used. Urine sodium was analyzed using flame photometry. Sodium excretion was significantly elevated in periods 3 and 4 in the S group when compared with corresponding periods in the NS group. Sodium excretion was significantly elevated in period 5 in the S+R group when compared with the NS+R. There were no differences between the S+R and the S groups. The DSC‐induced increase in sodium excretion is independent of retrograde signaling in the renal nerves. This research was funded by a departmental grant, in the Department of the Biological Sciences, Minnesota State University, Mankato, MN

NEUROPHYSIOLOGICAL ABNORMALITIES DURING STIMULUS PROCESSING IN YOUTH AT CLINICAL HIGH RISK FOR PSYCHOSIS: AN INTERIM ANALYSIS OF THE NAPLS DATA

Reduction in a pre-attentive measure of auditory change detection, mismatch negativity (MMN), is one of the most consistent findings in schizophrenia. Recently, our group showed a reduction in MMN to changes in the duration and intensity of background sounds in those within 5 years of illness onset, whereas reduced MMNs to changes in sound frequency were only seen in patients with longer illness duration. In this report, we examine whether reduced MMN, as well as P3a, another index of auditory deviance detection, to duration changes is evident even earlier in the illness, that is, in individuals in the first episode of a psychosis (FEP) and individuals identified as being at ultra-high risk of developing schizophrenia (UHR).Mismatch negativity and P3a were measured in 30 UHR individuals, 10 FEP individuals, and 20 healthy control subjects to both long (100 msec) and short (50 msec) duration deviant sounds.Mismatch negativity was reduced to both duration deviants not only in the FEP group but also in the UHR group. P3a amplitude was also reduced in the UHR group but at trend level only in FEP. However, MMN and P3a reductions were unrelated in both UHR and FEP groups, suggesting that they reflect distinct deficits.These results suggest that MMN, as well as P3a, to duration deviants are reduced in very early stages of a psychotic illness including those in an at-risk mental state. Both should be considered as potential markers of the prodrome.