Changes In Discharge Patterns Research Articles

Patient Outcomes After Long-Term Acute Care Hospital Closures

Long-term acute care hospitals (LTCHs) are common sites of postacute care for patients recovering from severe respiratory failure requiring mechanical ventilation (MV). However, federal payment reform led to the closure of many LTCHs in the US, and it is unclear how closure of LTCHs may have affected upstream care patterns at short-stay hospitals and overall patient outcomes. To estimate the association between LTCH closures and short-stay hospital care patterns and patient outcomes. This retrospective, national, matched cohort study used difference-in-differences analysis to compare outcomes at short-stay hospitals reliant on LTCHs that closed during 2012 to 2018 with outcomes at control hospitals. Data were obtained from the Medicare Provider Analysis and Review File, 2011 to 2019. Participants included Medicare fee-for-service beneficiaries aged 66 years and older receiving MV for at least 96 hours in an intensive care unit (ie, patients at-risk for prolonged MV) and the subgroup also receiving a tracheostomy (ie, receiving prolonged MV). Data were analyzed from October 2022 to June 2023. Admission to closure-affected hospitals, defined as those discharging at least 60% of patients receiving a tracheostomy to LTCHs that subsequently closed, vs control hospitals. Upstream hospital care pattern outcomes were short-stay hospital do-not-resuscitate orders, palliative care delivery, tracheostomy placement, and discharge disposition. Patient outcomes included hospital length of stay, days alive and institution free within 90 days, spending per days alive within 90 days, and 90-day mortality. Between 2011 and 2019, 99 454 patients receiving MV for at least 96 hours at 1261 hospitals were discharged to 459 LTCHs; 84 LTCHs closed. Difference-in-differences analysis included 8404 patients (mean age, 76.2 [7.2] years; 4419 [52.6%] men) admitted to 45 closure-affected hospitals and 45 matched-control hospitals. LTCH closure was associated with decreased LTCH transfer rates (difference, -5.1 [95% CI -8.2 to -2.0] percentage points) and decreased spending-per-days-alive (difference, -$8701.58 [95% CI, -$13 323.56 to -$4079.60]). In the subgroup of patients receiving a tracheostomy, there was additionally an increase in do-not-resuscitate rates (difference, 10.3 [95% CI, 4.2 to 16.3] percentage points) and transfer to skilled nursing facilities (difference, 10.0 [95% CI, 4.2 to 15.8] percentage points). There was no significant association of closure with 90-day mortality. In this cohort study, LTCH closure was associated with changes in discharge patterns in patients receiving mechanical ventilation for at least 96 hours and advanced directive decisions in the subgroup receiving a tracheostomy, without change in mortality. Further studies are needed to understand how LTCH availability may be associated with other important outcomes, including functional outcomes and patient and family satisfaction.

The Relative Importance of Hospital Discharge and Patient Composition in Changing Post-Acute Care Utilization and Outcomes Among Medicare Beneficiaries

The COVID-19 pandemic changed care delivery. But the mechanisms of changes were less understood. Examine the extent to which the volume and pattern of hospital discharge and patient composition contributed to the changes in post-acute care (PAC) utilization and outcomes during the pandemic. Retrospective cohort study. Medicare claims data on hospital discharges in a large healthcare system from March 2018 to December 2020. Medicare fee-for-service beneficiaries, 65 years or older, hospitalized for non-COVID diagnoses. Hospital discharges to Home Health Agencies (HHA), Skilled Nursing Facilities (SNF), and Inpatient Rehabilitation Facilities (IRF) versus home. Thirty- and ninety-day mortality and readmission rates. Outcomes were compared before and during the pandemic with and without adjustment for patient characteristics and/or interactions with the pandemic onset. During the pandemic, hospital discharges declined by 27%. Patients were more likely to be discharged to HHA (+4.6%, 95% CI [3.2%, 6.0%]) and less likely to be discharged to either SNF (-3.9%, CI [-5.2%, -2.7%]) or to home (-2.8% CI [-4.4%, -1.3%]). Thirty- and ninety-day mortality rates were significantly higher by 2% to 3% points post-pandemic. Readmission were not significantly different. Up to 15% of the changes in discharge patterns and 5% in mortality rates were attributable to patient characteristics. Shift in discharge locations were the main driver of changes in PAC utilization during the pandemic. Changes in patient characteristics explained only a small portion of changes in discharge patterns and were mainly channeled through general impacts rather than differentiated responses to the pandemic.

Early Outcome Trends of Unicompartmental Knee Arthroplasty in Patients With Morbid Obesity: A Potential for Outpatient Surgery

BackgroundElevated body mass index (BMI) was previously considered a contraindication to unicompartmental knee arthroplasty (UKA). This study sought to determine if outcomes following UKA in patients with elevated BMI have improved over the years. We hypothesized that operative times and length of stay (LOS) following UKA would significantly decrease, while discharge to home rates would increase across all BMI cohorts, especially those with a BMI > 40. MethodsUsing the National Surgical Quality Improvement Program registry, surgical cases categorized using the Current Procedural Terminology code 27446 for UKA with a recorded height and weight were included. Three BMI cohorts were created: BMI I (BMI < 30), BMI II (30 ≤ BMI ≤ 40), and BMI III (BMI > 40). Each BMI group was subclassified temporally by year of operation: Years A (2006-2009), Years B (2010-2014), and Years C (2015-2019). ResultsA total of 14,114 patients were included. For BMI III, both operative time (P < .001) and LOS (P < .001) significantly decreased over the Years cohorts. Discharge home rates increased from 88.3% to 94.4% in BMI III (P = .001). All BMI cohorts saw similar changes in discharge patterns, 30-day readmissions, and reoperations within 30 days in recent years. ConclusionThis study found that operative times and LOS have decreased significantly in patients with morbid obesity over the past 14 years, while more patients are being discharged home without being readmitted or reoperated on in the first month. As surgeons continue to improve their operative and reconstructive techniques, this study suggests that patients with elevated BMI should be considered candidates to undergo UKA procedures in ambulatory surgery centers or in hospitals with a rapid recovery unit.

Sympathetic neural recruitment strategies following acute intermittent hypoxia in humans.

We examined the effect of acute intermittent hypoxia (IH) on sympathetic neural firing patterns and the role of the carotid chemoreceptors. We hypothesized exposure to acute IH would increase muscle sympathetic nerve activity (MSNA) via an increase in action potential (AP) discharge rates and within-burst firing. We further hypothesized any change in discharge patterns would be attenuated during acute chemoreceptor deactivation (hyperoxia). MSNA (microneurography) was assessed in 17 healthy adults (11 male/6 female; 31 ± 1 yr) during normoxic rest before and after 30 min of experimental IH. Prior to and following IH, participants were exposed to 2 min of 100% oxygen (hyperoxia). AP patterns were studied from the filtered raw MSNA signal using wavelet-based methodology. Compared with baseline, multiunit MSNA burst incidence (P < 0.01), AP incidence (P = 0.01), and AP content per burst (P = 0.01) were increased following IH. There was an increase in the probability of a particular AP cluster firing once (P < 0.01) and more than once (P = 0.03) per burst following IH. There was no effect of hyperoxia on multiunit MSNA at baseline or following IH (P > 0.05); however, hyperoxia following IH attenuated the probability of particular AP clusters firing more than once per burst (P < 0.01). Acute IH increases MSNA by increasing AP discharge rates and within-burst firing. A portion of the increase in within-burst firing following IH can be attributed to the carotid chemoreceptors. These data advance the mechanistic understanding of sympathetic activation following acute IH in humans.

Long-term hydraulic behaviour and soil ripening processes in a dike constructed from dredged material

PurposeClimate change necessitates heightening and strengthening of dikes, requiring large volumes of suitable soil. This study investigated soil ripening and long-term development of hydraulic behaviour of a dike constructed from slightly contaminated, partially dewatered dredged material from the Port of Hamburg under realistic conditions of construction and operation.Materials and methodsTwo test fields of 126 m2 each were constructed in 2004 for long-term analysis of hydraulic behaviour in combination with the possible mobilisation of contaminants. In test field 1 (MS), the 1-m-thick cover above the sand core consisted of traditionally used alluvial marsh sediment (reference), while in test field 2, the lower 0.7 m of the cover was substituted with dredged material (DM + MS). An HDPE tray below each field served the collection of bottom fluxes and hence the quantification of discharges and analysis of their chemical composition. In 2012, an excavation was carried out to inspect the development of the soil structure.Results and discussionThe discharge pattern revealed three distinct phases related to the post-construction structure development and therefore physical ripening of the soils. Within a single year, bottom fluxes typically started in mid-winter and ended in late spring. The dike cover containing DM had a high water retention capacity; however, the vertically continuous primary shrinkage cracks led to higher total bottom fluxes compared to the dike constructed from MS only. System hydraulic conductivities increased by up to six orders of magnitude compared to the as-built condition before soil ripening and structuring. The dredged material maintained a reduced geochemical status for about two years after construction. After first shrinkage and intrusion of oxygen, the material changed to an oxidised state, earmarking the onset of the chemical ripening process. Oxidising conditions were sustained in the long term, seen from the absence of previously elevated ammonium concentrations in the dike seepage.ConclusionsSystem hydraulics of the test field with dredged material were mainly determined by the covering layer of marsh sediment. After construction, the dredged material underwent physical, chemical and biological soil ripening processes, coupled to a respective change in discharge patterns, which, however, did not impair dike stability. It is recommended that soil ripening processes are induced and completed as part of the material’s pre-treatment, precluding the formation of irreversible shrinkage cracks and changeover of redox conditions after construction. The findings contribute to assessing the feasibility of the beneficial use of dredged material.

Sympathetic Discharge Patterns and Neurovascular Transduction Following Acute Intermittent Hypoxia

BackgroundMuscle sympathetic nerve activity (MSNA) is augmented in patients with sleep apnea. This increase in activity is due to increases in firing probability and mean firing rates of individual vasoconstrictor neurons, in addition to multiple within‐burst firing; however, contributing mechanisms and the impact of such firing patterns on peripheral vascular tone are less clear. We examined the effect of acute intermittent hypoxia (IH) on sympathetic neural firing and recruitment strategies and the relationship between changes in MSNA and neurovascular transduction following acute IH. We hypothesized exposure to acute IH would increase MSNA via an increase in action potential (AP) discharge rates and within‐burst firing. We further hypothesized any change in discharge patterns following acute IH would be positively related to a change in neurovascular transduction.MethodsBlood pressure (brachial arterial catheter) and MSNA (microneurography of the peroneal nerve) were assessed in 17 healthy adults (11M/6F; 31 ± 1 yrs) during quiet normoxic rest prior to and following 30‐min of experimental IH [30‐s hypoxic (0.05 FiO2) exposures alternating with 90‐s room air breathing]. AP patterns were studied from the filtered raw MSNA signal using wavelet‐based methodology. The slope of the relationship between diastolic blood pressure (DBP) and the preceding MSNA burst area at a fixed cardiac cycle lag was used to quantify neurovascular transduction.ResultsIH resulted in 15 events where oxygen saturation was reduced (SpO2: 99 ± 1% vs 92 ± 1%, P&lt;0.01). Compared to baseline, multi‐unit MSNA burst incidence (33 ± 4 to 43 ± 5 bursts/100 heart beats), AP incidence (272 ± 50 to 501 ± 112 AP/100 heart beats) and AP content per integrated burst (7 ± 1 to 10 ± 1 AP/burst; 4 ± 1 to 5 ± 1 clusters/burst) were increased following IH (all P&lt;0.05). Neurovascular transduction was not altered following IH (P=0.34); however, there was a positive relationship between the change (Δ) in neurovascular transduction (mmHg/%/s) and changes in AP discharge rate (AP/100 heart beats; R=0.52, P=0.03) and within‐burst firing (AP/burst; R=0.38, P=0.14) following IH.ConclusionsAcute IH increases sympathetic neuronal discharge by increasing within‐burst firing of low‐threshold axons. A positive relationship exists between increases in the neural discharge rates and neurovascular transduction following acute IH, such that those individuals with the greatest increase in AP firing exhibited the greatest increase in transduction of sympathetic activity into blood pressure. These data may have important implications for mechanistic understanding of sympathetic activation in sleep apnea and its down‐stream effects, including the development of hypertension and cardiovascular disease.Support or Funding InformationFunding: NIH HL130339, Mayo Clinic Center for Biomedical Discovery, Mizzou HES PURE, APS UGSRF.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Same-day discharge after elective percutaneous coronary intervention: A single-center experience

Advances in vascular access techniques, stent technology, and anti-platelet therapy have facilitated changes in discharge patterns following percutaneous coronary intervention (PCI). Overnight stay strategy remains the reference attitude although no recommendation has been published regarding the optimal duration of surveillance after uncomplicated PCI. To assess the feasibility and safety of same-day discharge (SDD) after elective PCI in Rouen University Hospital. All consecutive patients with stable coronary artery disease (CAD) scheduled for elective PCI in Rouen University Hospital between October 2017 and May 2018 were prospectively enrolled in our study. The eligibility criteria of same-day discharge (after 4 to 6 hours of surveillance) have been defined a priori . We evaluated the feasibility of same-day discharge and its safety by a combined endpoint including 30-day mortality, myocardial infarction, stent thrombosis, stroke, vascular complication, and readmission. From October 2017 and May 2018, 246 patients were included and 52 (21%) were discharged the same day (SDD patients). SDD patients were significantly younger than patients with overnight hospitalization (66.5 ± 11.4 vs. 70.3 ± 11.2 years, P = 0.03). A radial approach was more frequent in the SDD group (88.4% vs. 63.9%, P = 0.001). No major complications occurred during hospital surveillance in both groups and no events occurred within 30 days in SDD patients. Same-day discharge after elective PCI is feasible and safe in patients with stable CAD. Further studies are required to confirm our results and to evaluate the medico-economic impact of this strategy.

Length of stay following percutaneous coronary intervention: An expert consensus document update from the society for cardiovascular angiography and interventions.

Since the publication of the 2009 SCAI Expert Consensus Document on Length of Stay Following percutaneous coronary intervention (PCI), advances in vascular access techniques, stent technology, and antiplatelet pharmacology have facilitated changes in discharge patterns following PCI. Additional clinical studies have demonstrated the safety of early and same day discharge in selected patients with uncomplicated PCI, while reimbursement policies have discouraged unnecessary hospitalization. This consensus update: (1) clarifies clinical and reimbursement definitions of discharge strategies, (2) reviews the technological advances and literature supporting reduced hospitalization duration and risk assessment, and (3) describes changes to the consensus recommendations on length of stay following PCI (Supporting Information Table S1). These recommendations are intended to support reasonable clinical decision making regarding postprocedure length of stay for a broad spectrum of patients undergoing PCI, rather than prescribing a specific period of observation for individual patients.

Investigation of flame structure in plasma-assisted turbulent premixed methane-air flame

The mechanism of plasma-assisted combustion at increasing discharge voltage is investigated in detail at two distinctive system schemes (pretreatment of reactants and direct in situ discharge). OH-planar laser-induced fluorescence (PLIF) technique is used to diagnose the turbulent structure methane-air flame, and the experimental apparatus consists of dump burner, plasma-generating system, gas supply system and OH-PLIF system. Results have shown that the effect of pretreatment of reactants on flame can be categorized into three regimes: regime I for voltage lower than 6.6 kV; regime II for voltage between 6.6 and 11.1 kV; and regime III for voltage between 11.1 and 12.5 kV. In regime I, aerodynamic effect and slower oxidation of higher hydrocarbons generated around the inner electrode tip plays a dominate role, while in regime III, the temperature rising effect will probably superimpose on the chemical effect and amplify it. For wire-cylinder dielectric barrier discharge reactor with spatially uneven electric field, the amount of radicals and hydrocarbons are decreased monotonically in radial direction which affects the flame shape. With regard to in situ plasma discharge in flames, the discharge pattern changes from streamer type to glow type. Compared with the case of reactants pretreatment, the flame propagates further in the upstream direction. In the discharge region, the OH intensity is highest for in situ plasma assisted combustion, indicating that the plasma energy is coupled into flame reaction zone.

Noise trauma induced plastic changes in brain regions outside the classical auditory pathway

The effects of intense noise exposure on the classical auditory pathway have been extensively investigated; however, little is known about the effects of noise-induced hearing loss on non-classical auditory areas in the brain such as the lateral amygdala (LA) and striatum (Str). To address this issue, we compared the noise-induced changes in spontaneous and tone-evoked responses from multiunit clusters (MUC) in the LA and Str with those seen in auditory cortex (AC) in rats. High-frequency octave band noise (10–20kHz) and narrow band noise (16–20kHz) induced permanent threshold shifts at high-frequencies within and above the noise band but not at low frequencies. While the noise trauma significantly elevated spontaneous discharge rate (SR) in the AC, SRs in the LA and Str were only slightly increased across all frequencies. The high-frequency noise trauma affected tone-evoked firing rates in frequency and time-dependent manner and the changes appeared to be related to the severity of noise trauma. In the LA, tone-evoked firing rates were reduced at the high-frequencies (trauma area) whereas firing rates were enhanced at the low-frequencies or at the edge-frequency dependent on severity of hearing loss at the high frequencies. The firing rate temporal profile changed from a broad plateau to one sharp, delayed peak. In the AC, tone-evoked firing rates were depressed at high frequencies and enhanced at the low frequencies while the firing rate temporal profiles became substantially broader. In contrast, firing rates in the Str were generally decreased and firing rate temporal profiles become more phasic and less prolonged. The altered firing rate and pattern at low frequencies induced by high-frequency hearing loss could have perceptual consequences. The tone-evoked hyperactivity in low-frequency MUC could manifest as hyperacusis whereas the discharge pattern changes could affect temporal resolution and integration.

Effect of public reporting on intensive care unit discharge destination and outcomes.

Public reporting of hospital performance is designed to improve healthcare outcomes by promoting quality improvement and informing consumer choice, but these programs may carry unintended consequences. To determine whether publicly reporting in-hospital mortality rates for intensive care unit (ICU) patients influenced discharge patterns or mortality. We performed a retrospective cohort study taking advantage of a natural experiment in which California, but not other states, publicly reported hospital-specific severity-adjusted ICU mortality rates between 2007 and 2012. We used multivariable logistic regression adjusted for patient, hospital, and regional characteristics to compare mortality rates and discharge patterns between California and states without public reporting for Medicare fee-for-service ICU admissions from 2005 through 2009 using a difference-in-differences approach. We assessed discharge patterns using post-acute care use and acute care hospital transfer rates and mortality using in-hospital and 30-day mortality rates. The study cohort included 936,063 patients admitted to 646 hospitals. Compared with control subjects, admission to a California ICU after the introduction of public reporting was associated with a reduced odds of post-acute care use in post-reform year 2 (ratio of odds ratios [ORs], 0.94; 95% confidence interval [CI], 0.91-0.96) and increased odds of transfer to another acute care hospital in both post-reform years (year 1: ratio of ORs, 1.08; 95% CI, 1.01-1.16; year 2: ratio of ORs, 1.43; 95% CI, 1.33-1.53). There were no significant differences in in-hospital or 30-day mortality. Public reporting of ICU in-hospital mortality rates was associated with changes in discharge patterns but no change in risk-adjusted mortality.

Study on Dynamic Bifurcation of the Hindmarsh-Rose Neuron under Parameters’ Changing

In the thesis, the dynamic bifurcation characteristics of the Hindmarsh-Rose neuron are analyzed and discussed by the neurodynamic theory and methods. Under the stimulation of the current, the neuron’s discharge pattern changes from the resting state to the tonic firing, which needs the current’s amplitude reaching a certain value. Moreover the stimulation strength threshold has something to do with the parameter r of the neuron. When the stimulation current increases gradually, the general trend of the membrane potential’s ISI is the gradual decrease(The discharge frequency of the neuron increases gradually). The discharge patterns of the neuron are changed, and the neuron undergoes the process of dynamic bifurcation. This bifurcation process of the neuron has something to do with the parameter r. and different parameter r causes different bifurcation. Under a certain current’s stimulation, the HR neuron has plenty of discharge patterns with the parameter r’s changing. From the view of neurodynamics, the discharge patterns of the HR neuron are changed, in substance, the HR neuron undergoes dynamic bifurcation process. Therefore, The HR neuron’s discharge patterns can be adjusted and controlled by the stimulation current I and the parameter r. This investigation is helpful to know and investigate deeply the dynamic characteristics and the bifurcation mechanism of the HR neuron; and it provides a certain theory assist to investigate many neurons’ synchronization and the neural network’s synchronization.

単一運動単位発火パターンの変化からみたヒト外側翼突筋下頭の筋疲労(大阪歯科大学大学院歯学研究科博士(歯学)学位論文内容要旨および論文審査結果要旨の公表)

単一運動単位発火パターンの変化からみたヒト外側翼突筋下頭の筋疲労(大阪歯科大学大学院歯学研究科博士(歯学)学位論文内容要旨および論文審査結果要旨の公表)

Fatigue-related changes in discharge patterns of motor units in the inferior head of the lateral pterygoid muscle in humans

To investigate single motor unit (SMU) firing patterns of the inferior head of the human lateral pterygoid muscle (IHLP) during sustained isometric contractions, and to examine IHLP fatigability. In 5 subjects, EMG was recorded from the right IHLP during generation of horizontal isometric mandibular force towards left side. Subjects tracked a target on an oscilloscope, slowly increasing the force to 25% of maximum voluntary contraction, and then maintained that force for 120 s (endurance task). Subjects rested for 30 s after each test, and three 10s recovery tests were performed every 30 s (recovery task). Fatigue data were obtained from 23 SMUs. Twelve of 23 SMUs (52.2%) continued to fire throughout the 120 s, and each subject had at least one of these units. These units were classified as tonic pattern (T-unit). The firing rate of 6 of the 12 T-units (50.0%) decreased gradually with time. Comparison of the mean firing rate and coefficient of variance (CV) of interspike interval (ISI) of the 12 T-units between pre-fatigue, post-fatigue and the three recovery tasks showed that the mean firing rate decreased and CV of ISI increased after fatigue. Mean firing rate and CV of ISI recovered after 30 s of rest after the endurance task. The firing patterns of IHLP units changed with the passing of time during sustained isometric contractions leading to fatigue.

Laying the groundwork for a bright future: Scholarship award contest promotes the use of nickel chrome and bright finishes in automotive design

1.1. The stimulation sequence provoked by a luminous point moving in front of a column of ommatidia was simulated for the eye of Squilla mantis.2.2. The output from the ommatidia is transferred to one tangential, integrating fiber as graded potentials. These potentials follow a gaussian-shaped angular sensitivity function for each ommatidium.3.3. The tangential fiber sums the inputs as they arrive and generates a spike if the sum is above threshold at one instant of time and at one point of the fiber.4.4. The histograms of instantaneous frequencies of spike discharge resemble the input-pattern histograms.5.5. The discharge pattern changes with distance and speed of the moving spot as well for the simulations as in electrophysiological recordings, and is adapted to the size of the animal.6.6. The shape of the histograms (i.e. the pattern of spike discharge) is assumed to transmit the information on the position, speed and size of a moving target.

Pathophysiology of Parkinson's disease: the MPTP primate model of the human disorder.

The striatum is viewed as the principal input structure of the basal ganglia, while the internal pallidal segment (GPi) and the substantia nigra pars reticulata (SNr) are output structures. Input and output structures are linked via a monosynaptic "direct" pathway and a polysynaptic "indirect" pathway involving the external pallidal segment (GPe) and the subthalamic nucleus (STN). According to current schemes, striatal dopamine (DA) enhances transmission along the direct pathway (via D1 receptors), and reduces transmission over the indirect pathway (via D2 receptors). DA also acts on receptors in GPe, GPi, SNr, and STN. Electrophysiologic and other studies in primates rendered parkinsonian by treatment with the dopaminergic neurotoxin MPTP have demonstrated a reduction of neuronal activity of GPe and an increase of neuronal discharge in STN, GPi. and SNr. These findings are compatible with the view that striatal DA loss results in increased activity over the indirect pathway. Prominent bursting, oscillatory discharge patterns, and increased synchronization of neighboring neurons are found throughout the basal ganglia. These may result from changes in the activity of local circuits (e.g., the GPe-STN "pacemaker") or from more global abnormalities of the basal ganglia-thalamocortical network. These findings have been replicated in human patients undergoing microelectrode-guided stereotactic procedures targeted at GPi or STN. PET studies in patients with Parkinson's disease have lent further support to the proposed circuit abnormalities. The current models of basal ganglia function have recently been criticized. For instance, the strict separation of direct and indirect pathways and the segregation of D1 and D2 receptors have been questioned, and the almost complete absence of motor side effects of pallidal or thalamic lesions in human patients and animals is inconsistent. These results suggest that changes in discharge patterns and synchronization between basal ganglia neurons, abnormal network interactions, and compensatory mechanisms are at least as important in the pathophysiology of parkinsonism as changes in discharge rates in individual basal ganglia nuclei. Lesions of GPi or STN are effective in treating parkinsonism, because they reduce or abolish abnormal basal ganglia output, enabling remaining circuits to function more normally.

A Twist-Type Rubber-Tube Pump

A twist-type rubber-tube pump, consisting of a tube with one side fixed and the other connected to a motor axis, has been developed. Liquid inside the tube is discharged according to the twist angle of the tube. Discharge volume ΔV of the pump is therefore approximated by the formula ΔV=[1-L0{L02+re2(θ-α)2}-1/2]S0L0, where S0 is the cross-sectional area of the tube, L0 is tube length, θ is twist angle, re is typical tube radius, and α is the delay angle of discharge. A prototype “twist pump” (tube inside diameter: 4mm; outside diameter: 8mm; length: 50mm) was evaluated by continuous pump tests. These tests showed that the prototype discharges 50µL of liquid at a maximum twist angle of 270° and has a long life; that is, the discharge pattern changes little after two million repetitions of the pump cycle.

Brainstem mechanisms for analyzing temporal patterns of echolocation sounds: a model for understanding early stages of speech processing?

Because of their stereotyped audio–vocal behavior and highly accessible brainstem circuitry, echolocating bats provide a good model system in which to study the neural mechanisms that underlie the analysis of temporal features of sound. This paper reviews the lower brainstem auditory circuitry and describes selected forms of information processing that are performed in the pathways of the lower brainstem and auditory midbrain (inferior colliculus (IC)). Several examples of neural circuits in echolocating bats point out the ways in which inputs with different properties converge on IC neurons to create selectivity for specific temporal features of sound that are common to speech and echolocation. The initial transformations of auditory nerve input that occur in the lower brainstem pathways include a change in sign from excitatory input to inhibitory output, changes in discharge pattern, and the creation of delay lines. Convergence of multiple inputs on neurons in the IC produces tuning for temporal features of sound including duration, the direction of frequency sweeps, modulation rate, and interstimulus interval. The auditory cortex exerts control over some of this processing by sharpening or shifting neuronal filter properties. The computational processes that occur in the IC result in integration across a time scale that is consistent with the rate at which biological sounds are produced, whether they be echolocation signals or human speech components.

Development of Twist-Type Rubber-Tube Pump.

We developed the twist-type rubber-tube pump which discharges its inner liquid according to the twist angle of the tube one side of which is fixed and the other is connected to the motor axis. The rubber's volume does not change when it is stretched. And the tube is fixed on both sides. Discharge volume ΔV of the pump is therefore approximated by the formula ΔV=[1-L0{L02+re2(θ-α)2}<1/2]S0L0, where S0 is cross-section area of the tube, L0 is length, θis twist angle, re is typical radius, and α is delay angle of discharge. We designed and made a prototype (tube inner radius : φ4 mm, outer radius : φ8 mm, length : 50 mm). The prototype can discharge 50 μL of liquid at a twist angle of 270°and has a long life, that is the discharge pattern changes little after 2 million repetitions.

Neural measurement of sound duration: control by excitatory-inhibitory interactions in the inferior colliculus.

In the inferior colliculus (IC) of the big brown bat, a subpopulation of cells ( approximately 35%) are tuned to a narrow range of sound durations. Band-pass tuning for sound duration has not been seen at lower levels of the auditory pathway. Previous work suggests that it arises at the IC through the interaction of sound-evoked, temporally offset, excitatory and inhibitory inputs. To test this hypothesis, we recorded from duration-tuned neurons in the IC and examined duration tuning before and after iontophoretic infusion of antagonists to gamma-aminobutyric acid-A (GABA(A)) (bicuculline) or glycine (strychnine). The criterion for duration tuning was that the neuron's spike count as a function of duration had a peak value at one duration or a range of durations that was >/=2 times the lowest nonzero value at longer durations. Out of 21 units tested with bicuculline, duration tuning was eliminated in 15, broadened in two, and unaltered in four. Out of 10 units tested with strychnine, duration tuning was eliminated in four, broadened in one, and unaltered in five. For units tested with both bicuculline and strychnine, bicuculline had a greater effect on reducing or abolishing duration tuning than did strychnine. Bicuculline and strychnine both produced changes in discharge pattern. There was nearly always a shift from an offset response to an onset response, indicating that in the predrug condition, inhibition arrived simultaneously with excitation or preceded it. There was often an increase in the length of the spike train, indicating that in the predrug condition, inhibition also coincided with later parts of excitation. These findings support two hypotheses. First, duration tuning is created in the IC. Second, although the construction of duration tuning varies in some details among IC neurons, it follows three rules: 1) an excitatory and an inhibitory event are temporally linked to the onset of sound but temporally offset from one another; 2) the duration of some inhibitory event must be linked to the duration of the sound; 3) an excitatory event must be linked to the offset of sound.