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PubMed2005

Evidence of PVT anomaly boundaries of water at high pressure from compression and NaCl.2H2O dehydration experiments.

Isothermal compression experiments on water have been performed between 0 to 80 degrees C and up to 1.3 GPa pressure. The compressibilities derived from the water compression experiments reveal a nonsmooth PVT behavior forming two anomaly boundaries. These boundaries originate at the melting line of ice III at about 0.25 GPa/-20 degrees C, and of ice VI at about 0.8 GPa/13 degrees C. Both boundaries have a positive sloped course separating three areas of different PVT properties of water. However, this P-T topology is obscured by an unresolved complication in the temperature range of 40-60 degrees C, which allows different topological interpretations of the data. As a cross-check for the compression experiment the dehydration boundary of sodium chloride-dihydrate (NaCl.2H2O) has been determined up to 1.5 GPa. The dehydration curve of NaCl.2H2O which traverses the two anomaly boundaries shows two inflections at the intersection, at 0.27 GPa/12 degrees C and at 0.77 GPa/22 degrees C, respectively. While the isothermal compressibility curves as well as the dP/dT course of the two anomaly boundaries give evidence of two densifications of water, the slope analysis of the inflections of the NaCl-2H2O dehydration curve suggests that the entropy change plays an important role. A recent model of water at high pressure conditions proposes a gradual structural transition from a low density water (LDW) at low pressures to a high density water (HDW) at high pressures. The compression data as well as the inflections of the dehydration boundary indicate, however, two discrete structural changes of water. Data comparison with that model suggests that the anomaly boundary at lower pressure corresponds to a volume fraction [V(HDW)/(V(LDW)+V(HDW))] of 0.8, while the upper one approaches a volume fraction of 1.

Journal Article↗

PubMed2001

Aging, cumulative disability, and the compression of morbidity.

The Compression of Morbidity paradigm emphasizes reduction in cumulative disability by postponing chronic infirmity. This article describes the model, reviews data suggesting morbidity compression over time, establishes associations between health risks and subsequent disability, and describes risk reduction interventions.

Activities of Daily Living↗

PubMed2003

Experimental verification of the roles of intrinsic matrix viscoelasticity and tension-compression nonlinearity in the biphasic response of cartilage.

A biphasic-CLE-QLV model proposed in our recent study [2001, J. Biomech. Eng., 123, pp. 410-417] extended the biphasic theory of Mow et al. [1980, J. Biomech. Eng., 102, pp. 73-84] to include both tension-compression nonlinearity and intrinsic viscoelasticity of the cartilage solid matrix by incorporating it with the conewise linear elasticity (CLE) model [1995, J. Elasticity, 37, pp. 1-38] and the quasi-linear viscoelasticity (QLV) model [Biomechanics: Its foundations and objectives, Prentice Hall, Englewood Cliffs, 1972]. This model demonstrates that a simultaneous prediction of compression and tension experiments of articular cartilage, under stress-relaxation and dynamic loading, can be achieved when properly taking into account both flow-dependent and flow-independent viscoelastic effects, as well as tension-compression nonlinearity. The objective of this study is to directly test this biphasic-CLE-QLV model against experimental data from unconfined compression stress-relaxation tests at slow and fast strain rates as well as dynamic loading. Twelve full-thickness cartilage cylindrical plugs were harvested from six bovine glenohumeral joints and multiple confined and unconfined compression stress-relaxation tests were performed on each specimen. The material properties of specimens were determined by curve-fitting the experimental results from the confined and unconfined compression stress relaxation tests. The findings of this study demonstrate that the biphasic-CLE-QLV model is able to describe the strain-rate-dependent mechanical behaviors of articular cartilage in unconfined compression as attested by good agreements between experimental and theoretical curvefits (r2 = 0.966 +/- 0.032 for testing at slow strain rate; r2 = 0.998 +/- 0.002 for testing at fast strain rate) and predictions of the dynamic response (r2 = 0.91 +/- 0.06). This experimental study also provides supporting evidence for the hypothesis that both tension-compression nonlinearity and intrinsic viscoelasticity of the solid matrix of cartilage are necessary for modeling the transient and equilibrium responses of this tissue in tension and compression. Furthermore, the biphasic-CLE-QLV model can produce better predictions of the dynamic modulus of cartilage in unconfined dynamic compression than the biphasic-CLE and biphasic poroviscoelastic models, indicating that intrinsic viscoelasticity and tension-compression nonlinearity of articular cartilage may play important roles in the load-support mechanism of cartilage under physiologic loading.

Animals↗

PubMed1999

[Ambulatory treatment of deep venous thrombosis using low-molecular heparin, compression and mobilization].

From data in the literature as well as the authors' own experience ensues that diagnosed and objectively confirmed deep venous thrombosis can be successfully treated in out-patients departments by low-molecular heparin and compression with full mobilization without any major risk of pulmonary embolism and without the need of hospital admission (65 out-patients). Despite the high price of low-molecular heparin, treatment is economical as it does not require monitoring of haemocoagulation for hospital admission. Partsch et al. 1997 proved unequivoca lambda y that the rate of new attacks of pulmonary embolism during treatment is significantly lower than during classical treatment with non-fractionated heparin and immobilization.

Ambulatory Care↗

PubMed1994

Automated ventilator testing.

A new era has arrived for the Biomedical Engineering Department at the Royal Women's Hospital in Melbourne. We have developed a system to qualitatively test for intermittent or unconfirmed faults, associated with Bear Cub ventilators. Where previous testing has been inadequate, computer logging is now used to interface the RT200 Timeter Calibration Analyser (TCA) to obtain a real time display of data, which can be stored and graphed. Using Quick Basic version 4.5, it was possible to establish communication between the TCA and an IBM compatible computer, such that meaningful displays of machine performance were produced. From the parameters measured it has been possible to obtain data on Peak Pressure, Inspiratory to Expiratory ratio (I:E ratio) Peak Flow and Rate. Monitoring is not limited to these parameters, though these were selected for our particular needs. These parameters are plotted in two ways: 1. Compressed average versus time, up to 24 hours on one screen 2. Raw data, 36 minutes displayed on each screen. The compressed data gives an overview which allows easy identification of intermittent faults. The uncompressed data confirms that the averaged signal is a realistic representation of the situation. One of the major benefits of this type of data analysis, is that ventilator performance may be monitored over a long period of time without requiring the presence of a service technician. It also allows individual ventilator performance to be graphically compared to other ventilators.

Australia↗

PubMed1995

Production of chronic compression of the cauda equina in rats for use in studies of lumbar spinal canal stenosis.

STUDY DESIGN: The pathophysiology of lumbar spinal canal stenosis was analyzed with a new model in rats. OBJECTIVES: To produce chronic compression of the cauda equina in rats for analysis of the pathophysiology of lumbar spinal canal stenosis. SUMMARY OF BACKGROUND DATA: Models of compression to date have involved acute or subacute compression. A model of chronic compression has not been available. METHODS: A stainless steel wire fastened around the spine at L5 in 3-week-old rats, with a plate inserted against the ventral aspect of the vertebra to protect it from the wire. as the rats grew, the wire cut into the spinal canal. One year after the operation, canal stenosis was present without paralysis of the back limbs. RESULTS: Stenosis seen in sagittal sections, as a percentage of the original width, was 51.6 +/- 6.2% (mean +/- standard deviation). In histologic analysis of the region near the wire, findings included axonal degeneration, demyelination, vacuolar degeneration of the nerve fibers, and narrowing the intradural blood vessels with a decrease in their number. Cephalad and caudad to the wire, congested intradural blood vessels, degenerative foci near these congested vessels, fibrosis around these foci, congested epidural vessels, and fibrosis around these vessels were observed. During electrophysiologic analysis (six rats with stenosis), the conduction velocity of the cauda equina was found to be delayed. CONCLUSIONS: The histologic and electrophysiologic findings in this animal model were similar to findings in human subjects, so rats prepared in this way should be useful for study of chronic compression of the cauda equina.

Animals↗

PubMed1996

Recent data on the pathophysiology of nerve root compression and pain.

Both mechanical and biochemical factors are involved in the pathophysiology of nerve root compression. Chronic compression produces severe demyelination and fibrosis of the nerve root. Similar lesions can result from exposure to irritant substances released from the nucleus pulposus. Pain sensations arise from the peripheral nervous system as a result of structural radicular damage and sensitization. Structural nerve root changes (deafferentation, formation of ephapses or microneuromas) increase the sensitivity of the spinal nociceptive neurones. Algogenic substances are released that lower the activation threshold of nociceptors, producing peripheral sensitization. In the central nervous system, neuroplasticity and increased transmission of nociceptive signals in the spinal cord result in permanent excitation and sensitization of the spinal convergent neurones. The practical implications of these data are discussed.

Biomechanical Phenomena↗

PubMed1992

The role of laminectomy in the combined treatment of metastatic spinal cord compression.

A retrospective analysis of clinical data concerning 140 patients with spinal cord compression is presented. Treatment consisted of a surgical decompressive laminectomy followed by radiation therapy in 127 cases. Primary radiation therapy supported by steroids was applied in only 26 cases. A dose of 30-40 Gy in 15-20 fractions was delivered to all patients. Treatment outcome was analyzed by comparing motor function (categories: no deficit, mild deficit ambulatory, paraparetic not ambulatory, paraplegic), sphincter function, and pain relief before and after treatment in both modalities. Following laminectomy and radiation therapy, 82% of paraparetic patients regained their ability to walk, sphincter function improved in 68%, pain relief was achieved in 88%. Following radiation therapy alone, 64% of paraparetic patients became ambulatory, 33% showed a normalization of sphincter function, and 72% became pain free. Our results indicate that laminectomy should play a major role in the treatment of patients with metastatic spinal cord compression. The decision as to the treatment of choice has to be made individually for each patient taking into consideration his general condition, life expectancy, and origin of the primary.

Adult↗

PubMed2003

Modular data logger system for physical workload measurements.

Direct technical measurements of physical workload have advantages in studies of work-related musculoskeletal disorders. A data logger has been developed, based on 20 and 40 Mbyte PCMCIA (Personal Computer Memory Card International Association) flash memory cards, for electromyography (EMG), inclinometry and goniometry. They are provided with an input for marking of events that can be used for synchronization with other loggers and with video recordings. To make the data easier to access by the preceeding analysis software, application software has also been developed that reorganizes the data. The loggers are easy to operate and enable whole-day ambulatory field recordings without any need for reduction or compression of the data.

Electronic Data Processing↗

PubMed1976

Elastic area compressibility modulus of red cell membrane.

Micropipette measurements of isotropic tension vs. area expansion in pre-swollen single human red cells gave a value of 288 +/- 50 SD dyn/cm for the elastic, area compressibility modulus of the total membrane at 25 degrees C. This elastic constant, characterizing the resistance to area expansion or compression, is about 4 X 10(4) times greater than the elastic modulus for shear rigidity; therefore, in situations where deformation of the membrane does not require large isotropic tensions (e.g., in passage through normal capillaries), the membrane can be treated by a simple constitutive relation for a two-dimensionally, incompressible material (i.e. fixed area). The tension was found to be linear and reversible for the range of area changes observed (within the experimental system resolution of 10%). The maximum fractional area expansion required to produce lysis was uniformly distributed between 2 and 4% with 3% average and 0.7% SD. By heating the cells to 50 degrees C, it appears that the structural matrix (responsible for the shear rigidity and most of the strength in isotropic tension) is disrupted and primarily the lipid bilayer resists lysis. Therefore, the relative contributions of the structural matrix and lipid bilayer to the elastic, area compressibility could be estimated. The maximum isotropic tension at 25 degrees C is 10-12 dyn/cm and at 50 degrees C is between 3 and 4 dyn/cm. From this data, the respective compressibilities are estimated at 193 dyn/cm and 95 dyn/cm for structural network and bilayer. The latter value correlates well with data on in vitro, monolayer surface pressure versus area curves at oil-water interfaces.

Cell Membrane↗

PubMed1981

[Compressed spectral EEG analysis of patients with acute cerebral circulatory disorders].

The use of a new examination method -- compressed spectral analysis of EEGs by way of computerized Fourier's transformation -- is described. The method was used for examining 43 patients with cerebral stroke. Real-time comparisons of EEGs and data of their compressed spectral analysis were made in healthy subjects and patients with cerebral strokes of various character. Data on long-time on-line registration of the EEG spectrograms in patients with the cerebral strokes are presented, and the time course of the changes of those spectrograms in patients with the ischemic and hemorrhagic stroke is followed up. Prognostic criteria of the EEG spectrograms in cerebral strokes of various gravity are determined.

Acute Disease↗

PubMed2005

Biomechanical comparison of unipedicular versus bipedicular kyphoplasty.

STUDY DESIGN: A cadaveric study comparing the biomechanics of unipedicular versus bipedicular kyphoplasty in the treatment of osteoporotic vertebral compression fractures. OBJECTIVES: The objectives of this study were to compare unipedicular kyphoplasty to bipedicular kyphoplasty in restoring strength, stiffness, and height to osteoporotic vertebral compression fractures and to study the degree of unilateral wedging when using a unipedicular versus bipedicular approach to kyphoplasty. SUMMARY OF BACKGROUND DATA: Osteoporotic vertebral compression fractures are a common ailment of the elderly that can lead to chronic pain and deformity. Recently developed treatments known as vertebroplasty and kyphoplasty provide pain relief by percutaneously augmenting the fractured vertebral body with polymethyl methacrylate via a transpedicular approach. Vertebroplasty via a unipedicular approach has been shown to provide comparable restoration of vertebral body stiffness when compared to a bipedicular approach. The anticipated benefits of a unipedicular approach include reduction in patient risk, operative time, radiation exposure, and cost. No studies have evaluated the efficacy of unipedicular kyphoplasty. MATERIAL AND METHODS: Two fresh-frozen human cadaveric spines (T3-L5) were disarticulated, and the vertebral bodies (n = 30) were compressed using an Instron 8521 machine, recording load versus displacement. The fractured vertebral bodies then underwent kyphoplasty via either a unipedicular or bipedicular approach. The augmented vertebral bodies were then recompressed. The strength, stiffness, and height restoration of the groups were compared. Following recompression, the risk for lateral wedging was evaluated by comparing lateral height measurements. RESULTS: Following fracture and subsequent kyphoplasty augmentation, the mean strength of the bipedicular group was 1.40 kN (+/- 0.38) versus 1.57 kN (+/- 0.55) in the unipedicular group. Average stiffness in the bipedicular group was 0.4387 kN/mm (+/- 0.2095) compared to 0.6880 kN/mm (+/- 0.3179) in the unipedicular group. Postcompression vertebral body height was restored to 96% of prefracture height in the bipedicular group and 94% of prefracture height in the unipedicular group. The mean absolute value of the difference in height between right and left side of the vertebral bodies was 1.06 mm (+/- 1.01) in the bipedicular group, whereas the unipedicular group had a mean of 1.78 mm (+/- 1.84). Statistical analysis using 1-way analysis of variance revealed no significant difference in any of the outcome measurements between the unipedicular and bipedicular groups (P < 0.05). CONCLUSIONS: Unipedicular kyphoplasty is comparable to bipedicular kyphoplasty in the restoration of vertebral body strength, stiffness, and height in experimentally induced vertebral compression fractures. There was no greater risk for lateral wedging in the unipedicular group compared to the bipedicular group. Given the advantages of a unipedicular approach with respect to vertebral pedicle cannulation risk, operative time, radiation exposure, and cost, this study would support the use of a unipedicular approach to kyphoplasty in the treatment of vertebral compression fractures.

Aged, 80 and over↗

PubMed1999

Long-term trends in childhood infectious disease mortality rates.

OBJECTIVES: This study assessed long-term trends in US childhood infectious disease mortality rates (CIDMR). METHODS: We calculated age-adjusted and age group-specific US CIDMR (1968-1996) by using data from the Compressed Mortality File (1968-1992, 1996) and Multiple Cause of Death Files (1993-1995) of the National Center for Health Statistics and English data for historical comparison (1861-1964). RESULTS: US CIDMR declined continuously from 1968 to 1996, although the rate of decline slowed after 1974. Respiratory and central nervous system categories declined most; HIV-related deaths offset these declines somewhat. CONCLUSIONS: CIDMR declined nearly 200-fold between 1861 and 1996, but no substantive improvement occurred after 1986.

Adolescent↗

PubMed1995

Ligamentum flavum hematoma presenting as progressive root compression in the lumbar spine.

STUDY DESIGN: This is a case report. OBJECTIVES: To provide a better understanding of a rare entity, ligamentum flavum hematoma, based on a successfully treated patient. SUMMARY OF BACKGROUND DATA: Lumbar root compression is frequently caused by disc herniation. Canal stenosis, epidural hematoma, or tumors are less common. Few cases of hematoma in the ligamentum flavum causing lumbar root compression have been described. METHODS: A patient was treated for ligamentum flavum hematoma causing progressive lumbar root symptoms. Clinical and radiologic features, including magnetic resonance images, were recorded. RESULTS: Symptoms consisted of progressive lumbar root deficit after mild physical exertion. On magnetic resonance images, a mass continuous with the ligamentum flavum, compressing the dural sac and roots, was found. Areas of high signal in T1 were present in it. In this patient, removal of the ligamentum flavum (degenerated tissue containing hematoma) resolved all of the symptoms. The diagnosis could have been suspected based on clinical history and magnetic resonance imaging. CONCLUSIONS: Magnetic resonance imaging can provide a basis for diagnosing ligamentum flavum hematoma. Removal of ligamentum flavum is the treatment of choice.

Aged↗

PubMed2004

Primary and secondary osteoporosis' incidence of subsequent vertebral compression fractures after kyphoplasty.

STUDY DESIGN: Retrospective review of prospective database. OBJECTIVES: Define the incidence of adjacent and remote fractures after kyphoplasty vertebral augmentation, and identify vulnerable subpopulations at increased risks. SUMMARY OF BACKGROUND DATA: Painful osteoporotic compression fractures can be effectively treated with methyl methacrylate vertebral augmentation, but the effect of intervention on the generation of future remote and adjacent fractures has not been identified. No paper has analyzed the association of long-term steroid use to subsequent compression fractures. METHODS: A total of 175 patients were treated for compression fractures, from October 1999 to November 2001, 60 patients were excluded due to insufficient follow-up (less than 3 months) or malignancy related fracture. The remaining 115 patients' charts and radiographs were then individually analyzed. New fractures were identified based on changes from baseline imaging studies (). Demographic information, vertebral levels treated, adjacent fractures, and remote fractures underwent statistical analyzed (P < 0.05). RESULTS: A total of 225 vertebral bodies were treated in 115 patients using the kyphoplasty technique; of those, 26 patients developed 34 subsequent compression fractures. The mean follow-up was 11 months (range, 3-33 months). The incidence of subsequent fracture per procedure per kyphoplasty was 15.1% (34 of 225), overall incidence per patient was 22.6% (26 of 115). There were 80 patients with primary osteoporosis and 35 patients with secondary steroid-induced osteoporosis. These populations were similar in terms of demographics, single or multiple sites, along with two or three adjacent levels treated. Seventeen of the 26 (65%) patients with subsequent fracture had secondary steroid-induced osteoporosis, while only 9 of the 26 (35%) patients had primary osteoporosis. Therefore, the incidence of post-kyphoplasty VCF in the primary osteoporotic patient was 11.25% (9 of 80) and the incidence in the steroid-induced osteoporotic patient was 48.6% (17 of 35). This increased fracture rate in the steroid-dependent patients was significant (P < 0.0001), along with adjacent fractures (12 of 19 on steroids, P = 0.0009), and remote fractures (7 of 9 on steroids, P = 0.027). CONCLUSIONS: Steroid-induced compression fractures appear to have an increased incidence of subsequent fractures after the kyphoplasty procedure. The kyphoplasty protocol with concurrent medical osteoporotic regimen does not appear to increase, and may serve to reduce, the incidence of remote and adjacent fractures for primary osteoporotic fractures.

Aged↗

PubMed1997

Lower urinary tract symptoms in lumbar root compression syndromes: a prospective survey.

STUDY DESIGN: A prospective, observational survey. OBJECTIVES: To describe lower urinary tract symptoms in uncomplicated lumbar root compression syndromes with special reference to prevalence, nature, and severity, and to analyze whether the occurrence of lower urinary tract symptoms correlates with age, pain, analgesic intake, or the type and level of compression. SUMMARY OF BACKGROUND DATA: Lower urinary tract symptoms with lumbar root compression are well known in the classic but rather rare cauda equina syndrome. However, micturition difficulties seem to be far more frequent in lumbar root compression syndromes. METHODS: One hundred eight male patients admitted for surgery for lumbar disc herniation or spinal stenosis were investigated with an extensive questionnaire about their micturition. RESULTS: Fifty-five percent had significant lower urinary tract symptoms. Eighty percent of the patients with spinal stenosis had symptoms. Thirty-three patients had irritative symptoms, 36 had obstructive symptoms, and 23 had retention symptoms. Twenty-four had severe symptoms. Median compression resulted in more symptoms than paramedian compression. There was no correlation between age, level of compression, drug intake, or pain score and lower urinary tract symptoms. CONCLUSIONS: Lower urinary tract symptoms of mixed type occur with a high prevalence in male patients with lumbar root compression syndromes referred for neurosurgical evaluation and treatment.

Adult↗

PubMed2005

Irreducible anterior atlantoaxial dislocation: one-stage treatment with a transoral atlantoaxial reduction plate fixation and fusion. Report of 5 cases and review of the literature.

STUDY DESIGN: Retrospective report of five surgical cases and review of the literature. OBJECTIVES: To report the clinical application of a novel internal fixation device in the treatment of irreducible atlantoaxial dislocation with ventral spinal cord compression. SUMMARY AND BACKGROUND DATA: Irreducible atlantoaxial dislocation with ventral spinal cord compression is difficult to treat. Traction is not uniformly successful at either reducing the dislocation or decompressing the spinal cord. Direct anterior decompression of the spinal cord may be necessary, in addition to the need for surgical stabilization of the upper cervical spine. Numerous methods have been described for surgical stabilization following transoral decompression, which generally require a second-stage posterior instrumentation and fusion procedure. Complication rates remain noteworthy for any of these strategies. METHODS: A novel transoral atlantoaxial reduction plate (TARP) system was designed to facilitate a one-stage anterior operation capable of simultaneously decompressing the ventral spinal cord as well as reducing and fusing the atlantoaxial segment. The procedure and TARP implant has been employed for five patients with irreducible atlantoaxial dislocation because of trauma or congenital disorders. Following transoral decompression and excision of scar, ligament and osteophytes, the TARP was used to affect reduction and fixation of the atlantoaxial joints. The decorticated atlantoaxial joint surfaces were grafted with autogenous iliac crest bone. The histories of these cases were reported in detail. RESULTS: The five case examples demonstrate the efficacy of this one-stage approach to the surgical treatment of irreducible anterior atlantoaxial dislocation with spinal cord compression. The role of the TARP in affecting and maintaining the reduction while promoting successful fusion is illustrated. CONCLUSION: The authors' one-stage anterior procedure employing their TARP for the surgical treatment of irreducible anterior atlantoaxial subluxation was effective in these five cases. This method was able to avoid the need for interval traction and/or a second stage posterior instrumentation and fusion procedure.

Adult↗

PubMed1992

Dynamic range of neural rate responses in the ventral cochlear nucleus of awake cats.

1. Response thresholds and dynamic range properties of neurons in the ventral cochlear nucleus (VCN) of awake cats were measured by fitting a computational model to rate-level functions for best frequency (BF) tone bursts and for bursts of broad-band noise. Dynamic range measurements were performed in quiet and in the presence of continuous background noise. 2. The sample of neurons obtained in the VCN of awake cats exhibited a variety of peristimulus histograms (PSTHs) and thresholds. All PSTH response types previously described in the VCN of anesthetized cats were found in awake cats. The lowest thresholds for neural responses were observed at sound pressure levels that were equivalent to behavioral thresholds of absolute auditory sensitivity. 3. When responses to BF tones or bursts of broad-band noise were recorded in quiet backgrounds, the dynamic range properties of most units in the VCN of awake cats were not significantly different from dynamic range properties of auditory nerve fibers (ANFs) in anesthetized cats or VCN units in decerebrate cats. All auditory units showed a larger dynamic range for noise bursts than for tone bursts, but VCN units with primary-like and onset PSTHs showed larger dynamic ranges for responses to noise bursts than that of ANFs and VCN chopper units. 4. When tests were performed in the presence of continuous noise, rate-level functions for BF tone bursts shifted to higher tone levels and showed a more compressed range of driven rates in comparison with data obtained in quiet. Compression of the rate-level function in noise resulted from an increase in driven rate at low tone levels and a decrease in rate at high tone levels. These changes in the rate-level function suggest that noise may reduce the range of BF tone levels that are potentially encoded by a unit's rate responses. By exhibiting larger shifts and less compression in background noise, VCN units in awake cats better preserved the dynamic range of their rate responses to BF tones than ANFs in anesthetized cats or VCN units in decerebrate cats. 5. Rate-level functions were obtained from a small sample of VCN units not only with the cat performing the behavioral task but also with the cat awake and sitting quietly in the testing apparatus. No differences in noise-induced shift or compression were noted between the two testing conditions.(ABSTRACT TRUNCATED AT 400 WORDS)

Acoustic Stimulation↗