A neural network learning algorithm tailored for VLSI implementation.

This paper describes concepts that optimize an on-chip learning algorithm for implementation of VLSI neural networks with conventional technologies. The network considered comprises an analog feedforward network with digital weights and update circuitry, although many of the concepts are also valid for analog weights. A general, semi-parallel form of perturbation learning is used to accelerate hidden-layer update while the infinity-norm error measure greatly simplifies error detection. Dynamic gain adaption, coupled with an annealed learning rate, produces consistent convergence and maximizes the effective resolution of the bounded weights. The use of logarithmic analog-to-digital conversion, during the backpropagation phase, obviates the need for digital multipliers in the update circuitry without compromising learning quality. These concepts have been validated through network simulations of continuous mapping problems.

Microbial flora on doctors' white coats.

OBJECTIVE: To determine the level and type of microbial contamination present on the white coats of doctors in order to assess the risk of transmission of pathogenic micro-organisms by this route in a hospital setting. DESIGN: Cross sectional survey of the bacterial contamination of white coats in a general hospital. SETTING: East Birmingham Hospital, an urban general hospital with 800 beds. SUBJECTS: 100 doctors of different grades and specialties. RESULTS: The cuffs and pockets of the coats were the most highly contaminated areas. The level of bacterial contamination did not vary with the length of time a coat had been in use, but it increased with the degree of usage by the individual doctor. Staphylococcus aureus was isolated from a quarter of the coats examined, more commonly from those belonging to doctors in surgical specialties than medical specialties. Pathogenic Gram negative bacilli and other pathogenic bacteria were not isolated. CONCLUSIONS: White coats are a potential source of cross infection, especially in surgical areas. Scrupulous hand washing should be observed before and after attending patients and it may be advisable to remove the white coat and put on a plastic apron before examining wounds. There is little microbiological reason for recommending a more frequent change of white coat than once a week, nor for excluding the wearing of white coats in non-clinical areas.

Acute atraumatic subdural hematoma associated with moyamoya disease in an African-American.

A 57-year-old black woman with an atraumatic subdural hematoma was treated for congestive heart failure and was found to have moyamoya disease. The association of these two lesions is rare and has never been described in an African-American. High cerebral venous pressures and changes in cerebral perfusion caused by congestive heart failure and the loss of cerebrovascular autoregulation in moyamoya disease may explain the spontaneous occurrence of a subdural hematoma. Recommendations for management are discussed.

Moyamoya-like disease associated with a lenticulostriate region aneurysm. Case report.

A case of moyamoya-like disease associated with an intracerebral hemorrhage and an unusual aneurysm is reported. The patient's clinical status and the initial and follow-up angiographic appearance of the aneurysm are presented. The etiology of the moyamoya phenomenon and of associated aneurysms is discussed.

Noncortical origins of the spinal motor evoked potential in rats.

Motor evoked potentials (MEPs) were recorded from the spinal cord, sciatic nerve, or both during transcortical electrical stimulation in the rat. Four peaks could be consistently identified in the spinal MEP. The latency and amplitude of the peaks varied differentially with intensity and polarity of stimulation. Conduction velocity for Peak 1 of the MEP was 43 m/sec. Bilateral sciatic nerve MEPs were present after unilateral cortical stimulation. The spinal MEP was elicited by stimulation of areas outside the motor cortex, and the response persisted during subcortical stimulation and after motor cortex ablation. We present evidence suggesting that components of the spinal MEP in rats arise from pathways outside the motor cortex.

The feasibility of low dose barbiturate administration by intra-carotid infusion to achieve EEG burst suppression--a preliminary report.

More than 10 years have elapsed since the introduction of high dose barbiturate administration in the management of patients with severe head injuries. Barbiturate therapy became an accepted method of treatment for increased intracranial pressure when other measures fail. One of the major limiting factors in the use of high dose barbiturate therapy is its significant hypotensive effect on the systemic arterial blood pressure. In seeking ways and means of minimising this hypotensive effect, we designed a study in which the systemic administration of barbiturates is avoided and replaced by selective perfusion of the concerned hemisphere with the drug utilising the intra-carotid route. Twenty-two rats, divided into two groups, were used in the study. Since monitoring of electroencephalographic (EEG) burst suppression serves as a good indicator of the lowest level of cerebral metabolic activity, we used this as the method for determining the desired endpoint of sodium amytal administration in both groups of animals. Group I, the intravenous group, consisted of eleven animals who received sodium amytal intravenously until burst suppression on the EEG was documented. Group II, the intra-carotid group, comprised eleven animals who received intra-carotid sodium amytal until EEG burst suppression was induced. In the intravenous group, a mean dose of 35 mg/kg of sodium amytal was administered before EEG burst suppression was achieved. This dose, however, was accompanied by an almost 50% reduction in systemic blood pressure compared to the pretreatment level. The intra-carotid group required a mean dose of 3.8 mg/kg sodium amytal and this was accompanied by only minor changes in systemic arterial pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of etoposide-induced blood-brain barrier disruption on brain water, intracranial pressure, and cerebral vasomotor tone.

This study investigated the effects of hypertension and water loading on etoposide-induced, reversible blood-brain barrier disruption in a rat model. Twenty-nine animals were divided into four groups: group 1--intracarotid (i.c.) injection of saline followed in 1 h by 5 ml i.c. water; group 2--i.c. etoposide followed by i.c. water; group 3--i.c. saline followed by i.v. metaraminol to increase systemic blood pressure; group 4--i.c. etoposide followed by i.v. metaraminol. Systemic blood pressure and intracranial pressure were monitored continuously. Evans blue staining of the brain was used as a monitor of blood-brain barrier disruption. Animals were killed 1 h after either aramine or water infusion, and the brains removed and inspected for the degree of disruption. After dehydration, brain water was calculated for each hemisphere. Two-thirds of the animals infused with etoposide had evidence of barrier disruption, whereas none of the control animals infused with saline were disrupted. Neither control groups 1 or 3 showed significant change in intracranial pressure after water loading or augmentation of systemic blood pressure, respectively. Group 4 animals failed to demonstrate any significant change in intracranial pressure despite marked barrier disruption and acute hypertension (within the limits of normal autoregulation). A small but statistically significant increase in intracranial pressure was noted in group 2 animals with the greatest degree of barrier disruption. A significant increase in brain water was observed ipsilateral to etoposide infusion in only those animals with the most marked barrier disruption. These results indicate that etoposide-induced blood-brain barrier disruption caused significant increases in brain water without significant alteration of cerebral vasomotor tone or increases in intracranial pressure after water loading except in the most severe disruption. The classic untoward consequences of vasogenic edema were not encountered in the present model.

Physiological and electrophysiological consequences of etoposide-induced blood-brain barrier disruption.

The present study investigates the effects of etoposide-induced blood-brain barrier (BBB) disruption on systemic blood pressure (SBP), intracranial pressure (ICP), and electroencephalographic (EEG) activity. A total of 29 rats were divided into two groups. In Group 1, 8 control animals received intracarotid normal saline; in Group 2, 21 animals received intracarotid etoposide. SBP, ICP, and EEG were monitored continuously under general anesthesia and controlled ventilation after tracheostomy. Intravenous Evans blue dye was used for determination of BBB disruption. Although none of the Group 1 animals showed BBB disruption, 57% of the animals in Group 2 showed marked BBB disruption (3+). A slight but statistically significant increase in ICP was noted in the Group 2 animals with 3+ BBB disruption, although lesser degrees of barrier disruption (1+ or 2+) resulted in no significant alteration in ICP. The amplitude and frequency of the EEG decreased significantly ipsilateral to the side of intracarotid infusion in all animals with 3+ barrier disruption with a tendency to return toward normal within 2 hours. The degree of transient EEG change observed correlates well with the degree of barrier disruption, potentially allowing clinical determination of BBB disruption by this method.

Neurological deterioration after lumbar puncture below complete spinal subarachnoid block.

The risk of neurological deterioration after removal of cerebrospinal fluid below the level of a complete spinal subarachnoid block is generally accepted. The actual incidence of deterioration after lumbar puncture in the presence of a complete block remains unknown. The present retrospective case analysis includes a review of 100 patients found to have complete block on myelography: 50 cases with a lumbar puncture and 50 cases with a C1-2 puncture. Each group consisted of a similar age range, neurological status prior to myelography, level of block, and nature of disease. Seven patients (14%) had significant neurological deterioration after lumbar puncture, while no deterioration was seen after a C1-2 puncture. A summary of those cases in which deterioration followed lumbar puncture is presented and the possible pathophysiology is discussed. From this analysis, the estimated risk of downward spinal coning after lumbar puncture below a complete spinal subarachnoid block caused by a mass lesion is at least 14%.

Diabetic ketoacidosis due to insulin resistance treated by haemodialysis.

A 14-year-old female patient with insulin resistance is reported in whom it appeared that initially insulin breakdown was unusually rapid. Subsequently there was in addition evidence of reduced insulin sensitivity. The rapidly increasing requirement of insulin (1600 units daily), given by continuous IV infusion, was dramatically reduced by haemodialysis, and was maintained subsequently. We suggest that insulin aggregates which may have blocked insulin receptor sites, causing insulin resistance, were removed by haemodialysis.

Advancement to independent living: a model behavioral program for the intermediate care of adults with behavioral and emotional problems.

This article describes and evaluates the treatment effectiveness of a behaviorally oriented intermediate day-care clinic for adults with psychiatric disturbances. The goals of the program included reducing the number of psychiatric hospital admissions and readmissions, providing a community-based controlled environment to assist patients in the modification of specific problem behavior, improving interpersonal relations with "significant others" in the natural environment, teaching patients how to use community resources, and preparing them for employment and/or continued outpatient treatment. The program was structured so that patients advance through a series of four achievement levels for a variety of extrinsic and intrinsic reinforcers. While in the program, patients were introduced to available community resources, and were gradually phased into follow-up services. Results showed that 79% of all patients thus far treated partially, if not completely, advanced through the levels. There was also a high probability that a patient would advance from any given level. Outside-clinic behavior showed sustained improvement, with the authors concluding that the day-care clinic offered promise for the future.