Schedule-induced drinking as a function of percentage reinforcement

Drinking was recorded in rats while lever pressing was maintained on a series of percentage reinforcement schedules in which the per cent of 1-min fixed intervals terminating with food was 100, 90, 30, 70, 10, 50, and 100%. Intervals in which a pellet was omitted were terminated by brief light flash and click stimuli that were also correlated with food presentations. Drinking failed to develop in five of six subjects following intervals in which the brief stimuli were presented regardless of percentage reinforcement. Postpellet drinking, which followed intervals terminated with pellet delivery, however, increased in both duration and amount ingested per interval as percentage reinforcement was systematically decreased. The increase in postpellet drinking above that produced by 100% reinforcement was interpreted as an analogue of the positive-contrast effect observed with food-reinforced operants

Hip Arthroplasty after Previous Arthrodesis

Total hip arthroplasty after previous arthrodesis has been associated with increased complications and decreased survivorship of the prosthesis. We evaluated pain, function, and the factors influencing survivorship of total hip arthroplasties after previous arthrodesis between 1985 and 2000 and compared these results with those obtained in prior years with the same procedure and in the same institution. We retrospectively reviewed 30 patients who had previous spontaneous or surgical arthrodesis. The minimum followup was 2 years (mean, 10.4 years; range 2–20.5 years). Seven failures were identified (23%). The overall survival free of failure was 86% at 5 years and 75% at 10 years. At last followup, 27 of the 30 patients (91%) had no or slight pain, 26 (87%) had a limp, and 18 (61%) needed a gait aid. Surgical arthrodesis, age younger than 50 years at the time of arthroplasty, and length of arthrodesis less than 30 years independently predicted failure. Conversion of arthrodesis to hip arthroplasty reliably decreases pain and improves function, but many patients will limp and require a gait aid. Our outcomes were similar to those after revision rather than after primary hip arthroplasty

Genetic drivers of cerebral blood flow dysfunction in TBI: a speculative synthesis

Cerebral autoregulatory dysfunction after traumatic brain injury (TBI) is strongly linked to poor global outcome in patients at 6 months after injury. However, our understanding of what drives this dysfunction is limited. Genetic variation among individuals within a population gives rise to single nucleotide polymorphisms (SNPs) that have the potential to influence a given patient’s cerebrovascular response to an injury. Associations have been reported between a variety of genetic polymorphisms and global outcome in patients with TBI, but few studies have explored the association between genetics and cerebrovascular function after injury. In this Review, we explore polymorphisms that might play an important part in cerebral autoregulatory capacity after TBI. We outline a variety of SNPs, their biological substrates and their potential role in mediating cerebrovascular reactivity. A number of candidate polymorphisms exist in genes that are involved in myogenic, endothelial, metabolic and neurogenic vascular responses to injury. Furthermore, polymorphisms in genes involved in inflammation, the central autonomic response and spreading cortical depression might drive cerebrovascular reactivity. Identification of candidate genes involved in cerebral autoregulation after TBI provides a platform and rationale for further prospective investigation of the link between genetic polymorphisms and autoregulatory function

Twenty-Five Years of Intracranial Pressure Monitoring After Severe Traumatic Brain Injury: A Retrospective, Single-Center Analysis.

BACKGROUND: Intracranial pressure (ICP) is a clinically important variable after severe traumatic brain injury (TBI) and has been monitored, along with clinical outcome, for over 25 yr in Addenbrooke's hospital, Cambridge, United Kingdom. This time period has also seen changes in management strategies with the implementation of protocolled specialist neurocritical care, expansion of neuromonitoring techniques, and adjustments of clinical treatment targets. OBJECTIVE: To describe the changes in intracranial monitoring variables over the past 25 yr. METHODS: Data from 1146 TBI patients requiring ICP monitoring were analyzed. Monitored variables included ICP, cerebral perfusion pressure (CPP), and the cerebral pressure reactivity index (PRx). Data were stratified into 5-yr epochs spanning the 25 yr from 1992 to 2017. RESULTS: CPP increased sharply with specialist neurocritical care management (P < 0.0001) (introduction of a specific TBI management algorithm) before stabilizing from 2000 onwards. ICP decreased significantly over the 25 yr of monitoring from an average of 19 to 12 mmHg (P < 0.0001) but PRx remained unchanged. The mean number of ICP plateau waves and the number of patients developing refractory intracranial hypertension both decreased significantly. Mortality did not significantly change in the cohort (22%). CONCLUSION: We demonstrate the evolving trends in neurophysiological monitoring over the past 25 yr from a single, academic neurocritical care unit. ICP and CPP were responsive to the introduction of an ICP/CPP protocol while PRx has remained unchanged

Behavioral momentum in the treatment of noncompliance.

Behavioral momentum refers to the tendency for behavior to persist following a change in environmental conditions. The greater the rate of reinforcement, the greater the behavioral momentum. The intervention for noncompliance consisted of issuing a sequence of commands with which the subject was very likely to comply (i.e., high-probability commands) immediately prior to issuing a low-probability command. In each of five experiments, the high-probability command sequence resulted in a "momentum" of compliant responding that persisted when a low-probability request was issued. Results showed the antecedent high-probability command sequence increased compliance and decreased compliance latency and task duration. "Momentum-like" effects were shown to be distinct from experimenter attention and to depend on the contiguity between the high-probability command sequence and the low-probability command