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PubMed2004

Treatment of nasal inflammation decreases the ability of subjects with asthma to condition inspired air.

We previously showed that individuals with seasonal allergy have a reduced ability to condition air, which was improved by nasal inflammation. We also showed that subjects with asthma have a reduced ability to condition air. Because individuals with asthma usually have inflammation in the nose, we hypothesized that treatment with an intranasal steroid would reduce nasal inflammation and further decrease nasal conditioning capacity. We performed a randomized, double blind, placebo-controlled, 2-way crossover study on 20 subjects with asthma comparing the effect of treatment with intranasal budesonide for 2 weeks on nasal conditioning. Treatment with budesonide caused no significant effect on nasal conditioning as compared with placebo. When we evaluated the subgroup of nonsmoking subjects, budesonide caused a significant reduction in nasal conditioning. We speculate that nasal inflammation in nonsmoking individuals with asthma increases the conditioning capacity and reducing it with an intranasal steroid worsens the ability of the nose to condition air. In addition, smoking causes an increase in nasal conditioning capacity by non-steroid-dependent factors. These observations help us understand the pathophysiology of nasal conditioning, but do not negate the positive clinical benefits of budesonide on treating nasal inflammation.

Administration, Intranasal↗
PubMed2002

A national study of medical care expenditures for respiratory conditions.

This study was undertaken to estimate the magnitude of medical care expenditures among persons with respiratory conditions in the USA in 1996, and the increment in expenditures attributable to these conditions. The study data were derived from the 1996 Medical Expenditure Panel Survey, a national sample of 21,571 persons. Of the 21,571, 1,027 reported one or more respiratory condition. After weighting, the individuals may represent about 12.1 million persons in the USA. All medical care expenditures of these individuals were tabulated, stratified by comorbidity status, and then compared to those among persons with nonrespiratory conditions or with no conditions. Regression techniques were then used to estimate the increment of healthcare expenditures attributable to the respiratory conditions. From a national total of $45.3 billion, medical care expenditures averaged $3,753 among persons with respiratory conditions. Hospital stays comprised the largest component (45%). The per capita increment in total expenditures attributable to respiratory conditions ranged from $1,003-2,588, from a national total ranging from $12.1-31.3 billion. The total medical care expenditure of persons with respiratory conditions was estimated to be $45.3 billion, of which $12.1-31.3 billion represents an increment in expenditures associated with the conditions themselves.

Case-Control Studies↗
PubMedDate not supplied

Access to care, unmet health needs, and poverty status among children with and without chronic conditions.

OBJECTIVES: To compare insurance coverage, access to care, and unmet health needs of children with and without chronic conditions in a national probability sample of the US population and to examine the role of poverty status in any demonstrated differences between the 2 groups. DESIGN: We analyzed parent-report data on children 0-17 years old from the 1994 National Health Interview Survey Disability Supplement (NHIS-D) and from the health insurance and access to care files of the 1994 Family Resources Supplement to the NHIS. In the NHIS-D, 4452 (14.8%) of the 30032 children were identified as having a chronic condition by a noncategorical method. We compared insurance coverage, access to care, and unmet needs of children with and without conditions overall and also compared them within 3 different income levels relative to the national poverty index: 1) below, 2) within 100%-200%, and 3) >200% above poverty level. RESULTS: In bivariate analyses, children with chronic conditions were more likely to be covered by some type of health insurance (odds ratio [OR], 1.3) and to have a usual provider both for medical ("sick") care (OR, 1.4) and for routine or preventive care (OR, 1.4). They also were more likely to have the same provider for medical care and routine or preventive care (OR, 1.2) and to have seen their health care provider in the last year (OR, 1.8) than children without chronic conditions (all P <.0001). Nonetheless, children with chronic conditions were twice as likely to have had at least 1 unmet need from a list of 4 services that included dental care, prescription medications, eyeglasses, and mental health services (OR, 2.0). They also were more likely to have more than 1 unmet need from the list (OR, 3.1), to have been unable to get needed medical care (OR, 3.1), and to have delayed obtaining medical care because of worry about its cost (OR, 1.8). Children with chronic conditions were at greater risk for unmet needs than were children without conditions across all income levels. The magnitude of the disparity between the groups increased with family income level. Differences persisted even after controlling for sociodemographic variables and insurance status. CONCLUSION: Despite higher levels of insurance coverage and greater access to regular providers of medical and routine care compared with healthy peers, children with chronic conditions are reported by their parents to be less likely than other children to receive the full range of needed health services. The magnitudes of the differences are small, yet the pattern of disadvantage in meeting health care needs among children with conditions compared with healthy peers is consistent across many different variables and it exists across income levels.

Child↗
PubMed2001

Excess risk of severe acute illness in children with chronic health conditions.

UNLABELLED: We estimated the relative risk (RR) of an unscheduled pediatric intensive care unit (ICU) admission as a marker for severe acute illness in children with chronic health conditions, compared with previously healthy children. Potentially preventable events that lead to acute illness were identified to develop preventive strategies. METHODS: Children with chronic conditions were defined as those who have a chronic physical, developmental, behavioral, or emotional condition and who also require health and related services of a type or amount beyond that required by children generally. RR was estimated from admissions and regional population data. Potentially preventable events that lead to ICU admission of chronically ill children were identified retrospectively from hospital records. RESULTS: Children with chronic health conditions had an RR of 3.3 for an unscheduled ICU admission related to their chronic condition, compared with previously healthy individuals (95% confidence interval [CI] = 2.5-4.2). The risk of severe acute illness in the small subgroup that received technology-assisted care was much greater (RR = 373; 95% CI = 330-422) than for the large group of chronically ill patients who did not require technology-assisted care (RR = 2.3; 95% CI = 1.7-3.0), each expressed relative to previously healthy children. Acute illness related to chronic health conditions accounted for 45% of 251 unscheduled ICU admissions during the 1-year study. Thirty-two percent of admissions that were related to chronic conditions were judged to have been potentially preventable. Preventable events were more common for those who did not require technology-assisted care, occurring in 38% of admissions, compared with those who received technology-assisted care, for whom 19% of admissions involved a preventable event. Fifty-six percent of potentially preventable events involved the physical or social environment and decisions made by the family, whereas 64% could be attributed to health care system factors. CONCLUSIONS: Children with chronic health conditions account for a substantial share of severe acute illness in a region. Because their underlying conditions have already been identified, problems may be anticipated. The small number of children who receive technology-assisted care each have such a high risk of severe and unavoidable acute illness that individualized emergency care plans are justified. For the remainder of children with chronic conditions, investigation of health system strategies to improve families' ability to anticipate, minimize, or prevent related acute illness is warranted.

Acute Disease↗
PubMed2003

Length of stay for common pediatric conditions: teaching versus nonteaching hospitals.

OBJECTIVE: Pediatric teaching hospitals provide particular expertise in caring for children with complex or severe illnesses, yet most patients within teaching hospitals have common pediatric conditions. No study has determined whether children with common conditions remain hospitalized at teaching institutions longer than at nonteaching institutions. The objective of this study was to compare length of stay (LOS) for common pediatric conditions between teaching and nonteaching hospitals. METHODS: This study uses Massachusetts's hospital data for all discharged children ages 0 to 17 years for 1995 and 1996. Discharges were included when the principal diagnosis indicated asthma, bacterial pneumonia, convulsions, dehydration, failure to thrive, gastroenteritis, or urinary tract infections. Hospitals were classified as either teaching or nonteaching using the 1995-1996 American Hospital Association Guide. Children were identified as having a chronic condition when any discharge diagnosis was 1 of those on a previously published catalog of chronic childhood illnesses. The analysis tested the association of hospital type with LOS, controlling for chronic conditions, insurance type, age, race, diagnosis, mortality, and disposition using multivariate linear regression. RESULTS: Of 17 890 discharges for a common pediatric condition during the study period, 52.3% were from teaching hospitals. Twelve percent of common condition discharges also had a chronic disease diagnosis; 75.1% of these were discharged from a teaching hospital. LOS from nonteaching hospitals was shorter than from teaching hospitals (2.42 days vs 3.20 days). Although LOS for stays with a chronic diagnosis were longer than those without (4.75 days vs 2.56 days), controlling for chronic illness and other covariates did not eliminate the difference between LOS for nonteaching hospitals versus teaching hospitals (1.65 days vs 2.23 days). CONCLUSION: Pediatric patients with common conditions have a shorter LOS in nonteaching hospitals than those admitted to teaching hospitals by a little more than half a day. These results are unchanged when accounting for chronic conditions despite the expected results of preferential admissions to teaching hospitals for this group of patients. Additional studies should better characterize differences in patient populations, describe differences in processes, and identify differences in patient experience and outcomes to understand better the potential benefits of treating children with specific conditions at particular types of hospitals.

Asthma↗
PubMed1995

Seven chronic conditions: their impact on US adults' activity levels and use of medical services.

OBJECTIVES: This paper analyzes the impact of seven chronic conditions (three nonfatal: arthritis, visual impairment, hearing impairment; four fatal: ischemic heart disease, chronic obstructive pulmonary disease, diabetes mellitus, malignant neoplasms) on US adults aged 18 and older. Impact refers to how readily a condition prompts activity limitations, physician visits, and hospital stays. METHODS: Data come from three national health surveys and vital statistics. For comparability, a single disease classification scheme was applied, and new rates were estimated. Frequency, impact, and prominence of the target conditions are studied via rates, ratios of rates, and ranks, respectively. RESULTS: In young adulthood, the nonfatal conditions prompt limitations less readily than do the fatal ones, but by older ages, arthritis and visual impairment have a limiting impact equivalent to that of fatal conditions. Despite high prevalence and limitations, nonfatal conditions stand well below fatal conditions for health services use. CONCLUSIONS: Although statistics on frequency, impact, and prominence all indicate conditions "importance," they give only weak clues about specific service needs of affected persons. The persistent finding that nonfatal conditions do not receive health services care commensurate with their prevalence and impact reflects long-standing imbalanced attention on fatal conditions in research and medical care.

Adolescent↗
PubMed1996

Chronic gynecological conditions reported by US women: findings from the National Health Interview Survey, 1984 to 1992.

OBJECTIVES: This study sought to describe prevalence rates of chronic gynecological conditions and correlates of these conditions in a representative sample of US women. METHODS: National Health Interview Survey data from 1984 through 1992 for women aged 18 to 50 were used. RESULTS: The estimated annual prevalence rate for the reported presence of one or more gynecological conditions was 97.1 per 1,000 women. Menstrual disorders were most common, with an annual prevalence rate of 53.0 per 1,000 women. Adnexal conditions and fibroids were the next most common conditions, with rates per 1,000 women of 16.6 and 9.2, respectively. Prolapse, endometriosis, and fibroids were the conditions most likely to lead to hysterectomy within the year prior to the interview. More than three quarters (77.1%) of women with gynecological conditions had talked with a doctor in the previous year concerning their condition, and 28.8% reported spending 1 or more days in bed in the previous year because of their condition. CONCLUSIONS: Nearly a tenth of American women aged 18 to 50 report having one or more chronic gynecological conditions annually, the most common being disorders of menstruation.

Adolescent↗
PubMed2006

Chest wall motion after thixotropy conditioning of inspiratory muscles in healthy humans.

Inspiratory muscle conditioning at a lower or higher lung volume based on the principles of muscle thixotropy causes acute changes in end-expiratory chest wall and lung volumes. The present study aimed to demonstrate the time course of effects of this conditioning on both end-expiratory chest wall volume and thoracoabdominal synchrony. We measured chest wall motion with respiratory induction plethysmography at 0.5, 1, 2, 3, and 6 min after conditioning at three different lung volumes in 15 healthy men. After conditioning at total lung capacity - 20% inspiratory capacity, increases in end-expiratory chest wall volume were significant at 0.5, 1, and 2 min (P < 0.05), being most obvious at 0.5 min (Delta 0.24 +/- 0.20 liter). After conditioning at residual volume, reductions in end-expiratory chest wall volume were significant at any time point (P < 0.05), being most obvious at 0.5 min (Delta 0.16 +/- 0.08 liter). Conditioning at functional residual capacity had little effect on the volume. Spirometric inspiratory capacity at 6 min after conditioning at residual volume (2.68 +/- 0.35 liter) was higher than the baseline value (2.53 +/- 0.31 liter, P < 0.05). Reductions in the phase angle, quantified by the Konno-Mead diagram, occurred after conditioning at residual volume at any time point (P < 0.05), being most obvious at 2 min (Delta 3.47 +/- 3.02 degrees). In conclusion, there is a 6-min time course of changes in end-expiratory chest wall volume after conditioning. More synchronous motion between the rib cage and abdomen occurs after conditioning at residual volume.

Adult↗
PubMed1998

Estimates of driving abilities and skills in different conditions.

OBJECTIVES: This research was a preliminary effort to determine whether various driving situations seemed to require different driving skills and abilities and to identify the relative demands of specific physical, perceptual, cognitive, behavioral, and operational skills and abilities in different driving situations. METHOD: Experienced driver evaluators and trainers estimated the magnitude of driving abilities and skills for different photographed driving situations. Pictures of driving scenarios were counterbalanced for road type, traffic condition, and weather condition. RESULTS: A multifactorial analysis of variance of the total score for each scenario revealed significant main effects for road type and traffic condition but not for weather condition. Highway and city driving were rated as significantly more demanding overall than residential driving, but no difference was found between city and highway driving. Estimates of the overall demands for driving in heavy traffic were significantly greater than in light traffic. However, driving in inclement weather was not regarded as significantly more demanding than driving in sunny weather. Additionally, significant interaction effects were found for road type by weather condition and traffic by weather condition but not for road type by traffic condition. Through multivariate methods to evaluate the significance of individual abilities and skills across conditions, significant main and interactive effects were found for road type, traffic condition, and weather condition. Post hoc analyses showed the impact of these effects on such abilities and skills as scanning, attention and concentration, information-processing speed, and others. CONCLUSION: Evaluators' quantified estimates of driving demands showed driving as a complex task that (a) requires high levels of abilities and skills in all situations; (b) demands greater abilities in some situations than in others; and (c) involves different kinds and various degrees of abilities and skills, depending on the demand characteristics of the situation.

Adult↗
PubMed2006

Comparing the population health impacts of medical conditions using routinely collected health care utilization data: nature and sources of variability.

Prevention activities are designed and resourced based on perceptions of the relative population health impacts of various conditions. We examined the nature and variability of rankings of "conditions" based on how they are defined and how their population health impacts are measured. The first listed diagnosis from all hospitalizations and ambulatory visits of U.S. service members during 2002 was used to rank conditions (as defined by two standard classification systems) using five different measures of population health impacts. Less than 10% of all conditions accounted for more than one-half of total population health impact, regardless of how conditions were defined or impacts measured. However, specific conditions with the largest impacts varied depending on the classification system and impact measure. Four groups of related conditions--acute musculoskeletal injuries, pregnancy-related conditions, respiratory infections, and mental disorders (including substance abuse)--accounted for disproportionately large impacts regardless of the measure. The identification of conditions with the largest population health impacts depends on the nature and degree of aggregation in defining conditions and the measure of impact. The findings are relevant to prevention planning and resourcing.

Acute Disease↗
PubMed1993

The role of D1 and D2 dopamine receptors in the acquisition and expression of cocaine-induced conditioned increases in locomotor behavior.

Certain motoric effects of cocaine increase in intensity with repetitive administration. Conditioned drug effects are among primary determinants of such sensitization. The purpose of these experiments was to evaluate the role of D1 and D2 dopamine (DA) receptor mechanisms in the acquisition and expression of cocaine conditioning. On Day 1, rats were injected with cocaine (40mg/kg) either before (PAIRED) or after (UNPAIRED) exposure to a locomotor activity chamber. On Day 2, all animals were injected with a low dose of cocaine (10mg/kg) prior to placement in the locomotor chambers. Conditioning on Day 2 was evidenced by significantly higher activity levels in the PAIRED group relative to the UNPAIRED or saline-treated groups. Pretreatment with D1 (SCH 23390) or D2 (raclopride, sulpiride, haloperidol) DA antagonists on Day 1 prevented the development of conditioning as assessed on Day 2, indicating that both receptor subtypes are involved in acquisition. However, pretreatment with raclopride or SCH 23390 on Day 2, prior to cocaine injections, did not eliminate the differences in behavior between the conditioned and non-conditioned groups. Neither D1 (SKF 82958, SKF 38393) nor D2 (quinpirole) agonists administered alone were effective in establishing conditioning, while a combination of SKF 82958 and quinpirole was effective, suggesting that conditioning in this experimental paradigm requires the concurrent activation of both receptor subtypes. In the final study it was found that conditioned cocaine effects could be revealed only in the presence of quinpirole or apomorphine on Day 2. The D1 agonists (SKF 38393 and SKF 82958) were ineffective. This would suggest either that only quinpirole and apomorphine are effective in amplifying the conditioned effects of cocaine on Day 2 or that the cues produced by these drugs are more similar to those produced by cocaine than those produced by D1 agonists.

Journal Article↗
PubMed2001

Laparoscopic nephrectomy for inflammatory renal conditions.

PURPOSE: Inflammatory and infectious renal conditions may result in severe perirenal fibrosis, making the laparoscopic approach challenging. The theoretical advantages of laparoscopy for managing inflammatory and infectious renal conditions have been questioned. We identified whether laparoscopy for inflammatory renal conditions is associated with higher morbidity than for other benign renal conditions. Furthermore, several technical modifications are discussed that may help to improve the outcome. MATERIALS AND METHODS: We retrospectively reviewed the records of all patients who underwent laparoscopic nephrectomy for inflammatory and infectious renal conditions between 1998 and 2000. The transperitoneal approach was used and specimens were removed after morcellation. Operative data were compared with those from a similar group of patients who underwent laparoscopic nephrectomy for other benign conditions. RESULTS: Laparoscopic nephrectomy done for inflammatory or infectious conditions in 12 cases and for other benign conditions in 9 matched cases was completed successfully in 10 (83%) and 9 (100%), respectively. In the inflammatory and benign groups mean blood loss plus or minus standard deviation was 155 +/- 163 and 59 +/- 23 ml. (p = 0.099), mean operative time was 284 +/- 126 and 226 +/- 62 minutes (p = 0.225), and mean postoperative hospital stay was 4.1 +/- 2 and 3 +/- 1 days (p = 0.157), respectively. CONCLUSIONS: Laparoscopic nephrectomy can be performed safely in most cases of inflammatory renal conditions. Although they were not statistically significant, a higher conversion rate and longer operative time should be expected. Early conversion may be required due to failure to progress. Similar advantages were observed in patients with inflammatory and other benign renal conditions via the laparoscopic approach.

Adult↗
PubMed1997

The effect of ischemic conditioning on gastric wound healing in the rat: implications for esophageal replacement with stomach.

BACKGROUND: Esophagectomy, with gastric pull up replacement, is not uncommonly complicated by leakage from the esophagogastrostomy anastomosis. Occult ischemia of the mobilized gastric fundus is a major etiological factor for anastomotic leakage. Gastric tissue perfusion can be improved by ischemic conditioning ("delay" phenomenon). OBJECTIVE: To test the hypothesis that ischemic conditioning will improve gastric wound healing, and reduce the incidence of anastomotic dehiscence, in a rodent model of partial gastric devascularization. EXPERIMENTAL DESIGN: Laboratory study of gastric wound healing in rats. ANIMALS: Forty-five Sprague-Dawley rats (3 groups of 15 rats). INTERVENTIONS: All animals underwent laparotomy on day 0. Group 1 (control) and group 3 (acute ischemia) rats had sham laparotomies done. Group 2 (ischemic conditioning) rats underwent laparotomy and left gastric artery ligation. On postoperative day 14, all animals underwent repeat laparotomy; gastrotomy wounds were created and sutured. Group 1 (control) and group 2 (ischemic conditioning) rats had gastrotomy alone, while group 3 (acute ischemia) rats also underwent left gastric artery ligation. All rats were sacrificed 5 days after gastrotomy and wound healing was assessed. MEASURES: Gastrotomy wounds were assessed for dehiscence, bursting strength, and hydroxyproline concentration. RESULTS: Anastomotic dehiscence did not occur in group 1 (control) or group 2 (ischemic conditioning) rats. Four of 15 rats (27%) in group 3 (acute ischemia) suffered anastomotic dehiscence (p = 0.028). Wound bursting pressure in the three groups was not significantly different (group 1--96.3 +/- 8.3 mmHg, group 2--91.1 +/- 4.8 mmHg, group 3--70.9 +/- 12.7 mmHg, p = 0.13). Wound hydroxyproline concentration in the control group was significantly higher than in the other 2 groups (group 1--0.124 +/- 0.005 mumol/mg, group 2--0.113 +/- 0.007 mumol/mg, group 3--0.102 +/- 0.006 mumol/ mg, p = 0.04), but there was no difference between the acute ischemia and the ischemic conditioning groups (p = 0.24). CONCLUSIONS: In this rodent model of partial gastric devascularization, ischemic conditioning reduced the incidence of anastomotic dehiscence. Wound bursting strength and hydroxyproline concentration were not affected by ischemic conditioning. Therefore, the harmful effect of ischemia, and the beneficial effect of ischemic conditioning, are probably not primarily related to synthesis of wound collagen. Ischemic conditioning of the stomach is a concept that may prove clinically useful in reducing the incidence of leakage from esophagogastrostomy anastomoses.

Anastomosis, Surgical↗
PubMed1998

Conditioning, awareness, and the hippocampus.

For the past 50 years, psychologists have wrestled with questions regarding the relationship between conscious awareness and human conditioned behavior. A recent proposal that the hippocampus mediates awareness during trace conditioning (Clark, Squire, Science 1998;280:77-81) has extended the awareness-conditioning debate to the neuroscience arena. In the following commentary, we raise specific theoretical and methodological issues regarding the Clark and Squire study and place their finding into a broader context. Throughout our discussion, we consider the difficulties in assessing subjective awareness, the importance of establishing necessary and sufficient conditions for cognitive mediation effects, the influence of conditioned response modality, and the nature of hippocampal requirements across conditioning protocols. It is clear that trace eyeblink conditioning is a hippocampal-dependent task, but whether awareness is a necessary component of trace conditioning is not definitively proven. We propose that future functional neuroimaging studies and behavioral experiments using on-line measures of awareness may help clarify the relationship among classical conditioning, awareness, and the hippocampus.

Animals↗
PubMed2004

Attenuation of d-amphetamine-induced disruption of conditional discrimination performance by alpha-flupenthixol.

RATIONALE: Previous evidence suggests that manipulation of forebrain dopamine (DA) systems may impair the use of conditional information to inform goal-directed performance, and this may be related to impairments in the ability to use task-setting cues in schizophrenia. OBJECTIVE: To investigate, using the indirect DA agonist d-amphetamine and the D1/D2 receptor antagonist alpha-flupenthixol, the influence of DAergic manipulation on discrimination performance that requires the use of conditional information to inform goal-directed performance. METHODS: Both instrumental and Pavlovian conditional discriminations were employed in which rats learned to respond appropriately according to the presence of auditory conditional stimuli, and results from these experiments were contrasted with a control Pavlovian-instrumental transfer task. RESULTS: Experiment 1 showed a disruption of instrumental conditional discrimination performance by d-amphetamine at 1.5 mg/kg and attenuation of correct responding following 1.0 mg/kg. Disruption with both doses was observed in experiment 2 using a conditional discrimination based on Pavlovian, conditioned responding. Results from a control Pavlovian-instrumental transfer task (experiment 3) revealed that d-amphetamine (0.5, 1.0 and 1.5 mg/kg) did not have any detrimental effect on subjects' basic sensory, motor or motivational processes. Experiment 4 showed that d-amphetamine disruption of instrumental conditional discrimination was attenuated by pre-treatment with the D1/D2 receptor antagonist alpha-flupenthixol. CONCLUSION: These results demonstrate that tasks dependent on conditional relationships are highly sensitive to manipulation of DAergic systems.

Animals↗
PubMed2003

Single-cue delay and trace classical conditioning in schizophrenia.

BACKGROUND: Classical conditioning provides a means of addressing mechanisms of learning and can therefore help understand the pathophysiology of memory alteration in schizophrenia. METHODS: Single cue delay and trace eyeblink conditioning were used in patients with schizophrenia and matched normal control subjects to explore, respectively, cerebellar and hippocampal integrity during learning. We measured percent of conditioned (CRs) and unconditioned responses (URs), their amplitude, and onset and peak latencies. We also accounted for spontaneous blink rates and stimulus-induced responses before learning. RESULTS: During delay conditioning, patients showed CRs with longer onset and peak latencies and improved efficiency compared to normal volunteers without there being differences between patients and normal control subjects in the percentage of CRs. During trace conditioning, neither group showed an increase in CRs as a function of conditioned stimulus-unconditioned stimulus pairings, in part because the level of spontaneous blink rates exceeded the level of CRs; however, patients with schizophrenia showed increased responding 150-400 msec after the conditioned stimulus and in the last 100-150 msec before the unconditioned stimulus, whereas normal control subjects showed only the latter type of responses. The former type of response was more frequent in patients with schizophrenia even before either trace or delay conditioning. CONCLUSIONS: These results suggest integrity of cerebellar mechanisms underlying conditioning, although the altered timing of CRs in patients may indicate differences in the modulation of such responses. Both the greater CR onset latency during delay and the presence of early nonadaptive responses during trace are compatible with the pattern of responding seen in animals with hippocampal damage.

Blinking↗
PubMed1985

Age-related disruption of trace but not delay classical conditioning of the rabbit's nictitating membrane response.

Young (6 months of age) and old (36-60 months) New Zealand albino rabbits underwent classical conditioning of the nictitating membrane response in either a delay conditioning (Experiment 1) or a trace conditioning (Experiment 2) paradigm. There was no difference between old and young animals in acquisition of the conditioned response in the delay paradigm, nor were there any age-related differences in generalization to the tone conditioned stimulus (CS) or in sensitivity to the tone CS or eye shock unconditioned stimulus. In the trace conditioning paradigm, however, old animals acquired the conditioned response significantly more slowly than young rabbits. Because the same stimulus parameters and the same response were used in both experiments, it is unlikely that age-related differences in trace conditioning were due to stimulus sensitivity, motivation, or fatigue. The results are discussed in terms of how brain changes that accompany aging could differentially affect these two types of classical conditioning.

Aging↗
PubMed1995

Differential effects of forebrain 5-hydroxytryptamine depletions on Pavlovian aversive conditioning to discrete and contextual stimuli in the rat.

The experiments examined the effects of depleting forebrain 5-hydroxytryptamine (5HT) on Pavlovian aversive conditioning to discrete and contextual stimuli. Rats were lesioned with intracerebroventricular injections of the neurotoxin 5,7-dihydroxytryptamine and then conditioned in a distinctive environment (termed the context) to a 30 s auditory stimulus. In 50% of animals the interval between the offset of the discrete auditory stimulus and the reinforcer, a mild foot-shock (0.5 mA, 0.5 s), was 5 s (the short-trace group) and in the other 50%, 30 s (the long-trace group). Theory predicts that animals in the short-trace condition will learn more about the discrete stimulus as a predictor of shock and become strongly conditioned, while those in the long-trace condition learn relatively more about the context. The extent of conditioning to the discrete and contextual stimuli was assessed separately, in extinction, using lick-suppression and place-preference measures respectively. Under these conditions sham subjects exhibited the expected dissociation with respect to trace interval. However, lesioned animals exhibited a specific impairment in contextual conditioning. The results are discussed in terms of the behavioural, neurochemical and neuroanatomical specificity of 5HT function in aversive conditioning and the implications for general theories of the role of 5HT in aversive processes.

Animals↗