Changes in energy expenditure and work during response acquisition in rats

The principle of least effort predicts that behavior will tend to maximum efficiency. To test this prediction, changes in the energy expended (VO2) and work performed per reinforcement were monitored continuously as rats learned to press a beam with a criterion force for liquid food rewards. All 12 subjects exhibited significant decreases in energy expended per reinforcement over the 16 days of observation. Of these, 10 subjects also decreased the work performed per reinforcement. Analyses of motor performance were undertaken to determine how motor programs for changing efficiency were generated. The 10 animals showing decreased work reinforcement also exhibited significant decreases in the variability of temporal and kinetic response features and in mean response magnitude (time integral of force or work per response) as a function of practice. Adjustments in work output were primarily accomplished by modifying temporal response features (response duration and, initially, interresponse time). The kinetic features (response recruitment and peak force) remained relatively constant for these animals. The remaining 2 subjects differed in that response recruitment increased after Day 9, resulting in progressively larger amounts of work being performed to earn each reinforcement, and the interval between successive reinforcements decreased.     

Variation of Isometric Response Force in the Rat

Hungry, unrestrained rats (N = 7) were rewarded for pressing a response beam in excess of 11 different force requirements. Changes in peak force production as a function of peak force requirement were examined by analyses of the first four moments of distributions of peak response forces: constant error, the within-subject standard deviation, skewness, and kurtosis. Results were similar to those previously obtained with human subjects: Constant error was positive at low and negative at high force requirements, the within-subject standard deviation increased as a negatively accelerating function of force requirement, and skewness and kurtosis were positive at low force requirements and decreased to negative values at the highest increments. Additional analyses of response kinetics indicated that rats, like humans, meet increasing force requirements by altering the rate of rise of force. The performance similarities suggest that common processes are engaged by the human and rat motor control systems to solve the problem of generating forces that are appropriate to the prevailing environmental constraints.     

Energetic and motor responses to increasing force requirements

The effects of increasing work (force) requirements on energy expenditure and response topography were examined in 7 rats pressing a beam to earn food. For the 1st 16 days, the force requirement was 5.52 x 10(-2) N (5.625 g). This increased by 4.91 x 10(-2) N (5 g) every 7th session until Ss had experienced 10 upward shifts. Following the 54.57 x 10(-2) N (55.625 g) condition, the original criterion was reinstated. During the augmented phase. Ss maintained stable reinforcement rates across conditions by increasing the peak force of beam pressing. These higher forces, occurring within 20 reinforcements of changing the force criterion, were produced primarily by increases in the rate of change of force (delta F/delta T). Also, while the rate of work performed on the beam increased, the overall energy expenditure fell. In contrast to these rapid adjustments, reinstating the original 5.52 x 10(-2) N (5.625 g) criterion resulted in only gradual alterations in motor performance.     

Health worker attitudes toward peer workers in hepatitis C prevention

Attitudes toward people who inject drugs (PWID) and attitudes toward peer workers among a cross-section of 101 Australian hepatitis C health workers were assessed. A survey consisting of Likert-type questions and one open-ended question regarding training was used. Bivariate and regression analyses demonstrated that health workers' attitudes toward peer workers were associated with their attitudes toward PWID, independent of type of organization or time in the hepatitis C sector. Qualitative analysis revealed four training areas suggested by health workers for peer workers. Implications of these findings for staff and peer training are discussed and future research directions suggested.     

Implicit prejudice toward injecting drug users predicts intentions to change jobs among drug and alcohol nurses

The meaning and importance of implicit prejudice is a source of considerable debate. One way to advance this debate is to assess whether implicit prejudice can predict independent variance, beyond that predicted by explicit prejudice, in meaningful and unambiguous behaviors or behavioral intentions. In the current research, drug and alcohol nurses reported their level of stress working with injecting drug users, their job satisfaction, their explicit prejudice toward injecting drug users, and their intentions to leave drug and alcohol nursing. The nurses also completed the Single Category Implicit Association Test, which measured their implicit prejudice toward injecting drug users. Analyses revealed that implicit prejudice was a significant mediator, beyond explicit prejudice and job satisfaction, of the relation between job stress and intention to change jobs.     

Variation of Isometric Response Force in the Rat

Hungry, unrestrained rats (N = 7) were rewarded for pressing a response beam in excess of 11 different force requirements. Changes in peak force production as a function of peak force requirement were examined by analyses of the first four moments of distributions of peak response forces: constant error, the within-subject standard deviation, skewness, and kurtosis. Results were similar to those previously obtained with human subjects: Constant error was positive at low and negative at high force requirements, the within-subject standard deviation increased as a negatively accelerating function of force requirement, and skewness and kurtosis were positive at low force requirements and decreased to negative values at the highest increments. Additional analyses of response kinetics indicated that rats, like humans, meet increasing force requirements by altering the rate of rise of force. The performance similarities suggest that common processes are engaged by the human and rat motor control systems to solve the problem of generating forces that are appropriate to the prevailing environmental constraints.     

Classical heart-rate conditioning in the rat: The influence of curare and various setting operations

Conflicting reports concerning the success of classical conditioning of heart rate (HR) in curarized animals led to an experiment using a transfer design in which rats were classically conditioned either under curarized or restrained conditions. These conditions were then reversed for each group, giving a Curarized-Restrained (C-R) and a Restrained-Curarized (R-C) group. Results indicated that curare inhibits the conditional and unconditional HR response both during initial acquisition and after asymptotic levels of a HR CR have been attained. In addition, the C-R group did not acquire a CR during their later non-curarized restrained conditioning sessions, implying an inhibitory transfer from their earlier conditioning under curare. The UCRs during this period were normal for restrained rats. Analogous experimental“setting operations” prior to restrained conditioning were then explored by a second experiment which attempted to replicate the inhibitory transfer effect. The experimental operations investigated included: (1) restrained conditioning to investigate conditioned inhibition possibilities; (2) pseudo-conditioning types of randomized CS and UCS non-paired presentations to investigate associative vs. non-associative explanations; (3) CS-Only presentations to investigate possibilities that curare creates a blockage to the UCS, thus creating an inhibiting habituation to the CS; and (4) a group receiving curarization sessions, but no conditioning, to test the drug-only transfer effects. Results from the first and second experiments together indicated no inhibitory transfer effects under any prior experimental conditions except for those animals receiving classical conditioning while curarized. Only the CS-O group demonstrated any other kind of significant transfer effect; in this case a positive transfer accelerating later conditioning due to prior CS habituation sessions. These findings were discussed within the context of existing reports of curarized conditioning and setting operation effects on later conditioning, and various potential explanations and interpretations were explored.     

HCV knowledge among a sample of HCV positive Aboriginal Australians residing in New South Wales

Australian Aboriginal and Torres Strait Islanders are overrepresented in both the prevalence and incidence of the hepatitis C (HCV). HCV knowledge has been associated with a range of positive health behaviours. HCV knowledge has previously been investigated as a single construct; however examining different knowledge domains (i.e. transmission, risk of complications, testing and treatment) separately may be beneficial. This study investigated whether having greater HCV knowledge in different domains is associated with self-reported positive health behaviours. 203 Aboriginal people living with HCV completed a survey assessing HCV knowledge, testing and care, lifestyle changes since diagnosis and treatment intent. Respondents’ knowledge was relatively high. Greater knowledge of risk of health complications was associated with undertaking more positive lifestyle changes since diagnosis. Respondents testing and treatment knowledge was significantly associated with incarceration, lifestyle changes since diagnosis and future treatment intentions. This study illustrates the importance of ensuring that knowledge is high across different HCV domains to optimise a range of positive health behaviours of Aboriginal people living with HCV. Future health promotion campaigns targeted at Aboriginal people living with HCV could benefit from broadening their focus from prevention to other domains such as testing and treatment.