PubMed Health⌕ Search

Biomedical subjects

A H Robertson

Publications and source records attributed to A H Robertson.

9 recordsLinked to original sources
PubMed2002

The effect of excitotoxic lesions of the pedunculopontine tegmental nucleus on performance of a progressive ratio schedule of reinforcement.

The pedunculopontine tegmental nucleus has connections with sites in both dorsal and ventral striatum, and a number of studies have suggested that it has a role in reward-related behaviour. The present experiment aimed to investigate the perception of reward in pedunculopontine tegmental nucleus-lesioned rats responding for food under a progressive ratio schedule, which measures willingness to work for a given reward. Rats were trained on a progressive ratio-5 schedule for food reward, then given ibotenic acid or sham lesions of the pedunculopontine tegmental nucleus. Their performance under this schedule was examined again following recovery from surgery. Compared with sham-lesioned rats, those with lesions of the pedunculopontine tegmental nucleus showed significantly reduced breaking points and significantly longer post-reinforcement pauses. However, there was no difference between the groups in their latency to collect food pellets once earned, suggesting that pedunculopontine tegmental nucleus excitotoxin and sham-lesioned rats were equally motivated by the presence of food. Excitotoxin-lesioned rats made significantly more responses on the control lever and more entries to the food hopper as progressive ratio increment increased, but did not differ from controls when the schedule requirement was low. These results are interpreted as indicating no global loss of motivation, since lesioned rats performed normally at low schedule requirements, and were as fast as controls to collect pellets. But as the schedule requirement increased, excitotoxin-lesioned rats showed reductions in responding on the active lever (that is, a reduction in breaking point) and an increase in inappropriate responses towards the food hopper and the control lever.We consider these data to indicate that the behavioural deficits in pedunculopontine-lesioned rats arise not from a sensory or hedonic change, but from alteration in the control of motor output.

Animals↗
PubMed1978

Financial status of social security program after the Social Security Amendments of 1977.

The Social Security Amendments of 1977 resulted in substantial improvement in the current and projected financial condition of the OASDI program. This article reviews the causes of the recent operating deficits, describes the effects of the amendments that most influence the program's financial status, and gives projections of income and expenditures under the new law. The revised benefit formula eliminates the "over-indexing" expected to occur under the old provisions and results in stable earnings-replacement ratios under practically all future economic conditions. About one-half of the long-range actuarial deficit was resolved by this step alone. Increases in the contribution and benefit base, along with tax-rate reallocations and increases, prevent the imminent depletion of the OASI and DI trust funds. Increased income due to the higher wage bases is partially offset in later years, however, by greater benefit payments based on the increases in the coverage of total earnings. Overall, under the new law the OASDI program is projected to be financed adequately for about 50 years but significant operating deficits are expected after that. The financial condition of the hospital insurance program was substantially unchanged by the amendments, however, and the HI trust fund is expected to be exhausted in 1988.

Costs and Cost Analysis↗
PubMed1977

OASDI (Old-Age and Survivors Insurance): fiscal basis and long-range cost projections.

A thorough understanding of the financing structure of social security is a prerequisite to serious discussion of the financial condition of the program. In examining this structure, it becomes clear that the most important test of the program's financial soundness is whether expected future income to the funds equals expected future expenditures. Short-range and long-range cost estimates indicate that this condition does not exist and that an actual deficit of 7.96 percent of taxable payroll, equivalent to $4.3 trillion, needs to be eliminated--half of it perhaps by stabilizing benefits at current levels in relation to preretirement earnings. In addition, an unfunded accrued liability of $3.1 trillion exists, although there is no indication that this liability needs to be funded.

Accounting↗