Biomedical subjects

C J Pietras

Publications and source records attributed to C J Pietras.

3 recordsLinked to original sources

PubMed2003

Early and late cognitive changes following temporal lobe surgery for epilepsy.

OBJECTIVE: To evaluate early and late postoperative cognitive changes in adult patients who had a standardized temporal lobe resection for control of intractable complex partial seizures and to relate quality of life measures at the long-term follow-up to seizure control and a verbal memory skill. METHODS: Patients in this longitudinal study had intractable epilepsy and had cognitive tests at the initial surgical evaluation, 1 year later, and at a long-term follow-up (at least >9 years later). Mean follow-up was 12.8 years. Participants were 44 patients who had an en bloc left (LTL) or right (RTL) temporal lobe resection and 8 nonsurgical patients with epilepsy. RESULTS: Patients with LTL surgery showed selective early decreases in verbal memory. At the long-term follow-up, further decreases in verbal memory and visual memory scores were seen for all patient groups. In general, the nonmemory scores remained stable over time. LTL surgery and initial high scores were predictors of verbal memory decreases seen at the early follow-up. Late memory declines were predicted by higher 1-year scores. LTL surgery was an additional predictor of late decline on a verbal memory task sensitive to the integrity of the left hippocampus. Higher quality of life scores of patients at the long-term follow-up were associated with both better seizure control and a higher everyday verbal memory skill: prose recall. CONCLUSIONS: Surgery-induced verbal memory deficits following LTL surgery continue 13 years after surgery. Late, possibly age-related, declines in multiple memory scores are seen in patients with temporal lobe surgery and nonsurgical patients with epilepsy. Patients with LTL surgery may be at risk for a more rapid decline in selective verbal memory skills. Evaluations of treatments for intractable epilepsy that compromise memory functions should consider the further quality of life impact of late age-related memory declines.

Adult↗

PubMed2001

Risk-sensitive choice in humans as a function of an earnings budget.

Risky choice in 3 adult humans was investigated across procedural manipulations designed to model energy-budget manipulations conducted with nonhumans. Subjects were presented with repeated choices between a fixed and a variable number of points. An energy budget was simulated by use of an earnings budget, defined as the number of points needed within a block of trials for points to be exchanged for money. During positive earnings-budget conditions, exclusive preference for the fixed option met the earnings requirement. During negative earnings-budget conditions, exclusive preference for the certain option did not meet the earnings requirement, but choice for the variable option met the requirement probabilistically. Choice was generally risk averse (the fixed option was preferred) when the earnings budget was positive and risk prone (the variable option was preferred) when the earnings budget was negative. Furthermore, choice was most risk prone during negative earnings-budget conditions in which the earnings requirement was most stringent. Local choice patterns were also frequently consistent with the predictions of a dynamic optimization model, indicating that choice was simultaneously sensitive to short-term choice contingencies, current point earnings, and the earnings requirement. Overall, these results show that the patterns of risky choice generated by energy-budget variables can also be produced by choice contingencies that do not involve immediate survival, and that risky choice in humans may be similar to that shown in nonhumans when choice is studied under analogous experimental conditions.

Adult↗

PubMed2000

Timeout postponement without increased reinforcement frequency.

Three experiments were conducted to examine pigeons' postponement of signaled extinction periods (timeouts) from a schedule of food reinforcement when such responding neither decreased overall timeout frequency nor increased the overall frequency of food reinforcement. A discrete-trial procedure was used in which a response during the first 5 s of a trial postponed an otherwise immediate 60-s timeout to a later part of that same trial but had no effect on whether the timeout occurred. During time-in periods, responses on a second key produced food according to a random-interval 20-s schedule. In Experiment 1, the response-timeout interval was 45 s under postponement conditions and 0 s under extinction conditions (responses were ineffective in postponing timeouts). The percentage of trials with a response was consistently high when the timeout-postponement contingency was in effect and decreased to low levels when it was discontinued under extinction conditions. In Experiment 2, the response-timeout interval was also 45 s but postponement responses increased the duration of the timeout, which varied from 60 s to 105 s across conditions. Postponement responding was maintained, generally at high levels, at all timeout durations, despite sometimes large decreases in the overall frequency of food reinforcement. In Experiment 3, timeout duration was held constant at 60 s while the response-timeout interval was varied systematically across conditions from 0 s to 45 s. Postponement responding was maintained under all conditions in which the response-timeout interval exceeded 0 s (the timeout interval in the absence of a response). In some conditions of Experiment 3, which were designed to control for the immediacy of food reinforcement and food-correlated (time-in) stimuli, responding postponed timeout but the timeout was delayed whether a response occurred or not. Responding was maintained for 2 of 3 subjects, suggesting that behavior was negatively reinforced by timeout postponement rather than positively reinforced by the more immediate presentation of food or food-correlated (time-in) stimuli.

Animals↗