Motivating operations as contexts for operant discrimination training and testing.

Two groups of mice were exposed to stimulus discrimination training and testing under different motivational conditions to study interactions between motivating operations (MOs) during initial discrimination training and MOs when performance is tested following training. One group received all discrimination training sessions under 24-h food deprivation while the other received all sessions under 0-h food deprivation. The number of responses allowed during discrimination training sessions was limited such that the two groups experienced the same number of response-outcome contingencies. The groups then received two post-discrimination training tests: one conducted under 24-h food deprivation and the other conducted under 0-h food deprivation. Results indicated no difference between groups in terms of discrimination ratio. However, subjects trained under 24-h deprivation made more responses in the 24-h test, while subjects trained under 0-h deprivation made more responses in the 0-h test. These results are discussed in terms of motivational state-dependent learning.

Interactions between the effects of food and water motivating operations on food- and water-reinforced responding in mice.

Two experiments examined interactions between the effects of food and water motivating operations (MOs) on the food- and water-reinforced operant behavior of mice. In Experiment 1, mice responded for sucrose pellets and then water reinforcement under four different MOs: food deprivation, water deprivation, concurrent food and water deprivation, and no deprivation. The most responding for pellets occurred under food deprivation and the most responding for water occurred under water deprivation. Concurrent food and water deprivation decreased responding for both reinforcers. Nevertheless, water deprivation alone increased pellet-reinforced responding and food deprivation alone likewise increased water-reinforced responding relative to no deprivation. Experiment 2 demonstrated that presession food during concurrent food and water deprivation increased in-session responding for water relative to sessions where no presession food was provided. Conversely, presession water during concurrent food and water deprivation did not increase in-session responding for pellets. These results suggest that a) the reinforcing value of a single stimulus can be affected by multiple MOs, b) a single MO can affect the reinforcing value of multiple stimuli, and c) reinforcing events can also function as MOs. We consider implications for theory and practice and suggest strategies for further basic research on MOs.

Evaluation of the behavioral characteristics of the mdx mouse model of duchenne muscular dystrophy through operant conditioning procedures.

The mdx mouse is an important nonhuman model for Duchenne muscular dystrophy (DMD) research. Characterizing the behavioral traits of the strain relative to congenic wild-type (WT) mice may enhance our understanding of the cognitive deficits observed in some humans with DMD and contribute to treatment development and evaluation. In this paper we report the results of a number of experiments comparing the behavior of mdx to WT mice in operant conditioning procedures designed to assess learning and memory. We found that mdx outperformed WT in all learning and memory tasks involving food reinforcement, and this appeared to be related to the differential effects of the food deprivation motivating operation on mdx mice. Conversely, WT outperformed mdx in an escape/avoidance learning task. These results suggest motivational differences between the strains and demonstrate the potential utility of operant conditioning procedures in the assessment of the behavioral characteristics of the mdx mouse.

Hippocampal volume and memory performance in a community-based sample of women with posttraumatic stress disorder secondary to child abuse.

Childhood abuse is linked to posttraumatic stress disorder (PTSD), which follows abuse survivors into adulthood. This study identified the neuropsychological and neuromorphological sequelae of PTSD among prepubescently abused women. Right-handed women aged 20-40 years were placed into PTSD and abuse, abuse only, and normal control groups (n = 17 per group). Participants were screened for trauma history and psychiatric symptoms, demographically matched, and given neuropsychological tests and a magnetic resonance scan of their brain. Women with PTSD did not express significant deficits in memory performance or hippocampal volume when compared with the abuse and normal control groups.