Behaviorally inhibited temperament is associated with severity of post-traumatic stress disorder symptoms and faster eyeblink conditioning in veterans

Prior studies have sometimes demonstrated facilitated acquisition of classically conditioned responses and/or resistance to extinction in post-traumatic stress disorder (PTSD). However, it is unclear whether these behaviors are acquired as a result of PTSD or exposure to trauma, or reflect preexisting risk factors that confer vulnerability for PTSD. Here, we examined classical eyeblink conditioning and extinction in veterans self-assessed for current PTSD symptoms, exposure to combat, and the personality trait of behavioral inhibition (BI), a risk factor for PTSD. A total of 128 veterans were recruited (mean age 51.2 years; 13.3% female); 126 completed self-assessment, with 25.4% reporting a history of exposure to combat and 30.9% reporting current, severe PTSD symptoms (PTSS). The severity of PTSS was correlated with current BI (R(2) = 0.497) and PTSS status could be predicted based on current BI and combat history (80.2% correct classification). A subset of the veterans (n = 87) also completed the eyeblink conditioning study. Among veterans without PTSS, childhood BI was associated with faster acquisition; veterans with PTSS showed delayed extinction, under some conditions. These data demonstrate a relationship between current BI and PTSS, and indicate that the facilitated conditioning sometimes observed in patients with PTSD may partially reflect personality traits such as childhood BI that pre-date and contribute to vulnerability for PTSD.     

Differential effects of progesterone and medroxyprogesterone on delay eyeblink conditioning in ovariectomized rats

Ovarian hormones modulate acquisition processes involved in classical conditioning. Although progesterone has been indirectly implicated, its role in classical conditioning of the eyeblink response has not been directly investigated. We assessed the effects of daily dosing of progesterone or medroxyprogesterone (MPA), a non-metabolized synthetic progestin, upon the acquisition of a classically conditioned eyeblink response in ovariectomized (OVX) female rats. Rats were dosed 4h prior to each training session with 0.1 or 1.5 mg/kg of either of these hormones or sesame oil. A delay conditioning paradigm was employed using a 500 ms conditioned stimulus coterminating with a 10 ms 10 V unconditioned stimulus. At the low dose, progesterone and MPA rats did differ from each other, with MPA-treated rats learning slower, but neither group differed from OVX-oil or Sham-oil controls. No group differences in acquisition were observed at the higher dose. During extinction trials, high-dose MPA-treatment and OVX-oil groups extinguished quicker than the high-dose progesterone-treated group. In addition, unconditional response (UR) amplitudes were lower in all OVX groups, regardless of hormone or oil treatment, compared to the sham-oil group. Since MPA did not affect extinction, it is likely the slower extinction in the progesterone-treated rats is due to a metabolite of progesterone. Corticosterone is discussed as a likely candidate for such a role. In addition, we found chronic absence of ovarian hormones decreased UR amplitudes, although differences in UR amplitudes were not associated with changes in the acquisition process. These results are discussed with respect to differences in the hormonal effects upon acquisition versus extinction processes and how these data may explain reports of learning differences in women based on oral contraceptive usage.     

Refining the understanding of inhibitory processes: how response prepotency is created and overcome

Understanding (a) how responses become prepotent provides insights into when inhibition is needed in everyday life. Understanding (b) how response prepotency is overcome provides insights for helping children develop strategies for overcoming such tendencies. Concerning (a), on tasks such as the day‐night Stroop‐like task, is the difficulty with inhibiting saying the name of the stimulus due to the name being semantically related to the correct response or to its being a valid response on the task (i.e. a member of the response set) though incorrect for this stimulus? Experiment 1 (with 40 4‐year‐olds) suggests that prepotency is caused by membership in the response set and not semantic relation. Concerning (b), Diamond, Kirkham and Amso (2002) found that 4‐year‐olds could succeed on the day‐night task if the experimenter sang a ditty after showing the stimulus card, before the child was to respond. They concluded that it was because delaying children’s responses gave them time to compute the correct answer. However, Experiment 2 (with 90 3‐year‐olds) suggests that such a delay helps because it gives the incorrect, prepotent response time to passively dissipate, not because of active computation during the delay.     

The roles of encoding,retrieval, and awareness

In the experiment reported here, we examined the processes by which expected (probable) changes are detected more frequently than are unexpected (improbable) changes (the change probability effect; Beck, Angelone, & Levin, 2004). The change probability effect may be caused by a bias toward probable changes during encoding of the prechange aspect, during retrieval of the prechange aspect, or during activation of an explicit response to the change. Participants performed a change detection task for probable and improbable changes while their eye movements were tracked. Change detection performance was superior for probable changes, but long-term memory performance was equivalent for both probable and improbable changes. Therefore, although both probable and improbable prechange aspects were encoded, probable prechange aspects were more likely to be retrieved during change detection. Implicit change detection was also greater for probable changes than for improbable changes, suggesting that the change probability effect is the result of a bias during the retrieval and comparison stage of change detection. The stimuli used in the change detection task may be downloaded from www.psychonomic.org/archive.     

The relationship among guilt, dysphoria, anxiety and obsessions in a normal population

Seventy-six college students reported intrusive thoughts and impulses on a checklist. These students also completed questionnaires assessing depression, trait anxiety and perceived guilt. Results indicated for this normal population that intrusive thoughts were more distressful, more difficult to dismiss and occur with a greater variety of content compared to intrusive impulses. Multiple regression analysis showed that guilt was the best predictor of intrusive thoughts and impulses. Self-reported depression and anxiety were not strong predictors with respect to nonclinical obsessions and impulses. Discussion focuses on the utility of assessing guilt with obsessional disorders, the lack of a relationship between self-report trait anxiety and nonclinical obsessions, and the need to examine the relationship between guilt and anxiety with clinically obsessional subjects.     

Comparison of PPVT-R and WISC-R in a mild/moderate handicapped sample

The Peabody Picture Vocabulary Test-Revised, Form L was compared with the Wechsler Intelligence Scale for Children--Revised with a sample of 32 mild/moderate handicapped students (24 boys, 8 girls). Significant correlations were found between the WISC-R Full Scale IQ (.46) and the WISC-R Verbal IQ (.50) and the PPVT-R, but no significant correlation was found between the WISC-R Performance IQ and the PPVT-R (.34). Mean scores on the PPVT-R and WISC-R were significantly different.