Wednesday, April 29, 2009

Repeated stress induces dendritic spine loss in the rat medial prefrontal cortex

Radley, J.J. et al. (2005). Repeated stress induces dendritic spine loss in the rat medial prefrontal cortex. Cerebral Cortex, 16, 313-320.

The medial prefrontal cortex (mPFC) plays an important role in higher cognitive processes and in the regulation of stress-induced HPA axis activity. This study investigated the effect of stress on dendritic spine density in the mPFC. Rats were restrained for 6 hours daily for 21 days with wire mesh. Following the 21 days of stress, stressed rats weighed less than controls, had a 20% decrease in overall apical dendritic length, a 16% decrease in apical dendritic spine density, and hence an estimated 33% reduction in the total number of axospinous synapses on apical dendrites of pyramidal neurons in the mPFC. These morphological changes may have a significant impact on the functional properties of this region. Clinically, mPFC dysfunction is associated with PTSD and depression. One potential neuroanatomical substrate relevant to these disorders is the mPFC-amygdala circuit. Normally, the mPFC may inhibit amygdala output through its connections on the GABAergic intercalated cells at the border of the lateral and central nuclei of the amygdala. Experimental lesions of the mPFC support this, leading to an enhancement of amygdala-dependent behaviors such as emotionality and fear conditioning. Future studies are needed to investigate the extent to which these morphological changes from chronic stress are reversible.

Comparisons of Stimulus Learning and Response Learning in a Punishment Situation

Bolles, R.C., Holtz, R., Dunn, T., & Hill, W. (1980). Comparisons of Stimulus Learning and Response Learning in a Punishment Situation. Learning and Motivation, 11, 78-96.

Early on in the study of learning, learning was believed to consist of the attachment of a response to a stimuli (an S-R association). Later, in contrast with the long-held conventional view that all learning was of the S-R form, alternative forms were proposed by Pavlov and others. Examples include stimulus learning (S-S*) and response learning (R-S*). What type of learning underlied punishment, for example? This stimulated debate. In common punishment paradigms, it became obvious that is was unclear whether the animal was learning that shock is correlated there contextually with the bar (stimulus) or whether shock is correlated with its behavior of pressing the bar (response). The purpose of this paper was to attempt to disentangle these different forms of learning experimentally. Four novel experimental paradigms were explored.

Experiment 1 contained one single bar in the chamber which could either be pressed or pulled. Animals had to alternate their behavioral response (press to pull, and back again) in order to be rewarded. Punishment was delivered on every tenth press for half the animals or every tenth pull for the other half. Results showed a rapid initial suppression (fear to environmental stimuli), but later a return to baseline for the unpunishment response and continued suppression for the punished response. This seems to be evidence for both types of learning taking place within one paradigm. Experiment 2 simply adjusted the response contingencies (up and down) to see if results would be sensitive to this type of experimental manipulation. Instead of an FR-10 punishment schedule, rats were shocked on FR-4 or FR-25. FR-4 showed dramatic differences in responding from the outset. FR-25 differences only emerged in the second day of punishment.

Experiment 3 used two bars, each of which could be either pressed or pulled. Thus, four punishment conditions were possible, punishing a left-press, a left-lift, a right-press, or a right-lift. Results showed that when a rat was punished for a left-lift, for example, it quickly stopped lifting AND pressing the left bar. However, it continued to lift AND press the right bar. Thus, learning, in this case, seems to be mostly about stimuli. Experiment 4, like Experiment 2, changed the contingencies. Punishment was shifted from an FR-1 schedule to an FR-10 schedule. Punishment conditions were: press or lift left bar, press or lift right bar, lifting left or right, and pressing left or right. Across the conditions, the general trend that emerged was a rapid emergence of stimulus learning and then a slower but undeniable development of response learning.

Wednesday, April 1, 2009

Getting comfortable with conversations about race and ethnicity in psychotherapy

Cardemil, E. V., & Battle, C. L. (2003). Guess who’s coming to therapy? Getting comfortable with conversations about race and ethnicity in psychotherapy. Professional Psychology: Research and Practice, 34, 278-286.

This article urges therapists to engage in open conversations with their clients about race and ethnicity as it applies to the client, the therapist, and the therapeutic alliance. By taking a more active stance and initiating such discussions, especially early in treatment, the therapist may enjoy improved treatment retention, therapeutic alliance, and treatment outcome. After defining race and ethnicity as similar but distinct constructs, the article acknowledges that such conversations will vary in terms of frequency and intensity over different clients and times. It then goes on to provide six recommendations for becoming more comfortable and knowledgeable with having such discussions.

First, it is acknowledged that a client's racial/ethnic background may not be obvious and that it is best to suspend preconceptions about a client and their family members. It is recommended that clients be asked early on in therapy how they identify themselves. Second, it is acknowledged that wide variability exists within racial and ethnic groups and that a client's racial identity development and acculturation process may change over time, thus affecting therapy. Third, it is important to consider how the therapist's own racial/ethnic background may affect the therapeutic process in terms of differences in communication styles and conceptualization of mental health/illness, self, and family/community. Fourth, it is acknowledged that racism, power, and privilege can affect the therapeutic process and that failing to acknowledge such societal issues may invalidate a client's painful personal experiences. Fifth, it is recommended that a client expressing reticence and/or frustration with the topics of race and ethnicity be met with an open and non-defensive explanation that such topics are relevant to many clients, but needn't be pursued if they are found irrelevant or uncomfortable. Lastly, resources for further education/training in race and ethnicity are provided.