Amygdalar Volume in Borderline Personality Disorder With and Without Comorbid Post-traumatic Stress Disorder: A Meta-analysis

IntroductionFour studies have found a smaller amygdalar volume in patients with borderline personality disorder (BPD) relative to controls, whereas four other studies have found similar amygdalar volume in BPD patients relative to controls. This study aims to compare amygdalar volumes of BPD patients with controls, and also to compare BPD patients with and without post-traumatic stress disorder (PTSD) with controls in order to determine whether PTSD can explain the heterogeneity of findings.MethodSystematic review and meta-analysis of magnetic resonance imaging studies that measured amygdalar volumes in BPD patients and healthy controls.FindingsA significant reduction of amygdalar volumes in BPD patients was confirmed (p < .001). However, data from the studies that discriminated BPD patients with and without PTSD indicated that amygdalar volumes were significantly smaller in BPD patients without PTSD relative to controls (left: p = .02; right: p = .05), but not in BPD patients with PTSD relative to controls (left: p = .08; right: p = .20).ConclusionThis meta-analysis suggests that amygdalar volumes are reduced in patients with BPD. This pattern is confirmed in BPD patients without PTSD, but not in BPD patients with PTSD, raising the possibility that reduced amygdalar volume in BPD patients cannot be explained by comorbid PTSD.     

THE BASIS OF SUPERSTITIOUS BEHAVIOR: CHANCE CONTINGENCY,STIMULUS SUBSTITUTION,OR APPETITIVE BEHAVIOR?

This research examined three explanations for the "superstitious" behavior of pigeons under frequent fixed-time delivery of food: accidental response-reward contingency, stimulus substitution, and elicited species-typical appetitive behavior. The behavior observed in these studies consisted of occasional postfood locomotion away from the food hopper, and a predominant pattern of activity directed toward the hopper wall (wall-directed behavior), including approaching, stepping side to side, scratching with the feet, bumping with the breast, pendulum movements of the extended neck, and head bobbing, though not pecking. The consistency of these behavior patterns argued against explanation by accidental response contingencies, and the complexity of behavior was incompatible with the classic stimulus-substitution account. These studies also showed that: (1) response contingencies and prior stimulus experience can modify wall-directed behavior, but within definable limits; (2) pecking sometimes can be obtained in birds of specific strains, and by providing extended training; (3) placing the hopper in the floor at the center of a large chamber replaces wall-directed behavior with circling in a manner that resembles ground foraging for food. We conclude that superstitious behavior under periodic delivery of food probably develops from components of species-typical patterns of appetitive behavior related to feeding. These patterns are elicited by a combination of frequent food presentations and the supporting stimuli present in the environment.     

Infants' perception of timbre: classification of complex tones by spectral structure

Infants 7 to 8.5 months of age were tested for their discrimination of timbre or sound quality differences in the context of variable exemplars. They were familiarized with a set of complex tones with specified spectral structure; members of the set varied in fundamental frequency, intensity, or duration. Infants were then tested for their detection of tones that contrasted in spectral structure but were similar in other respects. They successfully differentiated the two spectral structures in the context of these variations, indicating that they can classify tonal stimuli on the basis of timbre. When the stimuli were organized into arbitrary categories, infants were unable to differentiate these categories, indicating that their performance with nonarbitrary categories was not attributable to memorization of the familiarized set.     

The effects of unstable clients in adolescent treatment: contagion versus continuity

This study examined the effects of integrating an unstable group of seriously disturbed adolescents into an existing day treatment program. Behavioral data were collected for an established group of subjects who were in treatment one year prior to and one year after the arrival of a new group of severely disturbed adolescents. It was found that the disruptive behavior displayed by the new admission subjects was not imitated by the subjects of the established group. Rather, there was a significant decrease in aggression and in the overall number of psychiatric events for the established group. The treatment milieu was seen to be resistant to the effects of the new admissions largely due to the structured form of treatment.     

Components of rational-emotive imagery: Two experiments with nonassertive students

Unassertive students took part in two experiments to assess the contributions of emotional and cognitive rehearsal procedures in rational-emotive imagery. In each study participants received analogue treatment in groups, which met twice for one and a half hours. In Experiment 1 behavior rehearsal (BR) was more effective than emotional rehearsal (ER, which involved tryping to attenuate unwanted feelings in fantasy) and cognitive rehearsal (CR, which involved examining negative, and rehearsing helpful, self-statements) as assessed by a self-report measure of assertiveness. In Experiment 2 combinations of Experiment 1 procedures were tested in a factorial design. On a behavioral test, BR proved more effective than the treatment combinations, but on questionnaire measures of social anxiety and irrational beliefs rational-emotive imagery (the combination of CR with ER) was superior to the other treatment conditions. Results are encouraging in that rational-emotive imagery was more successful than either component in isolation, even within the limits of a brief analogue study. Further clinical trials are needed.     

The role of the magazine-response contingency on signal-directed responding in pigeons

Three experiments used a procedure for directly delivering water into the thirsty pigeon's mouth to explore the role that the instrumental magazine contingency plays in autoshaped responding. Magazine training was accomplished by requiring birds to contact a “magazine” key when it was illuminated, in order to obtain intraoral injections of water. Other subjects received water injections independent of a magazine-response contingency. Subsequently, magazine-trained subjects showed a transient enhancement in responding to the illumination of another “signal” key, whether that stimulus was presented alone or paired with water delivery. The overall level of maintained autoshaped responding was little influenced by the instrumental magazine contingency, although the within-trial time course of signal-directed responding was affected. When illumination of the signal key preceded access to water only when the signal was not contacted, pigeons directed many responses toward the signal key. However, there was no evidence that the instrumental magazine contingency enhanced responding on this omission schedule of reinforcement. These results thus confirm a small, but measurable contribution of the magazine-response contingency to signal-directed responding; they fail to support the conclusion that the instrumental magazine contingency greatly affects the outcomes of autoshaping studies.     

Trace autoshaping: Acquisition, maintenance, and path dependence at long trace intervals

The pigeon's tendency to acquire and maintain signal-directed key pecking under a trace conditioning procedure was parametrically examined. In Experiment 1, the percentage of CS trials with a key peck response was a decreasing function of the trace interval for separate groups of pigeons. The majority of subjects acquired signal-directed key pecking with trace intervals as long as 36 sec. In Experiment 2, differential maintenance of key pecking occurred across trace intervals in a within-subject procedure. Maintenance of key pecking at 36- and 60-sec trace intervals was path dependent in that responding depended on the subject's performance under the preceding trace interval.