Interhemispheric effects of simulated lesions in a neural model of letter identification

Experimental studies have produced conflicting results about the extent to which the intact, nonlesioned cerebral hemisphere is responsible for recovery from cognitive deficits following focal brain damage such as a stroke. To obtain a better theoretical understanding of interhemispheric interactions during recovery, we examined the effects of simulated lesions to a bihemispheric neural model of letter identification under various assumptions about hemispheric asymmetries, corpus callosum influence, and lesion size. Among other results, the model demonstrates that the intact hemispheric region's participation in the recovery process is a function of preexisting lateralization and lesion size, indicating that interpretation of experimental work should take these factors into account.     

A family study of outpatients with borderline personality disorder and no history of mood disorder

While several studies have examined psychiatric disorders in the relatives of individuals with borderline personality disorder, many of these studies have not employed a family study methodology and suffer from other methodological shortcomings. Thus, the conclusions from family data addressing the validity of borderline personality disorder, its relation to other conditions, and its distinction from mood disorders, continue to be debated. The present investigation employed a family study design with direct interviews with relatives, structured diagnostic interviews with both probands and relatives, and blind assessment of relatives. Rates of psychiatric disorders were examined in 563 relatives of outpatients with mood disorders (n = 119), 54 relatives of outpatients with borderline personality disorder and no history of mood disorder (n = 11), and 229 relatives of never psychiatrically ill controls (n = 45). Results indicate increased rates of mood disorders and personality disorders in the relatives of borderline probands compared with never psychiatrically ill controls. Familial aggregation of psychiatric disorders was generally similar for borderline personality and the mood disorder comparison group. The results suggest there may be common etiological factors between borderline personality disorder and mood disorders.     

Naive chimpanzees' (Pan troglodytes) observation of experienced conspecifics in a tool-using task

The authors investigated the occurrence of naive chimpanzees' (Pan troglodytes) spontaneous observation of experienced conspecifics during a tool-use task entailing honey fishing. The chimpanzees were presented with 20 kinds of "tools" of which 12 kinds were usable. Six pairs of naive and experienced chimpanzees were brought to this honey-fishing situation. A total of 40 observation episodes occurred between the naive and experienced groups, 34 of which were from naive toward experienced individuals. Naive chimpanzees never observed their partners after their own success but did so after their own failure or before their first attempts. In addition, there were 10 cases in which naive individuals used the left-over tools of the experienced ones. Two factors for the transmission of tool use were clearly evident in this study: (a) spontaneous observation of an appropriate behavioral sequence and (b) enhanced environmental cues made by skilled individuals.     

Structure of the Weinberger Adjustment Inventory Self-Restraint scale and its relation to problem behaviors in adolescence

The authors examined the structure of the Weinberger Adjustment Inventory (WAI) Self-Restraint scale in derivation (n = 1,286) and cross-validation (n = 1,154) samples of mostly African American 6th graders in 3 urban schools. Four models were compared: (a) a 1-factor model; (b) a hierarchical model in which factors representing Impulse Control, Suppression of Aggression, Responsibility, and Consideration of Others were subsumed by a higher order factor; (c) a model that represented these 4 factors as correlated but distinct constructs; and (d) a model that excluded Consideration of Others from the higher order factor. Consistent support was found for the last model based on confirmatory factor analyses and latent-variable analyses examining the relations among self-restraint scales, drug use, delinquency, and aggression. These findings have implications for using the WAI, particularly in studies of adolescent problem behaviors.     

Cardiovascular responses to open-field stress in rats: sex differences and effects of gonadal hormones

We studied sex differences in cardiovascular responses to stress using a new radio-telemetry model in which freely-moving Spontaneously Hypertensive rats (SHR) are exposed to open-field novelty stress. This model allowed simultaneous assessment of cardiovascular and behavioural responses to psychological stress. Female SHR in the diestrous stage of their estrous cycle had markedly greater pressor and tachycardic responses to open-field exposure when compared to either female rats not in diestrous or male SHR. Treatment of ovariectomized SHR with estrogen alone had no significant effect on cardiovascular reactivity, while a combined treatment of estrogen and progesterone slightly, but significantly attenuated their pressor response to open-field stress. In addition, treatment of castrated male rats with testosterone significantly enhanced their pressor responses to stress when compared to values obtained before treatment. None of the hormone treatments had any significant effect on heart rate responses to stress. Neither at different stages of the estrous cycle nor after hormone treatments were there any marked changes in behavioural responses in the open-field, making it unlikely that the differences in cardiovascular stress responses were caused by changes in behavioural activity. These data demonstrate differences in cardiovascular stress responses that seem to be dependent on the stage of the estrous cycle. They suggest that particularly androgens, such as testosterone, may enhance pressor responses to stress. On the other hand, a combination of estrogen and progesterone, rather than estrogen alone, may have a small attenuating effect on cardiovascular reactivity.     

Application of a trace model to the retention of information in a recognition task

A stochastic model is proposed to account for the behavior of subjects in recognition tasks in which stimuli are presented, one at a time, in a protracted sequence. The basic assumption is that the memory trace resulting from the presentation of a particular stimulus not only fades away during the presentation of subsequent stimuli but also diffuses in such a way as to become decreasingly stimulus specific. An account is thereby provided for both (a) the increase in the probability of false recognition with the total number of stimulus presentations and (b) the departure of curves of forgetting from the previously proposed simple exponential decay functions. An expression for the amount of information carried along when the number of stimulus presentations becomes large is then derived for subjects who conform with the model.The author has benefited from discussions of this work with J. W. Tukey, J. R. Pierce, E. N. Gilbert, and D. Slepian of the Bell Telephone Laboratories and with G. A. Miller of Harvard University.     

Reviews of current books

Pastoral Psychology -