Line bisecting as a predictor of personal optimism and desirability of risky behaviors.

Our goal was to test whether current hemisphere predominance is a predictor of scores on standardized measures of personal optimism and preference for risk. In two between-subject experiments, current hemisphere predominance was measured by the direction and extent of line bisecting errors. Pearson correlations and median splits of the line bisecting errors showed significantly greater personal optimism and preference for risk with left hemisphere predominance. These results support previous research in which manipulation of hemisphere predominance produced similar effects on personal optimism in normal individuals and on risk taking in lesioned and normal samples. We conclude that the association of optimism and risk with left hemisphere predominance can be observed in resting as well as in manipulated situations.     

The role of inhibition in a spreading-activation model of language production. II. The simulational perspective

This is the second part of a project aimed at establishing the role of lateral inhibition in spreading-activation models of language production. While the first part (Berg &; Schade, 1992) reviewed the psycholinguistic evidence for inhibition and established that indeed inhibition takes place, this paper addresses the issue from the implementational perspective. A series of computer simulations are reported in which spreading-activation models with or without inhibition are directly contrasted. The performance of the competing models is evaluated against two sets of criteria. On the more technical side, the “heat death” and the selection problems have to be solved. That is, the target must have a high and the nontarget units a low level of activation. Additionally, there are certain empirical effects from the production literature which may serve as test cases for deciding between the rival models. The results of the simulations indicate that only the inhibition-based model proves capable of meeting all challenges. All inhibitionless variants fail in one or more respects. It is further shown that the need for the inhibitory component increases with the size of the processing network and that one well-known production model can do without lateral inhibition only at the expense of introducing a concept which resembles inhibition in its effect but cannot replace it.     

Parallel distributed processing and neuropsychology: A neural network model of Wisconsin card sorting and verbal fluency

Neural networks can be used as a tool in the explanation of neuropsychological data. Using the Hebbian Learning Rule and other such principles as competition and modifiable interlevel feedback, researchers have successfully modeled a widely used neuropsychological test, the Wisconsin Card Sorting Test. One of these models is reviewed here and extended to a qualitative analysis of how verbal fluency might be modeled, which demonstrates the importance of accounting for the attentional components of both tests. Difficulties remain in programming sequential cognitive processes within a parallel distributed processing (PDP) framework and integrating exceedingly complex neuropsychological tests such as Proverbs. PDP neural network methodology offers neuropsychologists co-validation procedures within narrowly defined areas of reliability and validity.     

HIV infection--psychological coping and political reality

The authors warn against a trivialization of the AIDS problem and against the call for state control. Since sexuality is ultimately uncontrollable, they plead instead for the greater clarification of the conflicts which those who are infected with HIV and those who are not infected experience in dealing with each other. The continuing mystification of these conflicts would result in mutual jeopardy through acting-out.     

Development of stepping patterns in human infants: a dynamical systems perspective

Upright locomotion has been, perhaps, the most studied of all human motor behaviors. The acquisition of this motor milestone has been of major interest to developmentalists from the motor as well as the cognitive domains. Until recently, developmentalists have chosen a nonexperimental approach, opting instead to describe the motor behaviors that precede walking, assigning them precursor status, and attributing the sequence solely to maturation of the nervous system. In this paper, I will discuss evidence that suggests that we may better understand this and other aspects of motor development by viewing them from the theoretical perspective of nonlinear and complex dynamical systems. Focus will be on the availability of a coordinated and alternating stepping pattern throughout much of the first year of life. Factors that influence the expression of and variability in this movement pattern will also be discussed. In addition, I will address the need to understand the development of control of pattern formations as well as their coordination, and I will discuss one approach that may provide some insight; that is, to study the modulations and patterns of muscle and other forces underlying limb movements.     

A new quantitative approach to the assessment of stages of vigilance as defined by spatiotemporal EEG patterning

Electroencephalographically oriented research on vigilance needs valid measures for assessing the level of vigilance between wakefulness and sleep. When studying different psychologically, psychopathologically, and pharmacologically induced states, special attention has to be paid to minor alterations of the level of vigilance which are reflected, essentially, in topographical changes of alpha-activity (Stage A). Since vigilance is a dynamic process, brief fluctuations in the range of a few seconds must also be recorded. In our opinion existing methods of quantification do not fully meet these demands. We have, therefore, developed a relatively simple procedure which can be characterized as an attempt quantitatively to reconstruct visually, i.e., spatiotemporally defined patterns of vigilance. The usefulness of this method, which also has certain limitations, has been demonstrated in psychopharmacological studies.     

Effects of neonatal forebrain noradrenaline depletion on recovery from brain damage: performance on a spatial navigation task as a function of age of surgery and postsurgical housing

The experiments examined the contributions of forebrain noradrenaline and environmental enrichment to recovery of place navigation ability in rats after hemidecortication in infancy or adulthood. Noradrenaline depletion did not affect recovery from neonatal hemidecortication, although the early hemidecortications did allow sparing of function relative to adult operates. Noradrenaline depletion also failed to attenuate the positive effects of enriched housing on otherwise normal rats. Noradrenaline depletion did retard recovery of adult hemidecorticate rats housed in standard laboratory cages, but it did not retard recovery of adult hemidecorticate rats housed in enriched environments. The results suggest that noradrenaline is importantly involved in enhancing recovery from brain damage when other sources of compensation (e.g., neonatal injury, enriched environment) are absent.     

Sex differences in the effects of gonadectomy on amphetamine-induced rotational behavior in rats

The effects of gonadectomy on amphetamine-induced rotational behavior were studied in male and female rats. Different systemic doses were used to produce equivalent brain concentrations of the drug in each group, thereby controlling for sex differences in the metabolism of amphetamine. Ovariectomy of female rats significantly attenuated amphetamine-induced rotation, whereas castration of males was without effect. The results support the idea that in females, the endogenous gonadal hormones facilitate functional activity in the mesostriatal dopamine system.