A computerized system for monitoring and controlling intracranial electrical self-stimulation behavior

An automated system for measuring intracranial self-stimulation behavior is described. The system consists of two Commodore 6502 microcomputers interfaced with a constant-current generator and a standard operant chamber. The system hardware allows sine- and square-wave stimulation. Stimulus intensity can be varied in 256 steps between 0 and 100, 0 and 500, or 0 and 1,000 /µA. The system programs, which are written in machine language, allow the control of various schedules of reinforcement, the counting of operant responses and reinforcements, the measurement of interresponse intervals, and the storage of the data on disk. The software is designed for the determination of the threshold of reinforcement, on the basis of the titration of postreinforcement pauses caused by changeover in schedule control between concurrent continuous reinforcement and fixed ratio schedules.     

Components of Random Generation by Normal Subjects and Patients with Dysexecutive Syndrome

The study presents a hypothesis on how randomness could be simulated by human subjects. Three sources of deviation from randomness are predicted: (1) the preferred application of overlearned production schemata for producing sequences of digits, (2) a wrong concept of randomness, and (3) the impossibility to monitor for redundancies of higher- than those of first-order. Deviations of random generation of digits produced by healthy subjects, patients with chronic frontal lobe damage, and patients with Parkinson′s disease from random sequences produced by a computer program can be explained by the differential influence of these factors. Whereas incorrect concepts of randomness and limits on monitoring capacity distinguished all sequences produced by humans from actual random sequences, persistence on a single production strategy distinguished brain-damaged patients from controls. Random generation of digits appears to be a theoretically transparent and clinically useful test of executive function.     

Attention and personality in augmenting/reducing of visual evoked potentials

Earlier research has shown that extraverts tend to increase their visual evoked potential amplitudes with increasing light intensity (augmenting), while introverts reach their maximum amplitude at lower intensities (reducing). The evoked response has normally been measured from association areas of the brain (at the vertex). The present study measured VEP amplitudes over visual cortex and at the vertex, using four light intensities in two conditions, where attention was either directed towards the light stimuli, or away from them by a concurrent auditory task. Forty subjects were classified as extraverts or introverts based on the Eysenck Personality Inventory. The results show that attention interacted significantly with extraversion. Introverts exhibited a narrower focus of attention, while higher amplitudes and amplitude-intensity functions when attending to the light flashes and lower when distracted. Extraverts showed smaller differences between conditions, indicating a more evenly distributed attention. Higher arousal in introverts is the probable cause of their narrower focus of attention. There were marked differences in the distribution of activity between vertex and occipital cortex. Introverts showed relatively stronger occipital responses and extraverts stronger vertex responses across all intensities and in both conditions. The predisposition for mainly perceptual responses to aversive stimuli in introverts, and for general alerting and motor preparatory responses in extraverts, are interpreted as supportive of Brebner and Cooper's hypothesis that introverts are ‘geared to inspect’ and extraverts are ‘geared to respond’.     

Misalignment Between Research Hypotheses and Statistical Hypotheses: A Threat to Evidence-Based Medicine?

Topoi - Evidence-based medicine frequently uses statistical hypothesis testing. In this paradigm, data can only disconfirm a research hypothesis’ competitors: One tests the negation...     

Dying to be thin: the effects of mortality salience and body mass index on restricted eating among women

Following terror management theory, the authors suggest women's striving to attain a thin physique is fueled in part by existential concerns. In three studies, women restricted consumption of a nutritious but fattening food in response to reminders of mortality (mortality salience; MS). When conducted in private (Study 1), this effect was found among women but not men; when replicated in a group setting in which social comparison was likely (Studies 2 and 3), only women who were relatively less successful attaining the thin ideal (i.e., high body mass index; BMI) restricted eating after MS. In Study 3, MS caused high BMI women to perceive themselves as more discrepant from their ideal thinness; this perceived failure mediated the effects of MS and BMI on eating behavior. Findings are discussed from a self-regulatory framework, which considered in the context of pressures for women to be thin, can shed light on health risk behavior.     

A time to tan: proximal and distal effects of mortality salience on sun exposure intentions

According to the dual defense model of terror management, proximal defenses are engaged to reduce the conscious impact of mortality salience, whereas thoughts of death outside of conscious awareness motivate distal defenses aimed at maintaining self-esteem. Two experiments examined these ideas by assessing women's intentions to engage in tanning-related behavior. In Study 1, when concerns about death (relative to dental pain) were in focal attention, participants increased intentions to protect themselves from dangerous sun exposure. In contrast, when thoughts about death were outside of focal attention, participants decreased interest in sun protection. In Study 2, participants primed to associate tanned skin with an attractive appearance responded to mortality concerns outside of focal attention with increased interest in tanning products and services. These findings are discussed in relation to the dual-defense model of terror management, societal determinants of self-esteem, and implications for health risk and promotion.