Power spectral density analysis of lateral human standing sway

A number of investigators have used power spectral density (PSD) analysis to try to identify and quantify various sensory systems which are involved in upright standing. Using PSD analysis, over a frequency range from 0.02-2.5 Hz, the present study examined two trials of lateral sway in each of 80 men. The results showed that little change occurred in PSD values between the first and second trials. Exponential curves were fit to the averaged trials data of each subject. The values of the parameter estimates obtained from the curve-fitting were regressed on the values of various direct, and derived anthropometric variables to try to explain the variance of the parameter estimates in terms of the anthropometrics. The subject's center of gravity location accounted for no more than 15.8% of the parameter variance, whereas the remaining anthropometrics explained even less. The overall averaged data suggest that three functions (related to visual, vestibular, and proprioceptive processes) may underlie the sway pattern over this frequency range. PSD curves of individuals with a history of high-level athletic activity clearly differed from those of sedentary subjects.     

Lingual vibrotactile screening: an investigation of normal sensitivity based on multiple threshold determinations

This report describes a standardized training and sensory screening procedure which was used to obtain 7 separate lingual vibrotactile thresholds for each of 5 normal subjects during a 30-day interval. Baseline observations of lingual sensitivity were highly consistent and occurred within a narrow range of contractor displacements. The authors conclude that the screening method provides a quick and reliable clinical tool for general diagnostic use and discuss directions for continued research applications.     

Can we measure out a life in coffee spoons?

Public policy decisions in medicine and other fields necessitate careful weighing of choices and consequences. Cost-benefit analyses have been offered as one way to facilitate such decisions. In "Quantifying the value of human life," L. Eugene Arnold asserts that mathematical models such as his offer greater clarity in making public policy decisions than is possible with the "intuitive" or "emotional" approach. In our opinion, problems associated with this quantitative analysis demonstrate a need for caution in applying such mathematical models to public policy decisions....     

Effects of massed practice and cue-controlled relaxation on tic frequency in Gilles de la Tourette's syndrome

The effects of massed practice (MP) and cue-controlled relaxation on tic frequency were assessed in three single-case studies. Measures of tic frequency, subjective tension and fatigue, and physiological arousal were obtained throughout treatment.MP failed to produce any reduction in tic frequency in the three Gilles de la Tourette's syndrome patients studied. Cue-controlled relaxation resulted in a moderate decrease in tic frequency in only one patient.Tic frequency was related to physiological arousal, as assessed by skin conductance response frequency. No evidence was obtained in support of the suggestion that ticquers demonstrate a deficit in their habituation to sensory stimulation.     

A method for the objective study of tool-using behavior

Key pecking for food was shaped in four crows within a conventional operant-conditioning test chamber. When pecking stabilized, a metal screen with openings 2.5 cm high by 1.0 cm wide, was placed over the response key, so that the crow could still see but could no longer peck the key. At the same time, several dozen wooden matchsticks, which could be used to operate the key, were placed in the test chamber. The crows made no use of these during 50 to 75 hr of exposure to this condition. Subsequently, the behavior of two crows was shaped so that they approached the matchsticks, picked one up in their beaks, approached the response key with the matchstick in their beak, and finally operated the response key by poking the matchstick through the screen. This shaping procedure was ineffective with the two other crows. However, these birds were successfully trained through positional fading of the tool. This involved suspending a metal rod from the ceiling so that it hung directly in front of the response key, and the crow had only to peck it to operate the key. Then, the rod was gradually lowered by lengthening its tether until it eventually rested on the floor of the test chamber. The principal advantage of this methodology is the automatic recording of the terminal (tool-using) behavior under study.     

Is the reaction time-movement time relationship 'essentially zero'?

It was hypothesized that, if RM-MT correlations are "essentially zero," then the magnitude of that correlation should not be subject to variation due to the manipulation of various experimental variables. In this experiment, Ss were tested with either RT-MT together or done separately. Results indicated significant relationships for 18 males but not for 18 females. The "essentially zero" position was discussed as being procedurally specific.     

Effects of stimulus control and deprivation upon discriminative responding

Discriminative responding in pigeons was studied under multiple variable-interval extinction schedules in which extinction was correlated with either a tone or a white keylight. The two procedures resulted in weak and strong stimulus control, respectively. In the first experiment, there was no interaction between schedule components when stimulus control was strong and reinforcement was omitted under the previously reinforced component. However, there was marked induction between components when stimulus control was weak and responding was extinguished under the previously reinforced component. In the second experiment, hours of food deprivation was varied under two levels of stimulus control. Deprivation mainly influenced response rates under the extinction stimulus, with greater absolute rate increases occurring the lower the existing level of stimulus control. Increases in responding during the extinction stimulus were four times as great from 24 to 72 hours of deprivation as from 24 to 48 hours under conditions of both high and low stimulus control.     

Shock-induced aggression as a function of prior experience with avoidance, fighting, or unavoidable shock

Rats were trained in shock-induced aggression, free operant avoidance, or were presented with unavoidable shocks. Fighting in response to shock was subsequently measured by intermatching individual animals that had received the three training procedures. The fighting probabilities of animals with histories of avoidance and dominant animals with histories of fighting were higher than the fighting probabilities of non-dominant fighting rats or rats with a history of unavoidable shocks. Animals with higher fighting probabilities disrupted avoidance baselines more than animals with lower fighting probabilities. Control experiments suggested that fighting decrements produced by administration of prior grid-shock were due to the acquisition of behaviors incompatible with aggression.