Schedule-induced polydipsia and polyphagia in nondeprived rats reinforced by intracranial stimulation

Five rats, which were neither food nor water deprived, working on fixed or variable-interval schedules of reinforcement for intracranial stimulation developed consistent and excessive patterns of postreinforcement eating or drinking. The gradual deterioration of polydipsia and polyphagia in this situation points to a distinction between the acquisition and maintenance of these behaviors.     

Effects of glucose-saccharin preloads on schedule- and deprivation-induced drinking in rats

The present series of experiments found that high volumes of a glucose-saccharin solution consumed by rats prior to testing (i.e., a preload) produced a small, but significant suppression of established schedule-induced drinking (Experiment 2). This reduction in polydipsic drinking did not appear to be due to the caloric value of the preload (Experiment 1) or to any changes in food motivation, since Experiment 2 showed that there were no changes in lever pressing on a fixed-interval 1-min food schedule. In Experiment 3, the glucose-saccharin preloads produced a complete suppression of water deprivation-induced drinking. While schedule-induced drinking does appear to be a nonhomeostatic form of drinking, under certain testing conditions, it is sensitive to manipulations which affect homeostatic thirst mechanisms.     

Mental load,heart rate and heart rate variability

Summary Several investigators have shown that diminished sinus arrhythmia can be seen as an indication of increased mental load. The present experiment deals with the influence of different levels of mental load, operationalized as the number of binary choices per minute, on the regularity of the heart rate. Also we investigated the influence of four different rest conditions on the regularity of the heart rate.The results show that sinus arrhythmia scores differentiate significantly between several levels of mental load, but heart frequency appeared to be an even better indicator.No significant differences were found between the four rest conditions. Stability over three subsequent measurement sessions was satisfactory, and reliability within the measurement periods was very high.

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Zusammenfassung Mehrere Forscher haben gezeigt, daß abnehmende Sinusarrhythmie betrachtet werden kann als ein Indikator zunehmender mentaler Belastung.In der vorliegenden Untersuchung handelt es sich um den Einfluß verschiedener Niveaus der mentalen Belastung, operationalisiert als die Zahl der binären Wahlen pro Minute, auf die Regelmäßigkeit der Herzfrequenz.Außerdem untersuchten wir den Einfluß vier verschiedener Ruhezustände auf die Regelmäßigkeit der Herzfrequenz.Die Ergebnisse zeigen, daß auf Grund Sinusarrhythmiedaten differenziert werden kann zwischen verschiedenen Niveaus mentaler Belastung, aber die Herzfrequenz erweist sich sogar als ein besserer Indikator.Man stellte keine signifikanten Unterschiede zwischen den vier verschiedenen Ruhezuständen fest.Die Stabilität während drei verschiedener Meßperioden war befriedigend, und die Zuverlässigkeit der Messungen (reliability) innerhalb der Meßperioden war sehr groß.

     

Effects of voluntary wheel running on heart rate, body temperature, and locomotor activity in response to acute and repeated stressor exposures in rats

Stress often negatively impacts physical and mental health but it has been suggested that voluntary physical activity may benefit health by reducing some of the effects of stress. The present experiments tested whether voluntary exercise can reduce heart rate, core body temperature and locomotor activity responses to acute (novelty or loud noise) or repeated stress (loud noise). After 6 weeks of running-wheel access, rats exposed to a novel environment had reduced heart rate, core body temperature, and locomotor activity responses compared to rats housed under sedentary conditions. In contrast, none of these measures were different between exercised and sedentary rats following acute 30-min noise exposures, at either 85 or 98 dB. Following 10 weeks of running-wheel access, both groups displayed significant habituation of all these responses to 10 consecutive daily 30-min presentations of 98 dB noise stress. However, the extent of habituation of all three responses was significantly enhanced in exercised compared to sedentary animals on the last exposure to noise. These results suggest that in physically active animals, under some conditions, acute responses to stress exposure may be reduced, and response habituation to repeated stress may be enhanced, which ultimately may reduce the negative and cumulative impact of stress.     

Effects of incentive and preparatory interval on activity, heart rate, and reaction time in children.

To resolve certain empirical and theoretical difficulties concerning, primarily, the significance of phasic heart-rate deceleration prior to reaction signals, 48 children were employed to perform in simple reaction-time tasks while speed, heart rate, head movement, gross movement, and blink activity were recorded. The indeory intervals and level of incentives. Reaction time varied with incentive, with preparatory interval and mode of presentation. Phasic heart-rate deceleration varied with the intervals but not incentive or mode of presentation. There was little relation between deceleration and RT. Heart rate and somatic movement measures (especially of blinking) were roughly concordant at a group level but did not correlate.     

Effects of shifts in the rate of repetitive stimulation on sustained attention

The effects of shifts in the rate of presentation of repetitive neutral events (background event rate) were studied in a visual vigilance task. Four groups of subjects experienced either a high (21 events/min) or a low (6 events/min) event rate for 20 min and then experienced either the same or the alternate event rate for an additional 40 min. The temporal occurrence of critical target signals was identical for all groups, irrespective of event rate. The density of critical signals was 12 signals/20 min. By the end of the session, shifts in event rate were associated with changes in performance which resembled contrast effects found in other experimental situations in which shift paradigms were used. Relative to constant event rate control conditions, a shift from a low to a high event rate depressed the probability of signal detections, while a shift in the opposite direction enhanced the probability of signal detections.     

Personality,amphetamine and intracranial self-stimulation in rats

The relationship between open-field ambulation and intracranial self-stimulation (ICSS) at the lateral hypothalamic area was studied in rats. A treatment with i.p. saline of d-amphetamine was also applied to the animals prior to ICSS tests. High-ambulatory rats (comparable to human extraverts) showed an equally higher susceptibility to ICSS reward than low-ambulatory rats (comparable to human introverts) with both saline and amphetamine. These findings were interpreted comsidering the ICSS as a strong stimulation which would tend to produce ‘unconditioned inhibition’ much earlier in low-ambulatory rats than high-ambulatory rats thus leading to a better conditioning among the high-ambulatory Ss.