Each of four groups of rabbits received nictitating membrane (NM), heart rate (HR) and respiration rate (RR) classical discrimination conditioning to tones and shocks at inters timulus intervals of .25, .75, 2.25.and 6.75 sec. Percentages of NM CRs were inversely related to lSI; whereas magnitude of RR responding was directly related to lSI, and maximum HR conditioning occurred at 2.25 sec. Discrimination conditioning failed to occur in acquisition in the RR response system, and occurred maximally at. 75 sec in the NM system and 2.25 sec in the HR system.

Rabbits were given classical discrimination conditioning with one of two tones followed by shock. In Experiment I, 40 rabbits were trained under saline, 10, 18 or 26 mg/kg atropine sulfate or 18 mg/kg methylatropine. Six rabbits in Experiment 2 were conditioned, then given further sessions with saline, and 18, 26 and 34 mg/kg atropine sulfate and methylatropine. In Experiment 3, 18 rabbits were conditioned and then given two extinction sessions under saline or 34 mg/kg atropine sulfate or methylatropine followed by extinction under saline. Chief findings were (a) atropine sulfate but not methylatropine disrupted acquisition and maintenance of conditioned eyeblinks, (b) neither drug affected unconditioned blinks, (c) fewer blinks occurred in extinction under atropine sulfate than under methylatropine or saline, (d) rabbits extinguished under atropine sulphate showed higher percentages of eyeblinks when tested without drug. Disruptions in performance of learned eyeblink responses appeared to be due to drug interference with central cholinergic transmission.

No abstract

Steady state exercise is widely used for psychophysiological studies in which a constant heart rate at a predetermined level is desired. We have developed a microcomputer servo-controlled bicycle ergometer system that can be used for administering steady state exercise. Fourteen healthy male subjects, with a wide range of fitness levels (measured by VO2max) were exercised to either a fixed workload (130 watts) or a predetermined heart rate level (servo-heart rate) of 122 bpm (i.e., 65% of maximum calculated heart rate for the sample). Servo-heart rate was implemented using a feedback loop that automatically adjusted workload to compensate for immediate variations in heart rate, resulting in a more consistent heart rate. Heart rate varied from the predetermined value by 17 bpm during fixed workload but only 3 bpm during servo-heart rate (p less than .05). Therefore, by using the microcomputer servo-controlled bicycle ergometer, heart rate was maintained at a predetermined level regardless of the subject's fitness level. VO2max and workload during servo-heart rate were significantly correlated (r = .85, p less than .05). Therefore, the workload necessary to maintain heart rate at a constant level may provide an approximate index of aerobic fitness level.

A detailed description and analysis are presented of the psychological stress evaluator (PSE), an instrument purported to measure accurately and to portray graphically differential levels of stress in human speech. In addition, two studies are presented that attempt to validate this instrument against better known measures of stress or A-state anxiety. The PSE measures were compared with heart rate and State Trait Anxiety Inventory (STAI) A-state scores obtained under conditions where the level of stress was experimentally manipulated through threat of shock or the presentation of taboo words. The first study revealed that PSE, STAI, and heart rate measures accurately reflect different levels of stress and are significantly correlated with one another. The second study failed to replicate the validity of the PSE. This failure to replicate is attributed to lower levels of induced stress and a reduction in baseline measures of stress.