No abstract

Four monkeys were presented with 10 sec tones which terminated with shocks. The tones were immediately terminated without shock if the animal's diastolic blood pressure rose above a criterion level and remained high for 1 sec. Termination of the tone was followed by a 5 sec time out. Trials began whenever the pressure dropped below the criterion level. All subjects learned the avoidance task, showing diastolic elevations of up to 60 mm of mercury in response to the tones. A linear relationship was seen between the minimum pressure required for avoidance and the pressure achieved. No change in blood pressure accompanied a second stimulus which was never paired with shock. A fifth control monkey was yoked to one of the experimental monkeys and simultaneously received all shocks and tones as determined by the blood pressure of the experimental animal. The yoked control showed no pressure changes to the tones, but normal pressure elevations to shock.

A photoelectric triggering device has been developed with the aim of providing a minimum or maximum trigger on a blood pressure wave. The output from a strain gauge which measures blood pressure is displayed on an oscilloscope, and triggering is done by means of a miniature photocell mounted on a micrometric advance. A transistor circuit transforms the photocell pulse into a relay contact.