Responses of heart rate to CS and US. A. Response to the first presentation of CS in control and lidocaine-injected goldfish. Both control and lidocaine-injected fish showed an arousal/orienting response. B. The tenth trial of the habituation session. Note that there was no cardiac deceleration in response to CS. C. Averages of the cardiac responses in the first 10 trials during the acquisition session. Arrowhead denotes the time of US presentation. Large arrow denotes conditioned bradycardic response in control fish. Both control and lidocaine-injected fish showed unconditioned bradycardic responses (small arrows) followed by tachycardic responses (asterisks) to US. Average instantaneous frequencies in relation to the average levels during the 5-s period before CS presentations are shown.