Raymond Ducharme

Cardiac Activity in Rats during Bar-Press Avoidance and “Freezing” Responses

7 rats were trained to avoid shock by bar-pressing in an instrumental conditioning situation. The US was preceded by a 30-sec. sound signal (CS). The intertrial period was held constant (20 sec). HR was recorded at fixed intervals during 7 sequences (Intertrial-CS-US or Avoidance Response) in each 30-min. daily experimental session. 5 of the 7 initial Ss reached a high frequency of avoidance responses, while the other two failed to reach the fixed criterion adopting rather a freezing response. The animals were then placed in a situation leading to the experimental extinction of the instrumental avoidance response. The results show that, when the response is to be one of avoidance, the HR rises immediately upon CS-onset and remains at that high level until the response is effected. In between avoidance responses the base HR level is relatively high. on the other hand, in the case of a “freezing” non-avoidance response, the HR also rises upon CS-onset but drops immediately afterward to a level significantly lower than the pre-CS level. The intertrial HR frequency is also significantly lower than that observed between avoidance responses. The pre-CS and during-CS drops in HR become more and more important as the experiment progresses, providing evidence in favor of a learning process.

Effect of intertrial intervals on recovery and amplitude of electrodermal reactions

Convincing findings have been published about the importance of prior activity on electrodermal recovery. However, these studies mainly used tone tasks as an experimental paradigm. The present research investigated the influence of prior activity by changing the intertrial intervals (ITI) in cognitive and reaction time tasks. Results indicated that ITI had no effect on amplitude but had a significant effect on recovery time, a longer ITI period producing a longer recovery curve. No correlation was found between recovery and amplitude. Analysis also indicated that variable intervals should not be recommended between the tasks. These observations emphasize the importance of prior activity on electrodermal recovery in more complex tasks.

EFFECT OF LIGHT ON THERMAL REINFORCEMENT IN BEHAVIORAL THERMOREGULATION

The purpose of this study was to demonstrate the effect (reinforcing or aversive) of the combination of light and heat for the presentation of thermal reinforcement in behavioral thermoregulation. The results obtained indicate that the light-heat reinforcement group requires significantly less reinforcers and bar-presses for reaching the learning criterion than the heat-reinforced group. However, the time for reaching criterion and the performance observed after learning has occurred are not significantly different. The results show that light is not an aversive factor in this condition and are explained in relation to the temporary and transitory effect of sensory reinforcement suggested by Tapp and Simpson (1960).

MEMORY AND RIBONUCLEIC ACID (RNA): TRANSFER OF AN AVOIDANCE RESPONSE

4 groups of rats were used to test the hypothesis that learning can be “transferred” by means of “ribonucleic” acid (RNA). The experimental group was injected with RNA obtained from the brains of rats conditioned to an avoidance response. The control group received no RNA. A second control group was given RNA which came from the brains of non-conditioned rats. The fourth group received RNA extracted from the muscles of conditioned rats. The results did not confirm the transfer hypothesis since no RNA facilitating effect on subsequent avoidance training was observed.

Development of phasic heart rate patterns during recall and arithmetic tasks

Abstract Seventy-nine male subjects participated in an experiment to determine whether previously established individual differences in heart rate (HR) reactivity would affect the phasic HR variations which occurred during two different cognitive tasks, memory and arithmetic. Twenty trials of each task were given. Phasic HR pattern differences during the performance of auditory tasks had been reported by Lawler (1980) in subjects who differed in HR reactivity level. Lawlers reported effect was not replicated. The results were also compared to the results of Jennings and Hall (1980) who had reported data for a task which was analogous to the present memory task.

The Oppel-Kundt Illusion in the White Rat:

A technique was established to measure the Oppel-Kundt illusion in the white rat. Using Lashleys jumping stand, 11 pairs of hatched and non-hatched white lines were presented to 4 rats. Several factors were controlled; the stimuli were presented in a predetermined sequence in order to force the animals to choose only on the basis of the length of the figures. One rat underestimated the length of the hatched line, as previously hypothesized, while 3 rats overestimated it. It can be concluded that the Oppel-Kundt illusion exists in these rats and that both the procedure and the technique used are valid.

Short-term memory and effects of proactive interference on heart rate.

40 subjects were required to memorize different word lists. Each list contained three words, and each list corresponded to one trial. The Brown-Peterson paradigm was employed to induce proactive memory interference. For the experimental group the first three lists belonged to a negative affective encoding category, while the fourth belonged to a different encoding category. The control subjects memorized words from mixed encoding categories. In the experimental group proactive interference built up over trials with the same encoding category of words, resulting in a poorer performance at recall, during the second and third trials, and progressive decrease in heart rate. On the fourth trial of the Brown-Peterson task, proactive interference ceased, resulting in better recall than the previous interference trials, concomitantly with an increase in heart rate. These results are discussed within the context of Laceys hypothesis, according to which, heart rate should increase with cognitive activity requiring rejection of environmental stimuli.