Richard W. Thompson

The effect of scopolamine on the Kamin effect: A test of the parasympathetic overreaction hypothesis

The Kamin effect, the U-shaped curve of retention of a partially learned shuttle avoidance response, was replicated in animals trained and tested for retention after delays of 0, 1, 4, ov 24 h. Other animals treated with scopolamine hydrobromide, a cholinergic blocker, during the 1-h delay between learning and relearning showed no performance decrement. However, animals treated with methylscopoiamine, which does not cross the blood-brain barrier, during the 1-h delay did show the typical Kamin effect decrement in performance. The results were interpreted as supporting a central cholinergic basis for the Kamin effect.

The effect of epinephrine on tonic immobility (animal hypnosis) in chickens

To establish a dose-response relationship between epinephrine and tonic immobility (TI) in chickens, six groups of 10 cockerel chicks were given no injection, IP injection with saline, or injection with.125,.25,.5, or 1.0 mg/kg of epinephrine prior to three tests for duration of TI. Results indicated that TI was an increasing function of epinephrine dosage.

Scopolamine, methylscopolamine, and response conditioned inhibition in rats

To test Carlton’s hypothesis that behavioral inhibition is mediated by central cholinergic systems, rats were trained to a 50% response to reinforcement criterion on drl and were injected IP with a.5 mg/kg of saline, methylscopolamine, or the centrally active anticholinergic scopolamine. Scopolamine significnatly reduced the ratio of reinforcements to responses and significantly increased the variability of emitted responses. Whereas the methylscopolamine reduced the number of responses, the ratio of reinforcements to responses was not significantly different from the saline control. The results give support to Carlton’s hypothesis.

The effects of age and CS complexity on the acquisition of an avoidance response in rats

Two groups of 25 day old and two groups of 95–105 day old rats were used to investigate the effects of age and CS complexity on the acquisition of a one way avoidance response. A group at each age was trained using the opening of a guillotine door as the CS, and a group at each age was trained using the opening of a guillotine door and onset of a buzzer as the CS. Ss trained with the buzzer and opening of the guillotine door CS met the learning criterion in significantly fewer trials than Ss trained using only the opening of the guillotine door as the CS. There was no significant effect of age or interaction of age with CS complexity on trials to criterion.

Stimulus complexity. free looking time. and Inspective exploration

Fourteen Ss rated 59 objects on a seven point complexity scale. From these ratings 10 objects were chosen at the high, middle, and low levels of complexity, and 35 mm slides were made of these 30 objects. Fifteen Ss manipulated and inspected each of the objects for as long as they wished and a second group of 15 Ss viewed slides of the objects for as long as they wished. Analysis of the time scores from these two groups revealed that both inspective manipulation time and free looking time increased as a function of stimulus complexity. Inspective manipulation time was greater than free looking time except at the low complexity level.

Termination of tonic immobility in chickens by auditory stimulation

The experiment investigated the effects of 60-, 70-, 80-, or 90-dB, 250-Hz tones presented at 30-sec intervals during tonic immobility (TI) on the duration of the response. Results indicated that all birds in the 90-dB condition terminated TI with tone onset, 60% of the birds in the 80-dB condition showed the maximal response (1800 sec), and 30% terminated with tone onset. Two parallel responses were hypothesized to result from such stimulation: (l)fear, which increases TI duration and (2) a startle reaction, which terminates TI.

The effect of age and postweaning and adult handling habituation on activity and exploration in the rat

Activity and exploratory behavior in rats was examined on 2 consecutive days of testing at 35 and again at 90 days of age using Greek cross mazes, proportional in size to the subject, having black, white, striped, and checkered arms. Half of the young animals received handling habituation prior to testing and half of each of these groups were handled prior to testing in adulthood. Young rats were more active than adults and handling, either postweaning or in adulthood, increased activity and exploratory behavior. Results also indicated that early handling potentiates the effects of later handling.

A further investigation of familiarization effects on ECS-produced retrograde amnesia

The effectiveness of a single posttrial electroconvulsive shock (ECS) in producing retrograde amnesia (RA) of a one-trial passive avodiance response for rats given three trials of 0, 5, 10, 15, 20, or 37.5 sec familiarized (FAM) with the apparatus prior to training was investigated. The results indicate that FAM of up to 37.5 sec duration does not significantly affect ECS-produced RA, all FAM-ECS groups having shorter latencies than the corresponding pseudo-ECS control groups.

Magnesium pemoline: Facilitation of one way and two way avoidance learning

Rats injected with magnesium pemoline required fewer trials to reach criterion on both a one way and two way avoidance task. However, there was no effect of the drug on latency measures. Magnesium pemoline did not appear to have its facilatory effect by reducing freezing or decreasing response latency.

Classical and avoidance conditioning of the nictitating membrane in frogs (Rana pipiens) and toads (Bufo Americanus)

Classical and avoidance conditioning of the nictitating membrane, using a tactile CS and UCS, was studied in two experiments with frogs and one experiment with toads. In Experiment 1, a classical conditioning procedure did not produce acquisition in frogs although presentation of the CS to the nostril area produced greater responding than did a CS delivered to the cephalic region. In Experiment 2, frogs failed to acquire either classical or avoidance conditioning of the same response, and mode of housing the animals (refrigeration or aquarium) was ineffective in altering response rates. Experiment 3 demonstrated rapid and reliable classical and avoidance conditioning of this response in toads, when the same procedures were employed. It was suggested that the findings might reflect marked differences in degree of passivity of frogs and toads.