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PubMed1984

On the directionality of classically-conditioned glycemic responses.

Rats were administered either exogenous insulin or glucose as the unconditioned stimulus paired with a distinctive stimulus complex. Following several such pairings, the administration of a saline (test) solution to the animal in that environment produced, in both cases, a reduction in blood-glucose levels (hypoglycemia) as compared to control animals who received saline injections throughout. We suggest that, contrary to previous researchers' assumptions, direct changes in blood glucose levels immediately following the administration of either glucose or insulin should not be treated as the unconditioned response. The response of the CNS to the glucose or insulin, and not the immediate effect of increases or decreases in blood glucose levels, must be considered. Our reanalysis suggests, then, that in the case of glucose conditioning the conditioned response produces hypoglycemia which is in the same direction as that of the unconditioned response. In the case of insulin conditioning, the unconditioned response has not been well identified and consequently the conditioned response may be in the same or opposite direction to that of the UR.

Animals↗
PubMed1985

Effects of morphine and LSD on the classically conditioned nictitating membrane response.

Two experiments were carried out to determine the effects of LSD and morphine on the unconditioned nictitating membrane response of the rabbit elicited by 5 intensities of a 100 msec puff of air directed at the cornea, and on the acquisition of conditioned responses to a tone and light conditioned stimulus using the air-puff as an unconditioned stimulus. In Experiment 1, LSD tartrate (0.013 mg/kg) had no effect of the frequency, amplitude, magnitude or latency of the unconditioned response. However, LSD significantly enhanced the rate of acquisition of conditioned responses to both tone and light conditioned stimuli. In Experiment 2, morphine sulfate (5 mg/kg) had no effect on the frequency, amplitude, magnitude or latency of the unconditioned response, but significantly retarded the acquisition of conditioned responses to both tone and light conditioned stimuli. The results indicated that the enhancement of acquisition produced by LSD and the retardation of acquisition produced by morphine were not due to effects of the drugs on either the sensory processing of the air-puff unconditioned stimulus or on the motoric expression of the unconditioned response.

Animals↗
PubMed1994

Nitrous oxide: sensory, motor, associative, and behavioral tolerance effects in classical conditioning of the rabbit nictitating membrane response.

Experiment 1, of a series of six experiments with the rabbit nictitating membrane response (NMR) preparation, revealed that nitrous oxide (0%, 33%, 67%) impaired acquisition of conditioned responses (CRs). Subsequent experiments indicated that nitrous oxide (N2O) had no reliable effects upon nonassociative processes (Experiment 2); impaired unconditioned response (UR) amplitude (Experiment 3); attenuated tone-conditioned stimulus (CS) intensity (Experiment 4); decremented tone-induced reflex modification of the unconditioned NMR (Experiment 5); and demonstrated no reliable evidence of behavioral tolerance (Experiment 6). It was concluded that N2O's impairment of CR acquisition was attributable to its attenuation of the intensity of tone CSs and shock USs and/or UR amplitude. These findings are consistent with the behavioral laws of conditioning: the attenuation of the intensive sensory properties of the CS and US and/or UR components of conditioning affect their ability to enter into the establishment of CS-CR connections and, therefore, the development of associative learning.

Acoustic Stimulation↗
PubMed1990

Animal models of anxiety based on classical conditioning: the conditioned emotional response (CER) and the fear-potentiated startle effect.

Stimuli consistently paired with shock become capable of suppressing ongoing operant or consummatory behavior (the conditioned emotional response--CER) or elevating the amplitude of the startle reflex (fear-potentiated startle). These changes are used to infer a central state of fear which involves the central nucleus of the amygdala and its efferent projections to the brainstem. The present paper reviews how psychoactive drugs affect these measures. Both the CER and fear-potentiated startle are reduced by benzodiazepines, barbiturates and opiates. Advantages and disadvantages of these animal tests of anxiety are discussed.

Animals↗
PubMed1986

P300-like potentials in the normal monkey using classical conditioning and an auditory 'oddball' paradigm.

Endogenous components of evoked potentials resembling P300 in humans were sequentially studied in 3 cynomolgus monkeys (Macaca fascicularis) using an auditory 'oddball' paradigm. The two different auditory stimuli were 500 Hz and 4000 Hz tones, designated as the 'frequent' and 'rare' stimuli, respectively. The probability of 'rare' tone presentation was initially 0.2. We further used probabilities of 0.1, 0.3 and 0.5. The 'rare' stimulus was reinforced by electrical stimulation, which followed the onset of the high tone by 700 msec. After 3-5 training sessions, a late positive wave was observed following the 'rare' tone. The latency of this P300-like signal was 314 +/- 16.2 msec, and the amplitude was 23.6 +/- 3.14 microV. The amplitude of this potential was modified by changes in stimulus presentation probability and by withholding reinforcement.

Animals↗