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Biomedical subjects

R F Thompson

Publications and source records attributed to R F Thompson.

At least 181 records · Page 10Linked to original sources
PubMed1982

Selective, naloxone-reversible morphine depression of learned behavioral and hippocampal responses.

Morphine administered intravenously causes immediate and complete abolition of a simple learned response (classically conditioned nictitating membrane extension in rabbit) and of the associated learning-induced increase in hippocampal neuron activity. Both effects are completely reversed by low doses of naloxone. Morphine has no effect at all on behavioral performance of the unconditioned reflex response.

Animals↗
PubMed1982

Concomitant classical conditioning of the rabbit nictitating membrane and eyelid responses: correlations and implications.

Simultaneous recordings of muscle unit activity from the muscles of the left and right eyelids (M. obicularis oculi) and recordings of the movement of the left nictitating membrane (NM) were taken during classical conditioning in the rabbit using a tone CS paired with an airpuff UCS to the left cornea. The unconditioned eyelid responses were found to be bilateral. The conditioned eyelid responses were also bilateral in most animals. Both the conditioned and unconditioned eyelid responses were larger on the left side. The conditioned responses of the left and right eyelids and the left NM were found to increase in magnitude and decrease in latency from the onset of the CS over training trials in almost the exactly same manner (correlations as high as .99). Behaviorally, the three responses could occur independently, suggesting that the cranial nuclei which control them (left abducens/accessory abducens, left facial nucleus, right facial nucleus) are not strongly coupled. Thus, for the learned response, it is suggested that the three nuclei are controlled by a common central system. This finding has implications for the nature of the engram--the essential neuronal circuitry encoding the learned response.

Abducens Nerve↗
PubMed1982

Hippocampal cellular plasticity during extinction of classically conditioned nictitating membrane behavior.

Hippocampal unit responses were recorded during extinction of classically conditioned nictitating membrane (NM) behavior in the rabbit. Prior studies have shown that during the acquisition phase of nictitating membrane conditioning, the frequency of hippocampal cell firing increases at a faster rate (across trials) than learned behavior. Results reported here show that, during the early phases of extinction, conditioned hippocampal unit responses decrement at a faster rate than learned NM behavior. Furthermore, only certain components of the conditioned hippocampal unit response display robust spontaneous recovery across successive days of extinction training. In all, results show that changes in the activity of hippocampal neurons predict changes in learned behavior over trials of conditioning and extinction, and demonstrate that hippocampal cellular activity is particularly sensitive to stimulus configurations or environmental contingencies that produce changes in behavior.

Action Potentials↗
PubMed1982

Auditory signal detection and decision processes in the nervous system.

Neuronal unit activity was recorded from auditory nuclei, and dorsal hippocampus, and the cerebellum in rabbits behaviorally detecting a threshold-level constant intensity white noise stimulus. Stimulus-evoked neuronal unit activity was present and identical on both detection and nondetection trials in auditory nuclei but was dichotomous in the hippocampus and in the cerebellum, the latter two systems predicting the occurrence of behavioral detection. It is concluded that the behavioral absolute auditory threshold is not determined by differential activation of neurons in the primary auditory relay nuclei.

Animals↗
PubMed1982

Opiates and classical conditioning: selective abolition of conditioned responses by activation of opiate receptors within the central nervous system.

It has previously been shown that opiates produce selective abolition of aversively motivated classically conditioned responses in the rabbit. The experiments reported here show that these effects are mediated by specific activation of opiate receptors within the central nervous system in that this central activation is both necessary and sufficient to produce opiate-induced abolition of conditioned responding. Further characterization suggests that selective activation through opiate-mu-receptor interactions within the periaqueductal gray/periventricular region of the fourth ventricle may be critical in mediating this abolition.

Avoidance Learning↗
PubMed1982

Initial localization of the memory trace for a basic form of learning.

Electrophysiological recording of neuronal unit activity during paired training trials from various regions of the ipsilateral cerebellum in rabbits well trained in the classically conditioned eyelid/nictitating membrane response have revealed both stimulus-evoked responses and responses that form an amplitude/temporal model of the learned behavioral response. Ablation of the ipsilateral, lateral cerebellum completely and permanently abolished the behavioral conditioned response in well-trained animals but had no effect at all on the unconditioned reflex response. In marked contrast, conditioned responses were easily trained in the eye contralateral to the cerebellar lesion. We suggest that at least part of the essential neuronal plasticity that codes the learned response may be localized to the cerebellum.

Animals↗
PubMed1980

Reciprocal anatomical connections between anterior thalamus and cingulate--retrosplenial cortex in the rabbit.

Reciprocal anatomical connections between posterior limbic (i.e. cingulate-retrosplenial) cortex and anterior thalamus in the rabbit were investigated using horseradish peroxidase histochemistry. Results showed that the cells of origin for corticofugal fibers are contained only within deep cortical layers, while thalamofugal projections terminate only within superficial laminae. That is, only layer VI neurons of cingulate-retrosplenial cortex project to thalamic regions, while cortical layers I and IV are the primary targets of thalamic afferents.

Animals↗
PubMed1980

Hippocampal unit-behavior correlations during classical conditioning.

The correspondence that develops over the course of classical conditioning between the temporal distribution of increased unit activity in the rabbit hippocampus and the amplitude--time distribution of the behavioral nictitating membrane response is analyzed. Results reveal a high degree of correspondence between neural and behavioral measures. The real time correlation between the within-trial probability and increased hippocampal unit discharge and amplitude--time course of the nictitating membrane response grows substantially with learning. Further analyses reveal that this apparent increase in correlation results from a growth in amount of hippocampal unit activity per se (i.e., a differentiation of the hippocampal unit response from background firing rates), rather than an increase in the correspondence between cellular and behavioral measures (i.e. a repatterning of hippocampal discharges to more accurately code spatio-temporal aspects of the behavioral response). These and other results indicate that the neuronal 'temporal model' of the behavioral response either develops within the hippocampus from the first few conditioning trials or develops first in entorhinal cortex to subsequently influence hippocampal discharge patterns. On the other hand, the increase in amount of hippocampal unit activity developing with conditioning appears to occur within the hippocampus.

Animals↗
PubMed1980

Alterations in spontaneous miniature potential activity during habituation of a vertebrate monosynaptic pathway.

Intracellular recordings of spontaneous miniature synaptic potentials were made from motoneurons of the isolated spinal cord of the frog, as a function of habituation of the monosynaptic pathway originating with lateral column fibers. The frequency and amplitude of spontaneous miniature potentials were used to assess the possibility of several proposed mechanisms underlying habituation in this system. These studies provide clear evidence in eliminating the role of transmitter depletion, incomplete vesicle filling and receptor desensitization in the habituation process occurring within this vertebrate central nervous system.

Animals↗
PubMed1980

Reciprocal anatomical connections between hippocampus and subiculum in the rabbit evidence for subicular innervation of regio superior.

Anatomical connections between the dorsal hippocampus and subiculum were examined in the rabbit, using horseradish peroxidase (HRP) and autoradiographic methods. A previously undescribed pathway was found to project from the dorsal prosubicular-subicular region to dorsal hippocampal cell fields CA1 and CA2. Autoradiographic findings showed that subicular afferents travel via two routes. One pathway projected through the alveus and stratum oriens, with results suggesting collateral input to the basal dendritic pyramidal cell region. The other projection coursed through the stratum lacunosum-moleculare with apparent termination onto CA1 and CA2 apical dendrites. Regions of subiculum providing afferents to hippocampus were compared with subicular areas receiving efferent terminations from hippocampal CA1 and CA3 cell zones. Distribution of hippocampal-subicular terminations were regionally distinct from subicular retrograde cell fields in rostral areas of the subicular complex, extended over a much wider area of subiculum than was seen for retrograde-labeled cells, and was cytoarchitectonically organized. In total, findings indicated that a reciprocal anatomical relationship exists between dorsal hippocampus and subiculum in the rabbit.

Animals↗
PubMed1980

Effect of the interstimulus (CS-UCS) interval on hippocampal unit activity during classical conditioning of the nictitating membrane response of the rabbit (Oryctolagus cuniculus).

Neuronal activity (multiple unit) was recorded from the dorsal hippocampus during classical conditioning of the nictitating membrane response in the rabbit. Groups of subjects were trained with conditioned stimulus/unconditioned stimulus (CS-UCS) interstimulus intervals of 250 msec, 150 msec, or 50 msec, and an additional group received unpaired presentations of the CS and UCS, with a tone CS and a corneal air puff UCS. Increased hippocampal unit activity and nictitating membrane conditioned responses (CRS) occurred only in the 250 msec and 150 msec groups. Both the temporal distribution of hippocampal unit activity and the averaged CR topographies were strongly and similarly influenced by the CS-UCS interval, with both neuronal and behavioral response peaks occurring near the time of UCS onset. The peak of hippocampal unit activity preceded the peak of the nictitating membrane CR by 30-60 msec. When the 250 msec group was shifted to a CS-UCS interval of 500 msec, the peaks of both the hippocampal unit response and the behavioral CR topography shifted in the same direction. The shift appeared to occur sooner in the hippocampal unit response. It is suggested that the hippocampus may function to provide a "temporal map" for learned behaviors.

Animals↗
PubMed1980

Classical conditioning of the rabbit (Oryctolagus cuniculus) nictitating membrane response, with electrical brain stimulation as the unconditioned stimulus.

Rabbits were given classical conditioning training by using paired tone CS (conditioned stimulus) and brain-shock UCS (unconditioned stimulus), with the stimulating electrode localized in the vicinity of the abducens (6th nerve) nucleus such that the electrical stimulus elicited a low-threshold nictitating membrane (NM) extension response as the unconditioned response. Eight of the 27 animals developed clear conditioned NM responses to the tone CS. Control procedures, e.g., subsequent explicity unpaired training, argue against sensitization, pseudoconditioning, and "kindling" as possible explanations. There was no clear-cut anatomical differentiation of electrode-tip locations between learners and nonlearners. Both learners and nonlearners were subsequently trained with paired tone-corneal air puff, and neuronal unit activity was recorded from the stimulating electrode. Animals that had learned with the prior brain-shock UCS exhibited substantially greater increases in neuronal unit activity during air-puff training, which suggests the existence of a differentially effective anatomical-physiological substrate for conditionability.

Abducens Nerve↗
PubMed1979

Medial septal lesions retard classical conditioning of the nicitating membrane response in rabbits.

Lesions of the medial septum were produced in 7 of 14 rabbits prior to classical conditioning of the nictitating membrane response. Lesions significantly altered the hippocampal electroencephalogram, attenuated conditioned hippocampal unit responses, and slowed the behavioral rate of acquisition. The contrast of the behavioral results with those of studies of massive septal or hippocampal ablation suggests a functional subdivision of the septo-hippocampal system in learning.

Animals↗
PubMed1979

Neuronal unit activity in the abducens nucleus during classical conditioning of the nictitating membrane response in the rabbit (Oryctolagus cuniculus).

Neuronal unit activity was recorded from the abducens (6th nerve) nucleus, the "final common path," during classical conditioning of the nictitating membrane (NM) response in the rabbit, with the use of a tone conditioned stimulus, an air puff unconditioned stimulus (UCS), 250-msec interstimulus interval, and 60-sec intertrial interval. Animals were given 2 days of conditioning training (104 trials in eight blocks per day) and 1 day of extinction. Control animals were given comparable periods of stimulus presentations, explicitly unpaired. Activity of small clusters of units--"multiple unit" recording--was compared with the amplitude-time course of the NM response. Between-blocks comparisons of neural and behavioral responses indicated an essentially perfect correlation during acquisition of the conditioned response (Day 1, r = .99; Day 2, r = .98) and a slightly lower correlation during extinction (r = .93) for the conditioning animals. Within-blocks comparisons indicated a close correspondence between the histograms of unit activity and the amplitude-time course of the NM response for the conditioning animals in all phase of training and for the control animals in the UCS trial blocks.

Abducens Nerve↗