Search PubMed⌕ Search

Biomedical subjects

R F Thompson

Publications and source records attributed to R F Thompson.

At least 145 records · Page 8Linked to original sources
PubMed1987

Initial localization of the acoustic conditioned stimulus projection system to the cerebellum essential for classical eyelid conditioning.

Previous experiments have demonstrated a sufficient and necessary involvement of mossy fibers in projecting conditioned stimulus information to the cerebellum during classical eyelid conditioning in rabbits. Presented here are electrophysiological, anatomical, and lesion data that suggest that cells within the lateral pontine nuclear region may be essentially involved in projecting information concerning the occurrence of acoustic conditioned stimuli to the cerebellum during classical conditioning.

Acoustic Stimulation↗
PubMed1987

Cerebellar GABAergic processes: evidence for critical involvement in a form of simple associative learning in the rabbit.

Converging evidence from electrophysiological recording and lesion studies suggests an essential role for the cerebellum in classical conditioning of the nictitating membrane response in the rabbit. The present study begins to delineate within this structure neurotransmitter systems that appear critical for the expression of this form of simple associative learning. Experiments reported here demonstrate that microinfusion of gamma-aminobutyric acid (GABA) antagonists (either bicuculline methiodide or picrotoxin) into specific areas of the medial dentate/lateral interpositus nuclei or into the cerebellar cortex of lobule HVI can selectively and reversibly abolish conditioned responding, while leaving the unconditioned reflex response intact. The results are consistent with the suggestion that GABAergic synapses play an essential role in the circuitry that mediates the conditioned response.

Animals↗
PubMed1986

The neurobiology of learning and memory.

Study of the neurobiology of learning and memory is in a most exciting phase. Behavioral studies in animals are characterizing the categories and properties of learning and memory; essential memory trace circuits in the brain are being defined and localized in mammalian models; work on human memory and the brain is identifying neuronal systems involved in memory; the neuronal, neurochemical, molecular, and biophysical substrates of memory are beginning to be understood in both invertebrate and vertebrate systems; and theoretical and mathematical analysis of basic associative learning and of neuronal networks in proceeding apace. Likely applications of this new understanding of the neural bases of learning and memory range from education to the treatment of learning disabilities to the design of new artificial intelligence systems.

Animals↗
PubMed1986

Rapid transfer of training occurs when direct mossy fiber stimulation is used as a conditioned stimulus for classical eyelid conditioning.

Fifteen rabbits were classically conditioned using stimulation of the right pontine nuclei as a conditioned stimulus and a corneal airpuff as an unconditioned stimulus. After conditioning criterion was reached, the stimulation conditioned stimulus was transferred to the left pontine nuclei and the rate of conditioned response acquisition observed. Our results indicate that when electrodes were placed symmetrically in the right and left pontine nuclei, extremely rapid transfer of training occurred. Together with previous data, the present data supply further indirect evidence that the site of neural plasticity which underlies acquisition and retention of classically conditioned skeletal muscle responses is located efferent to the pontine nuclei, namely in the cerebellum.

Animals↗
PubMed1986

Hippocampus and trace conditioning of the rabbit's classically conditioned nictitating membrane response.

Rabbits received classical conditioning of the nictitating membrane response (NMR) in a trace conditioning paradigm. In this paradigm, a 250-ms tone conditioned stimulus (CS) occurs, after which there is a 500-ms period of time in which no stimuli occur (the trace interval), followed by a 100-ms air puff unconditioned stimulus (UCS). In Experiment 1, lesions of the hippocampus or cingulate/retrosplenial cortex disrupted acquisition of the long-latency or adaptive conditioned response relative to unoperated controls and animals that received neocortical lesions that spared the cingulate/retrosplenial areas. When animals with hippocampal or cingulate/retrosplenial lesions were switched to a standard delay paradigm in which the CS and UCS were contiguous in time, they acquired in about the same number of trials as naive rabbits. In a second experiment multiple-unit activity in area CA1 of the hippocampus was examined during acquisition of the trace conditioned response (CR). Three groups of animals were tested: animals that had a 500-ms trace interval (Group T-500), animals that received explicitly unpaired presentations of the CS and UCS (Group UP), and animals that underwent conditioning with a 2,000-ms trace interval (Group T-2000). Animals in Group T-500 acquired the CR in about 500 trials. Early in training, and well before any CRs occurred, there was a substantial increase in neuronal activity in the hippocampus that began during the CS and persisted through the trace interval. There was also an increase in the UCS period that modeled the amplitude-time course of the behavioral unconditioned response. Later in conditioning as CRs emerged, there was no longer neuronal bursting throughout the CS + trace period. Rather, the activity shifted to later in the trace interval and formed a model of the amplitude-time course of the behavioral CR. Activity during the UCS period was similar to that seen earlier in conditioning. Animals in Group UP showed no behavioral conditioning and no increase in neuronal activity. Animals in Group T-2000 showed no long-latency behavioral conditioning and no increase in neuronal activity. The data are discussed in terms of the role of the hippocampus in conditioning during situations in which the CS and UCS are not contiguous in time.

Animals↗
PubMed1986

Classical conditioning of the rabbit eyelid response with a mossy-fiber stimulation CS: I. Pontine nuclei and middle cerebellar peduncle stimulation.

The nictitating membrane/eyelid responses of 18 rabbits were classically conditioned using cerebellar mossy-fiber stimulation as a conditioned stimulus (CS) and air puff as an unconditioned stimulus (US). The dorsolateral, lateral, and medial pontine nuclei and the middle cerebellar peduncle were effective stimulation-CS sites for training. In one group of rabbits, robust conditioned eyelid responses were produced with paired trials and subsequently extinguished with CS-alone and explicitly unpaired presentation of the CS and US. In a second group of rabbits, no conditioned responses were evident for 4 days of unpaired CS and US presentations. Conditioned responses did develop, however, after paired training was begun. Lesions of the interpositus nucleus of the cerebellum completely abolished the conditioned responses of a third group of rabbits overtrained with the mossy-fiber CS and air-puff US. These results support previous studies which have demonstrated that the cerebellum is critically involved in acquisition and retention of simple learned responses. In addition, the present results support previous theories of cerebellar function which have proposed that mossy fibers supply critical "learning" input to the cerebellum for acquisition and retention of motor skills.

Animals↗
PubMed1986

Classical conditioning using stimulation of the inferior olive as the unconditioned stimulus.

We show that conditioned eyelid responses develop when the unconditioned stimulus is electrical stimulation of the dorsal accessory nucleus of the inferior olive. When compared to conditioning using a standard unconditioned stimulus (air puff), the conditioning produced in this manner appears quite normal: the responses develop at a similar rate, are of comparable magnitude and topography, and demonstrate a steep interstimulus interval function; and response topography varies according to the interstimulus interval. These data indicate that activation of neurons in the dorsal accessory olive is a sufficient condition for a stimulus to be an effective unconditioned stimulus. Previous experiments indicate the dorsal accessory olive is necessary in that lesions have effects functionally equivalent to removal of the unconditioned stimulus. These data indicate that the dorsal accessory olive forms a portion of the pathway conveying information about the occurrence of an unconditioned stimulus to sites of synaptic plasticity responsible for conditioning.

Animals↗
PubMed1985

Lesions of the inferior olivary complex cause extinction of the classically conditioned eyeblink response.

The dentate-interpositus nuclei of the cerebellum are known to be critically involved in the production of the classically conditioned eyeblink response in the rabbit. The rostro-medial portions of the inferior olivary complex (rmIO) project to these nuclei as well as receive projections from the fifth sensory nuclei. Lesions of the rmIO caused a previously classically conditioned eyeblink response to slowly decrease in amplitude and frequency with continued paired conditioned stimulus-unconditioned stimulus (CS-UCS) training in a manner which was identical to extinction of the learned response in control animals. The lesion had no effect on the performance of the unconditioned response. Lesions of the rmIO before training prevented learning from occurring. Lesions of other portions of the IO or of the reticular formation did not specifically affect the learned response. We conclude that the rmIO is critically involved in the learning and maintenance of the classically conditioned eyeblink response. We propose that the rmIO may serve as a pathway for information from the unconditioned stimulus to reach the cerebellum, and as such may in fact be the essential reinforcing or teaching input for the learning of classically conditioned responses. These results support the hypothesis that the cerebellum contains neuronal changes which are a critical portion of the memory trace for the conditioned response.

Animals↗
PubMed1985

Trace conditioning: abolished by cerebellar nuclear lesions but not lateral cerebellar cortex aspirations.

The trace conditioning paradigm in which the conditioned stimulus-unconditioned stimulus (CS-US) interval is longer and the US and CS do not overlap requires retention of a 'trace' of the CS to associate it with the US. This task is difficult, requiring for learning about 5 times the number of trials to criterion as the standard delay task. The present study was undertaken to determine if: the cerebellar interpositus nucleus is essential in trace as well as in delay conditioning; and the lateral cerebellar cortex is involved when CS-US association over longer time intervals is required. Sixteen adult male New Zealand white rabbits had recording and in some cases lesion electrodes surgically implanted before training. They were trained daily with 126 paired trials of tone CS and airpuff US. The trace period between CS offset and US onset was 500 ms. Mean number of trials to criterion of 8/9 CRs was 466.9 trials. After a day of overtraining the animals had one of 3 surgeries: electrolytic lesion of the left cerebellar interpositus nucleus (n = 3); aspiration of the left lateral cerebellar cortex (HVI and HVIIA) and underlying cerebellar nuclei (n = 4); or aspiration of HVI and HVIIA only (n = 9). Rabbits with only HVI and HVIIA removed exhibited a transient decrease in CRs but relearned with significant savings. The amplitude, area and latency of pre- and postlesion conditioned responses (CRs) was similar. When the interpositus nucleus was damaged, the animals' capacity for CRs on the side ipsilateral to the lesion was permanently abolished. It is concluded that the cerebellar interpositus nucleus but not the overlying lateral cerebellar cortex is essential for retention of trace classical conditioning. Nevertheless, the temporary abolition of CRs by removal of lateral cerebellar cortex suggests that the cerebellar cortex does play an important role in learning and retention of the trace conditioned response.

Animals↗
PubMed1985

Unit activity recorded from the globus pallidus during classical conditioning of the rabbit nictitating membrane response.

Single and multiple unit activity were recorded from the region of the globus pallidus (GP) in rabbits during classical conditioning of the nictitating membrane response. The most common response recorded in the GP was a short latency (less than 60 ms) change in firing following presentations of the pure tone conditioned stimulus (CS) and the corneal airpuff unconditioned stimulus (US). This response pattern was present in 39% of the pallidal records, and appeared to be elicited by the auditory components of the CS and US. Similar response patterns were seen in a few records from the putamen, entopeduncular nucleus, and ventral pallidum/substantia innominata. All of the single units that displayed this response pattern had a very sporadic pattern of spontaneous activity. Several other records from the GP displayed short latency responses after US presentations that appeared to be related to the tactile component of the airpuff. Responses of pallidal neurons to the CS and US were largely unaffected by the training procedures. It is concluded that this structure is most likely not directly involved in the classical conditioning of simple, striated muscle responses.

Animals↗
PubMed1985

Effect of kainic acid lesions of the cerebellar interpositus nucleus on eyelid conditioning in the rabbit.

It has been shown previously that unilateral electrolytic lesions of the cerebellar dentate-interpositus nuclei selectively abolish or prevent a classically conditioned nictitating membrane/eyelid response in rabbits but do not prevent retention or learning on the contralateral side. The present study demonstrates that kainic acid lesions of the dorsal interpositus nucleus are sufficient for this effect.

Animals↗
PubMed1985

Age, sex and strain comparison of habituation of the startle response in the rat.

Habituation and sensitization of the acoustic startle response were studied in young (3 month) and aged (26 month) male and female Fischer 344 rats and in young (3 month) and aged (32 month) male Sprague Dawley rats. Tones were presented on 25 consecutive trials for a session, one session on each of four consecutive days. An air puff stimulus immediately preceded trial 20 on each day to test sensitization. All aged rats demonstrated greater short-term (within session) relative habituation than their younger counterparts. Across sessions, aged male rats of both strains habituated more quickly than younger males. Aged female rats habituated more slowly. Sensitization was more likely to occur in younger rats.

Acoustic Stimulation↗
PubMed1985

Cerebellar lesions abolish an avoidance response in rabbit.

Unilateral lesions of the cerebellar dentate-interpositus (DI) nuclei abolished or impaired the reacquisition of a nictitating membrane (NM) conditioned avoidance response (CAR) in rabbits. Animals that sustained damage to the DI nuclei and surrounding areas displayed little or no reacquisition of the NM-CAR ipsilateral to the lesion, but displayed excellent acquisition of the response when training was shifted to the contralateral eye. These results agree with previous investigations of the effects of cerebellar lesions on the classically conditioned NM and leg-flexion responses. The DI nuclei appear to be essential for the retention of conditioned responses in a variety of associative paradigms.

Acoustic Stimulation↗
PubMed1985

Cochlear nucleus, inferior colliculus, and medial geniculate responses during the behavioral detection of threshold-level auditory stimuli in the rabbit.

Rabbits were conditioned to respond behaviorally to auditory stimuli by pairing a white-noise conditioned stimulus (CS) with a corneal airpuff unconditioned stimulus (US). The conditioned response (CR) was movement of the nictitating membrane (NM). After the subjects were responding at better than the 90% correct level, the intensity of the auditory stimulus was reduced to behavioral threshold using a staircase procedure. Simultaneous measurements of neural unit activity and behavioral NM responses were then made in rabbits performing at behavioral threshold. After the experiment was completed neural unit responses during behavioral detection trials were compared to neural responses made during nondetection trials. Neural unit responses to a constant intensity, white-noise stimulus at behavioral threshold were well defined and essentially identical on behavioral detection and nondetection trials in the ventral cochlear nucleus, the ventrolateral division of the central nucleus of the inferior colliculus, and the ventral division of the medial geniculate body. This suggests that an auditory stimulus can be neuronally "detected" without being behaviorally detected, and that the neural "decision" to respond behaviorally is not made in these nuclei. Responses recorded from the dorsomedial division of the central nucleus of the inferior colliculus, the pericentral nucleus of the inferior colliculus, and less commonly in the medial division of the medial geniculate body were also clearly present and nearly identical during the onset of the auditory stimulus, but were sometimes consistently different for detection and nondetection conditions during the latter part of the auditory stimulus. These brain regions appear to receive both auditory and nonauditory inputs, and show responses which are more highly correlated with detection behavior.

Acoustic Stimulation↗