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E J Kehoe

Publications and source records attributed to E J Kehoe.

At least 19 recordsLinked to original sources
PubMed2002

Temporal discrimination using different feature--target intervals in classical conditioning of the rabbit's nictitating membrane response.

In a typical conditional discrimination, a target stimulus (X) is reinforced during one feature cue (A-->X+), but not during another feature cue (B-->X-). The present experiments used only a single "feature" cue (a 66-sec tone). On half of the trials, the target stimulus (a 400-msec light) was paired with the reinforcer when the feature-target interval was one duration (e.g., 5 sec). On the remaining trials, the interval was different (e.g., 45 sec), and the target stimulus was presented without the reinforcer. All the animals acquired this temporal discrimination, and subsequent testing with other feature-target intervals yielded generalization-like gradients. These results provide solid evidence that each portion of a feature cue is encoded in a distinctive fashion. Had temporal encoding not occurred, the feature cue would have been just as ambiguous a predictor of the reinforcer as was the target stimulus, and discrimination would not have been possible. The integration of real-time temporal encoding mechanisms into models of conditional discrimination is discussed.

Animals↗
PubMed1999

Conditioning and reflex modification of the rabbit nictitating membrane response using electrical stimulation in auditory nuclei.

Electrical brain stimulation (EBS) was applied to four nuclei in the auditory system, namely, the cochlear nucleus (CN), superior olive (SO), inferior colliculus, and medial geniculate. EBS was also applied to the pontine nuclei, which are the main relays for transmitting auditory conditioned stimuli (CSs) into the cerebellar pathways for conditioning of the nictitating membrane response (NMR). EBS of the CN, but no other site, yielded reflex modification, which was an increase in the unconditioned NMR to an airpuff unconditioned stimulus (US) when preceded by EBS. Throughout the experiment, EBS of the SO produced a distinctive distribution of NMRs, in which a high proportion had latencies less than 50 ms. When EBS was repeatedly paired with the airpuff US, conditioned responses (CRs) were acquired to comparable levels across all sites. At each site, response likelihood was an increasing function of the EBS parameters of pulse amplitude, pulse frequency, and pulse width. Combined with anatomical findings, these results indicate that multiple encodings of an auditory CS are sent to the pathways for the NMR.

Animals↗
PubMed1997

Fos-like immunoreactivity in locus coeruleus after classical conditioning of the rabbit's nictitating membrane response.

We investigated the changes in Fos-like immunoreactivity in the locus coeruleus (LC) after classical conditioning of the rabbit's nictitating membrane. Specifically, we compared unpaired versus paired presentations of a tone conditioned stimulus (CS) and a tactile unconditioned stimulus (US; near the eye). After two training sessions, only paired presentations resulted in acquisition of a conditioned response. This was associated with comparatively less LC Fos expression than with unpaired presentations. Similar observations have been reported for the ventrolateral medulla which is a major source of afferents to LC. The present results are consistent with a role of LC in attention and learning: activity increases as the animal attends to the CS and US. When the relationship between CS and US has been established, LC activity decreases.

Animals↗
PubMed1997

Elicitation, modification, and conditioning of the rabbit nictitating membrane response by electrical stimulation in the spinal trigeminal nucleus, inferior olive, interpositus nucleus, and red nucleus.

Elicitation of responses by electrical brain stimulation (EBS) was related to the synaptic distance of the target nucleus from the accessory abducens. Specifically, responses to EBS in the spinal trigeminal nucleus (TRIG) and red nucleus (RN) increased as a positive function of stimulation parameters. Responding to EBS in the interpositus nucleus (IP) was lower, and responding to EBS in the inferior olive (IO) was negligible. EBS in the TRIG, IP, and RN nuclei was then paired with a tone conditioned stimulus (CS). The CS modified responses for EBS in RN and TRIG but not IP. CS-EBS pairings yielded conditioned response (CR) acquisition, in which Groups TRIG, IP, and RN reached asymptotes of 90%, 70%, and 43% CRs, respectively. Thus, contrary to previous findings, EBS in the efferent pathway can support CR acquisition. The results are discussed with respect to the role of projections from the RN to the cerebellar cortex and the TRIG nucleus.

Abducens Nerve↗
PubMed1997

Transfer and counterconditioning of conditional control in the rabbit nictitating membrane response.

Two experiments using the rabbit nictitating membrane response investigated whether training in one conditional discrimination (A-->X+, B-->X-), enabled the feature cues (A and B) to modulate responding to another CS (Y) trained as a target stimulus in a second conditional discrimination (C-->Y+, D-->Y-). There was near-complete transfer of the feature cue's conditional control, indicating that the feature cue's ability to modulate responding is not based on an association specific to the training target. Experiment 2 also revealed that the role of a stimulus to act as a conditional cue is affected by its ability to act as a simple conditioned excitor or inhibitor. Following initial acquisition of two conditional discriminations, two feature cues were reinforced in a pattern consistent with the initial conditional discrimination (A-->+, B-->-), where as the other two feature cues were reinforced in the reverse pattern to that of the original conditional discrimination (C-->-, D-->+). Subsequent tests revealed that the reversed training of the feature cues interfered with the original conditional discriminations. The results are consistent with theories that the feature cue gains an association with a representation of the emotional attributes of the US, which acts to modulate responding to the target stimulus through a diffuse change in motivational level. However, hierarchical theories of conditional discriminations that assume a lack of CS-specificity may also be able to explain the findings.

Analysis of Variance↗
PubMed1995

Acquisition of a conditioned reflex in New Zealand white rabbits from three sources.

In studies of learning using rabbits, there has been standardization of behavioural procedures across laboratories. Less attention has been paid to variation that may arise from genetic differences and/or differences in rearing conditions. The present experiment revealed that acquisition of a conditioned reflex can be affected dramatically by such differences. Specifically, the acquisition of a conditioned reflex in New Zealand White (NZW) rabbits from 3 different suppliers was compared. All rabbits received behavioural training in which a tone or a light signalled an electrotactile stimulation of the trigeminal nerve near the rabbits' right eye. This tactile stimulus reliably elicited an eyeblink. Repeated presentations of the auditory and visual signals followed by the tactile stimulus yielded the acquisition of a conditioned response (CR), namely closure of the eyelids during the warning period provided by the signal stimuli. Two of the groups showed steady CR acquisition at a rate that matched previous results in other laboratories as well as in the senior author's laboratory. However, the third group of rabbits showed very slow acquisition, and some rabbits failed to show any CR acquisition.

Animal Husbandry↗
PubMed1993

Real-time processing of serial stimuli in classical conditioning of the rabbit's nictitating membrane response.

Real-time models contend that a conditioned stimulus (CS) gives rise to a cascade of hypothetical stimuli that govern conditioned responses (CRs) on a moment-by-moment basis. Experiments with the rabbit nictitating membrane response successfully extended these models to external stimuli. CSs were trained in sequence with an unconditioned stimulus (CSA-CSB-US). When the CSA-CSB interval was shortened, the CR was compressed; when the CSA-CSB interval was lengthened, the CR was broadened. Peaks appeared at 2 places, namely, 1 following CSA by a period equal to its CS-US interval and another following CSB by its CS-US interval. Outside the sequence, the individual CSs evoked CRs located between their respective CS-US intervals. When, however, the 2 CSs were trained separately, the CRs were appropriate to their respective CS-US intervals when tested alone or in sequence. The results are discussed in terms of the J.E. Desmond and J.W. Moore (1988) and S. Grossberg and N.A. Schmajuk (1989) models.

Animals↗
PubMed1992

Rapid reaquisition in conditioning of the rabbit's nictitating membrane response.

Reacquisition after extinction often appears faster than original acquisition. However, data from conditioned suppression studies indicate that this effect may arise from spontaneous recovery and reinstatement of unextinguished contextual stimuli related to the unconditioned stimulus (US). In the present experiments using the rabbit nictitating membrane preparation, spontaneous recovery was eradicated before reaquisition training. US contextual stimuli were controlled by retaining the US during extinction through explicit unpairings of the conditioned stimulus (CS) and US. Attempts were also made to drive the associative strength of the CS into the inhibitory region by differential conditioning and conditioned inhibition procedures. In all cases, reacquisition was very rapid in comparison with a rest control. The results are discussed with respect to their implications for CS and US processing models of conditioning.

Animals↗
PubMed1991

Conditioning of the rabbit's nictitating membrane response to a CSA-CSB-US serial compound: manipulations of CSB's associative character.

Response acquisition to a trace conditioned stimulus (CSA) can be facilitated by insertion of a second stimulus (CSB) at the end of the trace interval just before the unconditioned stimulus (US). This effect may arise from serial mediation of trace conditioning, second-order conditioning, or both. Whereas serial mediation relies only on the presence of CSB, associative transfer relies on CSB's associative strength. In the present experiments, the presence of CSB was fixed, whereas CSB's associative strength was manipulated by (a) extinction of CSB, (b) latent inhibition of CSB, and (c) prior CSB-US pairings. In the first 2 cases, the level of responding to CSA was reduced in a fashion parallel to that of CSB. However, in the third case, partial blocking of conditioned response (CR) acquisition to CSA was observed. The results are discussed with reference to the role of associative transfer to both facilitating and blocking CR acquisition to CSA.

Animals↗
PubMed1991

In the blink of an eye: real-time stimulus factors in delay and trace conditioning of the rabbit's nictitating membrane response.

Since Pavlov, theories of conditioning have assumed that CR evocation is governed by a series of internal stimuli generated by the CS. This hypothesis was tested in conditioning of the rabbit's nictitating membrane (NM) response by attempting to manipulate the internal sequence through truncating a delay CS and extending a trace CS on test trials. These perturbations of CS duration produced large deficits in CR likelihood and smaller alterations in the CR's time course. As predicted by many models of conditioning, the onset of the CS appeared to play a large but not exclusive role compared to CS duration and CS offset in both evocation and timing of the CR. The results are discussed with respect to their implications for real-time models of conditioning.

Animals↗
PubMed1991

Temporal specificity in cross-modal transfer of the rabbit nictitating membrane response.

Two experiments examine cross-modal transfer of response features specific to the interstimulus interval (ISI) between a conditioned stimulus (CS) and an unconditioned stimulus. Rabbits were given initial training with a stimulus (CSA) in one modality (e.g., tone) at a designated ISI (e.g., 600 ms). Training was then shifted to a new stimulus (CSB) in another modality (e.g., light) at a new ISI (e.g., 400 ms). The timing of early conditioned responses (CRs) to CSB reflected the ISI of CSA. Ultimately, CRs to CSB shifted to a temporal location conforming to the ISI of CSB. When the ISI of CSB was shorter than that of CSA, CRs to CSA also shifted to a locus conforming to the ISI of CSB. The present results confirmed previous findings that training in one CS modality accelerates CR acquisition to a CS in another modality. The findings are compared with the transfer of response patterns in instrumental learning sets and are discussed regarding their implications for theories of cross-modal transfer.

Animals↗
PubMed1989

Temporal patterns of the rabbit's nictitating membrane response to compound and component stimuli under mixed CS-US intervals.

The acquisition of the rabbit's nictitating membrane response to a tone and light compound and to its components was examined when compound presentations were reinforced at one conditioned stimulus-unconditioned stimulus (CS-US) interval and individual component presentations were reinforced at another CS-US interval. Examination of the time course of the CRs revealed that (a) despite the mixture of CS-US intervals, conditioned response (CR) timing remained accurate, that is, CRs reached their peaks at the alternative points of US delivery; (b) the momentary magnitude of the CR to the compound was predominantly an additive function of the CR magnitude to the individual components; but (c) there was modest evidence of differentiation between the compound as a unit and the individual components. The results are discussed in terms of their implications for the study of the neural substrates of temporal and sensory integration as they modulate CR acquisition.

Acoustic Stimulation↗
PubMed1989

Connectionist models of conditioning: A tutorial.

Models containing networks of neuron-like units have become increasingly prominent in the study of both cognitive psychology and artificial intelligence. This article describes the basic features of connectionist models and provides an illustrative application to compound-stimulus effects in respondent conditioning. Connectionist models designed specifically for operant conditioning are not yet widely available, but some current learning algorithms for machine learning indicate that such models are feasible. Conversely, designers for machine learning appear to have recognized the value of behavioral principles in producing adaptive behavior in their creations.

Journal Article↗
PubMed1987

Differential conditioning of the rabbit's nictitating membrane response to serial compound stimuli.

Three experiments were conducted to determine the time course and contents of CS representations through an examination of differential conditioning of the rabbit's nictitating membrane response to two serial compounds. One compound (A-X+) was always paired with the unconditioned stimulus, and the other (B-X-) was always presented alone. All three experiments entailed manipulation of the interstimulus interval between the initial distinctive element of each compound (A and B) and the second, shared element (X). The joint results revealed that (a) conditioned response acquisition to the initial elements depended on the presence of X in the A-X+ compound; (b) differentiation between A and B appeared across interstimulus intervals up to 4,600 ms; and (c) conditional control over responding following A and B appeared at interstimulus intervals of at least 4,600 ms and perhaps up to 12,600 ms. The results are discussed with respect to mechanisms of occasion setting, generalization, and configuration.

Animals↗
PubMed1983

CS-US contiguity and CS intensity in conditioning of the rabbit's nictitating membrane response to serial compound stimuli.

The present experiments examined acquisition of the rabbit's nictitating membrane response to serial compound stimuli. Each compound consisted of two distinctive conditioned stimuli (CSA and CSB) that were followed by a shock unconditioned stimulus (US). In Experiment 1, CSA was a highly salient 93-dB tone, and CSB was a moderately salient flashing light. The CSA-US interval was 800 msec, and the CSB-US interval was varied across 400, 600, and 800 msec. In Experiment 2, the flashing light served as CSA, and CSB was either a 73-, a 85-, or a 93-dB tone. The CSA-US interval remained 800 msec, and the CSB-US interval was fixed at 400 msec. The experiments revealed that the CSB-US interval and CSB intensity determined the rate of conditioned response (CR) acquisition to the compound. Yet, CR acquisition to CSB as measured on test trials showed impairments relative to the level of responding in single CS-control conditions. However, the impairment in CR acquisition to CSB was attenuated by increasing CSB-US contiguity, that is, by decreasing the CSB-US interval (Experiment 1) or by increasing CSB intensity (Experiment 2). In Experiment 1, the impairment in acquisition to the light CSB appeared to be primarily a consequence of the tone CSA's greater salience. However, in Experiment 2, impairments in CR acquisition to CSB appeared even when CSB had the combined advantages of CS-US contiguity and great salience relative to CSA. Thus, the results indicated a role for CSA's temporal primacy in determining CR acquisition to the components of a serial compound. The results are discussed in terms of selective-attention, generalization-decrement, and information hypotheses.

Acoustic Stimulation↗
PubMed1982

Overshadowing and summation in compound stimulus conditioning of the rabbit's nictitating membrane response.

The present experiments examined acquisition of the rabbit's nictitating membrane response to a light + tone simultaneous compound stimulus and its components as a function of the intensity of the tone. In Experiment 1, the tone intensity was varied across the values of 85, 89, and 93 dB, and the CS-US (conditioned stimulus-unconditioned stimulus) interval was 400 msec. In Experiment 2, the tone intensities were 73, 85, and 93 dB, and the CS-US interval was 800 msec. Experiments 3 and 4 further examined the effects of the 73-dB tone at CS-US intervals of 400 and 800 msec, respectively. All experiments included control groups, which were trained with either a light or a tone CS. In brief, the experiments revealed repeated instances of overshadowing, i.e., the impairment of conditioned response (CR) acquisition to one or both of the components of a compound. Moreover, two types of summation were obtained: within-subjects summation, in which rabbits trained with a compound showed a higher level of responding to the compound than to either of its component CSs (Experiments 2, 3, and 4), and between-groups summation, in which a group trained with a compound showed faster CR acquisition than either of its corresponding control groups trained with a single CS (Experiments 1 and 2). The results are discussed in terms of perceptual and distributive processing models of compound stimulus conditioning.

Animals↗