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Biomedical subjects

J D Delius

Publications and source records attributed to J D Delius.

At least 19 recordsLinked to original sources
PubMed1998

Visual discrimination in pigeons impaired by glutamatergic blockade of nucleus accumbens.

The nucleus accumbens septi (Acc) is thought to be involved in the control of cognitive processes and to be implicated in the pathophysiology of schizophrenia. Because perceptual-cognitive distortions are a core symptom in schizophrenia, any evidence that the Acc intervenes in a sensory recognition task in an animal species would be of interest. Pigeons were instrumentally trained to discriminate visual shapes. The acute effects of drug microinjections into the Acc on the discrimination of the training shapes, on the correction responding after errors, and on the generalisation to different shapes were examined. The effects of conduction blockade with lidocaine, glutamatergic blockade with 7-aminophosphonoheptanoic acid, and dopaminergic stimulation with apomorphine on behavioural performance were tested. No effects were observed with lidocaine and apomorphine. A significant and reversible performance disruption to near chance levels was obtained after aminophosphonoheptanoic acid injections into the Acc. It appears that a glutamatergic blockade of the Acc interferes with the visual discrimination processes of pigeons.

2-Amino-5-phosphonovalerate↗
PubMed1996

Influences of task concreteness upon transitive responding in humans.

The derivation of the conclusion "Anna is bigger than Mary" from the premises "Anna is bigger than Paul" and "Mary is smaller than Paul" is considered an instance of transitive deduction. For a non-verbal presentation, the premise statements were here transformed into a multiple operant discrimination task. Adult subjects were trained with overlapping pairs of a six-member stimulus series A+B-, A+C-, C+D-, D+E-, E+F-; +: choice rewarded, -: choice penalized). A computer game-type presentation that hid the actual problem structure from the subjects was employed. The effects of varying the presentation style of the task on the objective performance and the structure awareness of subjects were investigated. A first experiment used random polygons as stimuli and the relations between them were only signalled by the above reinforcement allocations. In a second experiment the stimuli were cartoon figures additionally involved in a dominance hierarchy that was suggested graphically. A third experiment used named items that were related through visible size differences in addition to the reinforcement allocations but was otherwise like an experiment using an abstract format reported by Werner et al. (1992). In all experiments a similar proportion of subjects responded transitively when subsequently tested with the pairs BD, BE and CE by preferentially choosing stimulus B or C. Each subject subsequently filled in a questionnaire, completed a stimulus ordering exercise, and was interviewed to find out whether they were explicitly aware of the stimulus hierarchy underlying each of the tasks. Although the proportion of subjects revealing an explicit transitive responding increased together with the concreteness of the stimuli and their relations across the experiments, the objective performance in terms of choice accuracy did not vary. The accuracy performance on tests could be accurately simulated with a modification of a simple conditioning model. It is concluded that an implicit mode of processing may underlie many instances of transitive responding in humans even when explicit task understanding is reported.

Adult↗
PubMed1995

Sensitization to apomorphine in pigeons: unaffected by latent inhibition but still due to classical conditioning.

When administered apomorphine, pigeons exhibit protracted bouts of pecking behavior. This response is subject to sensitization, as it initially increases with repeated drug injections. The hypothesis is examined that the sensitization is due to a Pavlovian conditioning of the drug-induced pecking to the environment in which it first takes effect. In a first experiment, we attempted to suppress this conditioning by extensively pre-exposing the birds to the test environment and saline injections (latent inhibition procedure). As the experiment yielded undiminished sensitization, it cast doubt on the conditioning hypothesis. However, while inhibitory pretraining also proved ineffective in a second experiment, a shortening of response latencies specific to the environment in which the animals had first experienced the apomorphine effect supported the conditioning hypothesis. It is suggested that the absence of latent inhibition may be due to the interference of a context-dependent conditioning effect. A third experiment that examined the hypothesis that the reinforcing properties of apomorphine might be attributable to its well known anorectic properties. The results provided some support for this notion. At the same time, they also confirmed that apomorphine-induced pecking conditions reliably to environmental cues. These cues are then by themselves capable of provoking conditioned pecking.

Animals↗
PubMed1995

Orientation invariant pattern recognition by pigeons (Columba livia) and humans (Homo sapiens).

The orientation invariance of visual pattern recognition in pigeons and humans was studied using a conditioned matching-to-sample procedure. A rotation effect, a lengthening of choice latencies with increasing angular disparities between sample and comparison stimuli, was replicated with humans. The choice speed and accuracy of pigeons was not affected by orientation disparities. Novel mirror-image stimuli, rotation of sample shapes, a delayed display of comparison shapes, and a mixed use of original and reflected sample shapes did not lead to a rotation effect in pigeons. With arbitrarily different odd comparison shapes, neither humans nor pigeons showed a rotation effect. Final experiments supported the possibility that the complete absence of a rotation effect in pigeons is because they are relatively better than humans at discriminating mirror-image shapes compared with arbitrary shapes.

Adult↗
PubMed1994

Processing of hierarchic stimulus structures has advantages in humans and animals.

Carmesin and Schwegler (1994) have determined theoretically that a linear hierarchical stimulus structure can be encoded by a parallel network of minimal complexity. The experiments reported here compare the efficiency with which humans and pigeons process sets of stimulus pairs embodying different inequality structures. Groups of subjects of each species were taught to discriminate all 10 pairwise combinations of 5 stimuli with an operant conditioning method. For one group, the reward/punishment allocations within the pairs agreed with a linear hierarchy. For a second and third group, the reinforcement allocations of one or three, respectively, of the stimulus pairs deviated from such ordering. The time it took the subjects to learn the tasks as well as the final choice latencies and/or error rates increased with the number of deviating inequalities. The results agree with the assumption that both humans and pigeons encode stimulus inequality structures with parallel processing neural networks rather than with a sequentially processing algorithm.

Adult↗
PubMed1994

Scratch and match: pigeons learn matching and oddity with gravel stimuli.

Two groups of 4 pigeons learned either matching-to-sample or oddity-from-sample by digging in white and black gravel for buried grain. Learning occurred as early as Trial 11, and acquisition was accelerated by as much as 100-fold compared with learning in traditional key-peck environments. Control experiments showed that performance was not controlled by cues other than the gravel stimuli and was not due to distributed practice effects of 8 trials per day and longer intertrial intervals.

Animals↗
PubMed1991

Grasping in the pigeon: control through sound and vibration feedback mediated by the nucleus basalis.

Pigeons were trained to detect auditory and vibratory stimuli in two separate experiments using an instrumental conditioning procedure. The discriminative stimuli became effective as the subjects grasped a probe with the beak. The pigeons learned to suppress responding upon this grasp-contingent stimulation. Bilateral lesions of the nucleus basalis prosencephali (Bas), known to be involved in the motor control of pecking and to receive short latency input of cochlear and trigeminal origin, eliminated the behavioral stimulus detection. The performance of a control color discrimination was not affected by the Bas lesions, demonstrating that these had a specific effect. The processing of peck-related feedback by the nucleus basalis during the normal food uptake of pigeons is discussed.

Afferent Pathways↗
PubMed1989

Sensitization to and conditioning with apomorphine in pigeons.

Pigeons that repeatedly experienced the effect of apomorphine in the same environment showed an augmented behavioural response to the same drug dose as compared with controls that experienced the effect of the drug dose in differing environments. Sensitization, an increase in the behavioural response that is observed in pigeons when the same dose of apomorphine is repeatedly administered, may thus be mainly due to a conditioning of the drug response to incidental environmental cues. Apomorphine injections also induced place preferences. Pigeons that had experienced a particular environment under the influence of apomorphine subsequently favoured that environment to one they had experienced while under saline. This suggests that apomorphine administration has reinforcing properties for birds, much as it has for mammals.

Animals↗
PubMed1988

Nucleus basalis prosencephali, a substrate of apomorphine-induced pecking in pigeons.

Microinjections of the dopamine agonist apomorphine into the nucleus basalis prosencephali of pigeons elicit stereotyped pecking behaviour. Injections of 6-hydroxydopamine, a toxic dopamine antagonist, into the same nucleus impair stereotyped pecking induced by systemic apomorphine administration, but do not interfere with pecking in the normal feeding context.

Animals↗
PubMed1988

Preventing a feature-positive effect in pigeons.

The feature-positive effect (FPE) is a widespread and robust phenomenon in the context of discrimination learning. It refers to the fact that a distinctive feature associated with a stimulus that is reinforced leads to efficient discrimination learning, whereas the same feature associated with the nonreinforced stimulus inhibits discrimination learning. Two experiments with pigeons showed that the FPE also occurs with a simultaneous discrimination paradigm involving brief discrete trials and no intertrial intervals. A pre-training treatment unexpectedly prevented the expression of the FPE in this discrimination task. The pretraining consisted of having pigeons discriminate the feature/nonfeature visual shapes from a plain background disc. Rewarding responses to the shapes, or alternatively to the blank disc, had the same FPE-preventing effect. A reversal of a feature/nonfeature stimulus discrimination led to an analogous erasure of the FPE. The results are discussed in terms of the concurrence or interference between the various associations that the subjects formed on the basis of the different stimulus-reward correlations they experienced in the different phases of the experiments.

Animals↗
PubMed1987

Apomorphine-induced pecking in pigeons classically conditioned to environmental cues.

The dopamine agonist apomorphine elicits protracted pecking when injected systemically (1 mg/kg) into pigeons. In two experiments it was investigated whether apomorphine would function as an unconditioned stimulus in the classical conditioning of pecking in these animals. An experimental design based on a differentiation procedure was used so that possible pseudoconditioning effects were controlled. Two differently coloured test chambers served as negative (CS-) and positive conditioned (CS+) stimuli. During the training phase the subjects experienced the former while injected with saline, and the latter while injected with apomorphine. In later tests not involving any injections the pigeons made significantly more pecks (conditioned response) in the CS+ chamber than in the CS- chamber. In the first and second experiments the conditioned stimuli were, respectively, discrete and diffuse visual cues, but both had similar effects. The conditioning obtained may explain sensitization effects that are observed with repeated apomorphine injections. Apomorphine probably also functions as a positive reinforcer for instrumental conditioning in pigeons.

Animals↗
PubMed1987

Orientation invariance of shape recognition in forebrain-lesioned pigeons.

Pigeons were trained to perform a visual orientation invariance task consisting of shape matching-to-sample or oddity-from-sample discriminations where the comparison forms differed in orientation from the sample forms, and the odd comparison forms were always a mirror image of the sample. They then received lesions affecting the visual projection area within the anterior hyperstriatum or the dorsal neostriatum, a control area with no known visual function. Both groups of birds evinced minor transient postoperative deficits of similar magnitude during the shape recognition task under orientation invariance conditions when the habitual training forms were used. When novel forms were introduced, the performance of hyperstriatal pigeons was significantly worse than that of the neostriatal pigeons, but still well above chance. The introduction of a delay between the offset of the sample and the onset of the habitual comparison stimuli did not yield any differential effect. It is concluded that orientation invariance of pattern recognition performance of birds, in contrast to that in mammals, is probably a midbrain, optic tectum function.

Animals↗
PubMed1986

Sensory projections to the nucleus basalis prosencephali of the pigeon.

The afferent pathways to the nucleus basalis prosencephali of the pigeon were studied by use of the horseradish peroxidase (HRP) technique. It was confirmed that this nucleus receives a direct pathway from the nucleus sensorius principalis nervi trigemini and that, as in the starling, it receives a direct input from the nucleus lemnisci lateralis, pars ventralis, an auditory relay. Totally novel is the finding that the nucleus basalis prosencephali is the target of a direct pathway originating in the medullary nucleus vestibularis superior. All three pathways bypass the thalamus. From within the telencephalon the nucleus basalis prosencephali also receives fibres from the tuberculum olfactorium and the peri-ectostriatal belt, suggestive of olfactory and visual input. Marked cell bodies were also found in the neostriatum frontolaterale. It is assumed that these arose from HRP uptake by axons of the tractus fronto-archistriatalis that course through the nucleus basalis prosencephali to the anterodorsal archistriatum. Marked fibres and bouton-like formations were observed in the latter structure. The afferents to the nucleus basalis prosencephali are discussed in conjunction with the probable role of the nucleus as a sensorimotor coordinator of the pecking/feeding behaviour of the pigeon.

Afferent Pathways↗
PubMed1986

Sensory inputs to the nucleus basalis prosencephali, a feeding-pecking centre in the pigeon.

Evoked potentials were recorded from the nucleus basalis prosencephali (Bas) of the pigeon through chronically implanted electrodes. The auditory sensitivity of the Bas was assessed by the amplitude of the potentials. Audiograms thus obtained were comparable to those similarly measured from stations of the orthodox auditory pathway and resembled those obtained by others with behavioural techniques from the same species. The sensitivity to vibration applied to the beak was also measured. The vibrogram revealed two separate optima, one located in the lower frequency and another in the higher frequency region. These were shown to be due to trigeminal mechanoreceptive sensitivity and to bone/cochlea mediated sound sensitivity, respectively. Evoked potentials of the Bas in response to vestibular stimulation are described for the first time. The possibility that they were artefacts was excluded with several control procedures. These findings confirm recent anatomical evidence of a direct pathway from the vestibular nucleus to the nucleus basalis prosencephali. All afferents to the Bas are discussed in conjunction with the probable function of the nucleus as a sensorimotor coordinator of the pigeon's pecking/feeding behaviour.

Acoustic Stimulation↗
PubMed1985

Scanning electron microscopy of the lateral ventricle of the pigeon brain.

Adult pigeons of both sexes were used for this study. Depending upon the distribution of various surface profiles, for example cilia, microvilli and blebs, ependymal areas with differing surface patterns were distinguished in the lateral ventricle. The topographical locations of these areas with respect to the underlying forebrain nuclei were determined in accord with the atlas of Karten and Hodos (1967). The medial surface (A) of the ventricle was much more densely ciliated than the lateral surface (B). There did not appear to be any correlation between a given surface pattern and a specific type of underlying nervous tissue. Comparison of the cell patterns seen in the pigeon brain with those seen in the analogous areas of the rat brain showed that it is not feasible to extrapolate from one zoological group to another. With the exception of the Kolmer cells populating the choroid plexus, there were remarkably few supraependymal cells in the pigeon lateral ventricle. Supraependymal nerve fibers were also extremely rare. Particular attention was given to the ependyma associated with the nucleus stria terminalis, to that of the lateral septal organ and to the choroid plexus. The possible classification of these areas into the group of the circumventricular organs is considered.

Animals↗
PubMed1984

Lateral telencephalic lesions affect visual discriminations in pigeons.

The importance of the lateral telencephalon of the pigeon for visual performance was examined. Lesions in this area markedly impaired both the acquisition and the retention of instrumentally learned hue, intensity and pattern discriminations. Comparable lesions of the thalamofugal visual projection in the dorsoanterior telencephalon did not have an appreciable effect. Laterally lesioned pigeons showed only a minor, non-significant impairment in an instrumental auditory discrimination task. These results generally agree with findings of other authors on domestic chicks but disagree with previous work on pigeons. The visual discrimination performance of laterally lesioned subjects improved gradually over the course of days and weeks without specific experience being necessary, and after 3 months the recovery was virtually complete. The effect of lateral telencephalic lesions is discussed in connection with known visual projections within the avian endbrain and their relationship with other functional systems.

Animals↗