Biomedical subjects

E A Gaffan

Publications and source records attributed to E A Gaffan.

At least 19 recordsLinked to original sources

PubMed2000

Perirhinal cortex ablation in rats selectively impairs object identification in a simultaneous visual comparison task.

In Experiment 1, rats discriminated among computer-generated visual displays (scenes) comprising 3 different shapes (objects). One constant scene (unrewarded) appeared on every trial together with a trial-unique variable scene (rewarded). Four types of variable scene were intermingled: (a) unfamiliar objects in different positions from the constant; (b) unfamiliar objects in same positions as the constant; (c) same objects as the constant in different positions; (d) same objects and positions, recombined. Aspiration lesions of perirhinal cortex impaired performance with type (b) only. Experiment 2 tested spatial delayed nonmatching-to-sample. The perirhinal group were impaired nonsignificantly, and less than fornix-transected rats in an earlier study. Rats' perirhinal cortex, like monkeys', subserves object identification in the absence of memory requirement but does not contribute substantially to hippocampal system spatial memory function.

Animals↗

PubMed1999

Scene and object vision in rats.

Dark Agouti rats learned to discriminate large visual displays ("scenes") in a computer-controlled Y-maze. Each scene comprised several shapes ("objects") against a contrasting background. The constant-negative paradigm was used; in each problem, one constant scene was presented on every trial together with a trial-unique variable scene, and rats were rewarded for approaching the variable scene. By varying the manner in which variables differed from the constant, we investigated what aspects of scenes and the objects comprising them were salient. In Experiment 1, rats discriminated constant scenes more easily if they contained four objects rather than six, and they showed a slight attentional bias towards the lower halves of the screens. That bias disappeared in Experiment 2. Experiments 3 and 4 showed that rats could discriminate scenes even if the objects that comprised them were closely matched in position, luminance, and area. Therefore, they encoded the form of individual objects. Rats perceived shapes of the same class (e.g. two ellipses) as more similar than shapes from different classes (e.g. ellipse and polygon) regardless of whether they also differed in area. This paradigm is suitable for studying the neuropsychology of perceiving spatial relationships in multi-object scenes and of identifying visual objects.

Animals↗

PubMed1998

Behavioural effects of long-term multi-sensory stimulation.

OBJECTIVES: Regular access to a multi-sensory environment (MSE or Snoezelen room) was compared with a non-complex sensory environment for individuals with learning disabilities. We also tested the prediction that those individuals whose challenging behaviour was maintained by sensory consequences would benefit most from exposure to the MSE. DESIGN: The conditions were compared over 16-week periods using a double crossover design, and were matched for social contact and attention from the enabler. Participants were randomly assigned to orders of treatments. METHODS: Participants were 27 adults with severe/profound learning disabilities who exhibited challenging behaviour. Behaviour was assessed before and after each treatment phase using both direct observation and standardized assessments (the Functional Performance Record and the Problem Behaviour Inventory). The behavioural observations formed the basis of a functional analysis of each individual's challenging behaviour. RESULTS: Some participants became more calm and relaxed while in the MSE, however, the objective measures of behaviour outside the treatment settings revealed no difference between the MSE and control conditions. Challenging behaviour maintained by sensory consequences showed no greater responsivity to the MSE than to the control condition. CONCLUSIONS: The multi-sensory environment had no effects beyond those that could be ascribed to the social interaction between participant and enabler. Anecdotal evidence of favourable responses within the MSE itself could not be confirmed outside the environment.

Adult↗

PubMed1997

Fear of water in children and adults: etiology and familial effects.

Water-fearful children (non-swimmers. 5-8 yrs and adults (non-swimmers or late learners, 23-73 yr) were compared with non-fearful controls of similar swimming ability. Parallel assessments were carried out with children and adults to investigate water-related experiences, water fear and competence in parents and siblings, and the relationship of water fear to other fear dimensions. Children were assessed behaviorally and by self and mother's report, adults by self-report. In neither children nor adults was there clear evidence that fearful and non-fearful groups differed in incidence of aversive water-related experience before fear onset. Parents usually believed that children's fear was present at first contact. In both samples, we found parent-offspring and sibling resemblances in fear. Analysis of details of children's contact with parents suggested that social learning within the family decreased water fear rather than increasing it; when both child and parent showed fear, that was as likely to reflect genetic influences as modeling. Young children's water fear forms part of a generic cluster, fear of the Unknown or Danger, while in adults it becomes independent of generic fears.

Adult↗

PubMed1997

Spatial memory impairment in rats with fornix transection is not accompanied by a simple encoding deficit for directions of objects in visual space.

In Experiment 1, rats learned 6 discriminations among pairs of complex wide-angle visual displays, presented concurrently, using a computer-controlled Y maze. Fornix-transected rats were unimpaired relative to controls regardless of whether the displays comprised a single large "objectlike" figure or "scenelike" arrays of spatially distributed figures. Experiment 2 compared 2 versions of a visual discrimination in which either object identity (independent of location within the visual field) or location within the visual field (independent of object identity) had to be used. The fornix-transected rats performed normally with either cue. In Experiment 3, however, the same group was clearly impaired on a standard spatial memory test, spatial delayed nonmatching to sample. Although the fornix-transected rats were more likely to choose rapidly and inaccurately, their deficit was not a by-product of impulsive responding. The spatial impairment was not merely a difficulty in encoding direction of a single item within visual space, but more complex configural deficits could not be ruled out.

Animals↗

PubMed1996

Anterior rhinal cortex and amygdala: dissociation of their contributions to memory and food preference in rhesus monkeys.

Rhesus monkeys were trained on 2 versions of delayed nonmatching-to-sample, one with multiple pairs of objects and the other with a single pair, to evaluate their ability to remember objects. They then received either bilateral aspiration lesions of the anterior rhinal cortex or bilateral excitotoxic lesions of the amygdala, or were retained as unoperated controls. On re-presentation of the multiple-pair task, monkeys with anterior rhinal cortex lesions failed to show the improvement observed in both other groups in remembering the objects over delay intervals ranging from 10 to 60 s. Also, monkeys with anterior rhinal cortex lesions were impaired relative to the controls in relearning the single-pair version of the task. Conversely, on a formal test of food preference, monkeys with amygdala lesions showed abnormal patterns of food choice, whereas monkeys with anterior rhinal cortex lesions did not. Visual memory impairments formerly attributed to amygdala damage are probably due to the rhinal cortex damage associated with aspiration lesions of the amygdala.

Amygdala↗

PubMed1995

A computer-controlled maze environment for testing visual memory in the rat.

A computer-controlled version of a Y-maze was developed to allow automated testing of rats' learning and memory with visual stimuli. Each of the 3 arms terminated with 2 adjacent monochromatic screens, 43 cm from the maze centre, providing a total stimulus area 47 cm wide by 18.5 cm high. The displays were abstract patterns extending across 2 screens, generated by algorithms which provided a large pool of discriminable patterns. The patterns used were of 2 general classes: Scenes (internally complex patterns with varying numbers of foreground shapes distributed across contrasted backgrounds) and Objects (internally homogeneous single figures, confined to the central part of the display). They could be stationary or have oscillatory movement. Subjects' location in the maze was monitored by infrared beam photodetectors; approach to correct patterns was rewarded with food. Pigmented rats of the Hooded Lister and Dark Agouti strains were tested. All could acquire 2-pair concurrent visual discriminations comprising 2 positive and 2 negative patterns, either Scenes or Objects; most could acquire 4-pair discriminations. Dark Agouti rats generally performed better than Hooded Listers. A novel training procedure using one positive and many negative patterns resulted in rapid learning of novel discriminations with either moving or non-moving patterns. The apparatus is an effective environment for visual learning by rats, suitable for a wide range of tasks in neuropsychology and psychopharmacology.

Animals↗

PubMed1995

Researcher allegiance and meta-analysis: the case of cognitive therapy for depression.

K. S. Dobson (1989) conducted a meta-analysis of 28 studies of cognitive-behavioral therapy for depression that used the Beck Depression Inventory as outcome measure. He concluded that the outcome of this type of therapy was superior to that of other forms of psychotherapy and to that of pharmacotherapy. The present study reanalyzed the same studies, and a further set of 37 similar ones published from 1987 to 1994, taking into account variations in sample size and researcher allegiance. This study confirmed Dobson's conclusions for his original sample but showed that about half the difference between CT and other treatments was predictable from researcher allegiance. However, comparable analyses of the later set of studies showed no effect of researcher allegiance. Two causes for these phenomena are (a) a historical effect, whereby both effect sizes and allegiance were large in earlier years and declined over time and (b) a treatment effect whereby effect size and allegiance were correlated, but more for some treatments than others. This correlation has also weakened over time.

Attitude of Health Personnel↗

PubMed1992

The performance of postencephalitic amnesic subjects on two behavioural tests of memory: concurrent discrimination learning and delayed matching-to-sample.

The performance of a group of three postencephalitic subjects with anterograde amnesia was examined on a series of concurrent visual discrimination problems and on a test of visual recognition, delayed matching-to-sample. These tests were chosen as they have been used to assess experimental models of anterograde amnesia in nonhuman primates. In comparison with a group of normal subjects the postencephalitic group were impaired on the more difficult concurrent discrimination problems. They also performed poorly on the matching-to-sample task when given lists of items to remember or given increased retention intervals. The pattern of performance of the postencephalitic group matched closely that of a group of Korsakoff subjects, indicating that these behavioural tests are equally sensitive to different types of anterograde amnesia.

Adult↗

PubMed1991

Amnesia following damage to the left fornix and to other sites. A comparative study.

Two memory-impaired patients, who had suffered damage to the left or both fornix columns during removal of a ventricular cyst, were compared with 3 others having left-sided hippocampal or thalamic lesions, and with normal controls. The tests used were nonverbal--scene recognition, delayed matching-to-sample and concurrent pattern and object discrimination learning. The last two are differentially sensitive to fornix transection and to hippocampal or thalamic ablations in monkeys; however, the patients with fornix damage did not show a distinctive pattern of impairment. The reasons for this discrepancy are discussed. The study adds to the evidence that fornix transection can cause wide-ranging memory disturbances in man.

Adult↗

PubMed1991

Amnesia in man following transection of the fornix. A review.

Published accounts of the effects of fornix damage on memory in man are critically evaluated. Most weight is given to cases of surgical transection of the fornix, though other causes of fornix damage are briefly discussed. It is concluded that fornix transection causes amnesia.

Amnesia↗

PubMed1990

Concurrent and sequential pattern discrimination learning by patients with Korsakoff amnesia.

Patients with Korsakoff's syndrome and alcoholic controls learned to discriminate sets of pairs of patterns presented concurrently, in order to test predictions based on monkeys' performance in similar tasks following medial temporal or diencephalic lesions. In Experiment 1 the subjects learned a 2-pair, a 6-pair and a 10-pair set; the Korsakoff group were impaired on the first and last, but not on the second set. In Experiment 2, the same subjects learned single pairs sequentially, and 2-pair and 8-pair sets concurrently. The effect of 2 types of feedback for correct responses (visual or non-visual) was also compared. The Korsakoff patients were markedly poorer than controls under all conditions; the type of feedback made little difference. In several respects the patients' impairment differed from what had been predicted from the animal experiments.

Alcohol Amnestic Disorder↗

PubMed1989

Visual-visual associative learning and reward-association learning in monkeys: the role of the amygdala.

Three Cynomolgus monkeys (Macaca fascicularis) took part in an experiment on visual learning set in an automatic apparatus. Each new visual discrimination problem was solved using a visual secondary reinforcer consisting of a white line. If the monkey chose the correct stimulus (by touching it), the white line appeared over the correct stimulus. Primary food reward was delivered only after a new problem was solved to a criterion, and the problem was then replaced by a new one. Thus, within-problem learning did not rely on primary reinforcement but on the visual secondary reinforcer. The animals were trained preoperatively in visual learning set with this procedure and were assessed postoperatively for their ability to learn new visual discriminations with the same procedure. Bilateral amygdalectomy did not significantly impair the animals' learning ability in this task. Learning remained unimpaired when transection of the uncinate fascicle and of the fornix was added to amygdalectomy. The effect of bilateral amygdalectomy in this task was much less severe than in a similar task we previously studied, with auditory secondary reinforcers. The results show that the involvement of the amygdala in processes of secondary reinforcement depends on the sensory properties of the secondary reinforcer. From these and other recent results, we conclude that the sensory attributes of a reinforcer are easily associated with a discriminative stimulus when they are in the same modality and same spatial location as the discriminative stimulus and that this sensory-sensory association is independent of the amygdala.

Amygdala↗

PubMed1988

Disconnection of the amygdala from visual association cortex impairs visual reward-association learning in monkeys.

Cynomolgus monkeys (Macaca fascicularis) were trained in a task that assessed their ability to associate visual stimuli with food reward. Acquisition of stimulus-reward associations was measured under 2 conditions, a 2-stimuli acquisition condition and a 1-stimulus acquisition condition. On each trial in the 2-stimuli condition, the positive (correct) and negative (incorrect) stimuli were presented side by side and the animal chose one by touching it; if the choice was correct, a food reward was dispensed. On each trial in the 1-stimulus condition, either the positive or the negative stimulus was presented alone; if the stimulus was the positive, it was followed by reward delivery, regardless of the animal's response to it, and if it was the negative, it was not followed by reward delivery. Thus, reward delivery was contingent upon the animal's response to the stimuli in the 2-stimuli condition but not in the 1-stimulus condition. The effect of acquisition trials under these 2 conditions was measured, in both conditions, by the animal's subsequent choice when presented with the 2 stimuli side by side. Following preoperative training in this task, the animals were first subjected to unilateral ablation of the inferotemporal cortex. This operation had little effect on the animals' learning ability. Then, the amygdala was ablated in the hemisphere contralateral to that in which the unilateral inferotemporal ablation had been carried out. This combination of crossed unilateral lesions of the amygdala and of the inferotemporal cortex, which disconnects the amygdala from the output of visual association cortex, produced a profound impairment in stimulus-reward-associative learning.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗

PubMed1986