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PubMed1979

Partial interocular transfer of brightness and movement discrimination by split-brain cats.

Interhemispheric transfer of discriminations of brightness and direction of movement, two types of stimuli which may be processed by midbrain visual areas, was compared to transfer of control patterns in cats with sections of the optic chiasm and forebrain commissures. Transfer in these split-brain cats was further compared to transfer in partially split-brain cats with sparing of either the splenium of the corpus callosum or the anterior commissure. An intact splenium was necessary for high levels of interhemispheric transfer of all of the discriminations, which implies a prominant role for cortical mechanisms in such tasks. However, animals with complete section of the corpus callosum often showed partial interocular transfer of both brightness and movement discriminations, which may reflect a limited but selective participation of subcortical areas in visual perception. Cats in which the anterior commissure was spared did not show greater transfer on any of these tasks than did cats with section of both callosum and anterior commissure.

Animals↗
PubMed1983

Enhanced preference for perceptual novelty in the monkey after section of the fornix but not after ablation of the hippocampus.

Previously uncovered discrepancies between the behavioral effects of fornix sections and hippocampal ablations in the monkey suggested that damage to the fornix but not that to the hippocampus may result in a motivational post-operative change. To test this notion, control monkeys and those with damage to either hippocampus or fornix were given an opportunity to choose freely between presentations of novel or repetitive stimuli in two modalities. In the visual mode, the choice was between viewing color slides which changed on every trial or repeated presentations of a geometric pattern (experiments 1 and 1a). In the auditory mode, the choice was between trains of identical clicks and different sound patterns (experiments 2 and 2a). Monkeys with sections of the fornix, but not those with ablations of hippocampus, showed an abnormally marked preference for novel stimuli in both modalities, even when perceptual novelty was designed to compete unfavorably with food reward (experiments 1b and 2b). These findings (a) provide another instance of functional dissociation between the effects of fornix and hippocampal damage and caution against assuming safely that data obtained with sections of the fornix will always mirror the behavioral consequences of hippocampal ablations; and (b) suggest that the hippocampus of primates may participate in the mediation of cognitive-motivational aspects of behavior which should be taken into account when the role of the hippocampus in memory processes is considered.

Animals↗
PubMed1994

Evidence for executive dysfunction in autism.

A group of young people with autism (ranging in ability from high functioning to moderately learning disabled), and ability-matched control groups of (i) non-autistic individuals with moderate learning disabilities, and (ii) normally developing children, were presented with two tests of executive function: the Intra-dimensional/Extra-dimensional set-shifting task and the Tower of London planning task. These tests were graded in difficulty and included internal control measures. On each task, the autistic group was differentially impaired with respect to both control groups. Moreover, this impairment was specific to the stages of each task which placed greatest demands upon executive control. This evidence for executive dysfunction in autism is discussed in the context of Norman and Shallice's (Centre for Human Information Processing Technical Report 99, 1980) "Supervisory Attentional System" model of frontal function.

Adolescent↗
PubMed2002

Differential learning abilities of 129T2/Sv and C57BL/6J mice as assessed in three water maze protocols.

Knockout mice are generated by using ES cells from 129 mouse strains and are frequently backcrossed with other strains, like C57BL/6. It is important to characterise the physiological and, in particular, the behavioural profile of each strain in order to correctly analyse the functional contribution of a single gene mutation on the 'cognitive' phenotype. The present study compared 129T2/Sv (129) and C57BL/6J (C57) mice in three different spatial learning protocols in the water maze, using a hidden platform. In the 'standard' reference memory protocol, 129 and C57 attained an equivalent level of performance as assessed by accuracy in reaching the platform (path length), despite a faster swim speed exhibited by C57 mice. In a stepwise learning task, C57 mice showed poorer performances over all stages of learning. However they performed better than 129 in a massed learning protocol which taxes short-term memory, and in which they exhibited lower levels of perseveration. The results emphasize the importance of using various tasks differing in cognitive demand, but using the same experimental environment and motivation, in order to 1) evaluate strain- or mutation-dependent learning abilities, and 2) dissociate the roles played by cognitive and non-cognitive factors in the behavioural requirements of the tasks.

Animals↗
PubMed2003

Backward conditioning: mediation by the context.

The information acquired in backward conditioning (i.e., outcome-->cue) was assessed in 3 Pavlovian lick-suppression experiments with water-deprived rats as subjects. Experiment 1 confirmed previous research that few outcome-->cue pairings made the cue into a conditioned excitor and additionally showed that massive posttraining extinction of the training context attenuated a backward-trained cue's excitatory value. Experiment 2 found that many outcome-->cue pairings made the cue into a conditioned inhibitor and that the same context manipulation attenuated this inhibitory value. Experiment 3 confirmed the observations of Experiments 1 and 2 and demonstrated that these effects of context extinction were specific to backward-trained cues conditioned in the extinguished context. These results are interpreted in terms of cue-->context and context-->outcome associations.

Animals↗
PubMed2005

Avoidance behavior can function as a negative occasion setter.

The authors put forward the hypothesis that avoidance learning can result from the fact that participants learn (a) that a stimulus is followed by an unconditioned stimulus (US) when the avoidance behavior is not emitted and (b) that the stimulus is not followed by the US when the avoidance behavior is emitted. As such, avoidance behavior is assumed to function as a negative occasion setter. The results of a contingency judgment experiment involving 65 students showed that avoidance behavior indeed has the unique functional properties of a negative occasion setter (resistance to counterconditioning and selective transfer of modulation).

Association Learning↗
PubMed2003

Backward inhibition as a means of sequential task-set control: evidence for reduction of task competition.

Endogenously initiated transitions between tasks are associated with inhibition of the attentional set for the task preceding the transition, as demonstrated by slowed reactions to a task most recently switched away from (U. Mayr & S. W. Keele, 2000). Using an altered methodological approach, the authors found that this backward inhibition counteracts perseverative tendencies when switching to a new task in that it selectively reduces interference exerted by the preceding task set. The reduction of interference was dependent on endogenous preparation for the new task and did not occur for unpredictable task switches or for task switches that were precued without information about the identity of the new task.

Adolescent↗
PubMed1979

Contrasting effects of lateral striate and superior colliculus lesions on visual discrimination performance in rhesus monkeys.

Rhesus monkeys with lesions of lateral striate cortex, monkeys with superior colliculus lesions, and unoperated monkeys were tested for retention of a preoperatively acquired pattern discrimination. The three groups of monkeys were then tested in two-choice, color, color discrimination tests, one involving varying degrees of stimulus-response (S-R) separation and the other, administered several months later, involving various directions of S-R separations. The monkeys were also tested in a series of two-choice pattern discriminations, following each of which they were tested for relearning when the patterns were masked with bars or circles. The monkeys with lateral striate lesions were moderately retarded in retention of the pattern discrimination, whereas those with superior colliculus lesions were not. The monkeys with colliculus lesions, but not those with lateral striate lesions, were impaired in both S-R separation tests, which demonstrates that their deficit was not transient or solely due to a difficulty in shifting the gaze in one direction. The lateral striate monkeys, unlike those with colliculus lesions, were dificient in relearning discriminations between masked patterns. These findings suggest that superior colliculus and striate cortex may be involved in two different aspects of attention: respectively, shifting attention (and orientation) from one spatial locus to another and maintaining attention on fixated stimuli. Alternative interpretations of the effects of the lesions, based on their retinotopic loci, are discussed.

Animals↗
PubMed1984

Preference in rhesus monkeys given a choice between cocaine and d,l-cathinone.

Previous experiments have shown that both cocaine and d,l-cathinone can function as positive reinforces when delivered intravenously to rhesus monkeys. However, the relative reinforcing efficacies of these compounds have not been established. In the present experiment, three rhesus monkeys were allowed to choose between saline and several doses of d,l-cathinone or cocaine as well as between several doses of both drugs in a discrete-trial choice procedure. Sufficient doses (.05 to .2 mg/kg/injection) of either drug maintained self-administration and the higher doses were reliably preferred to saline. Doses of d,l-cathinone that were preferred to saline were then compared to a range of cocaine doses in drug-drug choice. As the dose of d,l-cathinone that was available was increased, an increase in cocaine dose was necessary to maintain cocaine preference. Comparison of drug-drug choice data to dose combinations predicted to be chosen with equal frequency revealed that the reinforcing efficacy of d,l-cathinone was equivalent to that of cocaine.

Alkaloids↗
PubMed2004

Revisiting within-modality and cross-modality attentional blinks: effects of target-distractor similarity.

When two masked targets (T1 and T2) require attention and are presented within half a second of each other, the report accuracy for T2 is reduced, relative to when the two targets are presented farther apart in time. This effect is known as the attentional blink (AB). Potter, Chun, Banks, and Muckenhoupt (1998) argued that all AB-like effects observed when at least one of the targets was presented outside of the visual modality did not represent true instances of the AB, but instead were artifacts of task-set switching. However, in the Potter et al. experiments the presence or absence of task-set switching opportunities was confounded with the T2 task, as well as the alphanumeric class of T2 with respect to the distractors. In the present experiment, we examine the influence of T1 alphanumeric class, T2 alphanumeric class, and switching operations in a fully crossed design that unconfounds these factors. In contrast to the conclusions of Potter et al., the present results suggest that the T2 alphanumeric class can account for the pattern of ABs observed across conditions, without necessarily implicating a separate switch cost. The implications for theoretical models of the AB and the debate over the validity of cross-modal ABs are discussed.

Adolescent↗