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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing
    Psychophysiology 36 (1999), S. 0 
    ISSN: 1469-8986
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine , Psychology
    Notes: Physiological response stereotypy is a well-established psychophysiological construct. Unfortunately, specifying parameters of tasks that evoke differing physiological responses has proved difficult. We have recorded cardiovascular activity while subjects carried out executive and attentional tasks that differed not only psychologically but also in their sensitivity to brain pathology and to pharmacological manipulations. Finapres recordings were made of 30 healthy, normal subjects (mean age 24 years) performing two tasks involving differing aspects of sustained attention and two tasks involving differing aspects of spatial working memory and planning. Measures of heart rate and blood pressure, heart rate and blood pressure variability, and their spectral derivatives revealed differing patterns of cardiovascular adjustment between the “attentional” and “planning” tasks. Each test raised blood pressure, but changes in blood pressure and heart rate variability were confined to the attentional tasks. These findings suggest distinct brain mechanisms subserving different forms of arousal.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    European journal of neuroscience 4 (1992), S. 0 
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Peformance in a prelearned choice reaction time task was studied 6 months after surgery in rats with ibotenate-induced lesions of the striatum either with or without striatal grafts, and in sham-operated controls. The long postoperative interval allowed full transplant maturation and the establishment of appropriate connections by the transplants. The animals were trained prior to surgery on a visual choice reaction time task which requires that a movement is made away from stimuli signalling reward. The use of multiple measures allowed a thorough analysis of several aspects of the animals' performance. Whilst sham-operated control animals recovered normal (preoperative) performance rapidly, the lesioned animals had a severe performance deficit. Although the transplanted animals were initially at least as deficient in performance as the lesioned group, repeated testing led to an amelioration of the lesion-induced deficit according to two distinct measures of spatial bias and reaction time. On a third measure, latency to complete the lateralized movement, the grafted group were initially worse than the lesioned group but repeated testing resulted in significant recovery. These results suggest that postoperative training may help to optimize the efficacy of graft-induced recovery, and that animals may need to learn to use a transplant in order for it to confer functional benefit in complex prelearned tasks.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 12 (2000), S. 0 
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Recent studies have suggested a functional link between cortical cholinergic output and attentional task demands, whereby acetylcholine (ACh) release is regulated according to the outcome of ongoing behaviour. To explore this hypothesis we measured ACh efflux in the rat medial prefrontal cortex (mPFC) during between-session manipulations of the cognitive demands of an attentional task. Rats were trained to detect visual stimuli in a five-choice serial reaction time task (5-CSRTT) which involves sustained and divided attention. Following habituation to tethering and implantation with a microdialysis probe in the mPFC, rats were tested in the 5-CSRTT for three consecutive days, with different lengths of stimulus duration. During performance of the 5-CSRTT we measured robust, reproducible, task-related increases in ACh release in the mPFC across all sessions. Variations of the stimulus duration from the standard 0.5 s resulted in the predicted behavioural effects (reductions and increases in choice accuracy with 0.25 s and 5 s, respectively), but there was no evidence of either greater changes in ACh release in the more demanding condition or smaller changes in the less demanding condition. By contrast, in the session with 5-s stimulus duration there was a positive correlation between prefrontal cortical ACh efflux and the total number of trials completed. In summary, the present study shows that ACh efflux in the rat mPFC is increased during performance of a 5-CSRTT, but has found no evidence to support a specific relationship between cholinergic cortical output and attentional performance.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Solving challenging (‘effortful’) problems is known to involve the dorsal and dorsolateral prefrontal cortex in normal volunteers, although there is considerable individual variation. In this functional magnetic resonance imaging study, we show that healthy subjects with different levels of performance in the Tower of London planning task exhibit different patterns of brain activation. All subjects exhibited significant bilateral activation in the dorsolateral prefrontal cortex, the anterior and posterior cingulate areas and the parietal cortex. However, ‘standard performers’ (performance 〈 70% correct) and ‘superior performers’ (performance 〉70% correct) differed in the patterns of activation exhibited. Superior performers showed a significantly more spatially extended activation in the left dorsolateral prefrontal cortex than did standard performers, whereas the latter group tended to show increased activation of the anterior cingulate region.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The present study investigated the effects of excitotoxic lesions of the prefrontal cortex (PFC) on dopamine (DA) and excitatory amino acid (EAA) function in the nucleus accumbens core using in vivo microdialysis in freely moving rats. As a postsynaptic marker of neuronal function, the nuclear levels of the transcriptional factor CREB and its active phosphorylated form, CREB-P, were measured in the ventral tegmental area (VTA), and in the core and shell subregions of the nucleus accumbens of sham and lesioned animals. PFC-lesioned animals exhibited a greater locomotor response to novelty and amphetamine administration (125–500 μg/kg i.v.). No change was observed in extracellular levels of glutamate or saturable d-aspartate binding (a marker for the high-affinity EAA transporter) in the nucleus accumbens of PFC-lesioned animals. Extracellular levels of DA were comparable in sham and lesioned animals under tonic conditions, however, following amphetamine administration, DA efflux was significantly attenuated in lesioned animals. No correlation was observed between microdialysate levels of amino acids and the attenuated dopaminergic response to amphetamine in lesioned animals. Further, no effect of the lesion was found on nuclear CREB protein in saline- and amphetamine-treated rats. The density of CREB-P immunoreactive nuclei, while remaining unchanged in the VTA, increased in the nucleus accumbens shell following amphetamine treatment in lesioned animals. The results show that an important modulatory role of the PFC on the behavioural response to novelty and amphetamine is associated with the level of immediate-early gene regulation rather than levels of extracellular DA and amino acids in the ventral striatum.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 13 (2001), S. 0 
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: To gain insight into the nature and neural specificity of the relationship between simple problem solving, inhibitory control and prefrontal cortex, comparison of the effects of excitotoxic lesions of the orbitofrontal and lateral prefrontal cortex were examined on the performance of common marmosets on a detour reaching task. Monkeys were required to inhibit reaching directly for food reward in a transparent box and instead make a detour reach around to the side of the box either having had (i) no prior experience on the task (experiment 1) or (ii) previous experience in reaching around the sides of an opaque box (experiment 2). Whilst monkeys with orbitofrontal lesions had difficulty in inhibiting direct reaches to visible food reward (experiment 1), they could resist this prepotent response tendency following extensive prior experience of detour reaching with an opaque box (experiment 2). In marked contrast, monkeys with lateral prefrontal lesions exhibited no difficulty in inhibiting reaching to visible food reward or acquiring detour reaching per se (experiment 1). However, having been given the opportunity to acquire an efficient detour reaching strategy to hidden food reward these lateral prefrontal lesioned monkeys were impaired at transferring this strategy to the new context in which the food reward was made visible (experiment 2). This double dissociation between the effects of orbitofrontal and lateral prefrontal lesions on detour reaching provides evidence for a clear distinction in the level of control over responding exerted by the orbitofrontal and lateral prefrontal cortex, consistent with hierarchical ordering of response control processes within prefrontal cortex.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 264 (1976), S. 57-59 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The facilitation of behaviour by stimulants has been attributed to the enhancement of the effects of rewarding stimuli, by the potentiation of a brain reinforcement mechanism7. One of the major functions of reinforcement is to effect learning, an associative process, and it is possible for neutral ...
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 380 (1996), S. 69-72 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The apparent heterogeneity of functional deficits, and the variability of lesions resulting from frontal-lobe damage in man has made it difficult to assign specific functions to particular prefrontal regions26. But it is possible that this heterogeneity reflects impairments in a common set of ...
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-2072
    Keywords: Reinforcement ; Non-reinforcement ; Rate ; Choice ; Win-stay ; d-Amphetamine ; Chlordiazepoxide ; α-Flupenthixol ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The role of reinforcers in influencing choice was studied by use of a schedule that included a random intermixing of reinforced and explicitly non-reinforced components. The just-reinforced response had a high likelihood of being repeated (win-stay), although there was no differential reinforcement for doing so, whereas responses just followed by explicit non-reinforcement had a very low probability of repetition (lose-stay). Non-parametric indices based on the theory of signal detection were used to derive a choice measure of reinforcement which was independent of alterations in average response rate. Treatments with d-amphetamine (0.2–4.5 mg/kg), chlordiazepoxide (0.25–16 mg/kg) and α-flupenthixol (0.03–0.6 mg/kg) showed that changes in the choice measure could be dissociated from changes in the response rate. These findings were supported by extinction and satiation tests.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-2072
    Keywords: Rating scales ; Photocell activity cages ; Measurement ; Stereotypy ; d-Amphetamine ; Apomorphine ; Dopamine ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A novel means of measuring and analysing behavioural effects of dopamine agonists is described and illustrated by a comparison of the effects of d-amphetamine and apomorphine in the rat. d-Amphetamine (0–15 mg/kg IP) produced significant dose- and time-dependent changes in responses such as locomotion, rearing and sniffing, but not in licking or gnawing. In contrast, apomorphine (0–5 mg/kg SC) produced significant increases in licking and gnawing, as well as in locomotion and sniffing, but no changes in rearing. The results are discussed in comparison with those obtained by other methods, such as photocell beam interruptions or stereotypy rating scales, and may be of importance in elucidating the functions of the forebrain dopamine projections.
    Type of Medium: Electronic Resource
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