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Biomedical subjects

J Hardouin

Publications and source records attributed to J Hardouin.

7 recordsLinked to original sources
PubMed2003

Selective effects of low-dose dopamine D1 and D2 receptor antagonists on rat information processing.

It is well established that the dopaminergic system influences simple reaction time (RT) performance. However, the role of this system in more complex information processing remains to be clarified. The present study was aimed at addressing this issue. To this end, we used an inferential method that relies on choice RT procedures and allows one to identify information processing stages in both humans and rats. Long-Evans rats responded to lateral visual cues (left or right). Two task factors, signal intensity and foreperiod duration, were manipulated. Low doses of two pharmacological agents, SCH 23390 (a D1 receptor antagonist; 0.015 and 0.025 micromol/kg) and eticlopride (a D2 receptor antagonist; 0.01 and 0.02 micromol/kg), were administrated systemically. Both drugs increased choice RT: eticlopride interacted with signal intensity on RT, showing that D2 receptors mediate at least the sensory stage of stimulus preprocessing. In addition, eticlopride interacted with signal intensity on omission rate, thereby suggesting an involvement of D2 receptors in attentional processes; and SCH 23390 interacted with foreperiod duration on RT, indicating that D1 receptors specifically mediate the response adjustment stage. The effect of this drug on RT rests entirely in its interaction with foreperiod duration, allowing us to conclude that this D1 antagonist affects the response adjustment stage while sparing all other processing stages.

Animals↗
PubMed2000

The additive factor method in rat information processing.

Sternberg introduced the additive factor method as a tool for discovering and studying in choice reaction time situations in human subjects. Underlying the method is the notion that if information processing consists of successive stages, then different factors affecting different stages must have additive effects on reaction-time measurements. The additive factor method has been extensively used in humans but few attempts have been made to examine whether or not additive reaction time patterns were obtainable in rats. In the present work, the subjects (13 Long-Evans rats) had to press down a lever and to respond to a visual (right or left) stimulus by releasing the lever and introducing the head into a lateral (right or left) operandum. The present findings show an additive pattern of effects of signal luminance and foreperiod duration on the mean reaction time which suggests that we have successfully manipulated two stages of rat information processing - the preprocessing stage and the motor adjustment stage, respectively. Accordingly, the present study sets the basis for the basis for investigating the effects of invasive manipulations (pharmacological and/or lesional) on information processing stages.

Journal Article↗
PubMed1998

Evidence for the involvement of the rat prefrontal cortex in sustained attention.

Previous studies suggest that, in both humans and rats, the prefrontal cortex (PFC) is involved in both selective and divided attention. We have also shown that the PFC is involved in response selection and that its involvement is modulated by the cognitive effort required by the task. However, the role of the PFC is much less clear when no response selection is required. The purpose of the present experiments was to assess the role of the PFC in attentional functions with a low response-selection demand. We used two tasks in which information processing was effortful but where the demand on a response selection process is low. Moreover, we assessed two different types of visual attentional functions: selective attention (Experiment 1) and sustained attention (Experiment 2). The results showed a differential involvement for the PFC in the two tasks. Selective attention was not impaired by prefrontal lesions when the number of possible positions for the stimulus on which the subjects must focus was restricted to two (Experiment 1). In contrast, prefrontal rats were unable to sustain their attention long enough to detect, and react to, subtle variations in brightness (Experiment 2). This results suggests a dissociation between different types of attentional functions depending upon the integrity of the PFC. More specifically, results in Experiment 2 suggest an involvement of the PFC in sustained attention. Finally, the overall results show that even in tasks involving low demands on response selection the PFC is involved in attentional functions.

Animals↗
PubMed1997

Behavioural effects induced by nitrous oxide in rats performing a vigilance task.

Nitrous oxide (N2O) effects were evaluated, as a behavioural model of inert gas narcosis, in rats performing a vigilance task in which they were required to respond to a slight luminous increment of the house-light. A dose-related decrease of correct responses was produced by the tested range of concentrations of N2O (from 30 to 70% N2O), with a parallel increase of anticipatory responses up to 60% N2O and a dramatic increase of omissions at 70% N2O. The influence of preparatory period duration on hits delays suggested a 'conditional probability effect' conserved under N2O. Pretreatment of animals with flumazenil (a central benzodiazepine receptor antagonist) did not improve performance under 40% N2O. Naltrexone, an opiate receptor antagonist, however, increased the N2O-induced deficits. These results suggest that benzodiazepine receptors are not involved in N2O-induced impairments in this attentional task, but opiate mechanisms may be implicated.

Animals↗
PubMed1989

[Influence of partial and total castration on the growth and feed conversion performances of Poulfouli rams of the Far North Cameroon].

The authors compared the growth and feed conversion performances of groups of Burdizzo rams, castrated rams at an age of 6.5 months and partially castrated rams at 2 months by the short scrotum technique. After a 384-day experiment, the average weights are, respectively, 49.24 kg, 39.44 kg and 47.15 kg. The daily weight gains for the 244-day period following total castration are, respectively, 110 g, 75 g and 102 g (0.05 greater than p greater than 0.01). Full castration has consequently a depressive action on the weight gain. No significant difference is observed between totally and partially castrated rams. Heart girth and height at withers were not significantly influenced by these treatments. Consumption index and voluntary feed intake of the fully castrated rams are above those of the 2 other groups, which means a lower feed conversion and a higher cost of the weight gain.

Animal Nutritional Physiological Phenomena↗