Two-choice Paradigm Research Articles

Comparison of the action of the 5-HT 2 antagonists amperozide and trazodone on preference for alcohol in rats

Previous studies in the rat demonstrated that the 5-hydroxytryptamine 2 (5-HT 2) antagonist amperozide attenuates the volitional intake of both alcohol and cocaine solutions in a free-choice situation. However, another 5-HT 2 antagonist, ritanserin, has not been found to reduce alcohol drinking consistently in the rat. In this study, trazodone was compared to amperozide for its effect on the volitional consumption of alcohol because, like amperozide, trazodone is a potent 5-HT 2 receptor antagonist but a weak inhibitor of 5-HT reuptake. Male Sprague-Dawley rats were induced to drink alcohol by 10 mg/kg cyanamide injected for 3 days b.i.d. One week later the rats were offered a choice of water and increasing concentrations of alcohol solutions ranging from 3% to 30% v/v in a three-bottle two-choice paradigm. After the concentration of alcohol that produced maximal daily intake was determined for each rat, trazodone or amperozide was injected b.i.d. SC in doses of 1.0 mg/kg or 2.5 mg/kg for three days. Whereas the higher dose of amperozide produced a significant, 55.6% decrease from pretreatment baseline of alcohol intake, trazodone did not alter alcohol preference at either the 1.0- or 2.5-mg/kg dose. These results are discussed in terms of whether the antagonism of 5-HT 2 receptors by amperozide is critical to its attenuating effect on preference for alcohol solutions.

Amperozide, a 5-HT 2 antagonist, attenuates craving for cocaine by rats

Amperozide, a novel 5-HT 2 receptor antagonist with little affinity for the dopamine receptor, suppresses the intake of alcohol in rats without affecting food intake or inducing other side effects. Because of these actions, amperozide was examined for its efficacy on the oral preference by the rat for a solution of cocaine. In this study, rats were selected for their voluntary consumption of at least 10 mg/kg of cocaine per day in a two-choice paradigm. A solution of 0.02% to 0.06% cocaine plus 0.03% saccharin in water was offered to each animal simultaneously with a solution of only 0.03% saccharin in water. The consumption of food and both fluids, as well as body weight, was recorded daily for three successive periods: 4 days of pretreatment baseline; 3 days during injections of either amperozide or the saline vehicle solution; and 4 days postinjections. Amperozide was administered SC twice daily in a dose of 0.5, 1.0, or 2.5 mg/kg. The volitional intake of cocaine was significantly reduced not only during the 3-day period of injections of amperozide but also during the 4-day posttreatment period. Amperozide exerted little or no effect on the intake of food or on body weight. Radioligand binding experiments confirmed that amperozide has at least a twentyfold greater affinity for 5-HT 2 receptors in the frontal cortex of the rat, as compared to striatal DA 1 and DA 2 receptors, with the proportion value similar to that of the 5-HT 2 receptor antagonist, ritanserin. It is concluded, therefore that amperozide, which produces little or no adverse side effects, appears to be potentially useful for the treatment of the addiction to cocaine.

Auditory recognition of covey mates from separation calls in Northern Bobwhite (Colinus virginianus)

Two experiments were conducted to determine whether Northern Bobwhite (Colinus virginianus) discriminate covey mates from noncovey mates on the basis of recognition of the individual giving the separation call. Two possible modes of recognition, phenotype matching and call association, were tested. Artificially and naturally hatched quail chicks from two familial lines of linebred quail and quail of crossed lines were reared and tutored by either a related or an unrelated adult. Chicks were separated one at a time and visually isolated midway between their own adult tutor-parent and a strange adult or between their own covey and a strange covey in a two-choice recall paradigm for testing. In both linebred and crossed lines quail, chicks preferentially approached calls of the foster parent or covey mates with whom they were reared with no apparent predilection due to relatedness, with no regard for which birds answered the lost or separation call first, and with no dependency on similarity of call characteristics. All evidence indicated that association learning was the main factor in recognition with no evidence of kin recognition attributable to phenotype matching.

Responding for Sensory Change in a Causally Structured Environment: Effects Of Different Changes and Different Sensory Environments.

Earlier experiments have shown that responding for sensory change may be enhanced in a causally structured environment. In the present study further complexity was introduced but this did not produce increased responding. In addition, different environments and sensory changes were compared. It was found that the level of responding for an initial sensory change was determined by the stimulation level of the ongoing sensory environment rather than the type of change produced. On the other hand, the level of responding for a second, different change contingent on the first was determined by the type of change produced rather than the ongoing sensory environment. In the latter case, light changes (following initial sound changes) induced much higher levels of responding than sound changes (following initial light changes), whether increase or decrease in intensity was involved. This finding contrasted with that of an earlier experiment using a two-choice paradigm with no temporal constraints, where it was found that sensory changes producing reduced stimulation were preferred to those producing increased stimulation, regardless of modality.

Utility scaling of intracranial reinforcement duration

The purpose of the investigation was to apply signal detection theory to the utility scaling of train duration, a parameter of intracranial self-stimulation. Each of the four Charles River rats used was unilaterally implanted with bipolar stainless steel electrodes directed at the medial forebrain bundle. Prior to testing, the animals were trained in a two-choice paradigm to discriminate for brain stimulation between high and low frequency tones. Train duration utility functions were generated with each rat by systematically changing the reinforcement duration associated with the two classes of correct responses over a series of payoff matrices and observing corresponding shifts in response bias, the measure of relative reinforcement strength. Incorrect responses were followed by uniform short time outs. Least squares analysis found that negatively accelerating power functions (correlation coefficients were significant, p<0.01) described the relationship established between the reinforcement ratios (formed by the train durations associated with the two correct response alternatives) and the obtained betas (i.e., response bias).

Division of attention: evidence for a between-trial component of impaired performance.

Detection and recognition studies are reviewed, which show a dependency between errors on successive trials. They suggest the impairment accompanying the presentation of simultaneous signals may also involve a similar “between-trial” component. The hypothesis was tested using a two-choice recognition paradigm with bimodal signals. Dimensions presented simultaneously were interleaved on alternate trials with a single dimension presented alone. Interleaving two signals in the first experiment showed no effect on the following signal presented alone, compared to a control condition in which the signal always preceded itself. Interleaving four signals in the second experiment produced a significant impairment. Accounts of the results based on the length of the response interval, fluctuations of state variables such as arousal and decay of the memory trace are rejected. Accounts based on the impairment and set-size of preceding simultaneous signals are retained. Both suppose part of the impairment accompanying simultaneous signals to be a between-trial phenomenon. Implications of the results for work on divided-attention are considered and a method of experimental control proposed.

Division of attention between simultaneous and successive nonverbal signals varying in discriminability.

Impaired performance indexed by accuracy usually accompanies the division of attention between simultaneous difficult signals. Presenting the signals successively reduces the impairment. Presenting easy signals eliminates it. Both variables crucial to these findings, relative time of onset and discriminability, were manipulated in the first experiment using a two-choice recognition paradigm involving bimodal signals. The results showed that, when a difficult signal was followed by two simultaneous easy ones, in a different modality from the first, performance was significantly worse on each than on the same signals presented alone. Simultaneous presentation of all three signals further increased the impairment for the difficult signal, but not for the easy ones. In the second experiment, the discriminability of the following signals was varied. The results showed, that when a difficult signal was followed by either two simultaneous easy signals, in a different modality from the first, or by two difficult ones, performance was significantly worse than on the same difficult signal presented alone. Further, when the preceding difficult signal was auditory, but not when it was visual, performance was better with easy following signals than with difficult ones. It is argued that an adequate account of the results from the two experiments requires the following assumptions concerning the processing of multiple signals: (1) a loss associated both with the acquisition and the storage of information, (2) preferential processing of visual signals over auditory ones. Proposals are made for the incorporation of both assumptions into a single model of divided attention.