Behavioural brain research
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Comparative Study
Variation in visual acuity within pigmented, and between pigmented and albino rat strains.
Many researchers assume that laboratory rats have poor vision, and accordingly, that they need not consider differences in the visual function of rats as a consequence of strain or experience. Currently, it is not specifically known whether rat domestication has negatively affected the visual function of laboratory rat strains, what the effects of strain albinism are on rat visual function, or whether there are strain differences in the visual function of laboratory rats that are independent of pigmentation. In order to address these questions, we measured psychophysically the vertical grating acuity of three pigmented (Dark Agouti, Fisher-Norway, Long-Evans) and three albino (Fisher-344, Sprague-Dawley, Wistar) strains of laboratory rats, and compared their acuity with that of wild rats. ⋯ Domestication of Long-Evans and Dark Agouti strains does not appear to have compromised visual acuity, but in the case of Fisher-Norway rats, selective breeding may have enhanced their acuity. Strain selection associated with albinism, however, appears to have consistently impaired visual acuity. Therefore, a consideration of strain differences in visual function should accompany the selection of a rat model for behavioral tasks that involve vision, or when comparing visuo-behavioral measurements across rat strains.
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Using the ability of [11C]raclopride to compete with dopamine for D(2)/D(3) receptors, we investigated by positron emission tomography the effect of placebo (saline) injection on dopamine release in the ventral striatum of patients with Parkinson's disease. We found evidence for placebo-induced dopamine release of similar magnitude to that reported in healthy volunteers after amphetamine administration. ⋯ We conclude that the release of dopamine in the ventral striatum (nucleus accumbens) is related to the expectation of reward and not to the reward itself. These observations have potential implications for the treatment of drug addiction.
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Previous work has shown that systematic individual differences between male Wistar rats can be detected in tasks like the elevated plus-maze, or the open field. Here, we investigated whether individual profiles of anxiety, as measured with the plus-maze, may predict behavioral response profiles in other tasks where anxiety, aversion, or depressive behaviors are important. Male Wistar rats were initially screened: (A) in an open field; and (B) in an elevated plus-maze. ⋯ Finally, LA and HA rats behaved similarly in the forced swim test; however, the percentage changes of immobility time between test days 1 and 2 were negatively correlated to open field behavior, namely locomotor activity and center entries. On the other hand, the frequencies of rearing in the open field, which can also gauge functional differences between rats (for example responsiveness to novelty, psychomotor activation), were not substantially related to the behavioral profiles in the tests of anxiety and depression. These results show that individual differences of anxiety in the plus-maze can be predictive of behavior in other anxiety models, but not in forced swim test, indicating that they may be determined partly by similar functional and physiological mechanisms.
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The purpose of the present study was to investigate the effects on the duration of imagined movements of changes in timing and order of performance of actual and imagined movement. Two groups of subjects had to actually execute and imagine a walking and a writing task. The first group first executed 10 trials of the actual movements (block A) and then imagined the same movements at different intervals: immediately after actual movements (block I-1) and after 25 min (I-2), 50 min (I-3) and 75 min (I-4) interval. ⋯ The duration of imagined movements was very similar to those of actual movements, for both tasks, regardless of either the interval elapsed from the actual movements (first group) or the order of performance (second group). However, the variability of imagined movement duration was significantly increased compared to variability of the actual movements, for both motor tasks and groups. The findings give evidence of similar cognitive processes underlying both imagination and actual performance of movement.
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We investigated global motion detection in binocularly deprived cats (BD cats) and control cats (C cats). The cats were trained in the two-choice free running apparatus for a food reward. The positive stimulus was a moving random-dot pattern with all dots moving in one direction, the negative stimulus was the same random-dot pattern but stationary. ⋯ In contrast, their level of performance in a simple relative motion detection task (one square) did not differ from that in the C cats. However, in more complex relative motion detection task (two squares) the performance of the BD cats was impaired. The deficit in the detection of global motion in BD cats may be due to impairments of their Y-pathway.