Reversal discrimination tasks,

Dosed orally from birth to age 200 days with 100 pg lead (as Pb acetate)/kg BW, 5 times weekly, milk substitute diet Blood level of 254 pg Pb/L declined to 131 pg/L over next 100-150 days. At age 3 years, impaired ability to perform motor discrimination reversal tasks 21... 

Rice DC. 1990. Lead-induced behavioral impairment on a spatial discrimination reversal task in monkeys exposed during different periods of development. Toxicol Appl Pharmacol 106 327-333. 

M (decreased behavioral performance in nonspatial and spatial discrimination reversal tasks)... 

Cognitive enhancing effects of 5-HT3 receptor antagonists have been observed in several animal models, using both normal animals and animals in which a cognitive deficit has been induced by the administration of the muscarinic antagonist scopolamine [41]. An example is the Wisconsin test, in which marmosets learn to discriminate which of two objects conceal a food reward and, after learning this, the task is reversed such that the food is hidden beneath the other object. Treatment with ondansetron has been shown to enhance the ability of marmosets to learn the reversal task. 

Aged rhesus monkeys were assessed in several cognitive and motor tasks, acquisition of a visual object discrimination, reversal of a visual object discrimination, a delayed response task, a spatial working memory task, and a fine motor task. The S-HTj receptor antagonists ondansetron and SEC-579 at very low oral doses selectively enhanced acquisition of a visual object discrimination task but not the reversal or delayed tasks [Arnsten et al. 1997]. 

Once the task is learned, a discrimination reversal paradigm provides additional information on the animal s learning ability. The previously correct stimulus becomes the incorrect one so that the animal is required to learn a response opposite from the one previously learned. The discrimination reversal paradigm may often be more sensitive to neurotoxicity than simply acquisition of discrimination tasks, as has been found in monkeys exposed to lead early in life. 

Sensitivity and complexity represent challenges for ATR spectroscopy of catalytic solid liquid interfaces. The spectra of the solid liquid interface recorded by ATR can comprise signals from dissolved species, adsorbed species, reactants, reaction intermediates, products, and spectators. It is difficult to discriminate between the various species, and it is therefore often necessary to apply additional specialized techniques. If the system under investigation responds reversibly to a periodic stimulation such as a concentration modulation, then a PSD can be applied, which markedly enhances sensitivity. Furthermore, the method discriminates between species that are affected by the stimulation and those that are not, and it therefore introduces some selectivity. This capability is useful for discrimination between spectator species and those relevant to the catalysis. As with any vibrational spectroscopy, the task of identification of a species on the basis of its vibrational spectrum can be difficult, possibly requiring an assist from quantum chemical calculations. 

---