Repeated Acquisition Test

Psychostimulants have produced inconsistent effects on tests of cognition. Several studies have investigated the effect of cocaine on a test of repeated acquisition and performance of response sequences. In the acquisition component, subjects attempt to learn by trial and error a predetermined sequence of 10 numbers within 20 trials. Subjects learn a new sequence each time they perform the test. In the performance component, the response sequence remains constant throughout the experiment, and thus subjects repeat an already learned sequence. Two studies have reported no effect of either intranasal (IN) or IV cocaine on the test.37 40 However, Higgins et al.51 reported that cocaine (96 mg, IN) decreased response rate during the acquisition phase and increased response accuracy during the performance component. In a similar serial acquisition procedure, cocaine has been shown to have no effect.52 53... 

Marijuana has been shown to impair learning in the repeated acquisition and performance of response sequences tasks. Increased errors in the acquisition phase were reported after smoked marijuana (2.0 and 3.5% THC)244 and oral THC (10 and 20 mg) 247 However, other studies40,52 have found no effect of smoked marijuana on this test, and one study251 reported that oral THC (20 mg, q.i.d.) increased the number of completed trials. Block et al.233 reported that one marijuana cigarette (2.6% THC) impaired paired-associative learning. 

Another approach to reference memory is to use the radial maze task as a repeated acquisition task with different arms being baited during each test session (Levin et al. 1998). In this way the task can be modified to evaluate exclusively reference memory. As with repeated passive avoidance sessions, this use of the radial maze is very time-consuming, and we do not recommend it for safety pharmacology purposes. 

Repeat acquisition of the standard over a period of several minutes to test short-term frequency reproducibility. 

We have evaluated the dose-related effects of PCP, ketamine, and selected anticonvulsant drugs on seizure activity in the hippocampal model of kindled seizures. The hippocampal model is particularly well suited for the study of the anticonvulsant effects of drugs because of the slow rate of acquisition of the fully kindled seizure. Electrical stimulation of the dorsal hippocampus initially evokes a stereotyped sequence of behavior, accompanied by a characteristic EEG pattern. Repeated electrical stimulation eventually results in generalized kindled seizures. This allows the testing of drugs on the unkindled hippocampal seizure (afterdischarge) to be compared to effects on the fully kindled seizure in the same rats. 

An obvious and all-important aspect of Section 8 is that it is a mechanism to facilitate the acquisition of information that EPA needs. Accordingly, the proper test of EPA s performance under Section 8 is not the amount of information that EPA acquires or the number of companies required to report, but the Agency s success in building a data-base for accomplishing its specific risk assessment, testing and chemical control responsibilities under Sections 4, 5, 6 and 7 of TSCA. In view of this purpose, it was of great concern that EPA has repeatedly failed to define carefully, and then articulate fully, the connection between a proposal under Section 8, and a specific regulatory objective under some other provision of TSCA. 

Table 6.6 presents the individual tests of the NES2 battery. Motor ability, focused attention, selective attention, acquisition, and memory categories of tasks are included in this battery, in addition to a variety of other tasks. The battery is made up of separate tasks performance on combinations of these tasks is potentially altered by exposure to neurotoxic agents such as pesticides, solvents, or carbon monoxide. Many of the tasks are suitable for repeated testing of any individual. Five of the tests are similar to the core tests of the WHO battery.50... 

The nature of OA interaction with SC lipids in vivo was of significant interest, particularly in light of the IR results above. Reflectance IR spectroscopy in conjunction with the use of a deuterated probe once again proved to be a valuable approach for the noninvasive evaluation of this enhancer in humans [153]. Prior to treatment, test sites on the inner ventral forearm of volunteers were cleansed with water, after which the subject remained at constant temperature and relative humidity, while three pretreatment spectra were collected. The experimental site on one arm was treated with a 5% v/v solution of perdeuterated oleic acid ( H-OA) in ethanol, while the control site, on the contralateral arm, was treated with ethanol alone. Both formulations were applied under occlusion for 16 hours posttreatment, the sites were swabbed clean with ethanol and then air-exposed for 2 hours to allow the occluded skin to dry. An ATR-IR spectmm of the dosed site was then obtained. This site was then tape stripped once and a second spectral examination was made. This sequential tape stripping and spectral acquisition was repeated -20 times in order to obtain an incremental spectral profile as a function of SC depth (defined by the cumulative weight of SC removed with tape stripping). IR spectra thus collected yielded the following information (a) the distribution... 

In a second data set, repeat the above acquisition with the gradient amplitude set close to the maximum possible value ( -90% of maximum output) but with otherwise identical acquisition parameters to provide a test spectrum (trace B). 

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