Converging lines of evidence suggest that oligomers of amyloid-β play a role in the cognitive impairment characteristic of Alzheimer's disease, but only three studies have provided experimental evidence of such impairment. To provide additional information about the effects of these oligomers on memory, the present study examined the memory of groups of rats exposed to ICV injections of the culture media (CM) of Chinese Hamster Ovary cells that were (7PA2) and were not (CHO-) transfected with a human mutation of amyloid precursor protein that appears to cause early-onset Alzheimer's disease. The 7PA2 CM, which contained concentrations of soluble amyloid-β oligomers physiologically relevant to those found in human brain, significantly disrupted working memory in rats tested in a radial-arm maze. In contrast, CHO-CM, which did not contain such oligomers, had no effect on memory. The disruptive effects of 7PA2-derived amyloid-β oligomers, evident two hours after exposure, disappeared within a day. These findings are compared to results from 7PA2 CM tested under a complex procedure thought to measure aspects of executive function. The results confirm the disruptive effects of low-n amyloid-β oligomers and extend them to a well established rat model of memory.

Pigeons were exposed to a repeated acquisition procedure in which no delays were imposed and rate of responding was relatively high. They also were exposed to conditions in which delays were arranged between trials within chains or between completed chains, and rates of responding were lower. Number of trials, rate of reinforcement, difficulty of the discrimination, and motivating operations were held constant. Terminal accuracy was highest under the no-delay condition, in which rate of responding was highest. Effects of trial spacing on retention were mixed and depended on whether delays were imposed between trials within chains or between completed chains. These findings provide basic-research support for the rapid presentation of trials in direct instruction and for rate building in precision teaching.

In a study of working memory, the performance of rats under titrating-delayednonmatching-to-position (TDNMTP)

Ten participants from an online community of fiction writers were exposed to a treatment package intended to increase their writing productivity. The package consisted of graphic feedback provided through a Web page, praise for goal completion delivered via e-mail, and editing of manuscripts by other members of the community dependent on the completion of word-count goals. A multiple baseline design across groups was used to evaluate the effects of the intervention, which was successful in increasing the number of words written.

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