Mnemonic Role Research Articles

Amnesic Effects of Preacquisition, Postacquisition, or Preretrieval Tetrodotoxin Administration into the Medial Septal Area on Rat's Passive Avoidance Memorization

By means of local administration of tetrodotoxin (TTX) fully reversible functional inactivation of the medial septal area (MSA) of the rat was obtained in order to define the role of this structure in the retention of a conditioned passive avoidance response (PAR). In permanently cannulated animals, TTX (5 ng in 0.5 μl saline) or saline (0.5 μl) was injected in the MSA. TTX or saline was administered to six different groups of rats, respectively 1 h before PAR acquisition, immediately after PAR acquisition, and 1 h before PAR retrieval, performed 48 h after the acquisition trial. It was shown that MSA preacquisition and preretrieval TTX injections were followed by significant PAR retention impairment, while postacquisition TTX administration had no effect on PAR retention. The results indicate a well-defined mnemonic role of MSA during the acquisition and retrieval periods but not during the consolidation of PAR engram. The experimental evidence is discussed in relation to other reports and to MSA connectivity with other subcortical structures.

Factors influencing hand/eye synchronicity in the computer age.

In using a computer, the relation of vision to hand/finger actuated keyboard usage in performing fine motor-coordinated functions is influenced by the physical location, size, and collective placement of the keys. Traditional nonprehensile flat/rectangular keyboard applications usually require a high and nearly constant level of visual attention. Biometrically shaped keyboards would allow for prehensile hand-posturing, thus affording better tactile familiarity with the keys, requiring less intense and less constant level of visual attention to the task, and providing a greater measure of freedom from having to visualize the key(s). Workpace and related physiological changes, aging, onset of monocularization (intermittent lapsing of binocularity for near vision) that accompanies presbyopia, tool colors, and background contrast are factors affecting constancy of visual attention to task performance. Capitas extension, excessive excyclotorsion, and repetitive strain injuries (such as carpal tunnel syndrome) are common and debilitating concomitants to computer usage. These problems can be remedied by improved keyboard design. The salutary role of mnemonics in minimizing visual dependency is discussed.

The effects of mammillary body and combined amygdalar-fornix lesions on tests of delayed non-matching-to-sample in the rat

A series of experiments compared the effects of mammillary body lesions with those of combined damage to the amygdala and fornix on 2 tests of working memory, both of which used the delayed non-matching-to-sample rule. This comparison was based on evidence of the involvement of these regions in anterograde amnesic sydromes. The mammillary body lesions had no effect on the acquisition or subsequent performance of a non-spatial recognition task and had only a mild effect on the acquisition of a spatial forced-alternation task. Although the animals with combined amygdalar plus fornix lesions were able to master the non-spatial recognition task they were impaired when the levels of proactive interference were increased. The same animals were also severely impaired on the forced-choice alternation task. The overall pattern of results is seen as mirroring those found in primates and points to an underlying similarity in the mnemonic roles of these limbic regions.

Improvement of memory by a vasopressin fragment: importance of individual differences in mnemonic function.

Three studies examined the effect of AVP4-9 on memory in an appetitively motivated task (the radial maze) to ascertain the generality of the mnemonic effects seen with vasopressin analogues in avoidance paradigms. Both pre- and posttrial administration of this vasopressin fragment significantly alleviated the forgetting seen in the control condition. However, a significant relation was observed between the proficiency of the rats and the degree to which their performance was improved by the posttrial AVP4-9 treatment. The more proficient subjects did not benefit from this treatment despite the fact that their performance provided evidence of significant forgetting. This pattern of results suggests that physiological differences of animals varying in mnemonic ability may account for their disparate response to the peptide treatment. The present findings support vasopressin's putative mnemonic role but indicate that exogenous administration of vasopressinlike peptides may improve memory only in certain subgroups, and possibly only under particular testing conditions.

A selective mnemonic role for the hippocampus in monkeys: memory for the location of objects

Monkeys were trained preoperatively on a one-trial learning task in which they were required to associate in memory a novel object and the place in which it had just appeared. After learning the task to a level of 80% correct responses, they received bilateral ablations of either the hippocampal formation or the amygdaloid complex. The monkeys with amygdalectomy showed a small drop in performance initially but then regained their preoperative level. By contrast, the monkeys with hippocampectomy dropped to near-chance levels of performance and remained there throughout postoperative testing. Both groups performed at better than 90% correct responses on a test of recognition memory. These results, taken together with earlier work, suggest that although the hippocampus and amygdala appear to participate equally in object recognition, only the hippocampus is critical for the rapid formation of object-place associations.

A mnemonic role for vasopressin: The evidence for and against

This review critically evaluates the animal and human research concerning vasopressin's putative mnemonic role. Weaknesses in the interpretations of the early animal experiments as well as the implications of the later inconsistent findings are discussed. It is concluded that both the initial enthusiasm and the subsequent skepticism concerning this hypothesized role were premature. This conclusion applies equally to the human research. A review of these studies reveals that almost all of the negative reports involved cognitively-impaired individuals. The relatively few studies that have been conducted concerning vasopressin's effects in unimpaired human subjects are consistent with the hypothesis that vasopressin does affect cognition, though both the mechanism of action and the specific cognitive processes which are altered have yet to be elucidated.

Sentence Mnemonics and the Role of Verb-Class in Paired-Associate Learning

The effectiveness of sentence mnemonics in facilitating noun pair learning was examined as a function of the grammatical restrictiveness of the connecting verb. Noun pairs were presented in transitive, transitive-causative, and intransitive sentences or by themselves for learning. No effect due to type of sentence was found. However, presenting sentence mnemonics, regardless of structure, produced significant interference with learning. The role of idiosyncratic mnemonics formed by Ss was discussed. In addition the relation between rated imagery and meaningfulness of the sentence and learning was examined.