Showing papers on "Working memory published in 1984"

On the role of hippocampal connections in the performance of place and cue tasks: comparisons with damage to hippocampus.

Abstract: Behavioral changes following interruption of the main connections of hippocampus and closely related areas (entorhinal cortex, mammillary bodies, dentate gyrus) were determined and compared with findings of previous research that involved direct damage to hippocampus. By a within-subjects design, rats were trained to run in a radial maze with a procedure that involved two kinds of learning (place and cue) and two memory functions (working and reference memory). Rats with fimbria-fornix and entorhinal cortex lesions were impaired on both the place and the cue task. Specifically, the animals suffered a general impairment in working memory on both tasks but were impaired in reference memory only on the place task. Animals with lesions of the dentate gyrus and mammillary bodies were able to perform the complex place and cue tasks with minimal problems. In previous research it was found that direct damage to hippocampus (including all cell fields, alveus, fimbria) resulted in impaired performance only on the place task (Jarrard, 1983). Taken together, these findings indicate that interruption of hippocampal input/output pathways and/or damaging some closely related structures has a greater effect on the behaviors studied than does direct damage to hippocampus.

Differential effects of scopolamine on working and reference memory of rats in the radial maze

Abstract: Anticholinergics have often been found to impair choice accuracy in the radial maze. Some researchers have suggested that this indicates involvement of cholinergically innervated structures in cognitive mapping while others argue that these structures mediate working memory. However, most results are open to either interpretation since the baiting method did not allow a distinction between reference and working memory errors. To further test these hypotheses this study examined the effects of systemic scopolamine on radial maze performance, using a 4-out-of-8 baiting procedure. Food-deprived Wistar rats were pretrained until working memory choice accuracy stabilized to a criterion of 87% or better. Scopolamine (0.1, 0.4 and 0.8 mg/kg, IP, 30 min before a session) significantly increased the number of working memory errors (re-entries into baited arms) whereas reference memory errors (entries into never baited arms) did not change significantly. Observed deficits appeared not to be attributable to a drug-induced disruption of motivational systems. Results confirm the behavioural similarities between the memorial effects of hippocampectomy and anticholinergics, and implicate cholinergically innervated structures in working memory.

Fimbria-fornix lesions impair spatial working memory but not cognitive mapping

Abstract: Three experiments were designed to evaluate the relative merits of two theories of hippocampal function, the cognitive mapping theory and the working memory theory. Rats were tested in a series of maze tasks that varied in memory requirements. In the experiments that required cognitive mapping but not working memory (Experiments 1 and 3), rats with fimbria-fornix lesions reached stable levels of performance that were as accurate as those of control rats, and they also performed accurately during transfer tests, results demonstrating that they used a cognitive mapping strategy to solve the discrimination. In the experiment that required working memory (Experiment 2), rats with fimbria-fornix lesions performed at chance levels during all of postoperative testing, and they distributed their choices randomly between the correct and the incorrect goals. These results are seen as generally refuting the predictions made by the cognitive mapping theory and supporting the predictions made by the working memory theory. Additional analyses (Experiment 3) examined the nature of a transitory impairment exhibited by rats with fimbria-fornix lesions in two tasks that did not require working memory. Postoperatively, the performance of the rats with lesions was initially impaired but recovered to normal levels with a time course similar to that seen during preoperative acquisition. These results are seen as requiring an extension of the working memory theory of hippocampal function, and discussion is focused on the possibility of a temporary retrograde amnesia following fimbria-fornix lesions and the distinctions between different types of memory abilities.

Psychological theories of hippocampal function

Abstract: Theories and models of the hippocampus have typically linked this structure to various psychological processes, for example, internal inhibition, response inhibition, attentional shift, at-tentional “tuning out,” recognition memory, long-term memory selection, contextual retrieval, spatial memory, working memory, and chunking. Predictions made from various models are contrasted with reproducible hippocampal lesion data obtained from various experimental paradigms: habituation to novelty, acquisition, extinction, discrimination reversal, spontaneous alternation, latent inhibition, blocking, overshadowing, passive avoidance, maze learning, working memory procedures, latent learning, retrograde spatial memory, and conditioned inhibition. No single model correctly predicts all the empirical evidence. It is suggested that the hippocampal function, rather than subserving a unitary psychological function, might be better described as a computational-representational activity.

Human learning and memory

Abstract: Introduction Part I. Learning: 1. Some basic assumptions 2. Classical conditioning 3. Conditioning principles and theories 4. Reinforcement 5. Reinforcement applications 6. Punishment 7. Theories of reinforcement Part II. Memory: 8. Memory: an introduction 9. Sensory and working memory 10. Long-term memory 11. Retrieval 12. Practical applications Part III. Learning and Memory: 13. Neural networks.

Cholinergic mediation of spatial memory in the preweanling rat: application of the radial arm maze paradigm.

Abstract: These experiments assessed spatial memory capabilities in the developing rat by the radial arm maze paradigm. Subjects were trained and tested in the maze beginning at 16 days until they were 25 days of age. Results showed that animals that received training performed significantly better than those naive to the task, and better than chance, which suggests an early capacity for this type of learning. The second experiment investigated the neural mechanism that underlies spatial memory at this age as measured by the radial arm maze. In order to distinguish between the working and the reference memory components of the task, a modification of the basic radial arm maze paradigm was used. Subjects trained from 16 days received drug injections of saline, methylscopolamine, scopolamine, or arecoline prior to testing at age 25 days. Results indicated that central cholinergic antagonism severely impairs working memory while sparing reference memory. This finding is consistent with the existing literature that suggests a role for acetylcholine in adult learning and memory, specifically in working memory. Most important, these experiments document that (a) the radial arm maze paradigm can be used effectively for the developmental study of learning and memory in the rat and (b) cholinergic system(s) mediate working memory at an early age.

Developing the theory of working memory

Abstract: The theory of working memory was devised to explain the effects of a concurrent memory load in various experimental situations in terms of the operation of a central executive processor and a phonemic response buffer. It also explains the effects of phonemic similarity, articulatory suppression, word length, and unattended speech. Experiment 1 demonstrated that a concurrent memory load markedly reduced the phonemic similarity effect in immediate serial recall, which was taken to support the concept of a limited-capacity phonemic response buffer. A more detailed analysis of the results suggested that a concurrent memory load may affect the storage capacity of the central executive processor and the translation of orthographic stimuli into phonological representations, as well as the storage capacity of the phonemic response buffer. Experiment 2 showed that a concurrent free-recall task reduced the phonemic similarity effect in immediate serial recall, but only in the case of visually presented sequences of items. Moreover, unattended speech was found to have no effect upon performance in immediate free recall. These results were taken to imply that the phonemic response buffer contributes only to performance in cognitive tasks that require the accurate retention of serial-order information.

Why children have difficulty reasoning with three-term series problems

Abstract: This study examined a number of hypotheses as to why children have difficulty in solving three-term series problems. No support was found for the hypothesis that their difficulties arise because of their inability to understand transitive relations. In addition, the problems were present throughout the task, so that poor memory for the premises was ruled out as a contributory factor in reasoning difficulty. The children's performance was found to improve, however, when they were provided with an aid to reduce the demands of the task on working memory, although this advantage was not maintained in a later test without a memory aid. There was also evidence that, overall, the children had greater difficulty in solving problems that imposed a higher load on working memory.

Reading comprehension performance as a function of individual differences in working memory for texts of varying reading difficulty.

Abstract: Reading Comprehension Performance as a Function of Individual Differences in Working Memory for Texts of Varying Reading Difficulty September, 1984 Douglas Jay Lynch, B.A., Colorado College M.S., University of Wisconsin M.S., Ph.D., University of Massachusetts Directed by: Professor James M. Royer The construct of working memory is a critical feature in a commonly cited theory of reading comprehension (cf. Kintsch & van Dijk, 1978) . The dissertation identified good and poor working memory fourth grade subjects with a probe recall test. The subjects read text of increasing reading difficulty level (easy, moderate and difficult) and responded to a reading comprehension task called the sentence verification technique (cf. Royer, 1984) after reading the text. The experiment investigated the reading comprehension performance of good and poor working memory readers and the relationship between text microstructure and reading comprehension performance. Reading comprehension performance was significantly higher for good working memory readers compared to poor working memory readers at each level of text difficulty. Reading comprehension performance declined with an increase in text difficulty level, with a marginally significant working memory group X reading difficulty level interaction. There were no significant differences in reading time per passage between good and poor working memory readers. The sentence verification technique provided reading comprehension

Hippocampal afterdischarge interferes with storage of spatial information in a working memory test.

Abstract: In an attempt to impair spatial working memory by reversible functional blockade rather than by irreversible lesion of the hippocampus, eight male hooded rats were trained to asymptotic performance of 1.2 to 1.4 errors per trial in the spatial 12-choice apparatus ( Bure s et al. 1982), formally similar to the radial maze. The rats were implanted with hippocampal stimulating and recording electrodes, which were used for eliciting and monitoring hippocampal afterdischarge (HAD) lasting for at least 20 s. In Experiment 1, HAD elicited 1 or 10 min before testing increased the incidence of errors to 2.75 or 2.50 per trial, respectively, but the performance still remained above chance level (4.18). In Experiment 2, interruption of the trial by 1, 10, 20 and 30 min intervals inserted between choices 6 and 7 increased the incidence of errors in choices 7 to 12 to 1.0, 1.5, 2.1 and 2.5, respectively. HAD elicited immediately after choice 6 increased error incidence in the subsequent 6 choices performed after 1-min or 10-min intervals to 3.1 or 2.75, respectively, i.e. to the chance level of 3 errors in 6 choices. It is concluded that HAD elicits transient shortening of the memory span for newly acquired spatial information (anterograde effect) and erases the current spatial working memory record (retrograde effect).