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At least 1,693 records · Page 94Linked to original sources
PubMed2001

Unsupervised learning of granule cell sparse codes enhances cerebellar adaptive control.

Marr [J. Physiol. (1969) 202, 437-470] and Albus [Math. Biosci. (1971) 10, 25-61] hypothesized that cerebellar learning is facilitated by a granule cell sparse code, i.e. a neural code in which the fraction of active neurons is low at any one time. In this paper, we re-examine this hypothesis in light of recent experimental and theoretical findings. We argue that cerebellar motor learning is enhanced by a sparse code that simultaneously maximizes information transfer between mossy fibers and granule cells, minimizes redundancies between granule cell discharges, and re-codes the mossy fiber inputs with an adaptive resolution such that inputs corresponding to large errors are finely encoded. We then propose that a set of biologically plausible unsupervised learning rules can produce such a code. To maintain a low mean firing rate compatible with a sparse code, an activity-dependent homeostatic mechanism sets the cells' thresholds. Then, to maximize information transfer, the mossy fiber--granule cell synapses are adjusted by a Hebbian rule. Furthermore, to minimize redundancies between granule cell discharges, the inhibitory Golgi cell--granule cell synapses are tuned by an anti-Hebbian rule. Finally, to allow adaptive resolution, a performance-based neuromodulator-like signal gates these three plastic processes. We integrate these gated learning rules into a simplified model of the cerebellum for arm movement control, and show that unsupervised learning of granule cell sparse codes greatly improves cerebellar adaptive motor control in comparison to a "fixed" Marr--Albus-type model. Until recently, activity-dependent cerebellar plasticity was thought to be largely confined to the granule cell--Purkinje cell synapses. This static view of the cerebellum is, however, quickly being replaced by an extremely dynamic view in which plasticity is omnipresent. The present theoretical study shows how several forms of plasticity in the granular layer of the cerebellum can produce fast, accurate and stable cerebellar learning.

Algorithms↗
PubMed2001

On being forgotten and forgetting one's self.

This paper assumes that evocative constancy, the ability to evoke reliably good-enough images of self and object in times of stress, underlies not only self and object constancy, but also the development of memory and the symbolic processes. It is suggested that a crucial element in this development is the mother's ability to construct and retain a vivid, cohesive, and reliable memory of her child, and to engage--in a multitude of implicit ways--in a process of mutual holding in memory. Where this process is deficient, the child, and later the adult, may experience discontinuities of the self, which find expression in profound anxieties, phobias, and problems of memory and learning. As these discontinuities are revived in the transference and the countertransference, both patient and analyst must work together to keep each other reliably alive in memory.

Ego↗
PubMed2005

Liberating the potential: the role of non-nurses in adding value to nurse education.

In this paper, I have attempted to explore the role of non-nurse lecturers in adding value to nurse education programmes. In measuring "added-value" in higher education, I have embraced a more comprehensive approach including investigating the views of "Experts"; including the nurse and non-nurse lecturers themselves, and various United Kingdom stakeholders such as the Government, the Nursing and Midwifery Council and the Quality Assurance Agency. The students' views are also taken into account, when considering both the content of the programmes and how they are delivered. The complexity of "objective measurement" is considered, and the requirements of a "good" teaching experience. The potential areas for adding value include: health and social care policy priorities which encourage partnership working, the blurring of professional boundaries, and inter-professional working. Professional-specific changes embracing extended and enhanced roles and the concepts of specialist and assistant practitioners. Other areas include the Higher Education agendas including transferable skills and adult and student-centred learning. I conclude by discussing the latest policy changes and suggest that the role of the non-nurse lecturer needs more exploration to provide the best value for all.

Attitude of Health Personnel↗
PubMed2004

Odor discrimination assessment with an automated olfactometric method in a prosimian primate, Microcebus murinus.

The present study was aimed at adapting an automated olfactometer designed for use with rodents to a nocturnal lemur Microcebus murinus. This apparatus allows rigorous control of odor stimuli. We show that M. murinus could remain quiet and attentive for about 20 min in the test chamber, allowing daily sessions of 40 consecutive trials. This allowed us to train M. murinus subjects to learn a go/no-go discrimination procedure using fruity-odor cues. Each of seven subjects reached or exceeded a criterion of 33 correct responses in a block of 40 trials in a range of 4-14 training sessions. When trained on an odor reversal task, performance initially dropped sharply, followed by rapid acquisition of the new task. These outcomes demonstrate that, like rodents, M. murinus can be trained using operant conditioning in an automated olfactometer. This species should prove useful for investigating cognitive capacities and neurodegenerative disease in a primitive primate model.

Animals↗
PubMed2006

Implicit learning and statistical learning: one phenomenon, two approaches.

The domain-general learning mechanisms elicited in incidental learning situations are of potential interest in many research fields, including language acquisition, object knowledge formation and motor learning. They have been the focus of studies on implicit learning for nearly 40 years. Stemming from a different research tradition, studies on statistical learning carried out in the past 10 years after the seminal studies by Saffran and collaborators, appear to be closely related, and the similarity between the two approaches is strengthened further by their recent evolution. However, implicit learning and statistical learning research favor different interpretations, focusing on the formation of chunks and statistical computations, respectively. We examine these differing approaches and suggest that this divergence opens up a major theoretical challenge for future studies.

Attention↗
PubMed2000

Effectiveness of a CD-ROM multimedia tutorial in transferring cognitive knowledge essential for laparoscopic skill training.

BACKGROUND: Computer-assisted instruction (CAI) can benefit surgical education by improving efficiency, effectiveness, standardization, and access. This study compares knowledge gains for laparoscopic skill acquisition following a standardized tutorial delivered via CD-ROM versus live instructor. METHODS: A standardized tutorial was written and subsequently converted to multimedia CD-ROM format by its author (JR). During a laparoscopic development course, experienced US-trained surgeons (n = 52) participated in the tutorial delivered live by the author. The CD-ROM tutorial replaced the instructor for the following groups: (1) experienced US-trained surgeons (n = 27); (2) US-trained surgical residents (n = 59); and (3) Greek surgeons (n = 63). A 51-item knowledge test was administered before and after tutorial instruction. RESULTS: The mean increase in scores between pretest and posttest was significant (P <0.01) and of similar magnitude in each group, with nonsignificant posttest mean differences among US-trained groups. CONCLUSIONS: The CD-ROM tutorial effectively transfers cognitive information necessary for skill development. Distance learning modes of this tutorial program may be feasible.

CD-ROM↗
PubMed2002

A comparative study in rodents of standardized extracts of Bacopa monniera and Ginkgo biloba: anticholinesterase and cognitive enhancing activities.

Bacopa monniera and Ginkgo biloba are well-known cognitive enhancers in Indian and Chinese traditional medicine systems. Standardized extracts of B. monniera and G. biloba were used to evaluate the antidementic and anticholinesterase activities in adult male Swiss mice. Antidementic activity was tested against scopolamine (3 mg/kg ip)-induced deficits in passive avoidance test. Three different extracts of B. monniera (30 mg/kg) and extract of G. biloba (15, 30 and 60 mg/kg) were administered postoperatively, daily for 7 days and 60 min after the last dose, i.e., on Day 7, first trial was conducted. In passive avoidance test, increased transfer latency time (TLT) and no transfer response (NTR) were taken as criteria for learning. TLT and NTR were significantly increased and decreased in second trial, 24 h after the first trial in control group and scopolamine-dementia group, respectively. The B. monniera- and G. biloba-treated groups produced significant increase in TLT and NTR on second trial (40-80%) after scopolamine treatment, thus, attenuating its antidementic effect. Both the extracts showed a dose (10-1000 microg)-dependent inhibitory effect on acetylcholinesterase (AChE) activity (in vitro), performed spectrophotometrically. IC(50) of G. biloba was 268.33 microg, whereas none of the extracts of B. monniera showed more than 50% inhibition. At a dose concentration of 30 and 60 mg/kg, extracts of G. biloba showed a cognitive enhancing property and, at the same time, a significant decrease in AChE-specific activity in both per se and scopolamine-dementia groups. These extracts possess a significant anticholinesterase and antidementic properties, which may be useful in the treatment of dementia.

Acetylcholinesterase↗
PubMed1986

Distributional expectations and the induction of category structure.

Previous research on how categories are learned from observation of exemplars has largely ignored the possible role of prior expectations concerning how exemplars will be distributed. The experiments reported here explored this issue by presenting subjects with category-learning tasks in which the distributions of exemplars defining the categories were varied. In Experiments 1 and 2 the distributional form of a category was found to affect speed of learning. Learning was faster when a category's distribution was normal than when it was multimodal. Also, subjects in the early stages of learning a multimodal category responded as if it were unimodal. These results suggested that subjects enter category-learning tasks with expectations of unimodal, possibly normal, distributions of exemplars. Experiments 3 and 4 attempted to manipulate subjects' prior expectations by varying the distribution of exemplars in the first of two consecutive category-learning tasks. Learning a multimodal category was influenced by the shape of a previously learned distribution and was facilitated when the earlier distribution was either multimodal or skewed, rather than normal. These results are interpreted as support for a dual-process model of category learning that incorporates the effects of prior expectations concerning exemplar distributions.

Adolescent↗
PubMed1987

Attention and learning processes in the identification and categorization of integral stimuli.

The relationship between subjects' identification and categorization learning of integral-dimension stimuli was studied within the framework of an exemplar-based generalization model. The model was used to predict subjects' learning in six different categorization conditions on the basis of data obtained in a single identification learning condition. A crucial assumption in the model is that because of selective attention to component dimensions, similarity relations may change in systematic ways across different experimental contexts. The theoretical analysis provided evidence that, at least under unspeeded conditions, selective attention may play a critical role in determining the identification-categorization relationship for integral stimuli. Evidence was also provided that similarity among exemplars decreased as a function of identification learning. Various alternative classification models, including prototype, multiple-prototype, average distance, and "value-on-dimensions" models, were unable to account for the results.

Attention↗