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The dentate gyrus is part of the hippocampal memory system and special in that it generates new neurons throughout life. Here we discuss the question of what the functional role of these new neurons might be. Our hypothesis is that they help the dentate gyrus to avoid the problem of catastrophic interference when adapting to new environments. We assume that old neurons are rather stable and preserve an optimal encoding learned for known environments while new neurons are plastic to adapt to those features that are qualitatively new in a new environment. A simple network simulation demonstrates that adding new plastic neurons is indeed a successful strategy for adaptation without catastrophic interference.
In neurophysiology it is widely assumed that our mind operates in millisecond timescale. This view might be wrong, because if consciousness is quantum coherent phenomenon at the level of protein assemblies, then its dynamic timescale can be picosecond one.
In patients who undergo aborted sudden cardiac death or syncope of unknown origin (symptomatic Brugada syndrome), no one argues that the implantation of an ICD is the first-line therapy regardless of the findings of the EP study. For those patients, drug therapy plays not a contradictory but a complimentary role to the ICD by reducing the number of ICD shock deliveries. Prevention of VF contributes to the improvement in the quality of life of the patients by avoiding uncomfortable ICD shock deliveries. As mentioned above, Belhassen et al. 11, performed EP-guided medical therapy in 34 patients with idiopathic VF, in 5 of whom the criterion of Brugada syndrome were fulfilled, and reported excellent long-term results. Although medical therapy requires markers that can accurately predict the preventive effect of VF over a lon...
Conscious events interact with memory systems in learning, rehearsal and retrieval (Ebbinghaus 1885/1964; Tulving 1985). Here we present hypotheses that arise from the IDA computional model (Franklin, Kelemen and McCauley 1998; Franklin 2001b) of global workspace theory (Baars 1988, 2002). Our primary tool for this exploration is a flexible cognitive cycle employed by the IDA computational model and hypothesized to be a basic element of human cognitive processing. Since cognitive cycles are hypothesized to occur five to ten times a second and include interaction between conscious contents and several of the memory systems, they provide the means for an exceptionally fine-grained analysis of various cognitive tasks. We apply this tool to the small effect size of subliminal learning compared to supraliminal learning, to process dissociat...
In general, information about the environment (for instance a target) is not instantaneously available for the nervous system. A minimal delay for visual information to affect the movement of the hand is about 110 ms. However, if the movement of a target is predictable, humans can pursue it with zero delay. To make this prediction, information about the speed of the target is necessary. Our results show that this information is used with a delay of about 200 ms. We discuss that oculomotor efference is a likely source of information for this prediction.
In a recent paper, Flament et al (1999) studied the learning to flex the elbow fast. They concluded from their data that time-related parameters (e.g. movement time) changed faster during learning than magnitude-related parameters (e.g. peak velocity), and discussed this finding in terms of neural substrates responsible for the apparently different learning mechanisms. In this note, I will argue that finding different time constants does not imply different learning mechanisms. I will give a theoretical example of the development of parameters during learning to move faster. Despite the fact that I model only one learning process, various kinematic parameters show different time courses of learning. The differences the model predicts are comparable with the experimental results.
Human language is a unique ability. It sits apart from other systems of communication in two striking ways: it is syntactic, and it is learned. While most approaches to the evolution of language have focused on the evolution of syntax, this paper explores the computational issues that arise in shifting from a simple innate communication system to an equally simple one that is learned. Associative network learning within an observational learning paradigm is used to explore the computational difficulties involved in establishing and maintaining a simple learned communication system. Because Hebbian learning is found to be sufficient for this task, it is proposed that the basic computational demands of learning are unlikely to account for the rarity of even simple learned communication systems. Instead, it is the problem of *observing* t...
Punctuation has so far attracted attention within the linguistics community mostly from a syntactic perspective. In this paper, we give a preliminary account of the information-based aspects of punctuation, drawing our points from assorted, naturally occurring sentences. We present our formal models of these sentences and the semantic contributions of punctuation marks. Our formalism is a simplified analogue of an extension--due to Nicholas Asher--of Discourse Representation Theory.
Serious thinking about the computational aspects of situation theory is just starting. There have been some recent proposals in this direction (viz. PROSIT and ASTL), with varying degrees of divergence from the ontology of the theory. We believe that a programming environment incorporating bona fide situation-theoretic constructs is needed and describe our very recent BABY-SIT implementation. A detailed critical account of PROSIT and ASTL is also offered in order to compare our system with these pioneering and influential frameworks.
Situation theory has been developed over the last decade and various versions of the theory have been applied to a number of linguistic issues. However, not much work has been done in regard to its computational aspects. In this paper, we review the existing approaches towards `computational situation theory' with considerable emphasis on our own research.
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