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Biomedical subjects

C Lourenço

Publications and source records attributed to C Lourenço.

8 recordsLinked to original sources

Pattern segmentation in a binary/analog world: unsupervised learning versus memory storing.

We discuss the problem of segmentation in pattern recognition. We adopt the model and the general approach in the landmark paper by Wang, Buhmann and von der Malsburg (Neural Computation, (1990), 2, 94-106), and expand their model in a number of ways. We review their solution to the segmentation problem in associative memory, which consists in feature binding being expressed by synchrony relations between oscillators or populations of neurons. We extend the model by introducing a law of synaptic change, which allows the network to learn by structuring itself in response to stimuli with relevant features. We discuss the problem of interference between pattern completion and the learning of new memories. We also propose a form of multiplexing of input information taking advantage of the time-structure of the neurons' response. It is based on the assessment of analog as well as of binary properties of the stimuli and provides for an enhancement of the network's processing capacity. The relevance of the results for biological systems is pointed out.

Acetylcholine↗

Brain chaos and computation.

A model cortex comprising two interconnected spatiotemporal chaotic networks is considered. The system is able to discriminate between different patterns presented as input, and also detect motion and measure its velocity. Such cognitive processes are only possible if an "attentive" state arises in one of the networks, as a result of the stabilization of a periodic orbit out of the chaotic dynamics.

Attention↗

Control of spatiotemporal chaos in neuronal networks.

Different strategies for the control of chaotic neuronal networks and physical systems are presented. The variables of the dynamics span phase-spaces with very high dimensions. Novel control techniques are introduced that handle these high-dimensional cases. Depending on the system, several orbits with different spatiotemporal symmetries may be stabilized out of the chaotic attractor. The role of chaos control in information processing is pointed out.

Algorithms↗

Computation with chaos: a paradigm for cortical activity.

A device comprising two interconnected networks of oscillators exhibiting spatiotemporal chaos is considered. An external cue stabilizes input specific unstable periodic orbits of the first network, thus creating an "attentive" state. Only in this state is the device able to perform pattern discrimination and motion detection. We discuss the relevance of the procedure to the information processing of the brain.

Cerebral Cortex↗

[Pulmonary emphysema in a patient with Turner's syndrome].

Turner's Syndrome was first described in 1938 by Henry Turner and has an incidence of 1:3000 live female births. The authors present an unusual case of a 48-year-old woman with late diagnosed Turner's Syndrome. Whose karyotype was (46,X,i(Xq)), associated with a pulmonary emphysema and pulmonary hypertension. The case and the methods of study are presented. Some aspects of this case, namely the hypothesis of an association between the pulmonary emphysema and Turner's Syndrome are discussed.

Female↗

[Sexual orientation guide for patients with spinal cord injuries. Applied methodology and results].

The present work refers to the elaboration of a sexual orientation guide to spinal cord injured patients done by a nurse from the rehabilitation team in the Rehabilitation Medicine division at São Paulo University Medicine School Clinics Hospital. Its purpose is clarifying issues concerning sexual adjustment and helping those patients to express their sexuality in an appropriate way. Besides, nursing team can use it to improve rehabilitation nurse therapy even during health care educational groups.

Adult↗