Biomedical subjects
Publications and source records attributed to E Pessa.
In this paper we review the evidence for quantum phenomena underlying neuropsychiatric disorders. Existing data can be explained only by resorting to non-local correlations within brain activity, such as the ones predicted by quantum theory. Such a situation suggests that perhaps a quantum description may be the best description of interrelationships between neural and cognitive phenomena.
We show that particular features of prosopagnosic impairment can be simulated by a connectionist model trained with an unsupervised learning procedure. In particular we describe a Kohonen's neural network which is able to correctly recognize and categorize a series of digitized pictures of faces when learning is characterized by certain parameter values, but which shows a prosopagnosic behavior when lateral connections are lesioned. We discuss the relationship between this result and some neurophysiological hypotheses about prosopagnosia.
Inspired by the dissipative quantum model of brain, we model the states of neural nets in terms of collective modes by the help of the formalism of Quantum Field Theory. We exhibit an explicit neural net model which allows to memorize a sequence of several informations without reciprocal destructive interference, namely we solve the overprinting problem in such a way last registered information does not destroy the ones previously registered. Moreover, the net is able to recall not only the last registered information in the sequence, but also anyone of those previously registered.
Any mathematical description of structures should start from a precisely stated definition of the concept of "structure". Unfortunately no universally accepted definition of this type exists. All that can be said is that the concept of "structure" is changing together with the modern physico-mathematical thought, so that different 'points of view' on the problem of the mathematical description of structures can be distinguished. The aim of this paper is to compare the explicative and predictive power of these different 'viewpoints' without entering into historical detail, in order to critically examine the limits and powers of the mathematical tools available today.
In this paper two well-known homogeneous models of neural nets undergoing symmetry-breaking transitions are studied in order to see if, after the transition, there is the appearance of Goldstone modes. These have been found only in an approximate way; there are indications, however, that they can play a prominent role when the tissue is subjected to external inputs, constraining it to be slaved to the characteristics of those. This circumstance should be essential in explaining how a structured net can store complex inputs and give subsequently ordered outputs.
This study evaluates individual differences in hypnotizability as reflected in waking-state hemispheric engagement during recollection of 3 positively and 3 negatively valenced personal life events. The State-Trait Anxiety Inventory, Maudsley Personality Inventory, Tellegen Absorption Scale and Harvard Group Scale of Hypnotic Susceptibility (Form A) were administered. Electromyogram (EMG) and bilateral electroencephalogram (EEG) activities within the 40-Hz band were recorded during rest and task conditions in 22 high and 21 low hypnotizable women. Self-report rating scores for vividness of visual imagery and emotional feeling of the material recalled were evaluated. The 40-Hz EMG amplitude and both hemisphere 40-Hz EEG densities were obtained. A 40-Hz EEG ratio, as a measure of hemispheric asymmetry, and a hemispheric specificity index were also computed. High hypnotizables showed significantly lower 40-Hz EEG density than low hypnotizables in all experimental conditions. The relationship between lateralization of 40-Hz EEG and emotional processing was moderated by hypnotizability. High hypnotizables, with respect to rest condition, showed an increase of density over both left and right hemispheres during two of the three positive emotional tasks, while they showed a depressed activity over the left and an increased activity over the right during negative emotional tasks. Low hypnotizables, on the other hand, did not exhibit differential hemispheric patterns that could be attributed to different emotional valences. The high group showed greater hemispheric specificity in the predicted direction than the low group. High subjects exhibited greater ratings of absorptive ability and emotional feeling than low subjects. Anxiety and EMG levels did not differ between groups. EMG was dependent on the type of emotion which showed greater activity in the negative emotion condition compared with the positive one.