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The last two decades have been of fundamental importance in the study and understanding of the nervous system, this progress has not only addressed the neurochemical, neurophysiological, neuroanatomical, cytoarchitectonical, imageological phenomena underlying the cerebral mass but also the relationship of this knowledge with complex aspects of behavior and the psyche. The purpose of emphasizing a modern vision of the grasp of neuroscience must necessarily reflect a wider understanding of the reality of mental illness allowing a confluence between our biological, behavioral, psychic and social conditions. This article seeks to review the biological basis of mental disorders based on recent neurobiological investigations. The constituent elements of the superior mental functions are described in five functional blocks, portraying a vision of global organization as the basis for the interpretation of the processing of information and the origin of the different psychophatological manifestations that will be explained in part two, "Microstructure and the Processing of Information".
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The combined use of two anterograde axonal transport methods reveals that in the prefrontal association cortex of macaque monkeys, associational projections from the parietal lobe of one hemisphere interdigitate with callosal projections from the opposite frontal lobe, forming adjacent columns 300 to 750 micrometers wide. The finding of separate and alternating ipsilateral and contralateral inputs in the frontal association cortex opens up new possibilities for the functional analysis of this large but unexplored area of the primate brain.
A new psychosocial/biological model of the psyche is proposed, in which the affects play a central role in organising and integrating cognition. The psyche is understood here as a complex hierarchical structure of affective/cognitive systems of reference (or 'programmes for feeling, thinking, and behaviour'), generated by repetitive concrete action. These systems store past experience in their structure, and provide the functional basis for further cognition and communication. Affects endow these programmes with a specific qualitative value (such as motivation), connect cognitive elements synchronically and diachronically, and contribute to their storage and mobilisation according to context. They also participate in differentiating cognitive systems at higher levels of abstraction. These assumptions are supported by recent findings on the role of the limbic and hypothalamic system for the regulation of emotion, on neuronal plasticity, and on the phenomenon of state-dependent learning and memory. Refutable hypotheses are formulated for further research on the interaction of emotion and cognition.
Quantitative in vitro autoradiography was used to determine and compare the areal and laminar distribution of the major dopaminergic, adrenergic, and serotonergic neurotransmitter receptors in 4 cytoarchitectonic regions of the prefrontal cortex (Walker's areas 12, 46, 9, and 25) in adult rhesus monkeys. The selective ligands, 3H-SCH-23390, 3H-raclopride, 3H-prazosin, and 3H-clonidine were used to label the D1 and D2 dopamine receptor subtypes and the alpha 1- and alpha 2-adrenergic receptors, respectively, while 125I-iodopindolol was used to detect beta-adrenergic receptors. The radioligands, 3H-5-hydroxytryptamine and 3H-ketanserin labeled, respectively, the 5-HT1 and 5-HT2 receptors. Densitometry was performed on all cortical layers and sublayers for each of the 7 ligands to allow quantitative as well as qualitative comparison among them in each cytoarchitectonic area. Although each monoamine receptor was distributed in a distinctive laminar-specific pattern that was remarkably similar from area to area, there was considerable overlap among the dopaminergic, adrenergic, and serotoninergic receptors, while subtypes of the same receptor class tended to have complementary laminar profiles and different concentrations. Thus, the D1 dopamine, the alpha 1- and alpha 2-adrenergic, and the 5-HT1 receptors were present in highest relative concentration in superficial layers I, II, and IIIa (the "S" group). In contrast, the beta 1- and beta 2-adrenergic subtypes and the 5-HT2 receptor had their highest concentrations in the intermediate layers, IIIb and IV (the "I" group), while the D2 receptor was distinguished by relatively high concentrations in the deep layer V compared to all other layers (the "D" class). Consequently, clear laminar differences were observed in the D1 vs D2 dopaminergic, the alpha- vs beta-adrenergic, and the 5-HT1 vs 5-HT2 serotoninergic receptor subtypes in all 4 areas examined. The anatomical overlap of different monoaminergic receptors in the same cortical strata suggests that there may be families of receptors linked by localization on common targets, while the complementary laminar distribution of the D1 vs D2, the 5-HT1 vs 5-HT2 and the alpha- vs beta-adrenergic receptors raises the possibility that different subtypes within a given class may have distinctive actions in cortex by virtue of their localization on different cells or possibly different portions of the same cell. Understanding the anatomical arrangement of receptors within the cortical layers may aid in the analysis of monoaminergic modulation of higher cortical function.
Experiential phenomena that occur in temporal lobe seizures and can be reproduced by electrical stimulation of temporal lobe structures typically encompass perceptual, mnemonic and affective features, either in combination or in isolation, which commonly relate to the patient's individual past experience. These phenomena raise interesting questions concerning brain mechanisms involved in human psychophysiology. The anatomical substrates for the evocation of these phenomena are widely distributed within the temporal lobe and include temporal isocortex and limbic structures (amygdala, hippocampus and parahippocampal gyrus). Arguments are presented which indicate that experiential phenomena are positive expressions of temporal lobe and limbic function and do not result from its ictal paralysis. Recent concepts of parallel distributed processing (Rumelhart and McClelland, 1986) and the importance of parallel distributed cortical networks for higher cognitive functions (Goldman-Rakic, 1988a, b) provide a theoretical framework on which a hypothesis explaining experiential phenomena can be based. In conformity with these concepts the hypothesis assumes that temporal lobe epileptic discharge or electrical stimulation of temporal lobe structures can induce the elaboration of patterns of excitation and inhibition in widely distributed neuronal networks, some of which are capable of forming a specific matrix representing the substrate of a given experience. Neuronal networks engaged in parallel distributed processing (1) have the capacity to recreate the totality of a given experience when only a fragment of the network is activated, and (2) they tolerate a great deal of degradation by random inactivation of its components or by interference through random noise without serious loss of information content. These features are compatible with the assumption that localized epileptic neuronal discharge or electrical stimulation involving some temporal lobe structures could create a matrix representing features of individual experience of the kind activated in the course of temporal lobe seizures. Such an experience could, up to a certain limit, resist the degrading influence of mounting noise which inevitably must attend seizure discharge.
Experiential phenomena occurring in spontaneous seizures or evoked by brain stimulation were reported by 18 of 29 patients with medically intractable temporal lobe epilepsy who were investigated with chronic, stereotaxically implanted intracerebral electrodes. The phenomena mainly consisted of perceptual (visual or auditory) hallucinations or illusions, memory flashbacks, illusions of familiarity, forced thinking, or emotions. Experiential phenomena did not occur unless a seizure discharge or electrical stimulation involved limbic structures. For such phenomena to occur, seizure discharge or electrical stimulation did not have to implicate temporal neocortex. This was true even for perceptual experiential phenomena. Many experiential responses elicited by electrical stimulation, particularly when applied to the amygdala, were not associated with electrical afterdischarge. Limbic activation by seizure discharge or electrical stimulation may add an affective dimension to perceptual and mnemonic data processed by the temporal neocortex, which may be required for endowing them with experiential immediacy.
Fundamento biológico de la vivencia de la corporeidad
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