Self-organization: the basic principle of neural functions

The modular architecture and neurochemical patterns in the cerebellar cortex

The review deals with topical issues of the neuronal arrangement underlying basic cerebellar functions. The cerebellum and its auxiliary structures contain several hundreds of modules (so called "microzones"). Each module receives the corticopetal input specific for the lobule it belongs to and forms the topographic projection. The precision of the major input-output signal flow in the cerebellar cortex is provided by a pronounced stratification of its synaptic zones of a various origin and regular topography of its afferent connections, interneurons, and efferent neurons. There is a nice match between the anatomical and functional coordinates of the modules, whose spatial boundaries are determined by the spread of afferent excitation and local interneuron connections. The dynamic characteristics of the modules are analyzed by the example of the formation of the nitrergic neuron ensembles and cerebellar projections of corticopetal fibers. The authors discuss the cerebellar blood flow and its relation to the activity of NO/GABAergic Lugaro cells and other interneurons in the cerebellar cortex. A generalized scheme of intra- and intermodular communication is proposed.

The new brain: concepts, challenges, and opportunities for mental health nursing

The new paradigm that the brain is able change itself (neuroplasticity) is acknowledged and teased out in terms of the ramifications for mental illnesses. Parallel studies in pain (central sensitization) and mirror neurones are examined to conceptually clarify these ramifications in relation to mental health, and to expand our understanding of empathy and social inclusion beyond good ideas to being a part of our nature. The paper then focuses on making clear what the concepts, challenges, and opportunities for mental health nursing might be; even advancing possibilities for recovery through better understanding the third space or intersubjective. What ramifications this has for mental health nursing is reviewed in terms of a paradigm change and the necessity for conceptual clarity, as it relates to the uniqueness of the person right before our very eyes. The author contends that to embrace this new paradigm is not only necessary but ethically obligatory, as it opens up new possibilities for understanding ourselves and this changeable person.

Cytophysiology of spiny stellate cells in the striate cortex and their role in the excitatory mechanisms of intracortical synaptic circulation

Spiny stellate cells (SS) are an exclusive category of cortical interneurons and are the major component of intracolumnar, lateral, and callosal excitation of pyramidal and non-pyramidal neurons in the neocortex. The axons of SS make contact with the apical dendrites of pyramidal neurons, forming cartridge-type en passant synapses with them. SS establish recurrent connections with inhibitory interneurons and other SS, and also form autapses contacts. SS subtypes were identified and descriptions of their structure, neurochemical specialization, and spatial organization in the human and animal neocortex are provided. The results of our own studies, along with published data, are used to form a critical analysis of current concepts of the histophysiology of recurrent excitatory and inhibitory neurocirculation in cortical modules.

Thyroid Tuberculosis: Diagnosis and Treatment

OBJECTIVE

It was the aim of this study to report clinical characteristics and treatment of thyroid tuberculosis (TT).

METHODS

During 16 years, 2,426 patients have been operated on the thyroid in the surgical department 'A' in Ibn Sina Hospital, Rabat, Morocco. Anatomopathological results of the removed thyroid were analyzed for evidence of tuberculosis.

RESULTS

Eight cases of TT were diagnosed. Five patients had a goiter and 3 patients had an isolated nodule of the thyroid. In one case, fine-needle aspiration cytology gave the diagnosis of TT. This patient had a complete drainage of the abscess. In all other patients, the diagnosis was given after surgery. All patients received additional antituberculous drugs for 6 months, and follow-up was satisfactory.

CONCLUSION

TT does not have any consistent symptoms. Fine-needle aspiration is the best method for diagnosis and can result in the avoidance of surgery.

Alzheimer's disease as a disorder of mechanisms underlying structural brain self-organization

Mental function has as its cerebral basis a specific dynamic structure. In particular, cortical and limbic areas involved in "higher brain functions" such as learning, memory, perception, self-awareness and consciousness continuously need to be self-adjusted even after development is completed. By this lifelong self-optimization process, the cognitive, behavioural and emotional reactivity of an individual is stepwise remodelled to meet the environmental demands. While the presence of rigid synaptic connections ensures the stability of the principal characteristics of function, the variable configuration of the flexible synaptic connections determines the unique, non-repeatable character of an experienced mental act. With the increasing need during evolution to organize brain structures of increasing complexity, this process of selective dynamic stabilization and destabilization of synaptic connections becomes more and more important. These mechanisms of structural stabilization and labilization underlying a lifelong synaptic remodelling according to experience, are accompanied, however, by increasing inherent possibilities of failure and may, thus, not only allow for the evolutionary acquisition of "higher brain function" but at the same time provide the basis for a variety of neuropsychiatric disorders. It is the objective of the present paper to outline the hypothesis that it might be the disturbance of structural brain self-organization which, based on both genetic and epigenetic information, constantly "creates" and "re-creates" the brain throughout life, that is the defect that underlies Alzheimer's disease (AD). This hypothesis is, in particular, based on the following lines of evidence. (1) AD is a synaptic disorder. (2) AD is associated with aberrant sprouting at both the presynaptic (axonal) and postsynaptic (dendritic) site. (3) The spatial and temporal distribution of AD pathology follows the pattern of structural neuroplasticity in adulthood, which is a developmental pattern. (4) AD pathology preferentially involves molecules critical for the regulation of modifications of synaptic connections, i.e. "morphoregulatory" molecules that are developmentally controlled, such as growth-inducing and growth-associated molecules, synaptic molecules, adhesion molecules, molecules involved in membrane turnover, cytoskeletal proteins, etc. (5) Life events that place an additional burden on the plastic capacity of the brain or that require a particularly high plastic capacity of the brain might trigger the onset of the disease or might stimulate a more rapid progression of the disease. In other words, they might increase the risk for AD in the sense that they determine when, not whether, one gets AD. (6) AD is associated with a reactivation of developmental programmes that are incompatible with a differentiated cellular background and, therefore, lead to neuronal death. From this hypothesis, it can be predicted that a therapeutic intervention into these pathogenetic mechanisms is a particular challenge as it potentially interferes with those mechanisms that at the same time provide the basis for "higher brain function".

The brain as a hermeneutic device

An attempt has been made to reconcile the 'device approach' and the 'philosophical approach' to the brain. Systems exhibiting high structural and dynamic complexity may be candidates of being hermeneutic devices. The human brain, which is a structurally and dynamically complex device, not only perceives but also creates new reality: it is a hermeneutic device.

Vertical information flow in the brain: on neuronal micro events and consciousness

The consciousness problem and its relation to theories of spontaneous brain activity are discussed. It is argued that an evolutionary perspective suggests an interactionist solution of the consciousness problem, i.e., mental events interact with physical brain events. A specification of the physical events assumed to be associated with mental events is proposed to make the discussion of mind-brain theories more fruitful. An interactionist solution of the consciousness problem requires random spontaneous brain activity. A mechanism for such activity is proposed on the basis of experimental findings. Some new results from patch-clamp experiments on intact tissue (the hippocampal slice preparation) are presented. The results indicate that single channel events may cause random spontaneous neuronal activity, illustrating the phenomenon of micro events inducing macro or global brain events, and also the central theme of vertical information flow. The findings highlight the importance of understanding the stochastic nature of channel gating.

Neurodynamic system theory: scope and limits

This paper proposes that neurodynamic system theory may be used to connect structural and functional aspects of neural organization. The paper claims that generalized causal dynamic models are proper tools for describing the self-organizing mechanism of the nervous system. In particular, it is pointed out that ontogeny, development, normal performance, learning, and plasticity, can be treated by coherent concepts and formalism. Taking into account the self-referential character of the brain, autopoiesis, endophysics and hermeneutics are offered as elements of a poststructuralist brain (-mind-computer) theory.