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At least 721 records · Page 40Linked to original sources
PubMed1999

[Brain functional imaging using magnetoencephalography].

Neuromagnetism, the study of neural function by the measurement of magnetic fields, is a new, quickly developing branch of science. Magnetoencephalography is the measurement of weak magnetic fields generated by neuronal activity in the human brain. By measuring the magnetic field evoked around the head, a map of the functional organisation of the brain can be deduced with a sub-centimetre spatial resolution and a millisecond temporal resolution. Although MEG has been used since the early 1970 s it is only recently that large multi channel facilities have been combined with sophisticated analysis techniques and Magnetic Resonance Imaging to provide a tool for fundamental study of the brain. The author presents 9 the other functional imaging tools such as Positron Emission Tomography /PET/, functional Magnetic Resonance Imaging /fMRI/ et Encephalography /EEG/.

Brain Diseases↗
PubMed1997

Magnetic source imaging as a tool for presurgical functional brain mapping.

This article describes magnetic source imaging, a newly-developing technology which can be used to noninvasively map eloquent cortex prior to surgical procedures. It is based on large-array detection of extracranial magnetic fields arising from neuronal currents evoked by peripheral stimulation. A range of evoked and spontaneous neuromagnetic activities are discussed along with clinical examples of the utility of the technique and comparison to other brain mapping techniques, such as positron emission tomography, functional magnetic resonance imaging, EEG, and ECoG.

Adolescent↗
PubMed2006

Serum insulin-like growth factor I in brain function.

Insulin-like growth factor I (IGF-I) is present at high concentrations in the circulation. Tissue-specific genetic ablation has shown that the majority of serum IGF-I is secreted by liver cells, although all major organs synthesize it. IGF-I is an important signal during development, including brain growth. Although the biological role of IGF-I in organs such as muscle or ovary is reasonably well established, its biological significance in the adult brain is far from clear. In this regard, while local IGF-I synthesis decreases during brain development, protein levels remain relatively constant throughout life until old age, where a decline is found, not only in the brain but also in the bloodstream. This mismatch between declining local synthesis early after birth and steady protein levels may be explained by the ability of serum IGF-I to access the brain across the blood-brain-barrier. This peripheral IGF-I input to the brain is a physiologically meaningful process of potential impact in brain diseases. Numerous brain mechanisms are regulated by serum IGF-I. Many of these, such as cell energy modulation or growth and survival are common to other IGF-I target tissues but there are also a number of brain-specific mechanisms regulated by IGF-I which likely underlie the ability of serum IGF-I to modulate the major function of the brain: cognition. We propose that serum IGF-I forms part of the mechanisms involved in the "cognitive reserve" concept of brain responses to homeostasis breakdown. Based on IGF-I pleiotropy not only in brain but elsewhere, we consider that loss of IGF-I function is an important step towards disease.

Animals↗
PubMed1998

Collateral inhibition of transcallosal activity facilitates functional brain asymmetry.

The corpus callosum is the largest connection between the functionally asymmetric cerebral hemispheres. The objective of this study was to measure functional activity of callosal fiber tracts during speech processing. We analyzed the regional glucose metabolism of the corpus callosum and of speech-relevant cortical areas in 10 normal individuals at rest and during word repetition. We used three-dimensionally registered magnetic resonance imaging to visualize the individual brain morphology and high-resolution positron emission tomography for metabolic measurements. The task-induced metabolic changes of the callosal midbody and isthmus had a significant negative correlation with key regions of language processing in the left inferior frontal cortex (Brodmann's area 44) and in the right superior temporal cortex (Brodmann's area 22) (e.g., correlation of metabolic changes in the surface aspects of the right Brodmann's area 22 and the callosal midbody/isthmus: r = -0.91, P < 0.001). The study indicates that language processing in asymmetrically organized cortical areas inhibits the reciprocal transcallosal information exchange in favor of the lateralized mental operation. Our data agree with anatomic, electrophysiologic, and pharmacologic experiments that point to the important role of collateral inhibition for the transcallosal information exchange.

Adult↗
PubMedDate not supplied

[Features of using the second principle of thermodynamics for describing brain function].

It has been shown that negative production of information entropy at the expense of its normalization change under the influence of neuromediators is specific for the nervous systems and brain. Chemical synapses are calculation elements with a diffusion input to control information entropy normalization. Reproduction stability of the nervous system and brain, and their functioning as well, are determined due to Lyapunov criteria by the maximum of entropy production in combination with minimum for the entropy itself. As far as information in nervous systems is connected with an element of energy normalization that is much greater than the scales of molecular energy of single atoms, physical and information self-organization can simultaneously either correlate or be sufficiently independent, because entropy corresponds to statically unstable point, with its output being natural in different ways. In particular, the brain potentialities are the more, the further it is advanced in its evolution in the sense of entropy increase of its structure, i.e. evolution perfection of mind results from the elementary meaning of the second principle of thermodynamics but in combination of the biochemical peculiarity--the growth of brain is controlled by adrenogens and because of this correlates with productivity.

Brain↗