Indispensable role of quantum theory in the brain dynamics

Recently, Tegmark pointed out that the superposition of ion states involved in the superposition of firing and resting states of a neuron quickly decohere. It undoubtedly indicates that neural networks cannot work as quantum computers, or computers taking advantage of coherent states. Does it also mean that the brain can be modeled as a neural network obeying classical physics? Here we show that it does not mean that the brain can be modeled as a neural network obeying classical physics. A brand new perspective in research of neural networks from quantum theoretical aspect is presented.     

The spread of brain oedema in hypertensive brain injury

Severe hypertension in humans may lead to fibrinoid necroses of cerebral blood vessels with small hemorrhages and cystic necroses. Similar lesions have also been reported in the experimental model of stroke-prone spontaneously hypertensive rats (SHRSP). We examined the genesis and spreading pattern of the brain oedema in SHRSP. The extravasation of plasma proteins was visualized with the Evans-Blue or the immunoperoxidase method. Most commonly the leakage occurred in the grey matter of the cerebral cortex or basal ganglia. The spreading pattern followed that of vasogenic brain oedema with a local spread in the grey matter and an extensive one in the white matter. In addition, we detected a novel pathway upwards along the perivascular spaces of the penetrating vessels as well as laterally in the subpial zone. This route is likely to serve also as a drainage channel for the oedema into the cerebrospinal fluid in the subarachnoidal space. Transfer of the extravasated proteins from the white matter to the ventricles was also observed, confirming that this previously described pathway for the resolution of oedema fluid exists in the SHRSP model of vasogenic brain oedema.     

The social brain hypothesis

Conventional wisdom over the past 160 years in the cognitive and neurosciences has assumed that brains evolved to process factual information about the world. Most attention has therefore been focused on such features as pattern recognition, color vision, and speech perception. By extension, it was assumed that brains evolved to deal with essentially ecological problem-solving tasks. © 1998 Wiley-Liss, Inc.     

The blue brain project

IBM's Blue Gene supercomputer allows a quantum leap in the level of detail at which the brain can be modelled. I argue that the time is right to begin assimilating the wealth of data that has been accumulated over the past century and start building biologically accurate models of the brain from first principles to aid our understanding of brain function and dysfunction.     

The adaptive aging brain

The aging brain is shaped by many structural and functional alterations. Recent cross-disciplinary efforts have uncovered powerful and integrated adaptive mechanisms that promote brain health and prevent functional decline during aging. Here, we review some of the most robust adaptive mechanisms and how they can be engaged to protect, and restore the aging brain.     

The dynamic brain N-glycome

Glycoconjugate Journal - The attachment of carbohydrates to other macromolecules, such as proteins or lipids, is an important regulatory mechanism termed glycosylation. One subtype of protein...     

The generalized Bouman-van der Velden quantum coincidence detector

The (two-) quantum coincidence detector originally proposed by van der Velden (1944) is generalized to an arbitrary renewal process input and an arbitrary distribution of the duration of the integration periods. The Laplace transform of the distribution of the waiting time to a quantum coincidence is derived and several applications and further general results are presented. It is shown that the performance of the Bouman-van der Velden coincidence detector is relatively stable with respect to variability of the durations of the integration periods, a result, which lends further support to the validity of the quantum coincidence principle in visual psychophysics.     

The quantum efficiency of the bacteriorhodopsin photocycle.

The quantum yield of the primary photoprocess in light-adapted bacteriorhodopsin (phi 1) was determined at room temperature with low-intensity 530 nm neodymium laser excitation, with bovine rhodopsin as a relative actinometer. The observed value of phi 1 - 0.25 +/- 0.05, and the previously determined parameter phi 1/phi 2 - 0.4 [where phi 2 denotes the quantum efficiency of the back photoprecess from the primary species K (590)] imply that phi 1 + phi 2 approximately equal 1. This feature, also characterizing the photochemistry of rhodopsin, bears on the nature and mechanism of the primary event in both systems.     

The fluorescence quantum yield of vitamin A2

The fluorescence quantum yield of all-trans 3,4-didehydroretinol (vitamin A2) was measured in hexane at room temperature, using quinine sulfate as a standard. Unlike all-trans retinol (vitamin A1) which possessed a relative quantum yield of 0.0298, 3,4-didehydroretinol was 37 times lower in fluorescence (i.e. 0.0008). In addition, a significant bathochromic shift (both excitation and emission maxima) and a general broadening of the fluorescence spectra were noted for 3,4-didehydroretinol. This information is important not only for the understanding of the basic structure of vitamin A but also the photochemistry of vision.     

The restless brain: how intrinsic activity organizes brain function

Traditionally studies of brain function have focused on task-evoked responses. By their very nature such experiments tacitly encourage a reflexive view of brain function. While such an approach has been remarkably productive at all levels of neuroscience, it ignores the alternative possibility that brain functions are mainly intrinsic and ongoing, involving information processing for interpreting, responding to and predicting environmental demands. I suggest that the latter view best captures the essence of brain function, a position that accords well with the allocation of the brain''s energy resources, its limited access to sensory information and a dynamic, intrinsic functional organization. The nature of this intrinsic activity, which exhibits a surprising level of organization with dimensions of both space and time, is revealed in the ongoing activity of the brain and its metabolism. As we look to the future, understanding the nature of this intrinsic activity will require integrating knowledge from cognitive and systems neuroscience with cellular and molecular neuroscience where ion channels, receptors, components of signal transduction and metabolic pathways are all in a constant state of flux. The reward for doing so will be a much better understanding of human behaviour in health and disease.