Archive | May 2015

Reaction Diffusion and Self Organisation of the Brain

INTRODUCTION

Interactions between biochemical and mechanobiological activity and feedback loops

It is proposed that the formation and workings of the brain are influenced by an interplay between oscillatory biochemical (reaction-diffusion) and mechanobiological activity (including in response to external stresses), feedback loops, and stochastic resonance.

This relationship between biochemistry and mechanobiology has already been explored in other areas of science.  Waves in the BZ reaction in gels cause deformation, which in turn affects the spiral wave dynamics. Furthermore, a ‘‘chain reaction’’ of spiral wave births and deaths can result from an externally controlled deformation of a medium A. V. Panfilov 2005.  A Adamatsky (2010) describes a propagating excitation wave front inducing an associated mechanical wave of contraction.  Oscillatory dynamics have been found in organs e.g deformation can create spiral waves, and this has been explored in cardiac dynamics. Louis D. Weise et al 2011A. V. Panfilov 2005.

These types of interactions in biology can resemble “chicken or an egg” relationships, as a simple chain of cause and effect is not apparent.  In this paper, it is suggested that this relationship is taking place within a dissipative clock system linking circadian rhythms and cell cycles/oscillations and redox/the metabolism and using positive and negative feedback.  Circadian clocks do not operate in isolation, but rather are mutually dependent upon intrinsically rhythmic cytosolic signals (cAMP, Ca2+, kinases) such as that the cell as a whole has a resonant structure tuned to 24 hour operations. (Hastings et al 2008 in C Colwell 2015).

A fuller range of biological rhythms are explored by Goldbeter 2007.

Biological Rhythms –  (Goldbeter 2007). Period
Neural rhythms 0.001 s to 10 s
Cardiac rhythms 1 s
Calcium Oscillations Sec to min
Biochemical oscillations 30 s to 20 min
Miotic Oscillator 10 min to 24 h
Hormonal rhythms 10 min to 3-5 h (24 h)
Circadian rhythms 24 h
Ovarian cycle 28 days (human)
Annual Rhythms 1 year
Rhythm in ecology and epidemiology years
Segmentation Clock 90 mins
Biological Regulations Examples of Associated Cellular Rhythms
Ion Channel Neural and Cardiac rhythms
Transport Ca2+ oscillations
Gene expression Circadian rhythms, segmentation clock.

Under certain circumstances, entropy producing processes are able to organise themselves in the presence of noise, in a way that so called dissipative structures are formed (Prigogine and Lefever 1975, and Nicolis and Prigogine 1977).  Necessary conditions for the occurance of dissipative structure are that the system is open , that it is in a state far from equilibrium and that non linear processes occur within the system.  In these  conditions, internal small fluctuations may be amplified non linearly by a flow of mass and energy from the surroundings.  The system is then removed irreversibly from its initial state, in particular from any homogeneous or unorganised state that is characteristic for equilibrium conditions.  Therefore the new state is characterised by a more organised internal distribution of matter, energy and process rates.  G Bodifee 1986Goldbeter 2007.

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