Wave onset in central gray matter - its intrinsic optical signal and phasetransitions in extracellular polymers

Citation
Vm. Fernandes-de-lima et al., Wave onset in central gray matter - its intrinsic optical signal and phasetransitions in extracellular polymers, AN AC BRASI, 73(3), 2001, pp. 351-364
Citations number
26
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Multidisciplinary
Journal title
ANAIS DA ACADEMIA BRASILEIRA DE CIENCIAS
ISSN journal
0001-3765 → ACNP
Volume
73
Issue
3
Year of publication
2001
Pages
351 - 364
Database
ISI
SICI code
0001-3765(200109)73:3<351:WOICGM>2.0.ZU;2-1
Abstract
The brain is an excitable media in which excitation waves propagate at seve ral scales of time and space. "One-dimensional" action potentials (millisec ond scale) along the axon membrane, and spreading depression waves (seconds to minutes) at the three dimensions of the gray matter neuropil (complex o f interacting membranes) are examples of excitation waves. In the retina. e xcitation waves have a prominent intrinsic optical signal (IOS). This optic al signal is created by light scatter and has different components at the r ed and blue end of the spectrum. We could observe the wave onset in the ret ina, and measure the optical changes at the critical transition from quiesc ence to propagating wave. The results demonstrated the presence of fluctuat ions preceding propagation and suggested a phase transition. We have interp reted these results based on an extrapolation from Tasaki's experiments wit h action potentials and volume phase transitions of polymers. Thus, the sca tter of red light appeared to be a volume phase transition in the extracell ular matrix that was caused by the interactions between the cellular membra ne cell coat and the extracellular sugar and protein complexes. If this hyp othesis were correct, then forcing extracellular current flow should create a similar signal in another tissue, provided that this tissue was also tra nsparent to light and with a similarly narrow extracellular space. This con trol tissue exists and it is the crystalline lens. We performed the experim ents and confirmed the optical changes. Phase transitions in the extracellu lar polymers could be an important part of the long-range correlations foun d during wave propagation in central nervous tissue.