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Vortices in Brain Activity: Their Mechanism and Significance for Perception
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BibTeX
@MISC{Freeman_vorticesin,
author = {Walter J Freeman and Life Fellow},
title = {Vortices in Brain Activity: Their Mechanism and Significance for Perception},
year = {}
}
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Abstract
IEEE Neural Networks, doi:10.1016/j.neunet.2009.06.050. Abstract — Brains interface with the world through perception. The process extracts information from microscopic sensory input and incorporates it into the mesoscopic memory store for retrieval in recognition. The process requires creation of spatiotemporal patterns of neural activity. The construction is done through phase transitions in cortical populations that condense background activity through spontaneous symmetry breaking. Large-scale interactions create fields of synaptically driven activity that is observed by measuring brain waves (electrocorticogram, ECoG) and evaluated by constructing a mesoscopic vectorial order parameter as follows. The negative feedback among excitatory and inhibitory neurons creates spatially and spectrally distributed gamma oscillations (20-80 Hz) in the background activity. Band pass filtering reveals beats in ECoG log analytic power. In some beats that recur at theta rates (3-7 Hz), the order parameter transiently approaches zero, giving a null spike in which the microscopic activity is uniformly disordered (symmetric). A phase transition that is manifested in an analytic phase discontinuity breaks the symmetry. As the null spike terminates, the resurgent order parameter imposes mesoscopic order seen in spatial patterns of ECoG amplitude modulation (AM) that actualize and update the memory of a stimulus. Readout is through a divergent/convergent projection that performs on cortical output an irreversible spatiotemporal integral transformation. The ECoG reveals a conic phase gradient that accompanies an AM pattern. The phase cone manifests a vortex, which is initiated by the null spike, and which is inferred to help stabilize and prolong its accompanying AM pattern that might otherwise be rapidly degraded by the turbulent neural noise from which it emerges.
Keyphrases
brain activity background activity null spike phase transition band pas filtering reveals beat neural activity mesoscopic vectorial order parameter theta rate ecog log analytic power analytic phase discontinuity mesoscopic memory store microscopic sensory input cortical output 20-80 hz spatial pattern abstract brain interface conic phase gradient resurgent order parameter turbulent neural noise irreversible spatiotemporal integral transformation large-scale interaction null spike terminates inhibitory neuron spatiotemporal pattern gamma oscillation order parameter microscopic activity ieee neural network 3-7 hz mesoscopic order divergent convergent projection negative feedback phase cone brain wave cortical population spontaneous symmetry
