Freeman K-set

Freeman, Walter; Erwin, Harry

doi:10.4249/scholarpedia.3238

Cited by 46 publications

(36 citation statements)

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“…The curve in Fig. 14 running upwardly to the right across the imaginary axis represents the locus of predicted frequencies and decay rates of impulse responses in conditions of cortical dynamic symmetry, when the two positive feedback gains are equal to Kn, which results in polezero cancellation and reduction in the network to one negative feedback loop, the reduced KII set (Freeman, 2009b;Freeman & Erwin, 2008).…”

Section: Role Of Inhibition In Generating Oscillationsmentioning

confidence: 99%

“…Further information about stabilization of background activity has been derived by simultaneously recording the ECoG at the cortical surface above a microelectrode and the train of action potentials generated by a single neuron embedded in populations of excitatory and inhibitory neurons (Freeman, 2009b;Freeman & Erwin, 2008). The ECoG is superior to local field potentials (LFP) from the depth electrode, because the phase relations between the two time series are more clearly defined.…”

Section: Role Of Inhibition In Generating Oscillationsmentioning

confidence: 99%

“…Negative feedback (KII set ). Two sigmoid curves and their gain curves are shown for two behavioral states: rest and arousal, governed by the maximum normalized pulse density Q m = 2 at rest and 5 at work (Freeman & Erwin, 2008).…”

Section: Role Of Inhibition In Generating Oscillationsmentioning

confidence: 99%

“…The normalized conditional pulse probability density function has been fitted with an equation derived by a statistical generalization of the Hodgkin-Huxley equations (Freeman, 2009b;Freeman & Erwin, 2008). The derivative of the asymmetric sigmoid curve, dp/dv, gives the nonlinear gain (Kp, Fig.…”

Section: Role Of Inhibition In Generating Oscillationsmentioning

confidence: 99%

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Vortices in brain activity: Their mechanism and significance for perception

Freeman

2009

Neural Networks

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Brains interface with the world through perception. The process extracts information from microscopic sensory inputs 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 the 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. Read-out 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.

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Section: Role Of Inhibition In Generating Oscillationsmentioning

confidence: 99%

Section: Role Of Inhibition In Generating Oscillationsmentioning

confidence: 99%

Section: Role Of Inhibition In Generating Oscillationsmentioning

confidence: 99%

Section: Role Of Inhibition In Generating Oscillationsmentioning

confidence: 99%

See 2 more Smart Citations

Vortices in brain activity: Their mechanism and significance for perception

Freeman

2009

Neural Networks

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“…A topologia das conexões é modelada por redes de populações de neurônios excitatórias e inibitórias. A dinâmica é aproximada por partes não lineares de Equações Diferenciais Ordinárias (EDO) (FREEMAN;ERWIN, 2008), com parâmetros distribuídos para descrever dinâmicas de populações neurais começando de microcolunas a hemisférios (KOZMA; ).…”

Section: Organização Do Trabalhounclassified