Limits...
Being critical of criticality in the brain.

Beggs JM, Timme N - Front Physiol (2012)

Bottom Line: The hypothesis that the electrical activity of neural networks in the brain is critical is potentially important, as many simulations suggest that information processing functions would be optimized at the critical point.This hypothesis, however, is still controversial.Points and counter points are presented in dialog form.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Indiana University Bloomington, IN, USA.

ABSTRACT
Relatively recent work has reported that networks of neurons can produce avalanches of activity whose sizes follow a power law distribution. This suggests that these networks may be operating near a critical point, poised between a phase where activity rapidly dies out and a phase where activity is amplified over time. The hypothesis that the electrical activity of neural networks in the brain is critical is potentially important, as many simulations suggest that information processing functions would be optimized at the critical point. This hypothesis, however, is still controversial. Here we will explain the concept of criticality and review the substantial objections to the criticality hypothesis raised by skeptics. Points and counter points are presented in dialog form.

No MeSH data available.


Correlation length as a function of temperature for a simulation of the Ising Model. Near the critical temperature the correlation length rapidly approaches a maximum value. This sharp peak separates the ordered phase from the disordered phase and occurs at the phase transition point.
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Figure 4: Correlation length as a function of temperature for a simulation of the Ising Model. Near the critical temperature the correlation length rapidly approaches a maximum value. This sharp peak separates the ordered phase from the disordered phase and occurs at the phase transition point.

Mentions: Critio: In this example from a simulation, the dynamic correlation at the critical temperature extends about 15 lattice sites before it drops down to near 0. We call the distance at which the dynamic correlation first reaches 0 the “correlation length” and it is often given by the Greek capital letter gamma, Γ; in this case the correlation length is 15 lattice sites long. We didn’t build this length into the model – it merely emerged at the critical temperature. At this temperature, when one spin flips from down to up, for example, it might influence one of its nearest neighbors to also flip, which might in turn influence one of its nearest neighbors and so on. In this way, the movement at one lattice site can propagate beyond the nearest neighbor length. You could draw the correlation length as a function of temperature, and it would show a sharp peak at the critical point. [Critio asks another person sitting at the table for a fresh napkin and draws Figure 4.]


Being critical of criticality in the brain.

Beggs JM, Timme N - Front Physiol (2012)

Correlation length as a function of temperature for a simulation of the Ising Model. Near the critical temperature the correlation length rapidly approaches a maximum value. This sharp peak separates the ordered phase from the disordered phase and occurs at the phase transition point.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3369250&req=5

Figure 4: Correlation length as a function of temperature for a simulation of the Ising Model. Near the critical temperature the correlation length rapidly approaches a maximum value. This sharp peak separates the ordered phase from the disordered phase and occurs at the phase transition point.
Mentions: Critio: In this example from a simulation, the dynamic correlation at the critical temperature extends about 15 lattice sites before it drops down to near 0. We call the distance at which the dynamic correlation first reaches 0 the “correlation length” and it is often given by the Greek capital letter gamma, Γ; in this case the correlation length is 15 lattice sites long. We didn’t build this length into the model – it merely emerged at the critical temperature. At this temperature, when one spin flips from down to up, for example, it might influence one of its nearest neighbors to also flip, which might in turn influence one of its nearest neighbors and so on. In this way, the movement at one lattice site can propagate beyond the nearest neighbor length. You could draw the correlation length as a function of temperature, and it would show a sharp peak at the critical point. [Critio asks another person sitting at the table for a fresh napkin and draws Figure 4.]

Bottom Line: The hypothesis that the electrical activity of neural networks in the brain is critical is potentially important, as many simulations suggest that information processing functions would be optimized at the critical point.This hypothesis, however, is still controversial.Points and counter points are presented in dialog form.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Indiana University Bloomington, IN, USA.

ABSTRACT
Relatively recent work has reported that networks of neurons can produce avalanches of activity whose sizes follow a power law distribution. This suggests that these networks may be operating near a critical point, poised between a phase where activity rapidly dies out and a phase where activity is amplified over time. The hypothesis that the electrical activity of neural networks in the brain is critical is potentially important, as many simulations suggest that information processing functions would be optimized at the critical point. This hypothesis, however, is still controversial. Here we will explain the concept of criticality and review the substantial objections to the criticality hypothesis raised by skeptics. Points and counter points are presented in dialog form.

No MeSH data available.