Origin, structure, and role of background EEG activity. Part 4: Neural frame simulation

Abstract

AcknowledgmentI am grateful to Brian C. Burke for software development. Examples of simulated EEGs will be available for download from the above website. AbstractObjective: To develop a method for simulating background EEG based on the premise that the activity from synaptic excitation among populations of neurons can be modeled with the filtered output of a random number generator. Methods: The logarithm of the amplitude of activity was weighted in accordance with 1/f, the log frequency in both temporal (PSD T ) and spatial (PSD X ) spectra. The activity was spatially smoothed by volume conduction. Further deviation from full randomness was by sustained spatial coherence averaging 25% of total power. The departure from the background state to an active state, as seen in the awake EEG, was simulated by adding segments that were 90% correlated while attenuating by 50% the uncorrelated background activity in those segments. Spatial amplitude modulation was imposed on the correlated noise to create signals that simulated AM patterns. Results: The statistical properties of the EEG were replicated, including the PSD T , PSD X , point spread function (PSF), partitioning of the variance with PCA, and the percentages of correct classification of AM patterns. Conclusions: The essential change that identified a frame in EEG was transient increase in synchrony among a population of cortical neurons in the beta or gamma band of the PSD T . The limitation on classification efficacy was imposed by high variance in AM patterns in successive frames with the same artificial spatial pattern. Significance: This method of simulation provides a test bed with which to develop improved techniques for digital signal processing to extract behaviorally relevant information from the EEG at human-machine interfaces.Neural frame simulation 2Walter J Freeman

Indirect biological measures of consciousness from field studies of brains as dynamical systems

“…Goal-oriented behaviors have been described repeatedly in the 20 th century by pragmatists [Dewey, 1914], developmental psychologists [Piaget, 1930;Köhler, 1940], existentialists [Merleau-Ponty, 1945] and enactionists [Clark, 1996], however without benefit of nonlinear brain dynamics. Only in recent years have developments in dynamics and field theory provided the concepts required to model large-scale neural activity: scale-free dynamics [Breakspear, 2004;Chen and Shi, 2004;Freeman, 2006aFreeman, , 2006b], circular causality [Haken, 1983], stabilization of brains in pseudoequilibrium at self-organized criticality [Jensen, 1998], dissipative structures forming by phase transitions far from thermodynamic equilibrium [Prigogine, 1980], anomalous dispersion in the dissemination of phase transitions [Freeman, 2000], extensions of random graph theory into 'neuropercolation' [Kozma et al, 2005], and repetitive destabilization of cortical dynamics in spontaneous symmetry breaking as described in many-body physics Vitiello, 2006, 2007].…”

Comparison of spectral analysis methods for characterizing brain oscillations

“…This method of background estimation was introduced in Schiff et al (1994), but alternative background epochs could be used (e.g., time spent looking at a fixation cross before the task starts). This background is then fit with a linear function in log-log space, in accordance with the theoretical 1/f α power spectrum that EEG is thought to have (Freeman, 2006). This procedure will remove the frequency bias (higher power at lower frequencies).…”

New Issue to Modeling Intentionality in the Field of Consciousness

“…He started with the distinction of Heisenberg between potential and actual event. In Heisenberg, the notion of actual is related to measured events in the sense of the Copenhagen interpretation of the quantum physics 3 , whereas the notion of potential, of tendency, relates to the situation before measurements or expresses the idea of a reality independent of measurements. In the theory of Stapp, immediately after its actualization, each event holds the tendency for the impeding actualization of another subsequent actual event.…”

“…Today, a new issue is emerging to explain intentionality. It is based on three main approaches: the "intentional arc" and the "maximum grip" proposed in the philosophy of Maurice Merleau-Ponty [2]; the reflex stimulus-response arc developed in the neurophysiological and quantum theory of Walter Freeman [3]; and the quantum systems of dual modes conceived by Giuseppe Vitiello [4] [5] and Gordon Globus [6] on the basis of thermofield (dissipation) quantum principles. My purpose is to provide a review of these contemporary dynamic models.…”