Chaotic Oscillations and the Genesis of Meaning in Cerebral Cortex

Abstract

Single neurons generate action potentials that express their output in pulse frequencies, so that sensory stimuli can be microscopically expressed as spatial patterns of phase-locked firing of “feature detector” neurons. The visual, auditory, somatic, and olfactory cortices generate dendritic potentials that oscillate at frequencies from 1-100 Hz. These waves reveal macroscopic activity arising from synaptic interactions of millions of neurons. They share a spatially coherent oscillation as a “carrier,” by which spatial patterns of amplitude modulation (AM) are transmitted in distinctive configurations, when subjects receive sensory stimuli they have learned to discriminate. These spatial AM patterns are unique to each subject, are not invariant with respect to stimuli, and cannot be derived from the stimuli by logical operations. The carrier is aperiodic, usually dispersed over a wide spectral range. Our simulations of the carrier indicate that its dynamics is chaotic, and that sequential patterns are freshly constructed during perception, because chaotic systems can create as well as destroy information. The entire experience of a subject, which is embedded in synaptic connections in cortex that were modified during learning, can be brought instantly to bear at each state transition by which a new construction is initiated. It is suggested that “feature binding” revealed by microscopic recording is related to the formation of a “chaotic construct” early in the process of perception.