Neuroelectric Tuning of Cortical Oscillations by Apical Dendrites in Loop Circuits.

Bundles of relatively long apical dendrites dominate the neurons that make up the thickness of the cerebral cortex. It is proposed that a major function of the apical dendrite is to produce sustained oscillations at a specific frequency that can serve as a common timing unit for the processing of information in circuits connected to that apical dendrite. Many layer 5 and 6 pyramidal neurons are connected to thalamic neurons in loop circuits.

The cognitive significance of resonating neurons in the cerebral cortex.

Most neural fibers of the cerebral cortex engage in electric signaling, but one particular fiber, the apical dendrite of the pyramidal neuron, specializes in electric resonating. This dendrite extends upward from somas of pyramidal neurons, the most numerous neurons of the cortex. The apical dendrite is embedded in a recurrent corticothalamic circuit that induces surges of electric current to move repeatedly down the dendrite.

Theory of electric resonance in the neocortical apical dendrite.

Pyramidal neurons of the neocortex display a wide range of synchronous EEG rhythms, which arise from electric activity along the apical dendrites of neocortical pyramidal neurons. Here we present a theoretical description of oscillation frequency profiles along apical dendrites which exhibit resonance frequencies in the range of 10 to 100 Hz. The apical dendrite is modeled as a leaky coaxial cable coated with a dielectric, in which a series of compartments act as coupled electric circuits that gradually narrow the resonance profile.

The apical dendrite theory of consciousness.

The neural basis of consciousness is theorized here to be the elevated activity of the apical dendrite within a thalamocortical circuit. Both the anatomical and functional properties of these two brain structures are examined within the general context of the cortical minicolumn, which is regarded as the functional unit of the cerebral cortex. Two main circuits of the minicolumn are described: the axis circuit, which sustains activity for extended durations and produces our sensory impressions, and the shell circuit, which performs input-output processing and produces identifications, categorizations, and ideas.