FoundationalConceptsNeuroscience

All these cells and sub-cellular structures are replete with flowing
charged particles and are generating electromagnetic fields—fields
that influence the activity of nearby neurons. These electric fields are
called local field potentials, and their influence on nearby neurons is
known as ephaptic coupling (Greek ep = near, haptein = touch). Chem-
ical synapses, electrical synapses, local field potentials, and ephaptic
coupling—neuropil is an electrodynamic structure of extraordinary
complexity. The various oscillations recorded in electroencephalog-
raphy (EEG) and electrocorticography, from slow delta oscillations to
high-frequency synchrony at greater than 100 Hz, reflect the sym-
phony of complex interactions in the neuropil. This high density of
constant activity is responsible for most of the energy consumption
of the brain—the “dark energy” of cellular activity that is going, going,
going, all the time. This activity is modulated and perturbed by sig-
nals entering the brain via pathways from the various sensory organs.
Brains embody structural and functional complexity that has been
honed over hundreds of millions of years of evolutionary experimen-
tation and refinement. The notion that we will be able to figure out
the human brain by mapping the locations of all the cells and all of
their connections, and perhaps even construct a kind of replica using
integrated circuits, vastly underestimates the nuance and complexity
of what is going on. That’s not to say that great progress can, will, and
is being made in understanding the structure and operation of brains,
and many different approaches are contributing to this progress.
Nonetheless, what is going on within the unfathomable complexity
of neuropil, while intuitively graspable, is beyond detailed description
within of our current understanding of neurophysiology.
What has come to be called the field of neurodynamics is an en-
deavor to describe these processes involving large numbers of neurons
and their interactions. EEG is used to measure the collective electro-