Every spike in a biological brain neuron has nearly the same shape, so information is carried in timing and pattern rather than in amplitude. In modern research, twenty firing behaviours were catalogued that were recorded from real cortical cells and showed that one two-variable model reproduces them by changing a few parameters — evidence that neuronal diversity reflects a small number of dynamical structures rather than twenty separate mechanisms.
Biological brain neurons are living information-processing cells that receives thousands of inputs, integrate them through nonlinear internal dynamics, and decide whether to emit an action potential. Unlike an electronic transistor it has memory, feedback, several time constants, and a threshold that moves with recent history, so its response depends on its own state as much as on the stimulus.
These neurons behaviours form a computational vocabulary. Some cells report sustained magnitude; some subtract anything constant, through adaptation and accommodation; some report only edges; some prefer a rhythm; some accumulate regardless of rhythm; and some hold or switch between stable operating regimes. For example, when we consider how the interaction with a group of devices in our surroundings — a lamp, a LED tv screen, an air conditioner, a phone — reach the nervous system, we get mixed results.
Ranking those four by proximity inverts almost completely against ranking them by dynamical compatibility: the nearest object dominates for reasons unrelated to its distance, the furthest is effectively at zero distance because it acts through a well-mixed medium, and the physical quantity that falls off most steeply with range has no coupling coefficients.
However, the outside world does not reach neurons as fields. Sensory receptors cancel the external signal at the periphery and replace it with spike trains that cross the skull through legitimate foramina, so what a neuron receives is synaptic current, not a stimulus.
This is why light, sound and warmth matter and why ambient radio-frequency fields might not reach inside the skull: The distinction is not strength but access — sensing is a designed transduction chain with gain; field coupling is unassisted physics.
Meaning the failure is structural rather than quantitative: no plausible increase in transmitted power opens a channel that has no transducer, no impedance match, and no aperture at the end of it.
In addition, communication between the brain and its environment is fundamentally bidirectional. External stimuli travel through sensory organs into the brain, while extensive descending pathways continuously regulate the sensitivity of those same sensory organs.
Corticothalamic projections control sensory relay through the thalamus, the olivocochlear bundle adjusts cochlear amplification, descending spinal pathways regulate touch, cortical feedback modulates olfactory processing, and pupil diameter controls retinal illumination.
Perception is therefore an actively controlled feedback loop rather than passive reception, which means that identical external stimuli can evoke different neuronal responses depending on the brain's current operating state.
So, when large populations of neurons fire synchronously, for example, they also generate electric and magnetic fields that extend beyond the skull. These currents produce the microvolt scalp potentials measured by electroencephalography (EEG) and the faint magnetic fields detected by magnetoencephalography (MEG).
The signals become larger as neuronal synchronization increases, such as during sleep rhythms, but they remain extraordinarily weak because of current cancellation within the cortex, attenuation by the skull, and rapid decay with distance.
Consequently, these passive electromagnetic fields can be detected only by specialized scientific and medical instruments and may have little no effect ordinary electronic devices. The brain influences the outside world primarily through designed biological output pathways rather than electromagnetic radiation.
Neural activity is converted into speech, eye movements, facial expressions, limb motion, autonomic regulation, breathing, heart rate, pupil size, and hormonal secretion. These outputs are many orders of magnitude stronger than the faint electromagnetic fields leaking through the skull and represent the intended communication channels of the nervous system.
Within this framework, the twenty neuronal firing behaviours explain how sensory information is transformed into perception and behaviour. Different neuronal populations selectively encode sustained signals, reject constant backgrounds, detect changes, analyze temporal patterns, integrate evidence, or regulate transitions between wakefulness, sleep, and attention.
Their synchronized activity produces measurable but extremely weak external electromagnetic signatures, while their principal influence on the environment occurs through coordinated physiological and behavioral outputs, as stated above.
The nervous system should therefore be understood as a closed-loop dynamical system: sensory organs convert the external world into neural signals, neuronal networks in the brain process those signals according to their computational specialization, descending feedback continuously adjusts sensory gain, and motor and autonomic outputs act back on the environment, completing a fundamentally bidirectional interaction between the brain and world.
Figure: In each panel the coloured trace is the neuron's membrane voltage over time — the vertical axis runs from about −90 mV at rest to the +30 mV peak of a spike, so each sharp upstroke is one action potential — and the grey trace beneath is the current being injected into the cell, drawn on the same time axis so the response can be read directly against its stimulus; scale bars give the duration, and no vertical scale is marked because only the shape of each response matters, not its exact amplitude. (After Izhikevich, IEEE TNN 15(5):1063–1070, 2004.)
Disclaimer. Sensory pathways have safe exposure limits, set to protect the receptors, that should not be exceeded. Neuronal firing is not driven directly by external fields and may not scale with input power; but the pathway is a closed loop under descending control, so response depends on the state of the system, not on the stimulus alone. This is a note on biology application, not a safety assessment.
