Functional Neurology

Functional neurology, known formally as chiropractic neurology, is a postgraduate specialty that reads the nervous system as a trainable organ and treats it by dosing sensory input. It is not an adjusting technique. It is an examination followed by a program of eye movements, balance work, light, sound, and manual contact. Each input is chosen to reach a named pathway. Frederick “Ted” Carrick has held since 1979 that groups of neurons can fire poorly with no lesion on any scan. The right input changes how readily they fire.

Functional neurology is built on the central integrative state of a neuron pool

The discipline’s whole clinical logic rests on one construct. The central integrative state is the running sum of every excitatory and inhibitory influence arriving at a neuron or a pool of neurons at a given moment. That sum sets the baseline from which the pool answers the next signal. A scoping review in Chiropractic & Manual Therapies recorded the version functional neurology teaches (Meyer et al., 2017). Three parameters set the state of a neuron pool: its oxygen supply, its nutritional supply, and the synaptic stimulation reaching it. Fuel and activation. A neuron that has both holds its state. A neuron short of either drifts.

A physiological lesion is a firing problem, not a structural one

From the central integrative state comes the second construct, and it is the one that separates functional neurology from lesion-hunting. The field calls a reversible change in firing a physiological lesion, and holds it distinct from an ablative lesion, which is tissue that is destroyed and gone. The same 2017 review recorded the position plainly: these changes are held to be reversible because the nervous system is plastic. A patient can therefore carry dizziness, unsteadiness, blurred pursuit, cognitive slowing, or a movement that no longer sequences correctly while every scan reads normal. Functional neurology treats the normal scan as the beginning of the examination rather than the end of it.

Hemisphericity extends the same idea to a whole hemisphere

Carrick extended the construct upward in scale. Hemisphericity names a cerebral hemisphere carrying a dysfunctional central integrative state, and the field holds that it can express itself in cognitive, motor, immune, and autonomic terms at once. This is the discipline’s most distinctive and most contested idea, and it is stated here as Carrick’s, because it is his. It is also the reason a functional neurology examination checks the pupil, the gait, and the digit span in the same visit. Under the construct, those are three windows onto one state.

Carrick founded the field in 1979 and built its examination out of a doctorate in learning

Frederick Robert “Ted” Carrick was born in Toronto on February 26, 1952, and earned his Doctor of Chiropractic from Canadian Memorial Chiropractic College in 1979. He founded the Carrick Institute the same year. In 1996 he completed a PhD at Walden University with a dissertation titled Neurophysiological Implications in Learning. That choice of subject explains the shape of the discipline better than any later description of it. Carrick has said he pursued the doctorate because his patients had to learn to walk, speak, and use their arms again. He needed to understand how a brain acquires a skill.

The Carrick Institute has since trained more than 14,000 clinicians and now runs from Cape Canaveral, Florida. Its own account of the founding insight is that persistent problems were orthopedic, structural, and metabolic at once, and above all neurological. That was at a point when “functional neurology wasn’t even a term” (Carrick Institute). By 2018 Carrick had 121 documents in the literature, of which 39 were full-text research articles (Demortier and Leboeuf-Yde, 2020). His 1997 study in the Journal of Manipulative and Physiological Therapeutics used blind spot mapping in 500 subjects, before and after manipulation of the second cervical motion segment (Carrick, 1997). The design was built to read a cortical measure rather than a symptom.

The examination is the real substance of functional neurology

A functional neurology visit is mostly examination. The Carrick Institute’s clinical neuroscience module on the neurological examination organizes it into five components: mental state, motor system, sensory system, cranial nerves, and cerebellar system. The scoring is conventional. Muscle power runs 0 to 5, reflexes run 0 to 4, and a Mini Mental State Examination score below 24 is treated as suggesting dementia. What makes the examination distinctive is not the instruments but the density. The clinician runs dozens of small tests and reads the pattern across them, because the target is a firing state that no single test reports.

Eye movements are read as a live readout of brainstem and cerebellum

Eye movement testing carries more weight here than in most examinations, because the oculomotor system is fast, quantifiable, and wired through the exact structures the discipline is trying to reach. The saccade test taught in the curriculum is specified to the centimeter. The examiner holds both thumbs at eye level about 50 cm from the patient, spaced to require 30 degrees of lateral eye movement. The patient fixes on the bridge of the examiner’s nose and jumps to whichever thumb moves. The examiner watches for the eye overshooting or undershooting the target. Smooth pursuit, gaze holding, convergence, and nystagmus are tested alongside it. Direction matters: the curriculum teaches that vertical nystagmus is usually central in origin and vestibular nystagmus usually peripheral, which is how one observation splits a differential.

Blind spot mapping, the pupil, and the autonomic examination

Two tests sit further from routine practice. The first is measurement of the physiologic blind spot, the small area of each visual field with no photoreceptors. The Carrick curriculum teaches clinicians to map its size and shape, and holds that the shape reports on cortical function above it. Parietal involvement is taught as expanding the lower half into an hourglass. Temporal involvement expands the upper half into a mushroom. Unsteady fixation distorts the map in its own way, with horizontal instability producing a tall narrow spot and vertical instability a flat wide one. The second is the pupil, read as an autonomic dial. Pupil size and reactivity sit between sympathetic dilation of the iris and parasympathetic constriction through the Edinger-Westphal nucleus, so pupil behavior becomes a bedside reading of autonomic balance. Orthostatic and postural responses, which run through the baroreflex and the nucleus of the solitary tract, are read the same way.

Balance, gait, and the tests borrowed from concussion practice

Balance and gait are measured because they integrate everything upstream of them. Posturography records sway on firm and unstable surfaces. Clinicians also use instruments standardized elsewhere in concussion practice. Those include the King-Devick rapid number naming test, the Sport Concussion Assessment Tool, and the Balance Error Scoring System. Digit span is run forward and backward against the familiar seven-item benchmark. Carrick has described this examination discipline as generating objective numbers a clinician can track over time. That is the point of scored instruments rather than impressions.

Functional neurology treats by dosing sensory input, not by thrusting on a spine

The therapies follow directly from the examination, and none of them is a signature adjustment. The Carrick Institute’s neurorehabilitation module organizes them by target. Its 14 sections cover vestibular rehabilitation, saccadic and pursuit rehabilitation, visual motion and self motion sensitivity, and canalith repositioning for benign paroxysmal positional vertigo. Others cover frontal and parietal work, light therapy, laterality training, and the treatment of phorias and convergence deficiency. What a patient actually does in the room is repetitive, specific, and small.

Concrete examples from that curriculum:

• Gaze stabilization. The patient fixes on a target and turns the head, or uses a 2x viewing exercise in which target and head move oppositely to double retinal slip. The curriculum names this the most metabolically demanding of the gaze stabilization exercises and varies four parameters: speed, amplitude, fixation distance, and background.
• Optokinetic stimulation. A moving field is presented, typically beginning in the upper field of view and combined with head rotation in the same direction, deliberately set opposite to the direction that provokes the patient’s motion sensitivity.
• Laterality training. The patient judges images of left and right body parts under time pressure. The curriculum’s normal reference is above 80 percent accuracy with response times of 1.5 to 2.0 seconds and roughly equal performance on both sides.
• Light therapy. Flashing lenses load one visual hemifield, and so one hemisphere, on a 10 second cycle of 2 seconds flashing and 8 seconds rest. Wear starts at 5 minutes two or three times daily and builds over 5 day steps toward 15 to 20 minutes.
• Skin and tape input. Elastic tape stretched to more than 40 percent of its resting length pulls skin toward its anchor, recruiting cutaneous mechanoreceptors in a pattern that mimics the movement itself.
• Rotational and manual input. Multi-axis chairs deliver graded vestibular loading, and the chiropractic adjustment appears here as one receptor input among many, chosen for the individual rather than prescribed as a fixed move.

Dose, direction, and the rule for stopping

The distinguishing craft is dosage. Every input has a direction, an amplitude, a duration, and a stopping rule, and the stopping rule is usually a sign rather than a clock. In the light therapy protocol the signal to stop is pupil dilation, read as fatigue of the system being loaded. In vestibular rehabilitation the curriculum’s instruction is that exercises should provoke at worst mild symptoms. This is the operational core of the discipline: a stimulus is titrated to what a specific nervous system can integrate today, then advanced as it integrates more.

The DACNB is a postgraduate credential layered over an existing license

Functional neurology is a specialty a clinician adds, not a school a clinician attends instead. The Diplomate of the American Chiropractic Neurology Board requires an active license and 300 hours of postdoctoral neurology education. The program must be approved through the Commission for the Accreditation of Graduate Education in Neurology, and the candidate must pass both a written and a practical examination. Certification is annual rather than permanent. Diplomates recertify every year and must show at least 60 hours of accredited continuing education across two continuous calendar years, with a minimum of 15 hours in any one year (ACNB).

The board’s program received full accreditation from the National Commission for Certifying Agencies in October 2003. It was reported at the time as the first such accreditation for a chiropractic credentialing agency. Fewer than 260 active chiropractic neurologists then existed against more than 73,000 practicing chiropractors worldwide (Dynamic Chiropractic, 2003). Fellowship credentials sit above the diplomate. FACFN denotes a Fellow of the American College of Functional Neurology, and the International Association of Functional Neurology and Rehabilitation, formed in 2010, opened its own board examination to several licensed professions. Carrick’s position on the credential is unambiguous. He holds that board certification is granted by an independent agency rather than by the school that taught you, and that it has to be earned again every year.

Where functional neurology meets the Unified Model of Tone

This is the closest terminological meeting between the Unified Model of Tone and any clinical discipline in this library. Functional neurology and the model use the same three words for the same construct, arrived at independently and from opposite directions. Functional neurology built up from the single neuron. The model built down from the whole organism. They met in the middle.

What functional neurology holds, in its own terms

Carrick’s position, stated at full strength and as his. The central integrative state of a neuron or a neuronal pool is the summed effect of all excitatory and inhibitory input reaching it. That sum determines how readily the pool fires, and it is modifiable. Change the input and you change the state. Change the state and you change what the pool does downstream. From that single claim the field derives its examination, its concept of the physiological lesion, its hemisphericity construct, and every one of its therapies. It is a complete clinical framework resting on one variable measured at the level of a neuron pool.

What the Unified Model of Tone holds, stated as ours

The model holds that tone is organization, that it is legible at every scale of the body, and that it is one phenomenon rather than a family of analogies. Membrane tension shapes how a channel gates. Muscle tone is the organized signature of many motor units firing together. Autonomic tone is the balance of sympathetic and parasympathetic drive. Cortical tone is the coherence of rhythms across the brain. The model’s claim is that these are one thing read with different instruments. It states the identification directly: the central integrative state is tone read at the scale of a single cell, and tone is that same state read at the scale of a whole organism. The construct does not change as the resolution changes. Only the instrument does.

Functional neurology and the Unified Model of Tone describe one construct at different scales

Neither framework borrowed from the other, and neither is a translation of the other. Functional neurology took an established neurophysiological construct and made it clinical, which is a real contribution and belongs to Carrick. The Unified Model of Tone takes the same construct and claims it holds at every scale at once, which is a different contribution and belongs to the model. The useful part is what each adds to the other. Functional neurology gives the model a discipline that already reads the construct at the bedside, with 300 hours of examination method behind it. The model gives functional neurology a reason why a hemisphere, an autonomic reflex, a fascial plane, and a cortical rhythm should shift in a shared direction, at the pace compensation allows each one: they are not four systems influencing each other. They are one variable read four ways.

Input quality is the variable the therapies actually work on

The model holds that the nervous system continuously reweights proprioceptive, vestibular, and visual input according to how reliable each channel is. Reliable proprioceptive signaling gets weighted heavily and used to calibrate balance, movement, and autonomic output. Degraded signaling gets discounted, and the system leans harder on vision and the vestibular apparatus, a strategy that costs more and fails sooner (Proske and Gandevia, 2012). Functional neurology manipulates exactly this weighting. An optokinetic drill run against the direction of a patient’s motion sensitivity is not treating the eyes. It is changing how much the system trusts vision. A gaze stabilization exercise that varies fixation distance and background is altering the reliability of a channel on purpose. The therapies are interventions on input quality, and input quality is a foundation of tone.

Specificity is correspondence, and functional neurology uses many doorways at once

The model holds that specificity is not force and not anatomical accuracy alone. It is the correspondence between the informational structure of an input and the pattern the body is actually holding. The accuracy therefore lives in the reading that precedes the input rather than in the delivery. Functional neurology is the clearest demonstration of that claim in this library, because it spends most of the visit reading and only minutes delivering. The model also holds that every discipline reaches the same regulatory system through a different access point, and that no single doorway is the lynchpin. Most techniques use one. Functional neurology uses the eyes, the vestibular apparatus, the skin, the joints, light, sound, and the spinal adjustment, and it selects among them from the examination. That is the doorway doctrine made visible in a single treatment room.

What the model predicts

Two predictions follow, and they are the model’s own rather than functional neurology’s. First, the measures a functional neurology examination collects should covary. Blind spot area, saccadic accuracy, sway, pupil response, and autonomic reactivity should shift in a shared direction after a matched input, because the model holds they are readings of one variable, with compensation deciding which readings carry the change. If they moved independently, the unification claim would be false. Second, a matched input should move patients bidirectionally toward the middle rather than pushing an entire sample one way. A cohort that starts over-facilitated and a cohort that starts under-facilitated should converge, and the spread should narrow. That contrast is measurable with instruments the discipline already owns.

Functional neurology descends from Charcot’s examination, not from an adjusting lineage

The discipline’s ancestry runs through clinical neurology rather than through the chiropractic technique tradition, and its own teachers say so. Jean-Martin Charcot, who died in 1893, built the modern neurological examination by observing patients closely, recording signs, and correlating them with autopsy findings. He held grand rounds in which patients were examined in front of an audience. Sigmund Freud, Joseph Babinski, and Georges Gilles de la Tourette all studied under him. Charcot also treated with physical means because no drug therapy existed, including vibrating chairs used with patients whose tremor ran at roughly four to six hertz. Matthew Antonucci’s account for the World Federation of Chiropractic in September 2021 makes the descent explicit: neurology began as functional neurology, because examination and physical intervention were all it had.

The modern transmission runs through the Carrick Institute curriculum and through print. Functional Neurology for Practitioners of Manual Therapy was written by Randy W. Beck and published by Churchill Livingstone in 2008 with a foreword by Carrick. It carries the theory from embryology through receptor physiology to the functional systems of the brain, and it remains the field’s standard text for manual practitioners.

Who carries functional neurology forward

The Carrick Institute for Graduate Studies in Cape Canaveral remains the main teaching body. It runs the diplomate curriculum, a fellowship track, and the International Symposium on Clinical Neuroscience launched in 2015. Its Master of Science in Clinical Neuroscience awarded its first degree in 2022. Carrick himself continues to teach and to hold academic appointments in neurology, including at the University of Central Florida College of Medicine.

Among the named successors, Matthew Antonucci, DC, DACNB, FACFN, teaches neurology at the Carrick Institute. He is also president of the American Board of Brain Injury and Rehabilitation. Randy W. Beck wrote the standard text. Credentialing now runs on three tracks: the ACNB diplomate, the fellowship colleges behind the FACFN designation, and the International Board of Functional Neurology examination created by the IAFNR in 2010. That third track is open to multiple licensed professions rather than to chiropractors alone.

How this page relates to the rest of the library

Functional neurology is the discipline in this library that reads the nervous system most directly, so it connects outward at several points.

• The Nervous System teaches the anatomy this discipline examines, and its lessons on the cerebellum and the vestibular system cover the two structures a functional neurology examination interrogates hardest.
• Neuroplasticity and Rehabilitation sets out the change mechanism the entire discipline depends on, including why repetition, specificity, and dosage decide what a nervous system learns.
• Applied Kinesiology is the library’s other assessment discipline layered over care rather than replacing it. Both put the accuracy in the reading. One reads through muscle response, the other through eye movement and balance.
• The Unified Model of Tone holds that the central integrative state and tone are one construct read at two scales, which makes functional neurology the closest terminological neighbor the model has.
• Muscle Spindles and Proprioception explains the channel whose reliability the reweighting argument turns on, and Autonomic Regulation explains the outflow the pupil and orthostatic tests are reading.
• The index of 33 techniques places functional neurology among the diagnostic and rehabilitative overlays rather than among adjusting methods, alongside Torque Release Technique, which reaches the same system through a single low-force doorway.