Glossary of Scientific Terms

This post contains a glossary of some of the relevant scientific terminology for Alexander Technique and science with links to relevant articles and websites.

AccelerationChange in speed or velocity. Caused by an imbalance in forces.
Adaptable toneMuscle tone that changes its distribution automatically when position is changed. This occurs when muscles automatically reduce their tone/tonic activity when they are stretched so that they “let go” and increase their activity when they are shortened so that they “take up the slack”.
Alien hand syndrome A neurological disorder characterized by the loss of control or agency of one’s arm. For instance, the accredited arm may reach out to grab objects automatically. Sometimes patients have to use their unaffected arm to prevent unintended actions by physically wrestling with it. Alien hand syndrome can be caused by damage to pre-SMA which contributes to executive inhibitory control.
Anticipatory postural adjustment (APA)A planned postural correction that occurs before a disturbance. This occurs when the brain predicts a disturbance and stabilizes in advance. This is in contrast to a postural reaction where the brain detects and then reacts to a disturbance. APAs can be phasic or tonic and commonly occur before a movement takes place, for example, stabilising the legs and back before pulling on a heavy door that would otherwise pull the body forward.
AttentionIncreased brain monitoring of a specific spatial region, sensory input or neurological process. This can occur without awareness.
AwarenessA conscious registration of a stimulus or mental process.
AxonThe output portion of a neuron. It consists of a long thin tube that conducts impulses to signal other neurons. Axons are sometimes covered in myelin to increase the speed that impulses travel. Many axons bunched together are called a nerve.
BalanceThe behaviour concerned with preventing the body from toppling over due to gravity by keeping the centre of mass of the whole body above the base of support. More strictly, this requires the center of mass to be above the centre of pressure within the base of support.
Basal gangliaA collection of nuclei that form a loop through the cortex concerned with the initiation of actions. Parkinson’s disease damages one of these nuclei causing, among other things, difficulty initiating actions and slow movement.
Basic researchResearch aimed at understanding the mechanism of phenomena. In the biological sciences basic research is generally performed by different researchers, using different types of studies and published different journals than clinical research.
Body imagePerceptions attitudes and beliefs concerning one’s body. Unlike body schema this is not directly involved in the control over action.
Body Map.A colloquial term used to refer to the application of the study of anatomy on the AT. This term does not have a specific scientific meaning like body image and body schema.
Body schema A central representation of the body in the brain that is in some sense independent of sensory input. People experience phantom limbs after amputation because their body scheme still registers the missing limb even though there is no sensory input from it. The body schema is directly used for motor control.
BrainstemThe region just above the spinal cord that consists of the medulla, pons and midbrain and controls many automatic behaviours including muscle tone, breathing, and coughing. The brainstem is difficult to study in part because of its relatively inaccessible position deep within the brain.
CamptocormiaA disorder where the spine bends forward when standing upright, sometimes known as “bent spine syndrome“. There are many possible causes of camptocormia including Parkinson’s disease and weakness.
Central parent generator (CPG)A collection of interconnected neurons that generates the basic timing for a rhythmic motor behaviour. For instance there is a central pattern generator for walking in the spinal-cord and central pattern generators for breathing and chewing in the brainstem.
Centre of gravityLike the centre of mass except in a gravitational field.
Centre of massThe midpoint of the mass of a body, which is where the body would balance if supported from below. The centre of mass is not a fixed point and changes as the body changes shape. In fact it can lie outside the body. The centre of mass of the human body is often around the pelvis.
Centre of pressureThe midpoint of the pressure exerted by the floor on the region of contact. The centre of pressure for each foot lies somewhere within the foot’s boundary and can be moved through muscular action. For instance, contracting calf muscles pushes the toes down and moves the centre of mass towards the front of the foot.
CerebellumA structure protruding out the back of the brain that acts tune feedforward motor programs based on sensory error. For instance, consistent reaching to the left of a target will cause the cerebellum to tune the movement program to the right.
Clinical researchMedical research dealing with health, ailments or conditions. Clinical research differs from basic research and uses mechanisms such as randomised control trials.
CocontractionActivating muscles on both sides of a joint. As the forces are counterbalanced there is no movement but the joint becomes stiffer.
Cognitive flexibilityAn executive function concerned with flexibly altering actions or thoughts in non habitual ways.
Complex systemA system where there are many interconnected parts in parallel.  Typically it has elements of feedback, nonlinear behavior, and spontaneous organization.  A computer by this definition is not a complex system as the working is such that it executes one instruction at a time in a predictable, serial fashion.
Concentric contractionA contraction of muscle where the muscle shortens when activated. This occurs when the muscle force is greater than the forces opposing it.
Connective tissueOne of various types of noncontractile tissues that adheres across body organs. Is it typically compliant (ie not stiff) and doesn’t generate substantial force. An example of connective-tissue is the fascia surrounding muscle.
ConsciousnessAwareness of one’s body and environment. The neurological basis of this is not understood currently.
Contact forceA force that is generated through physical contact between two bodies. Contact actually generates two forces that are equal and opposite to one another, according to Newton’s third law. For instance, jumping off a rowboat produces a force that propels you forward and another that propels the rowboat backwards.
Corticospinal excitabilityA state of readiness in the motor cortex and spinal cord. It is often measured by stimulating a specific area of motor cortex with TMS and measuring the resulting twitch in muscle.
Craneo cervical flexion testA validated test for assessing the use of deep neck flexors vs superficial neck flexors (sternocleidomastoid).
DecerebrateRemoval of the brain’s higher centres. This used to be used for eliminating voluntary behaviour and exaggerating muscle tone. It is difficult to interpret how observations in decerebrate animals relate to normal animals.
DendriteThe part of the neuron that receives input from other neurons.
Eccentric contractionAn activation of muscle as it lengthens from external forces that exceed the muscle’s force. Eccentric contractions are used to slow or break an action.
EEGElectroencephalography. Measurement of brain activity with electrodes. It has the advantage over fMRI in that it measures quickly changing neural activity but has poor spatial resolution.
ElasticityThe ability of a material to resume its original shape after being stretched.
Electromyography (EMG)Measurement of muscle activity with electrodes. At the present time it is only possible to measure a limited number of muscles. While it is difficult to determine a muscle’s absolute activity, EMGs clearly indicate changes in activity.
Executive attentionThe process concerned with controlling attention at will as opposed to being drawn to something in the environment. Sometimes executive attention is considered an executive function.
Executive functionA set of cognitive processes that act at the highest level to flexibly control and monitor behaviour. These include working memory, executive inhibition, cognitive flexibility and sometimes executive attention.
Executive inhibitionAn executive function which is responsible for stopping the initiation of undesired automatic actions and thoughts.
External forceForces that act between the body and external objects. The two types of external forces are contact forces and gravitational force.
FasciaA type of connective tissue that encloses muscle and other organs. In most cases it is very thin and does not exert much force.
FeedbackMonitoring the result to tune control in real time. An example would be moving a mouse to point the cursor to a very small button.
FeedforwardA pre-planned action that doesn’t use feedback but merely executes without adjusting the plan.
fMRIFunctional magnetic resonance imaging. Different from a regular MRI in that it detects neural activity in the brain as opposed to tissue composition.
ForceAn interaction between two bodies to push or pull. Forces occur in equal and opposite pairs, one acting on each body. For instance pushing on a wall exerts a force on the wall and the wall exerts an equal and opposite force on your hand.
Force plateEquipment that measures the ground reaction force. A scale is a simple force plate however it only measures the vertical force and often very slowly.
Galvanic skin responseA change in the electrical resistance of the skin caused by emotional stress and effort.
GazeThe period when are eyes are fixed on a target.
Global inhibitionA form of executive inhibition that aims to prevent any action.
Ground reaction forceThe external contact force between a body and the ground, typically occurring under the feet.
Guy wireA diagonally oriented wire that acts to stabilise a mast or radio tower through tension.
Head forward postureForward posture of the head where it is carried in front of the body and the neck is inclined forward. Back and down in Alexander terminology.
Ideomotor theoryA theory that actions are represented in the brain by their perceivable effects. For instance, if you push a key that generates a sound the theory would suggest that the action is triggered by the thought of the sound itself, rather than the desire to produce the sound by pressing the key. This theory is not the same as the observation that thought affects action, of which there are countless examples of in modern neuroscience. Instead, Ideomotor theory surmises that the thought of the sensation in the end state itself triggers the plan. Ideomotor theory exists within the field of psychology and is not explored in modern neuroscience or motor control. Some researchers have recently considered it as unfalsifiable.
InertiaThe resistance of an object to changes in motion. The greater an object’s mass the greater its inertia.
Internal forceA force that occurs within the body. Muscular and ligamental forces are internal forces.
Internal modelThe representation within the brain of an object or process. For example, you have an internal model within your brain of how a car drives. The internal model of the body in space is called the body schema.
InterneuronA neuron that is neither a sensory or motor neuron, and therefore in the middle of a neuronal circuit. Most neurons in the brain by far are interneurons.
Isometric contractionMuscular activation that occurs without a change in position. Isometric contractions occur because the contractile force from activating muscle is exactly counterbalanced by an external force.
KinaesthesiaThe senses that signal body motion (as opposed to position). It can be assessed by one’s threshold to detect motion of a joint.
Kinetic chainA series of body segments linked to one after the other in a chain. Kinetic refers to forces being transmitted across the chain.
Kohnstamm phenomenonThe most typical example of this phenomenon on is pushing your arms against the wall or doorway and having them rise involuntarily afterwords.
Ligamentous spineThe spine with only ligaments attached.
LurchThe speeding up of forward motion when leaving the chair. This is accompanied by a fast weighting of the feet just before a lift off.
Magnus reflexA reflex that occurs when turning or flexing and extending the head. There are two types: the asymmetric tonic neck reflex where the limb in the direction of the head turn is flexed and the opposite extended, and the symmetric tonic neck reflex where both limbs are flexed when the head is flexed and both limbs are extended when the neck is extended. These reactions only minimally occur in healthy adults but are pronounced with brain damage or in infants.
MassQuantity of matter.
MatchingThe ability to oppose an external force precisely to maintain body position or only change it very slowly. The game of push hands in Tai Chi is an example of matching.
Millisecond (ms)1/1000 of a second.
Mirror neuronNeurons in the brain that are active both in action planning and action observation. For example, some mirror neurons are active when you perform a certain gesture or observe someone else performing it.
MomentumThe tendency of an object to continue in motion. Momentum increases with both greater speed and greater mass.
Motor controlThe field of science that studies the control of muscular activity. There is a large overlap of motor control with biomechanics and neuroscience.
Motor cortexThe part of cortex that is concerned with regulating muscular activity. Much of motor cortex is devoted to planning volitional movements.
Motor neuronNeurons that are directly connected to and activate muscle. For most muscles these occur in the spinal-cord.
MovementChange in position. Requires an imbalance of forces to cause acceleration and deceleration.
Muscle activityMuscle activity is produced thorough impulses from motor neurons and acts to shorten the muscle. However, the muscle will not actually shorten if opposed external forces, such as with eccentric or isometric contractions.
Muscle toneUnconscious tonic activation of muscle. This persistent activation results in an ongoing state of muscle tension. While clenching your fist tonically activates muscle it is not considered muscle tone because this is conscious.
NerveA bundle of many axons from motoneurons and/or sensory neurons carrying information from the nervous system to muscles or sensory information to the nervous system, respectively.
Neural inhibitionA process where a single neuron acts to reduce firing in another neuron. Not to be confused with executive inhibition.
Neural integratorA group of neurons that turns brief transient (ie phasic) input  into sustained (ie tonic) output.
NeuronA cell that is electrically active and can signal other neurons. Neurons are interconnected in circuits which perform specific functions. A neuronal system generally consists of a group of circuits.
NeuroscienceA fairly recent collective term uniting all the brain sciences, which used to be separately classified as neuroanatomy, neurophysiology, psychology, etc.
Newton’s third lawThe law that action has an equal and opposite reaction. If you jump off a boat there is a force applied by you to the boat while the boat applies an equal and opposite force on you.
Newtons second lawThis law states that the acceleration caused by a force is inversely proportional to the mass of the object (Acceleration = Force/Mass). For instance the same force will cause a large acceleration in a light object but only a small acceleration in a heavy object. In the example of jumping off a boat – if the boat weighs twice as much as you, the boat will travel backwards only half as fast as you move forward.
NucleusA cluster of interconnected neurons in the brain.
Parietal cortexThe region in the middle back of the cortex that is concerned with sensory and spatial information.
Passive stabilityStability resulting from tension and not requiring specific neuronal responses to disturbances.
PostureThe persistent configuration of body segments. While posture is casually thought of as position, it is regulated by a complex postural system. Thinking of posture as position only ignores the associated postural behaviour.
Peer reviewThe process where scientific work is submitted anonymously to experts in the field for critical review. Peer review is required for journal publication.
Phantom limbThe perception of a limb or body part even after it has been amputated.
PhasicBrief or transient. Phasic activation of muscle consists of activating it in brief bursts to produce brief forces as opposed to ongoing tension.
PlasticityThe brains ability to change and adapt as a result of experience. While plasticity occurs by definition during all learning, is not an explanation of what brain processes adapt or how the change. For example plasticity occurs whenever you form a memory as well as when you learn the Alexander Technique but these have different underlying neurological bases.
Postural alignmentThe position of body segments. For example the postural alignment of the spine is just the spinal curvature.
Postural frameThe mechanical frame of the body that results from matching or postural stiffness.
Postural reactionThis term refers to postural responses, which are usually phasic, that oppose a disturbance.
Postural setA state of the nervous system that affects postural reactions. Typically, postural set is used to refer to the setting of phasic postural reactions, as opposed to postural tone. A classic example of postural set is deciding whether to yield to or resist an upcoming force.
Postural swayThe path traced out on the ground by the Center of Pressure during quiet standing as the body maintains balance. The term is a misnomer as it really represents balancing activity.
Postural systemThe neurological system that regulates posture. It consists of subsystems that control postural tone as well as for counteracting phasic disturbances.
Postural toneMuscle tone that is directed at maintaining a posture. For example, the muscle tone that supports the body against gravity is postural tone, while the lower level muscle tone that occurs while lying down supported is not.
Pre-frontal cortexThe front-most region of the cortex that houses many of the executive functions.
Pre-SMAA cortical region near SMA that participates in executive inhibition.
Premotor cortexA cortical region dealing with motor planning.
Primary motor cortexThe output region of motor cortex. Primary motor cortex has a strong and direct effect on motoneurons in the spinal-cord.
Proactive inhibitionExecutive inhibition that acts in advance to eliminate responses. The opposite of this is reactive inhibition, which determines whether or not to inhibit based on the particular stimulus.
ProcessA phenomena that undergoes a sequence of transitions or changes over time. Movement of an arm is a process because it requires accelerating the arm and then decelerating it.
ProprioceptionSensory information that signals joint position or joint movement. Proprioception may be conscious or unconscious.
QuasistaticA quasistatic process is one that can be well approximated at any point by the static (non moving) structure. For example, if sit to stand is performed slowly and smoothly enough, each moment in the movement is approximately stable. In this case the movement can be called quasistatic.
ReflexThis term has a loose and a strictly defined meaning. Colloquially, a reflex refers to an automatic reaction. The strict definition refers to a specific physiological process with a simple and direct connection between input and output, called the “reflex arc”. A reflex redirects sensory information to activate muscles without processing it in a complex way. Once thought to be the building blocks of behaviour they are now know to play a very limited role.
SaccadeA brief movement of the eye between gaze locations.
Selective inhibitionA form of executive inhibition where only some behaviours or body regions prevented from acting.
SetA state of preparedness of the nervous system to act or react in a specific way.
SMASupplementary motor area. An area of motor cortex involved in producing motor plans.  SMA is active during motor imagery, such as imagining playing tennis. It’s activity can be used to predict a movement before a person is aware of deciding to move.
Smooth pursuit eye movementEye movement that tracks an object traversing the visual field.
Spinal-cordThe part of the nervous system that extends into the spinal canal.  It houses motoneurons for most muscles, axon tracks to and from the brain, and simple circuity such as the walking central pattern generator.
SpreadingThe propagation of muscle tension across body segments due to multi-articular muscles that span more than one joint or through neurological mechanisms.
StabilityThe property of a structure or system to return to its original state following a disturbance.
Startle reflexA brief protective response most often triggered by a loud noise. The startle reflex is phasic and cannot be prolonged.
StateOngoing property of a system. Muscle tone and set are examples of states.
StiffnessThe extent that an object resists deformation by a force. Muscles have increased stiffness when active.
StressA state of mental or emotional strain or tension resulting from adverse or demanding circumstances. Stress can be prolonged unlike startle.
Stretch reflexA specific reflex where stretch receptors act via reflex arc through the spinal cord to activate the stretched muscle. The knee jerk reflex is an example of a stretch reflex. Stretch reflexes require a very fast stretch and only briefly activate muscle, and therefore do not generate muscle tone.
TensegrityA mechanical system that consists of 2 types of elements: those in pure compression (struts) and those that in tension. The musculoskeletal system is not a tensegrity structure for various reasons including compressional joints and a lack of crossing struts.
TMSTranscranial magnetic stimulation. This uses a magnetic field near the head to stimulate inside the cortex.  It is fairly localised so that specific cortical regions can be activated. While imaging techniques can detect whether an area is active during a behaviour, TMS can be used to study whether the brain region causally affects it.
TonicOngoing or persistent. Used to describe activity in neurons or muscles.
TorqueA rotational force. Muscles produce works because the whole of the muscle and the resistance act together to produce rotation.
TorsionRotation along and axis as opposed to bending.  For the spine this equates to twisting.
Twister A device to measure postural tone in the neck trunk and hips. Twister measures resistance to twisting while subjects support themselves against gravity.
Vestibular ocular reflex A reflex that moves the eyes in the opposite direction as the head to maintain gaze location during imposed or unpredictable head motion.
WeightThe force produced on a mass by gravity. This is different from mass in that your weight on Mars is different from on Earth, even though the mass is the same, because Earth’s gravity is stronger.
Working memoryThe executive function that temporarily keeps in memory up to 7 things (approximately) at a time to be manipulated by other brain processes. For example keeping several things in mind to alphabetise them uses working memory.

14 thoughts on “Glossary of Scientific Terms

  1. Regarding “center/centre of mass,” should we use the same expression to refer to a part? Is there any time when “center of gravity” can be used when referring to body parts, or has that been a misnomer. The most typical circumstance is when locating this center of the skull forward and up of the atlanto-occipital joint. Should we only say “center/centre of mass” of the skull?

  2. Question: In the definition of matching, the word “external” hangs by itself (as a noun, not an adjective). Can anything be added after “external”? If I fill in “force,” I understand this concept of matching: an external force is applied to me and I match it to maintain my position. Does this definition need the word “force” or can it be an external “anything”? Or is it more accurate as is?

    Also, when researchers select a control group, I believe they match for characteristics such as age, weight, health, etc. Is that also called matching? Is there any confusing when using the term matching or is it always understood in context?

    1. Yes, the word force should be there after external. Matching in our definition is matching an external force. We are just using it for a shorthand as it comes up a lotOf course you can match other things. You can age-match, weight-match subjects etc.


  3. Hi Tim

    Could we have an example of feedforward please. Would make the distinction between it and feedback clearer.

    1. Hi Neil,

      Just to reiterate the definition first, feedback control is using sensory signals on an ongoing basis to guide an action, updating your action throughout its course. Tuning a guitar string is an example of feedback control – you are constantly evaluating how much to tighten the string by continually monitoring the pitch of the note until it’s correct. I believe the example Patrick gave is a sperm finding the egg. The sperm monitors the sensory signals (temperature, certain chemical gradients) to decide which way to swim. There is no complex plan, it is just adjusting its course by monitoring the available signals on an ongoing basis.

      In contrast to feedback control is feedforward control. This is where you formulate the plan in advance. An example is turn by turn directions. It is just a plan – turn right, go three blocks, turn left, go one mile etc. Most voluntary movement has a hight degree of such planned feedforward control because it can’t rely on sensory signals to be fast enough. When you get the information about your reaching, the hand is now in a different place.

      Experiments have shown the brain uses feedforward control by perturbing an arm while you reach. For example the arm is displaced, say, 2 cm to the left as you reach. If it was using feedback control the brain would recognise this offset and correct the action as its unfolding so that the arm winds up at the target. Instead, what happens is that the final position ends up being offset 2cm to the left. Of course, for big perturbations where the arm is obviously going to miss the brain will plan another feedforward action, and if you are reaching to a particular target and see that you missed, the brain will plan another action to correct.

      A way to think of feedforward control is that before the action the brain knows which muscles it will contract at which times. It then goes ahead and executes this plan.


  4. Hi Kristin,
    These definitions came from multiple sources but if you had a particular one in mind I could direct you. We don’t define AT terms purposefully. We can discuss definitions as the relevant topics come up in class.

  5. It is always so helpful to have the terms defined, thank you. Did these definitions come from a singular source? If you have access, can you please share your sources? Would you be comfortable sharing your definitions of the AT terminology? Thank you, Kristin

  6. Please add Body map to the glossary, highlighting the difference to body schema and body image. Thank you! Flora

      1. Still hoping we can add body map to the glossary, highlighting the difference to body schema and body image. Thank you.

  7. Tim and Patrick. Thank you for sharing this lexicon. I also appreciate the included links to understand terms like awareness, consciousness, attention. As a non scientist I have a tendency to use them inappropriately. All this work, articles and research ( yours and other’s) that you are sharing via the webinar will for me be precious to pursue my training as an AT with a scientific “direction”. I know that I am gaining much more from the webinar than I can share with you. Best.

    1. Thanks Georgette,

      Thanks for your kind comments. I’m of course pleased to hear you are finding it all helpful.


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