Pathological reflexes occur when there is nerve or brain damage. The best known pathological reflex is the Babinski reflex, which causes extension of the big toe and flexion of all other toes when the sole of the foot is brushed. It is one of the early childhood reflexes and is usually not triggerable after 12 months of age.
Babinski reflex in massive brain damage.
In cases of massive brain damage, as may occur after a cerebral hemorrhage or stroke, a positive Babinski reflex indicates severe cerebral damage. The reflex response is always evaluated in a side-by-side comparison-that is, on both arms or legs: a different reflex response, e.g., a unilateral weakening or strengthening of the reflex, indicates nerve damage.
Muscle reflexes in old age
In addition, with advancing age, there is often a weakening of many reflexes, but these reflexes then occur bilaterally and are not limited to one organ or muscle.
An increase mainly in muscle intrinsic reflexes is often seen in paralyzed muscles after a stroke – the extreme form is the so-called clonus, a rhythmic inexhaustible twitching of a muscle in response to a single stimulus. Clonus occurs when there is damage to the nerves coming from the cerebrum that excite the muscles.
What is a conditioned or conditioned reflex?
From the previously mentioned innate reactions, reflexive body reactions are distinguished that are learned or acquired. The best known in this context is certainly Pavlov’s dog experiment, which demonstrated that after coupling food with bell sound, dogs also responded to the sound of the bell alone by producing saliva.
Thus, in an acquired reflex, an innate reflex (salivation when food is expected) is coupled with another stimulus (in this case, bell sound) until conditioning is achieved so that the first stimulus (food) can be omitted. This process, which we are not consciously aware of, influences our development of behaviors, our learning of content, and also our adaptation to our environment.
Therapeutically, coupling is used in the field of psychotherapy for desensitization, in which a repeated pairing of an anxiety-provoking stimulus with a pleasant situation is established: The association of positive emotion with the negative stimulus causes it to gradually lose its effect.