Final answer:
The Babinski reflex is normal in newborns but indicates issues with the descending corticospinal tract in adults, potentially affecting balance and reflecting an upper motor neuron disease.
Step-by-step explanation:
The Babinski reflex, a common newborn reflex showcased as foot dorsiflexion with extension and splaying of the toes in response to the plantar reflex, is an expected finding in infants. This reflex is normally suppressed by corticospinal input in adults. In a neurological exam, a negative Babinski sign, where the toes curl and the foot exhibits moderate plantar flexion in response to stimulation of the sole, indicates mature neuromuscular function connected to walking ability. A positive Babinski sign in adulthood suggests a problem with the descending corticospinal tract, potentially indicating upper motor neuron disease and possibly interfering with the ability to maintain balance.
If superficial stimulation of the sole of the foot caused extension of the foot in an adult, maintaining balance could be more difficult. The change from a positive to a negative Babinski sign during normal development is related to the modulation of reflex responses by higher brain centers as a person matures.