Babinski Reflex/ Plantar Reflex. The Babinski reflex occurs after the sole of the foot has been firmly stroked. The big toe then moves upward or toward the top surface of the foot. The other toes fan out. Babinski reflex occurs/ positive in Upper Motor Nerve lesions and Infants. In Infants there's immature myelination in their Central Nervous System, so Babinski reflex is positive. In adults, Positive Babinski sign represents upper motor neuron lesions.