Physical Therapy Assistant Practice Exam

What reflex is indicated when an infant demonstrates increased flexor tone in the prone position?

1. Crossed extension reflex

2. D1 flexion pattern

3. Tonic labyrinthine reflex

4. Symmetrical tonic neck reflex

The correct answer is: Tonic labyrinthine reflex

The tonic labyrinthine reflex is a significant reflex observed in infants, which is characterized by changes in muscle tone in relation to the position of the head and body in space. When an infant is placed in a prone position, the reflex becomes apparent through increased flexor tone. This means that the infant's muscles, especially those of the arms and legs, contract, leading to a more curled posture. This reflex serves an important developmental purpose, as it helps the infant to maintain balance and alignment in relation to gravity. By demonstrating increased flexor tone while in a prone position, the infant is working to stabilize their body, which is crucial for developing motor skills such as rolling over and eventually crawling. Other reflexes listed do not specifically relate to the increased flexor tone observed in this scenario. The crossed extension reflex, for example, is more about the response to an external stimulus on one leg, affecting the opposite leg's extension. The D1 flexion pattern relates to coordinated movement patterns used in more advanced motor skills, and the symmetrical tonic neck reflex involves the extension of the arms and flexion of the legs when the head is tilted backward, contrary to the flexor tone in question. Thus, the tonic labyrinthine reflex accurately reflects the physiological changes