stand, then the child may develop motor control and balance normally. The vestibulo-ocular reflex (VOR) is a reflex eye movement that stabilizes images on the retina during head movement. It produces an eye movement in the direction opposite to head movement, thus preserving the image on the center of the visual field. Studies in fish and amphibians revealed a sensitivity in their VOR. They launched into space flight for 9-10, some with developing VOR's and others with already developed reflexes. The fish with developing reflexes developed an upward bend in their tails. The altered gravity resulted in a shift of orientation. Those who were already matured with the reflex were insensitive to the microgravity exposure. Memory Recent studies also support the possibility of a critical period for the development of neurons that mediate memory processing. Experimental evidence supports the notion that young neurons in the adult dentate gyrus have a critical period (about 1–3 weeks after neuronal birth) during which they are integral to memory formation. Although the exact reasoning behind this observation is uncertain, studies suggest that the functional properties of neurons at this age make them most appropriate for this purpose; these neurons: (1) Remain hyperactive during the formation of memories; (2) are more excitable; and (3) More easily depolarizable due to GABAergic effects. It is also possible that hyperplasticity makes the neurons more useful in memory formation. If these young neurons had more plasticity than adult neurons in the same context, they could be more influential in smaller numbers. The role of these neurons in the adult dentate gyrus in memory processing is further supported by the fact that behavioral experiments have shown that an intact dentate gyrus is integral to hippocampal memory formation. It is speculated that the dentate gyrus acts as a relay station for information relating to memory storage. The likelihood of a critical period could change the way we view memory processing because it would ultimately mean that the collection of neurons present is constantly being replenished as new neurons replace old ones. If a critical period does indeed exist, this could possibly mean that: (1) Diverse populations of neurons that represent events occurring soon after one another may connect those events temporally in the memory formation and processing; OR (2) These different populations of neurons may distinguish between similar events, independent of temporal position; OR (3) Separate populations may mediate the formation