The development of memory is a lifelong process that continues through adulthood. Development etymologically refers to a progressive unfolding. Memory development tends to focus on periods of infancy, toddlers, children, and adolescents, yet the developmental progression of memory in adults and older adults is also circumscribed under the umbrella of memory development. The development of memory in children becomes evident within the first 3 years of a child's life as they show considerable advances in declarative memory, a child's memory throughout their development. This enhancement continues into adolescence with major developments in short term memory, working memory, long term memory and autobiographical memory. The development of memory in adults, especially older adults, is often seen more negatively. Most adults will face symptoms of memory loss in both their short- and long-term memory; Alzheimer's is a prime example of this. Recent research on the development of memory has indicated that declarative, or explicit memory, may exist in infants who are even younger than two years old. For example, newborns who are less than 3 days old demonstrate a preference for their mother's own voice, demonstrating the significance of a strong and powerful connection to the mother. Cognitive Neuroscience of Memory Development Declarative memory develops very rapidly throughout the first 2 years of life; infants of this age show evidence of cognitive development in many ways (e.g., increased attention, language acquisition, increasing knowledge). There is a difference in the brain development of explicit and implicit memory in infants. Implicit memory is controlled by an early-developing memory system in the brain that is present very early on, and can be explained by the early maturation of striatum, cerebellum, and brain stem, which are all involved in implicit learning and memory. Development of explicit memory depends on a later developing memory system in the brain that reaches maturity between 8 and 10 months of age. Explicit memory depends heavily on structures in the medial temporal lobe, including the hippocampus and the parahippocampal cortex. Much of the brain system is formed before birth, however the dentate gyrus within the hippocampal formation has about 70% of the number of cells in adults. Rapid myelination of axons within the central nervous system occurs during first year of life which can dramatically increase the efficiency and speed of transmission in neurons. This can explain the higher processing speed of older infants as compared to younger ones. Working Memory