Does vitamin A aid learning?

Vitamin A deficiency is one of the most common nutritional problems in the world. It permanently blinds children, causes night blindness in adults, and weakens the immune system. A study of mice now hints that a lack of vitamin A causes learning and memory problems, albeit potentially reversible ones.

Investigators at the Salk Institute for Biological Studies in La Jolla previously studied mutant mice lacking the cell-surface proteins that vitamin A and its derivatives stimulate. These animals struggled more than normal with learning tasks. Intrigued, the researchers placed normal mice on a vitamin A--deficient diet and, at various times during the animals' lives, examined tissue from the brain's hippocampus.

The hippocampus is intimately involved in memory and learning. Many scientists believe its role in those processes depends on so-called long-term potentiation (LTP) and long-term depression (LTD)--the strengthening and weakening, respectively, of certain connections between brain cells. Hippocampal tissue of vitamin A--deficient mice shows impaired LTP and LTD processes, Salk's Sharoni Jacobs and her colleagues report.

Jacobs suggests that physicians should try to determine if people lacking vitamin A have subtle cognitive difficulties, especially since, in the mice, such shortfalls appear reversible. She notes that restoring vitamin-A to the diets of the deprived mice rescued their LTP and LTD functions.

Since a lack of vitamin A also causes blindness and general health problems in the mice, the researchers have had trouble confirming the learning and memory problems in the animals. To partially address that uncertainty, they intend to see if diets rich in vitamin A improve mouse learning and memory.