The ability of humans to learn, remember, and adapt is directly related to the changeableness (plasticity) of the human brain. Whenever we learn new information, the connections between nerve cells in the brain are modified. The activity of some connections (called synapses) increases, while the activity of other synapses decreases. The initial changes involve local chemical alterations in the way synapses transmit and receive information from other neurons. These initial chemical changes eventually lead to structural changes in the brain; that is, more connections and more complex connections form. The longer lasting of these changes require the turning on and turning off of specific genes; therefore, learning involves gene expression. Changes in synaptic connections represent a major way by which memories are formed. But some memories fade, and it is likely that the newly formed connections must be reinforced by ongoing brain activity in order for these connections to survive. The important points to remember are that learning alters the actual structure of the brain and that genes are involved in learning.

Neurogenesis

Neurogenesis (the formation of new nerve cells in the adult brain) is really part of the larger story about brain plasticity. Neurogenesis reflects the amazing resilience and plasticity of our brains. Expanding upon observations initially made years ago about birds, it has become clear that certain parts of the human brain are capable of generating new neurons throughout life, even during old age.  Not all regions of the brain appear to have this ability to grow new nerve cells, but two regions, the dentate gyrus of the hippocampus and the areas near the lateral ventricles in the olfactory system (which is involved in the sense of smell), are really good at it. The dentate gyrus plays a key role in the function of the hippocampus, the region that is so critical for memory processing. A thousand or more new neurons are born in this region each day and can be incorporated into the circuitry of the hippocampus where they help enhance certain types of learning. These new neurons may be particularly important for processing new information.