Editor’s note: Brain Basics from Scientific American Mind is a series of short video primers on the brain and how we feel, think and act. Below is a synopsis of the fifth video in the series written by a guest on this blog, Roni Jacobson, a science journalist based in New York City.

By Roni Jacobson

Scientists distinguish between two types of memories, implicit and explicit. Implicit memories are effortless recollections that we don’t consciously call to mind. We implicitly remember how to ride a bike, tie shoes or sing a familiar song, for example. In another type of implicit recall, words or other stimuli that we unconsciously encode may nonetheless influence what we do or think about later.

Explicit memory is the intentional recollection of events and facts about people, places and things—for example, what you ate for breakfast or how many justices there are on the Supreme Court. The hippocampus, a structure in the middle of the brain, transforms short-term explicit memories into conscious recollections that persist over time. After the hippocampus has prepared a memory for long-term storage, that memory is housed in the brain’s outer rind, the cerebral cortex.

At the cellular level, short-term memory depends on changes in the way nerve cells communicate across synapses, the tiny gaps between neurons. A memory becomes stable when the relevant nerve cells grow new branches and thereby create additional points of contact with each other. Those anatomical changes, in turn, result from the expression of genes for proteins and mRNA that are needed to build the new branches and synapses. These structural modifications underlie every long-term memory, whether it represents your grandmother’s maiden name or the automatic movements required to type her a thank-you letter.

Other Brain Basics videos:

Terrified or Hopping Mad? What's Going on Inside You

A Transformation of Light: How We See

Quick! What Is The Word for a Pair of Opposites?

The Hidden Power of Others Over You

Small image on blogs page: Courtesy of Genista via Flickr.