Virtually nobody has memories from very early
childhood but it's not because we don't retain
information as young children. Rather, it may be
because at that age, our brains don't yet function in a
way that bundles information into the complex neural
patterns that we know as memories.
It's clear that young children do remember facts in the
moment such as who their parents are, or that one
must say "please" before mom will give you candy. This
is called "semantic memory."
Until sometime between the ages two and four,
however, children lack "episodic memory" -- memory
regarding the details of a specific event. Such
memories are stored in several parts of the brain's
surface, or "cortex." For example, memory of sound is
processed in the auditory cortexes, on the sides of the
brain, while visual memory is managed by the visual
cortex, at the back. A region of the brain called the
hippocampus ties all the scattered pieces together.
"If you think of your cortex as a flower bed, there are
flowers all across the top of your head," said Patricia
Bauer of Emory University in Atlanta. "The
hippocampus, tucked very neatly in the middle of your
brain, is responsible for pulling those all together and
tying them in a bouquet." The memory is the bouquet
-- the neural pattern of linkages between the parts of
the brain where a memory is stored.
So why do kids usually fail to record specific episodes
until the two-to-four age range? It may be because
that's when the hippocampus starts tying fragments of
information together, said psychologist Nora
Newcombe of Temple University in Philadelphia.
And there may be a reason for this, Newcombe said.
Episodic memory may be unnecessarily complex at a
time when a child is just learning how the world works.
"I think the primary goal of the first two years is to
acquire semantic knowledge and from that point of
view, episodic memory might actually be a distraction,"
Newcombe said.




Source: livescience.com