region of the brain called hippocampus is responsible for formation and
storage of memories and in spatial relations.
remember a travel route between 2 random points, the brain should
therefore create memories that help navigation in both the onward as well
as the return direction.
in rats have shown that if there is a 'reward' at the end of the trip, the
neurons in the hippocampus replay the route taken to get the reward, but
these 'replays' and creation of memories only occur when the brain waves
calm down or the animal is in a relaxed state.
in the Brain
is what helps in recognizing people, places,
knowing where we are, and who we are to mention a few. It makes us feel happy
or sad and in short is very essential for going on about our daily routine and
activities without bungling.
region of the brain is
critical for forming and storing
memories and in spatial relations
(being aware of the location of a
specific object in relation to another object).
‘No prizes for forgetting your way! Hippocampus can be bribed to remember routes better.’
it plays a critical role in creating memories that may aid navigation or
remembering a certain travel route.
report deals with one such important aspect of memory, namely how mammals
remember important travel routes.
How the Rat Remembers Where to Find the Cheese
Neuroscientists at the
Johns Hopkins University
believe that they are closer to understanding how the brains of some mammals (rats
, in this case) are able to find their way or
navigate certain routes better.
presence of a reward at the end of the
trip (a chocolatey drink in this study) made the hippocampal neurons in the
rats brain replay the route
taken to achieve the reward, but
magnitude of the reward
too. The greater the reward, the more
number of times the animals replayed the route
, helping to solidify the
memory in their brain.
- I Need
importantly, these memory creations or
'replays' happened only when the rats paused or took a break
travels. This was established by recording the brain waves.
periods of activity, the brain waves oscillate up and down. When they pause or remain calm,
they are in slow-wave sleep
brain waves calm down, oscillating more gently, except for one or two "sharp
wave ripples" per second.
It was during these slow wave periods
that lasted around one-tenth of a second
that the 'replays' occurred.
replays occurred in the neurons of the
hippocampus called place cells.
Each place cell
has a 'favourite'
spot and fires at a particular location
in the surrounding.
How the Study Was
The study was
conducted by Dr. Foster
, associate professor of neuroscience at the
Johns Hopkins University School of Medicine
The rats were made to
run back and forth along a linear track between 2 points A and F.
before starting to scurry about, the rats
actually "envisioned" their routes
through the sequential firing of their
place cells. Sometimes, during pauses,
rats replayed the sequences in reverse
, but scientists did not know why.
While the rats were
running, the activity of more than 100
place cells in the hippocampus was monitored by placing around 40 miniature
(thinner than a human hair) in the hippocampus of the rat.
During trial runs,
were sometimes provided with a chocolatey liquid reward at either point A or
point F. However, it had no effect on the frequency of forward or backward
A rat enjoying its reward at F
would experience an equal number of forward and backward replays in any random
However, when the amount of
reward was altered
at point F, number of forward replays remained the same,
but the number of reverse replays
increased or decreased
in proportion with the change in the reward.
This led scientists to conclude that this change in frequency of
backward replays could probably mean
that the rats' brain was linking the reward with the path taken to obtain it
creating and solidifying that memory for future recall.
Results to Humans
Scientists believe that even
humans could also remember certain routes better using the same mechanism
Consider an instance of a person shipwrecked on an island, wandering off
and stumbling upon a stream containing fresh and tasty water. He does not know how he reached that spot
but now it is important that he remember the route.
To help him do so, his hippocampal neurons would replay the route
backwards and help him recall otherwise unimportant details on the way that
helped him in getting to the stream (the reward).
Dr. Foster says a lot more research is necessary to learn details about
the result of these reverse replays, and if their findings do indeed apply to
humans as well.
However, there is no countering the fact that one does definitely need to take a break from the rat race
the finer things in life. It is during
these periods of relaxation that such 'replay' events occur
, helping to
create and store memories of certain routes deemed important. In addition these
periods do wonders for one's overall well-being and health.
- Mechanisms for widespread hippocampal involvement in cognition - (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4065494/)