Neocortical-hippocampal
interactions
support
new
episodic
(event)
memories,
but
there
is
conflicting
evidence
about
the
dependence
of
remote
memories
on
hippocampus.
In
line
with
systems
consolidation
and
computational
theories
memory,
from
model
organisms
suggests
that
cornu
ammonis
3
(CA3)
hippocampal
subfield
supports
recent,
not
remote,
retrieval.
this
study,
we
demonstrated
recent
were
susceptible
to
a
loss
detail
in
human
participants
focal
bilateral
damage
CA3.
Graph
theoretic
analyses
7.0-Tesla
resting-state
fMRI
data
revealed
CA3
disrupted
functional
integration
across
medial
temporal
lobe
(MTL)
subsystem
default
network.
The
MTL
regions
was
predictive
autobiographical
retrieval
performance.
We
conclude
necessary
for
long
after
their
initial
acquisition
network
important
memory
Nature Communications,
Год журнала:
2021,
Номер
12(1)
Опубликована: Май 20, 2021
Abstract
When
exploring
new
environments
animals
form
spatial
memories
that
are
updated
with
experience
and
retrieved
upon
re-exposure
to
the
same
environment.
The
hippocampus
is
thought
support
these
memory
processes,
but
how
this
achieved
by
different
subnetworks
such
as
CA1
CA3
remains
unclear.
To
understand
hippocampal
representations
emerge
evolve
during
familiarization,
we
performed
2-photon
calcium
imaging
in
mice
running
virtual
compared
trial-to-trial
dynamics
of
place
cells
over
days.
We
find
fields
rapidly
tend
shift
backwards
from
remap
environment
a
day
later.
In
contrast,
gradually
show
more
stable
day-to-day
dynamics.
These
results
reflect
roles
processing
familiarization
constrain
potential
mechanisms
them.
Nature Communications,
Год журнала:
2020,
Номер
11(1)
Опубликована: Авг. 11, 2020
Abstract
Everyday
life
unfolds
continuously,
yet
we
tend
to
remember
past
experiences
as
discrete
event
sequences
or
episodes.
Although
this
phenomenon
has
been
well
documented,
the
neuromechanisms
that
support
transformation
of
continuous
experience
into
distinct
and
memorable
episodes
remain
unknown.
Here,
show
changes
in
context,
boundaries,
elicit
a
burst
autonomic
arousal,
indexed
by
pupil
dilation.
Event
boundaries
also
lead
segmentation
adjacent
later
memory,
evidenced
memory
for
temporal
duration,
order,
perceptual
details
recent
sequences.
These
subjective
objective
are
related
features
dilations
stability
more
prolonged
pupil-linked
arousal
states.
Collectively,
our
findings
suggest
measures
reflect
both
change
ongoing
mental
context
representations,
which
turn
shape
structure
memory.
While
memories
are
often
thought
of
as
flashbacks
to
a
previous
experience,
they
do
not
simply
conserve
veridical
representations
the
past
but
must
continually
integrate
new
information
ensure
survival
in
dynamic
environments.
Therefore,
‘drift’
neural
firing
patterns,
typically
construed
disruptive
‘instability’
or
an
undesirable
consequence
noise,
may
actually
be
useful
for
updating
memories.
In
our
view,
continual
modifications
memory
reconcile
classical
theories
stable
traces
with
drift.
Here
we
review
how
updated
through
recruitment
neuronal
ensembles
on
basis
excitability
and
functional
connectivity
at
time
learning.
Overall,
emphasize
importance
considering
static
entities,
instead
flexible
network
states
that
reactivate
evolve
across
experience.
Nature Communications,
Год журнала:
2020,
Номер
11(1)
Опубликована: Авг. 7, 2020
Recent
research
has
highlighted
a
role
for
the
hippocampus
and
Posterior
Medial
cortical
network
in
signaling
event
boundaries.
However,
little
is
known
about
whether
or
how
these
neural
processes
change
over
course
of
healthy
aging.
Here,
546
cognitively
normal
participants
18-88
years
old
viewed
short
movie
while
brain
activity
was
measured
using
fMRI.
The
regions
show
increased
at
boundaries,
but
boundary-evoked
responses
decrease
with
age.
Boundary-evoked
posterior
predicts
performance
on
separate
test
memory
stories,
suggesting
that
hippocampal
during
segmentation
may
be
broad
indicator
individual
differences
episodic
ability.
In
contrast,
medial
prefrontal
cortex
middle
temporal
gyrus
increase
across
age
range.
These
findings
suggest
aging
alter
segmenting
remembering
continuous
real-world
experiences.