2. Hippocampal Place Cells
• Neurons in
hippocampus that fire
when animal passses
through particular
region of environment
• Previously described in
rodents, monkeys,
Ulanovsky and Moss 2007
humans
3. Animal Trajectory
Both external following, we show analysis results th
In the
and internal
information alter place cell activity act
remapping of location-specific firing across
igation sessions are attributable to the factors k
discharges of hippocampal neurons: difference
• External: jectory, movement speed, head direction, or e
novel environments (McNaughton et al., 1983; Knierim et
mal
contextual changes animal trajectory, we first compared the averag
Calton et al 2003
• Internal:
idiothetic information
These dynamics were:
1) calculated with
Song et al 2005
population analyses
2) long time constants
4. Do individual place cells show rapid
dynamics in response to external
sensory information?
• Trigger place cell recording
off of a reproducible sensory/
behavioral event
Eptesicus fuscus
5. 70° tilted box Bat trajectory
(68 x 73 cm)
Polystyrene balls
“wall” (landmarks)
“floor”
Bats searched for randomly
placed mealworms
As bats crawled, they
echolocated with mean inter-call
interval ~236 ms
6. Spatially selective place cells in bat
hippocampus during mealworm-chasing task
Examples of
trajectory (grey) place fields
spikes (red)
Neural recordings: tetrodes in
dorsal CA1
7. Sonar call triggered place fields
Do spikes occurring late after an echolocation call
(spike 3) convey less spatial information than spikes
occurring early after a call?
8. Place cell spikes were binned into time windows following
echolocation calls
Both individual cells (above) and population averages show decrease
in field coherence (spatial selectivity) over time
9. This agrees with previous studies in rodents showing that
place field specificity decreases when sensory information is
poor
Removal of olfactory information
Removal of visual information
Save et al 2000
Markus et al 1994
Light Dark
But, occurs on a much fast time scale (~300 ms)...
10. Place cells can rapidly integrate incoming sensory
information, tuning spatial selectivity of place cells to match
spatial acuity of the new information
Bats primarily rely on
echolocation (visual info
not used when
echolocation available)
Effect of integrating
multiple sensory
modalities?
11. Bibliography
• Calton et al (2003). Hippocampal place cell instability after lesions
of the head direction cell network. J Neurosci 23(30): 9719-9731.
• Markus et al (1994). Spatial information content and reliability of
hippocampal CA1 neurons: Effects of visual input. Hippocampus
4(4): 410-421.
• Save et al (2000). Contribution of multiple sensory information to
place field stability in hippocampal place cells. Hippocampus
10:64-76.
• Song et al (2005). Role of active movement in place-specific firing
of hippocampal neurons. Hippocampus 15:8-17.
• Ulanovsky and Moss (2007). Hippocampal cellular and network
activity in freely moving echolocating bats. Nat. Neurosci 10(2):
224-233.
• Ulanovsky and Moss (2011). Dynamics of hippocampal spatial
representation in echolocating bats. Hippocampus 21:150-161.
