External sensory information and rapid dynamics of hippocampal place cells
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
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 informationThese dynamics were:1) calculated with Song et al 2005population analyses2) long time constants
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
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
Spatially selective place cells in bathippocampus during mealworm-chasing task Examples of trajectory (grey) place ﬁelds spikes (red)Neural recordings: tetrodes indorsal CA1
Sonar call triggered place ﬁeldsDo spikes occurring late after an echolocation call(spike 3) convey less spatial information than spikesoccurring early after a call?
Place cell spikes were binned into time windows following echolocation callsBoth individual cells (above) and population averages show decreasein ﬁeld coherence (spatial selectivity) over time
This agrees with previous studies in rodents showing thatplace ﬁeld speciﬁcity decreases when sensory information is poorRemoval of olfactory informationRemoval of visual information Save et al 2000 Markus et al 1994 Light DarkBut, occurs on a much fast time scale (~300 ms)...
Place cells can rapidly integrate incoming sensoryinformation, tuning spatial selectivity of place cells to matchspatial acuity of the new information Bats primarily rely on echolocation (visual info not used when echolocation available) Effect of integrating multiple sensory modalities?
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.