Transcript 91a26/Place Cells and Place Recognition

Place Cells and Place Recognition
Maintained by Direct
Entorhinal-Hippocampal Circuitry
Vegard H. Burn, Mona K. Otnaess, Sturla Molden, HillAina Steffenach, Menno P. Witter, May-Britt Moser,
Edvard I. Moser
Science VOL 296 , 21 June 2002
Presented by Min-Yu Sun
Department of Life Science
Outline
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Background Introduction
Material and Methods
Hypothesis
Material and Methods
Conclusion I
Material and Methods
Conclusion II
Material and Methods
Conclusion III
Summary
Background Introduction
• Hippocampus : a cognitive (認知) map
• Place cell: Hippocampal principal neurons,
exhibit location-specific firing.
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Place field
CA1
CA3
Entorhinal cortex
Background Introduction
• Place cells and place fields
Background Introduction
• Pyramidal cell: (CA3)
Background Introduction
• Hippocampus : a cognitive (認知) map
• Place cell: Hippocampal principal neurons,
exhibit location-specific firing.
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Place field
CA1
CA3
Entorhinal cortex
Background Introduction
CA3
CA1
Entorhinal cortex
Background Introduction
• Connection within the hippocampus
Whether Place Cells and Place Recognition
Maintained by Direct
Entorhinal-Hippocampal Circuitry?
Material and Methods
＊ Subjects and surgery
◆Rat’s Pyramidal cell (in hippocampus)
Group1: Excitotoxic lesions of CA3 by ibotenic acid.
Implant electrodes, record the firing spike.
Material and Methods
＊Recording
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11
procedures
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12
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2 (Hz)
Most of the pyramidal neurons had
distinct and well-defined place fields that
was stable and similar to those normal
rats.
Hypothesis
• Area CA3 may not be necessary for
establishing and maintaining place fields
in area CA1
• That spatial information from the neocortex
may reach the hippocampus primarily
through the alternative route: the direct
pathway from layer III of the entorhinal
cortex.
However, functions of hippocampal
neurons may be preformed with relatively
small portions of intact hippocampal tissue
The place-specific firing in area CA1, as
observed in CA3-lesioned rats, could reflect
input from remaining CA3 cells at the septal
pole or in more temporal parts of the
hippocampus.
To isolate the direct entorhinal pathway
to CA1 completely continue the exp…
Material and Methods
＊ Subjects and surgery
◆Rat’s
Pyramidal cell (in hippocampus)
Group2: 3-5 continuous cuts were made
between CA1 and CA3, to block
input from the anterior CA3
completely. (ibotenic acid
is also used.)
Material and Methods
• Remove CA3 Completely
• Normal
from
from
Entorhinal
Entorhinal
cortex
cortex
Material and Methods
＊Retrograde tracing : Inject a fluorescent
retrograde tracer that label pyramidal
neurons in CA3
＊Recording procedures (like group 1)
＊Recording procedures (run on a
linear track to test the directional
modulation)
Result of retrograde tracing
• Remove CA3 Completely
• Normal
Neurons from
Entorhinal
cortex are labeled
Pyramidal neurons
in CA3 are labeled
Neurons from
Entorhinal
cortex are labeled
Failed to label
neurons in CA3
Result of Recording procedures
--Disruption of CA3 input did not
attenuate the directional modulation ,
which is characteristic of place cells
in bidirectional environment .
(from the same rat)
＊Recording procedures : Color-code firing
rate map for a cell that was recorded for
five consecutive days in the lesioned rat
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11 (Hz)
Conclusion I
• Area CA3 may not be necessary for
establishing and maintaining place fields
in area CA1
• That spatial information from the
neocortex may reach the hippocampus
primarily through the alternative route:
the direct pathway from layer III of the
entorhinal cortex.
Discussion
• Whether removal of CA3 input had
more subtle effects on place cells in
area CA1?
Continue the exp to “Quantitative
description of place fields”…..
Material and Methods
＊Quantitative description of place fields
◆Rat’s Pyramidal cell (in hippocampus)
◆ Spike density function
◆ Rate map
◆ Sparseness
◆ Field size
◆ Stability
◆ Directional modulation
Result of Sparseness
• Distribution of place cells in categories of
increasing sparseness
Sparseness:
0.46 for lesioned rats
0.30 for intact rats
Result of Field Size
• Field Size
The size of the place fields
was not significantly altered:
Lesioned rats- 28.2% surface
Intact rats- 18.9% surface
The peak rate was reduced:
7.0 Hz for lesioned rats
10.3 Hz for intact rats
P < 0.05
Results of Sparseness and Field Size
• The result was independent of the type of
CA3 lesion.
• These effects were small compared to the
differences between the firing fields of
pyramidal cells and interneurons.
Material and Methods
＊Quantitative description of place fields
◆Rat’s Pyramidal cell (in hippocampus)
◆ Spike density function
◆ Rate map
◆ Sparseness
◆ Field size
◆ Stability
◆ Directional modulation
Result of Stability
• Stability of place fields in the box across a
1h interval or a 24h interval
Place fields were
Stable across
Sessions in both
lesioned rats
and control rats
(P > 0.05)
Result of Stability
• Removal of CA3 input had no significant
effect on how much the peak of the place
field moved across a 1- or 24- hour
interval.
Result of Directional Modulation
• Directional modulation
 No group difference in
average firing rate :
Lesioned rats :1.00Hz
Intact rats : 0.91Hz
P > 0.05
Blocking input from
area CA3 also failed
to change the proportion
of directionally modulated
place cells on the linear
track . (P > 0.05)
Conclusion II
• The direct pathway from the entorhinal
cortex thus seems to be sufficient for
establishing and maintaining
fundamental properties of place cells in
area CA1
Discussion:
Whether the reduced circuitry also
supported memory?
…… continue the exp
Material and Methods
＊ Subjects and surgery
◆Rat’s
Pyramidal cell (in hippocampus)
◆ Extensive ibotenate-induced CA3 lesions
＊ Recall and recognition tests
◆ Annular
water maze
◆ Morris milky water maze
Result of Recognition
• Annular water maze
Sham & CA3 P > 0.25
Sham & HPC P < 0.005
Result of Recall
• Morris water maze
Conclusion III
• Spatial recognition memory is fully
achievable with an isolated entorhinalCA1 network.
• The isolated entorhinal-CA1 circuit does
not support recall of remote locations or
trajectories toward these locations.
Summary
• Direct entorhinal-hippocampal connections
have significant capacity for transforming
weak location-modulated signals.
• The isolated entorhinal-CA1 circuit does
not support recall of remote locations or
trajectories toward these locations.
Summary
• These results suggest that the hippocampus
contains two functionally separable memory
circuits:The direct entorhinal-CA1 system is
sufficient for recollection-based recognition
memory, but recall depends on intact CA3CA1 connectivity.
Comment
• Form the result of Morris water maze…
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