Source Paper
The effects of changes in the environment on the spatial firing of hippocampal complex-spike cells
RU Muller, JL Kubie
Journal of Neuroscience • 1987
Source Paper
RU Muller, JL Kubie
Journal of Neuroscience • 1987
Using the techniques set out in the preceding paper (Muller et al., 1987), we investigated the response of place cells to changes in the animal's environment. The standard apparatus used was a cylinder, 76 cm in diameter, with walls 51 cm high. The interior was uniformly gray except for a white cue card that ran the full height of the wall and occupied 100 degrees of arc. The floor of the apparatus presented no obstacles to the animal's motions. Each of these major features of the apparatus was varied while the others were held constant. One set of manipulations involved the cue card. Rotating the cue card produced equal rotations of the firing fields of single cells. Changing the width of the card did not affect the size, shape, or radial position of firing fields, although sometimes the field rotated to a modest extent. Removing the cue card altogether also left the size, shape, and radial positions of firing fields unchanged, but caused fields to rotate to unpredictable angular positions. The second set of manipulations dealt with the size and shape of the apparatus wall. When the standard (small) cylinder was scaled up in diameter and height by a factor of 2, the firing fields of 36% of the cells observed in both cylinders also scaled, in the sense that the field stayed at the same angular position and at the same relative radial position. Of the cells recorded in both cylinders, 52% showed very different firing patterns in one cylinder than in the other. The remaining 12% of the cells were virtually silent in both cylinders. Similar results were obtained when individual cells were recorded in both a small and a large rectangular enclosure. By contrast, when the apparatus floor plan was changed from circular to rectangular, the firing pattern of a cell in an apparatus of one shape could not be predicted from a knowledge of the firing pattern in the other shape. The final manipulations involved placing vertical barriers into the otherwise unobstructed floor of the small cylinder. When an opaque barrier was set up to bisect a previously recorded firing field, in almost all cases the firing field was nearly abolished. This was true even though the barrier occupied only a small fraction of the firing field area. A transparent barrier was effective as the opaque barrier in attenuating firing fields. The lead base used to anchor the vertical barriers did not affect place cell firing.(ABSTRACT TRUNCATED AT 400 WORDS)
Objective: To investigate the response of hippocampal place cells to changes in the environment, specifically testing how place cell firing fields respond to rotation of a visual cue card in a recording cylinder
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Record place cell activity from animals moving freely in the standard cylindrical apparatus with uniform gray walls and white cue card
Note: The white cue card occupies 100 degrees of arc and runs the full height of the wall. The floor presents no obstacles to animal motion
“The standard apparatus used was a cylinder, 76 cm in diameter, with walls 51 cm high. The interior was uniformly gray except for a white cue card that ran the full height of the wall and occupied 100 degrees of arc”
Rotate the white cue card while continuously recording place cell firing to measure how firing fields respond to cue rotation
Note: This is the primary manipulation for testing cue-dependent place cell responses
“Rotating the cue card produced equal rotations of the firing fields of single cells”
Modify the angular width of the white cue card while recording place cell activity to test whether cue size affects firing field properties
Note: Cue width changes do not affect firing field size, shape, or radial position, though modest field rotation may occur
“Changing the width of the card did not affect the size, shape, or radial position of firing fields, although sometimes the field rotated to a modest extent”
Completely remove the white cue card from the cylinder and record place cell firing to test the necessity of the visual cue
Note: Firing field size, shape, and radial positions remain unchanged but fields rotate to unpredictable angular positions
“Removing the cue card altogether also left the size, shape, and radial positions of firing fields unchanged, but caused fields to rotate to unpredictable angular positions”
Record place cell activity in a cylinder scaled up by a factor of 2 in both diameter and height to test size-dependent scaling of firing fields
Note: 36% of cells showed scaling with same angular and relative radial positions; 52% showed different patterns; 12% were silent in both cylinders
“When the standard (small) cylinder was scaled up in diameter and height by a factor of 2, the firing fields of 36% of the cells observed in both cylinders also scaled”
Record place cell activity in both small and large rectangular enclosures to test whether results from cylindrical scaling generalize to different apparatus shapes
Note: Similar scaling results were obtained in rectangular enclosures as in cylindrical ones
“Similar results were obtained when individual cells were recorded in both a small and a large rectangular enclosure”
Record place cell activity in a rectangular apparatus after establishing baseline in the circular cylinder to test shape-dependent changes in firing patterns
Note: Firing patterns in one shape cannot be predicted from knowledge of patterns in the other shape
“When the apparatus floor plan was changed from circular to rectangular, the firing pattern of a cell in an apparatus of one shape could not be predicted from a knowledge of the firing pattern in the other shape”
Set up an opaque vertical barrier to bisect a previously recorded firing field while recording place cell activity
Note: Barrier occupies only a small fraction of the firing field area but nearly abolishes the field in almost all cases
“When an opaque barrier was set up to bisect a previously recorded firing field, in almost all cases the firing field was nearly abolished. This was true even though the barrier occupied only a small fraction of the firing field area”
Set up a transparent vertical barrier to bisect a previously recorded firing field while recording place cell activity to test whether visual properties of the barrier matter
Note: Transparent barrier is as effective as opaque barrier in attenuating firing fields, suggesting physical rather than visual properties are critical
“A transparent barrier was effective as the opaque barrier in attenuating firing fields”
Verify that the lead base used to anchor barriers does not independently affect place cell firing
Note: Control condition to ensure barrier effects are not due to the anchoring mechanism
“The lead base used to anchor the vertical barriers did not affect place cell firing”
Animals were recorded while moving in the apparatus