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: Investigate the response of place cells to changes in the animal's environment, specifically comparing place cell firing patterns when recording environments are scaled up by a factor of 2 in diameter and height
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Set up the standard small cylinder apparatus with uniform gray interior walls and a white cue card
Note: The cue card runs the full height of the wall and occupies 100 degrees of arc. 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”
Record place cell firing patterns in the standard small cylinder apparatus
Note: Establish baseline firing field characteristics including size, shape, and radial position
“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”
Construct and use a large cylinder apparatus with diameter and height scaled up by a factor of 2 from the standard apparatus
Note: Large cylinder dimensions are 152 cm diameter and 102 cm wall height
“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 firing patterns from the same cells in the large scaled cylinder apparatus
Note: Compare firing patterns to baseline recordings in small cylinder
“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”
Record place cell firing in both small and large rectangular enclosures to compare with cylinder results
Note: Similar scaling effects were observed as with cylindrical apparatus
“Similar results were obtained when individual cells were recorded in both a small and a large rectangular enclosure”
Record place cell firing when apparatus floor plan is changed from circular to rectangular
Note: Firing patterns were not predictable when changing apparatus shape
“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”
Rotate the white cue card and record resulting changes in place cell firing fields
Note: Cue card rotation produces equal rotations of firing fields
“Rotating the cue card produced equal rotations of the firing fields of single cells”
Change the width of the white cue card and record effects on place cell firing
Note: Width changes do not affect firing field size, shape, or radial position
“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”
Remove the white cue card entirely and record place cell firing patterns
Note: Removal leaves size, shape, and radial positions unchanged but causes unpredictable angular rotation
“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”
Place an opaque vertical barrier on the floor to bisect a previously recorded firing field
Note: Barrier occupies only a small fraction of firing field area but nearly abolishes the field
“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”
Place a transparent vertical barrier on the floor to test whether visual or physical obstruction is responsible for firing field attenuation
Note: Transparent barrier is as effective as opaque barrier in attenuating firing fields
“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 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 in various apparatus configurations