Vertical Barrier Obstruction Study — RU Muller | ReplicateScience

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Vertical Barrier Obstruction Study — RU Muller | ReplicateScience

View Abstract

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)

Protocol Steps

1

Establish baseline place cell recordings in standard cylinder

Record place cell firing patterns in the standard small cylinder apparatus with uniform gray interior, white cue card, and unobstructed floor

Not specifiedNot specified

Note: Standard apparatus dimensions: 76 cm diameter, 51 cm high walls. White cue card runs full height and occupies 100 degrees of arc.

View evidence from paper

“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.”

2

Place opaque vertical barrier to bisect firing field

Set up an opaque barrier into the previously unobstructed floor of the small cylinder positioned to bisect a previously recorded firing field

Not specifiedNot specified

Note: Barrier occupies only a small fraction of the firing field area. Barrier is anchored with lead base.

View evidence from paper

“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.”

3

Record place cell activity with opaque barrier in place

Record place cell firing patterns with the opaque barrier bisecting the previously recorded firing field

Not specifiedNot specified

Note: Observe effects on firing field size, shape, and position

View evidence from paper

“When an opaque barrier was set up to bisect a previously recorded firing field, in almost all cases the firing field was nearly abolished.”

4

Replace opaque barrier with transparent barrier

Remove the opaque barrier and place a transparent barrier in the same position bisecting the previously recorded firing field

Not specifiedNot specified

Note: Transparent barrier is anchored with lead base, same as opaque barrier

View evidence from paper

“A transparent barrier was effective as the opaque barrier in attenuating firing fields.”

5

Record place cell activity with transparent barrier in place

Record place cell firing patterns with the transparent barrier bisecting the previously recorded firing field

Not specifiedNot specified

Note: Compare effects to opaque barrier condition

View evidence from paper

“A transparent barrier was effective as the opaque barrier in attenuating firing fields.”

6

Control: Test lead base alone

Place the lead base anchor in the apparatus without any barrier attached to verify it does not affect place cell firing

Not specifiedNot specified

Note: Confirms that observed effects are due to barrier presence, not the anchor mechanism

View evidence from paper

“The lead base used to anchor the vertical barriers did not affect place cell firing.”