HIPPOCAMPAL PLACE FIELDS ARE ALTERED BY THE REMOVAL OF SINGLE VISUAL CUES IN A DISTANCE-DEPENDENT MANNER

Hippocampal CA3 cells were recorded in male Long-Evans rats that explo red a square recording chamber. Three of the 4 chamber walls held a re ctangular cue card, each of different size. Rotating the set of cue ca rds rotated the location of the place fields. Place fields were common close to the walls of the recording chamber, particularly the walls w ith cues. When single cues were removed, the spatial information conte nt decreased but returned to baseline levels when the cue was replaced . When a cue near a place field was removed, the place field firing ra te and area decreased; when a distant cue was removed, firing rate and area increased. Thus, removing single visual cues predictably and rev ersibly altered hippocampal place fields. Together, the results sugges t that hippocampal neurons may optimize the encoding of visual informa tion and are consistent with a distance-encoding hypothesis of CA3 net work function.