Save, E., Nerad, L. and Poucet, B. (2000). Contribution of multiple sensory information to place field stability in hippocampal place cells. Hippocampus, 10, 64-76.

Hippocampal place cells in rats display spatially selective firing in relation to both external and internal cues. In the present study, we assessed the effects of removing visual and/or olfactory cues on place field stability. Place cell activity was recorded as rats searched for randomly scattered food in a cylinder where the only available cue was a "cue card". Following an initial session with the lights on, three sessions were run in a row with the cue card removed. In addition, the lights were either turned off or left on and the floor was cleaned or left unchanged. Four conditions were used: dark/cleaning, dark/no cleaning, light/cleaning, and light/no cleaning. In the dark/cleaning and light/cleaning conditions most place fields were not stable (i.e. abruptly shifted position). In addition, half of the cells stopped firing in the dark/cleaning condition. In contrast, in the dark/no cleaning and light/no cleaning conditions most place fields remained stable across sessions. These results suggest that (1) rats are not able to rely on only movement related information to maintain a stable place representation, (2) visual input is necessary for the firing of a large number of cells, and (3) olfactory information can be used to compensate for the lack of visuospatial information.