Figure 2

Representative confocal images (scale bar = 10 μm) depict the compartmental expression of IEGs (above) and their temporal relationship to the experiences of the animals used in the experiments described here (below). Cells (counterstained with DAPI, blue) that exhibit high frequency firing of the type that characterize place fields begin to express IEGs such as zif268 (red) within minutes. When this activity occurs 30 minutes prior to the animal being killed (during the time in which both caged control and immediate animals are at rest in the home cage, while delay animals are exploring a novel environment), the transcripts migrate to the cytoplasm where they are apparent as a diffuse cloud (bottom left). In contrast, when this activity occurs within 5 minutes of the animal being killed (during the time in which both caged control and delay animals are at rest in the home cage and immediate animals are exploring a novel environment), the transcripts are visible as bright foci within the nucleus (bottom right). Cells active during both time periods will express zif268 within both cellular compartments (top).