Figure 1: Arc was expressed rapidly in the nucleus after 5-min image presentation, and translocated to the cytoplasm in 10–20 min.

(a) Experimental design. At P1, Chicks were individually put into the apparatus, exposed for 5 min to a moving red square presented on the monitor, returned to the dark incubator (except for 0 min condition) and VW cells were analysed at indicated time points. Chicks kept in the dark incubator (untreated; UT) were used as controls. (b) The expression pattern of Arc transcripts in the VW and schema showing the pathway for visual imprinting in the chick telencephalon. The square area shows regions analysed by FISH. (c) Representative images of cells with nuclear transcripts alone (upper), with both nuclear and cytoplasmic transcripts (middle; Nuc + Cyto cells), and with cytoplasmic transcripts alone (bottom). The upper and middle cells are Nuc cells, and the middle and bottom cells are Cyto cells. (d) Arc transcripts (green) in UT, at 0 min, and 20 min. Nuclei are stained with propidium iodide (PI, magenta). Nuclear and cytoplasmic localizations of Arc transcripts are prominent at 0 min and 20 min, respectively. (e) Temporal changes in the percentage of cells with nuclear transcripts (Nuc cells; upper left) and with cytoplasmic transcripts (Cyto cells; upper right). The percentage of Nuc cells was significantly high at 0 min and 10 min after presentation, and the percentage of Cyto cells increased at 10–120 min after presentation of the image. The number of analysed cells was not significantly different among conditions (bottom). (f) Schema indicating translocation of Arc transcripts with time. Arc is expressed in the nucleus immediately after the 5-min image presentation, and most of the transcripts translocate to the cytoplasm within 20 min after image presentation. Consequently, when the 2nd presentation is performed within 20–120 min after the first one, cells with both nuclear and cytoplasmic transcripts are regarded as the cells that responded to both stimuli. *p < 0.05; **p < 0.01. Scale bar = 250 μm (b), 5 μm (c), and 20 μm (d).