We imaged the same dendritic segments over imaging sessions separated by weeks. Most spines persisted over this timescale, although other spines appeared and disappeared31. We analyzed the visual responses of persistent spines. The percentage of spines that responded to visual stimulation was stable over a week (37/139 on day 1; 34/139 on day 8). Spines that responded during one imaging session were also likely to respond a week later (65%). Furthermore, visually responsive spines mostly retained their orientation tuning (Fig. 4i-k).
