Figure 2
Scheduled feeding rescued spatial working memory in circadian arrhythmic hamsters and phase-delayed the rhythm of test performance in entrained animals. (A,B) Time of food availability (red outline) increased food anticipatory activity (FAA) prior to the time of feeding in both entrained (n = 9) and arrhythmic animals (n = 12). Activity returned to baseline levels when animals resumed ad libitum feeding. Brackets indicate portions of the actograms subjected to periodogram analysis. Peaks in blue above the black lines indicate statistically significant rhythms as determined by chi-square periodogram analysis. (C,D) The mean (±SE) daily FAA ratio was calculated during SF (red, green circles) and ad libitum feeding (gray circles). Gray bars represent the alternation scores (right y-axis) during baseline and on day 21 of SF. *Indicates significantly different from chance (i.e., 50%); P < 0.01. (E,F) Waveforms for total (mean ± SE) hourly locomotor activity during each phase of the study (BL = baseline, SF = scheduled feeding, AL = ad libitum) were constructed with the last 5 days of each condition (i.e., the last 5 days in panels C,D during baseline, SF, and AL). Data for each hour were averaged and plotted at the end of that hour (e.g., ZT17 is the mean of data from ZT16-17). Black and white rectangles indicate the times of night and day, respectively. Time of SF indicated by vertical black dotted lines. (G,H) Alternation scores during baseline and SF conditions at four different zeitgeber times (ZT; *P < 0.01). ZT17 and ZT23 represent early and late night, respectively. Night and day are indicated by black and white rectangles in panels E,F. Sample sizes (n) for panels G,H: entrained (SF = 9; AL = 10), arrhythmic (SF = 12; AL = 9). All animals remained in a 16:8 light-dark cycle throughout the study.
