Fig. 1

Dietary fiber deficiency for 15 weeks promoted cognitive impairment and alteration in synaptic ultrastructure. The object location, temporal order memory and nest-building tests were performed to evaluate mice’s cognition (A–F) (n = 15). A, B The object location test. A Percentage of time spent with the object in the novel place to total object exploration time. B Representative track plots of Con and FD groups recorded by SMART Video tracking system in the testing phase. Blue dot and yellow crucifix denote an object retained in the old place and moved to the novel place in the testing phase. C, D The temporal order memory test. C The discrimination ratio. D Representative track plots of Con and FD groups recorded by SMART Video tracking system in the testing phase. Blue dot and yellow crucifix denote an old familiar object and a recent familiar object in the testing phase, respectively. E, F The nest-building test was used to assess the activity of the daily living of mice. E Untore nestlet weight. F Representative nest of Con and FD groups. G The ultrastructure of synapses on the electron micrograph in the hippocampus CA1 region of mice fed with different diets (scale bar: 500 nm). The second row’s enlarged images were from the first row in the area indicated with a dotted line box (scale bar: 200 nm). H, I Image analysis of the width of the synaptic cleft and the thickness of PSD (n = 3). PSD: postsynaptic density; SC: synaptic cleft; SV: synaptic vesicle. J, K The protein level of SYN and PSD95 in the hippocampus (n = 6). Values are mean± SEM. *p < 0.05 fiber deficiency (FD) group vs. control (Con) group