Figure 4.

Aging decreases neuronal calcium activity in the motor cortex during resting and movement states. (A) Analysis of the animals’ gait patterns when walking on a treadmill. Old mice displayed higher proportions of drag, wobble, and sweep but less steady run after 1-h training. (B) Treadmill performance in young adults, mature adults, and old mice. Treadmill performance is expressed as a percent increase in the fraction of time spent in a steady run between post-training and pre-training (n = 10, 8, 13 mice per group). (C) Schematic showing two-photon Ca²⁺ imaging in the primary motor cortex of head-restrained mice walking on a treadmill. (D) Representative images of L5 somas expressing GCaMP6s when the treadmill is off and on. Scale bar, 20 μm. (E) Calcium fluorescence traces of representative pyramidal somas in young adult and old mice. (F) The average integrated activity of somatic calcium transients while the treadmill is off and on (Young: n = 116 cells from 6 mice; Old: n = 187 cells from 9 mice). (G) Normalized somatic calcium activity in young adult and old mice during treadmill training. Individual circles represent data from a single cell. Summary data are presented as mean ± SEM. *P < 0.05, ***P < 0.001, ****P < 0.0001 by two-tailed Student’s t-test in panel (B) and two-tailed Mann–Whitney tests in panels (F,G).