Table I. Functional enrichment of differentially expressed proteins. Significantly enriched (Fisher's exact p value < 0.05) functional protein groups (according to Ref. 20) are indicated per age group.

Functional group	Proteins	Fold enrichment	Fisher's exact p value
Early-aged
Cell metabolism	GSTP1, GAPDH, GOT1, ENO1, ENO2, GDA, PIP5K1C, PRDX1	4.1	0.0003
Structural plasticity	CFL1, TUBB4, TUBB5, DPYSL2, MTAP6, GAP43, TUBB3, TPPP	2.2	0.0219
Middle-aged
Cell adhesion/transsynaptic signaling	GPC1, NTM, HAPLN1, NCAN, IGSF8, BCAN	4.9	0.0005