Ageing is associated with a functional decline of the nervous system. This comes along with an overall decrease of brain mass and an altered synaptic function. Many proteins involved in synaptic function are glycosylated. Glycosylation plays a prominent role in protein stability and conformation, cell-to-cell communication, cell matrix interaction, adhesion, protein targeting and folding. Abnormal glycosylation of proteins can induce deleterious effects as observed in congenital disorders of glycosylation, which often result in serious, sometimes fatal malfunctions of different organ systems such as brain and muscle. While changes in protein glycosylation in the diseased brain are well characterized, it is yet unclear whether alterations in protein glycosylation may contribute to age-dependent changes in synaptic function and thus brain function. Therefore, we will assess the glycoproteome of the aging brain. For selected candidates we will then address how age-associated changes in glycosylation might contribute to the age-dependent decline of brain function.