Neural dedifferentiation in the aging brain: the role of GABA and implications for motor performance

Older adults typically demonstrate bimanual coordination deficits that are at least partially attributed to age-related changes in the structural as well as functional properties of the brain. In this PhD thesis, neural dedifferentiation, i.e. an aging-induced process during which brain activity and connectivity pattern partially loose their selective nature, was critically investigated. In a first part, age-related alterations in functional connectivity patterns within the brain were examined using task-related functional magnetic resonance imaging and transcranial magnetic stimulation. Results indicated an increased connectivity within as well as between networks in older as opposed to young adults, pointing towards an (unintended) spread of neuronal activity that did not benefit motor performance. In a second part, gamma amino-butyric acid (GABA), i.e. the principal inhibitory neurotransmitter within the human brain, was investigated as its concentration is hypothesized to decrease with advancing age, thereby contributing to the process of neural dedifferentiation. Results indicated that age-related differences in GABA levels could at least partially be attributed to the well-known aging-induced gray matter atrophy. Furthermore, results indicated that the association between GABA levels and motor performance was task-selective and age-dependent. Lastly, a task-related transient modulation of GABA was observed in response to performance of an action selection task. The more pronounced task-related decrease of regional GABA, the higher task-related brain activity within that particular brain region was observed. Notably, in older adults, the modulatory capacity of GABA levels was also related to bimanual motor performance.

Publication year:2021

Accessibility:Open