GAP43 and early-onset autosomal dominant Alzheimer disease: GAP-43 is essential for pre-synaptic terminal and axonal growth as well as learning and memory functions, all of which play a pivotal role in neuronal development, synaptogenesis and hippocampal function.6,23,24 Among patients diagnosed with MCI or Alzheimer’s disease, CSF GAP-43 levels have been shown to negatively correlate with global cognition.6,20,25,26 Studies using transgenic mice have also associated the overexpression of the GAP-43 protein with memory dysfunction,27 but limited literature has examined the associations between CSF GAP-43 and specific cognitive domains in humans.