increased error scores across all t

increased error scores across all tasks (Cummings et al, 1996) (Figure 35-2).Functional Changes in the Aging Brain In addition to macroscopic and microscopic morphologic changes in the aging canine brain, there is also evidence of functional change.CHANGES IN THE BLOOD-BRAIN BARRIER WITH AGE The BBB is a collective term for the complex vascular systemof endothelial cells, astrocytes, pericytes and basement membranes surrounding the brain. The BBB allows for selective transport of nutrients from the blood to neuronal cells (Khan, 2005). An MRI study involving 18 beagles (four to 15 years old) showed a non-significant increase in BBB permeability with age; surprisingly, one six-year-old beagle, in which no pathology was expected,had severe BBB leakage and dysfunction,enlarged ventricles,Aβdeposition and cognitive dysfunction (Su et al, 1998). Another study reported a direct link between vascular Aβdeposition and vessel wall integrity; leptomeninges obtained from old dogs affected by cerebral amy721Cognitive