ABSTRACT
The idea of reserve against brain damage stems from the repeated observation that there does not appear to be a direct relationship between the degree of brain pathology or brain damage and the clinical manifestation of that damage. Two interrelated concepts have been proposed. Brain reserve is an example of what might be called a passive model of reserve, where reserve derives from brain size or neuronal count. The model is passive because reserve is defined in terms of the amount of brain damage that can be sustained before reaching a threshold for clinical expression. In contrast, the cognitive reserve (CR) model suggests that the brain actively attempts to cope with brain damage by using pre-existing cognitive processing approaches or by enlisting compensatory approaches. Individuals with more CR would therefore be more successful at coping with the same amount of brain damage. As will become clear throughout this volume, these models are by no means mutually exclusive.
