Cognitive deficits in mild cognitive impairment

Mild Cognitive Impairment (MCI) describes older adults whose cognitive and functional status is considered in-between normal cognitive aging and dementia. MCI is an heterogeneous entity with a number of subtypes each with a different neuropsychological profile. The MCI amnestic type is the better known of the subtypes and many patients with this clinical and cognitive profile will develop Alzheimer's disease. Although the amnestic MCI concept emphasizes memory loss, other cognitive functions are frequently affected, namely semantic fluency, attention/executive functions, visuo-spatial abilities and language comprehension. MCI criteria make use of scores in delayed recall of episodic memory tasks to establish the presence of memory impairment. Poor delayed recall can, however, reflect deficits in distinct memory processes. Difficulties in the learning process of MCI patients have also been documented. During the acquisition of semantically structured lists of words, these patients employ less semantic clustering strategies than controls. However, if attention is called to the semantic structure, they can make use of it on subsequent trials in order to improve learning. Detailed knowledge of the memory processes disturbed in MCI should contribute to the understanding of the pathophysiology of MCI, allow a more precise identification of patients with high probability of progression, and help to delineate future rehabilitation interventions in these patients.