No abstract

The frontal lobes constitute two thirds of the human brain, yet the functions performed by them remained mysterious for a long time. Apart from their well-known involvement in motor function and language, little was previously known about the functions of the frontal lobes. Recent advances have uncovered important roles for the frontal lobes in a multitude of cognitive processes, such as executive function, attention, memory, and language. The importance of the frontal lobes in processes underlying affect, mood, personality, self-awareness, as well as social and moral reasoning, is also a renewed area for research. This article focuses on recent advances in understanding frontal lobe functions.

Background: Amnestic mild cognitive impairment (aMCI) is considered a transition stage between normal aging and Alzheimer’s disease (AD). Two main clinical subtypes of aMCI have been identified: (1) single-domain aMCI (aMCI-SD), with isolated episodic memory impairments, and (2) multiple-domain aMCI (aMCI-MD), with episodic memory impairments and deficits in one or more other cognitive domains. Aims: To map the pattern of gray matter (GM) atrophy associated with aMCI-SD, aMCI-MD and mild AD. Methods: A group of aMCI-SD, aMCI-MD characterized by executive function disorders, mild AD and cognitively unimpaired subjects underwent a comprehensive neuropsychological assessment and a high-definition MR brain scan. Voxel-based morphometry analysis was used to characterize the GM tissue loss in each patient group, and the common pattern of GM atrophy in aMCI-SD and aMCI-MD. Results: aMCI-SD and aMCI-MD are characterized by a common pattern of GM atrophy within the medial temporal cortex, predisposing to AD and correlating with the severity of verbal memory symptoms. Moreover, the pattern of GM atrophy observed in aMCI-SD, aMCI-MD and mild AD revealed that, from an anatomical point of view, these three clinical syndromes could represent three severity points along the continuum between normal aging and AD.