ABSTRACT
BACKGROUND: Brain regions critical to episodic memory are altered during the preclinical stages of Alzheimer's disease (AD). However, reliable means of identifying cognitively-normal individuals at higher risk to develop AD have not been established. OBJECTIVE: To examine whether functional MRI can detect early functional changes associated with scene encoding in a group of presymptomatic presenilin-1 (PSEN1) E280A mutation carriers. METHODS: Participants were 39 young, cognitively-normal individuals from an autosomal dominant early-onset AD kindred, located in Antioquia, Colombia. Participants performed a functional MRI scene encoding task and a post-scan subsequent memory test. RESULTS: PSEN1 mutation carriers exhibited hyperactivation within medial temporal lobe regions (hippocampus,parahippocampal formation) during successful scene encoding compared to age-matched non-carriers. CONCLUSION: Hyperactivation in medial temporal lobe regions during scene encoding is seen in individuals genetically-determined to develop AD years before their clinical onset. Our findings will guide future research with the ultimate goal of using functional neuroimaging in the early detection of preclinical AD.
Subject(s)
Alzheimer Disease/genetics , Alzheimer Disease/physiopathology , Brain/physiopathology , Memory/physiology , Presenilin-1/genetics , Visual Perception/physiology , Adult , Age of Onset , Alzheimer Disease/psychology , Asymptomatic Diseases , Brain Mapping , DNA Mutational Analysis , Female , Heterozygote , Humans , Magnetic Resonance Imaging , Male , Mutation , Neuropsychological Tests , Photic StimulationABSTRACT
The hemispheric lateralization of memory has largely been informed through the study of patients with temporal lobe epilepsy originating from medial temporal sources (mTLE). The material-specific model of memory relies on the basic framework that the left temporal lobe mediates verbal memories, while the right temporal lobe mediates non-verbal memories. Over the years, this model has been refined, and even challenged, as our understanding of the material-specific memory deficits in mTLE has been further elaborated in the neuropsychological and neuroimaging literature. The first goal of this mini-review is to highlight the major findings in the mTLE literature that have advanced and expanded our understanding of material-specific memory deficits in mTLE. Second, we will review how functional neuroimaging patterns of material-specific hemispheric lateralization in mTLE are being translated into the innovative clinical application of preoperative fMRI memory mapping.
