A method for the assessment of the functional neuroanatomy of human sleep using FDG PET

Although sleep is characterized by relative behavioral inactivity, cortical activity is known to cycle in well-defined periods across this state. Cognitive function during sleep has been difficult to define, although disturbances in sleep are known to result from, and to cause, various human pathologies, including neuropsychiatric disorders. Assessment of brain function in humans (related to cognitive operations) during sleep has been limited, until recently, to surface electrophysiologic recordings that limit analysis of regional function, particularly in deep structures. The current report describes one method of assessing human forebrain activation during sleep using the [18F]2-fluoro-2-deoxy-d-glucose ([18F]FDG) method and positron emission tomography (PET) measures of regional cerebral glucose utilization. In comparison with other functional brain imaging techniques (e.g., assessment of blood flow or functional magnetic resonance imaging), this method offers the advantage of a more naturalistic study of sleep since subjects do not have to sleep in a scanning device. This leads to a higher rate of successful completion of studies. The primary disadvantage of this method is the decreased temporal resolution necessitating assessments of global sleep states (e.g., REM or NREM) as opposed to assessing events within a sleep state (e.g., sleep spindles or rapid eye movements).