Robinson, G; (2008) The effects of sleep deprivation on brain fMRI activation during motion detection and tracking. Doctoral thesis , UCL (University College London).

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Abstract

Sleep deprivation is common and leads to inattention and impaired vigilance. Sleep deprived drivers have an increased road traffic accident rate. Police data suggest that sleep deprivation accounts for up to 23% of all accidents on UK roads. How sleep deprivation leads to impaired driving is uncertain. The skills needed for error free driving are the detection of moving objects, and the ability to track. Work using Functional Magnetic Resonance Imaging (fMRI) has established which brain areas are active during tracking manoeuvres. This study used fMRI imaging to assess the effects of sleep deprivation on visual stimulation and visuo-motor tracking in normal subjects, hypothesising that sleep deprivation in normal subjects leads to impaired tracking and impaired motion detection, with reduced fMRI activation of the brain areas normally activated during performance of these skills. I hypothesised that similar effects would be seen in patients with the sleep fragmentation of OSA, and that any impairments would be reversed by successful CPAP treatment. Ten normal subjects underwent visual stimulation and performed a tracking task during fMRI imaging, before and after total sleep deprivation. Tracking and steering simulator performance were impaired following sleep deprivation. fMRI analysis showed reduced activation of visual cortex area V5 (an area integral to visual motion detection) and increased frontal lobe activation following sleep deprivation. During tracking, there was preservation of precuneus activation following sleep deprivation. Coherent visual motion detection in 24 normal subjects showed impaired motion detection following sleep deprivation, in those subjects who were sleep deprivation vulnerable, correlating with the functional imaging abnormality demonstrated. fMRI imaging during visual stimulation in 17 patients with obstructive sleep apnoea (OSA), before and after continuous positive airways pressure (CPAP) treatment showed increased activation of the frontal lobe pre treatment, and increased precuneus activation post treatment, but no differential visual cortex effect. These results suggest potential mechanisms for the impaired driving seen in association with sleep deprivation and with the sleep fragmentation of untreated OSA. Impairment of attention, preservation of an 'idyling' or 'passive' state, and deficits in visual motion detection may contribute to the driving deficits seen.

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