SD Lapse Brain Activation Changes

The study investigates the association between lapses during sleep deprivation (SD) and changes in brain activation. Participants underwent functional magnetic resonance imaging (fMRI) scans while performing a task, with one session conducted after SD and another after regular wakefulness. Results showed that SD was associated with slower and less accurate responses, reduced task-related activity, and peristimulus signal reduction. The study suggests that lapses during SD are related to reductions in visual sensory function and top-down control deficits, highlighting the importance of understanding these phenomena for improving sleep deprivation research.

Notes for paper: Lapsing during Sleep Deprivation Is Associated with Distributed Changes
in Brain Activation (Chee et al., 2008).
Aim(s):
 To identify the association between lapses occurring during SD and task related brain
activation changes.
Participant:
 n= 24 (mean age 22.5 +/- 1.6 years).
 13 females, 11 males; all right handed individuals.
Study Design:
 Participants had at least 6.5 hours of sleeping every night since a month before the
study.
 Morningness-eveningness score less than 22.
 Without any sleep disorder.
 Without any psychiatric disorder.
Protocol:
 Vigorous activity, smoking or consuming alcohol was prevented.
 Actigraph was presented in the first visit to monitor sleep patterns.
 fMRI imaging was done on the next two visits.
 SD and RW sessions were separated by a week.
 Participants took part in non-strenuous activity during SD session.
Measures:
 Local and global letters task stimuli

 3 T Allegra system (Siemens) for imaging
 Brain Voyager QX version 1.8.6 for image processing
 Voxel for task related activation
 Trial-by-trial analysis and direct comparison
Results:
 SD responses were slower and less accurate than RW.
 Correct trial response distribution had a pronounced long right tail
 Incongruent trials had slower response than congruent trials.
 Significant reduction in task related activity in SD compared to RW.
 Lapse related cortical responses showed peristimulus signal reduction.
 No difference in this reduction between RW and SD states.
 Association observed between increased peak signals and lapses in regions that
control cognition.
 More pronounced signal elevation in RW.
 SD lapses associated with reduced extrastriate signals.
 Greater task related thalamic activation in SD.
Interpretation:
 Reduction in task-related extrastriate activation during SD lapses proves that low
visual sensory function is a contributory factor.
 Top-down control deficits are associated with lapses during SD.
 Neuronal loss and lowering in time during SD recruits the frontoparietal neurons can
to compensate for attention lapses.
 Wake state instability is visible while considering trial-by-trial fluctuations in
response time, during SD state.

 Lapses in RW and SD state differ in several ways. The most relevant difference is in
extrastriate activation attenuation that precedes a widespread close down of external
environment responsiveness.
 A thorough understanding of SD lapses will benefit from teasing out reduction in top-
down attention control, attenuated visual cortex contributions and neurotransmitters
involved in rapid transition from putative microsleep to wakeful alertness.