State Instability and Cognitive Performance

The study investigated the effects of sleep deprivation on brain function and cognitive performance, specifically examining the state instability hypothesis and the prefrontal cortex impairment hypothesis. The findings did not support the state instability hypothesis, failing to show a link between state instability and increased sleep drive or variable neurobehavioral performances. However, the study did partially support the prefrontal cortex impairment hypothesis, showing that moderate task complexity was less affected by sleep deprivation due to better attention engagement and top-down effects from the frontal lobe on thalamus activity.

To what extent is the state instability hypothesis supported by the study?
The hypothesis postulates that state instability is associated with an increase in sleep drive
and it leads to variable neurobehavioral performances. The research fails to support the
hypothesis. The study illustrated the application of functional magnetic resonance imaging to
analyze the function of adult working memory. It attempted to show association between
manipulation and maintenance tasks after sleep deprivation with their response time. The
results established link between better performances to the more complex task and also
showed activation of the cortical regions of the parietal, frontal and thalamic regions of the
brain. It did not utilize any parameter to depict degradation in waking state function due to
attention lapses after sleep deprivation. Thus, the study failed to establish how cognitive skill
deficits accounted for an increase in performance variability. It did not illustrate the multiple
neurobiological mechanisms that govern interaction between states of sleep and wakefulness.
Thus, it did not support the hypothesis.
To what extent is the prefrontal cortex impairment hypothesis supported?
This hypothesis states that sleep deprivation creates negative effects on cognitive
performance and alertness and this is related to brain activity and function decrease in
thalamic and prefrontal cortex activity. These regions are involved high cognitive skills,
alertness and attention. The study investigated the interaction between task complexities and
activation of prefrontal cortex regions in the brain. It assessed the domain of working
memory and tried to correlate between decline in cognitive skills and physiological changes
in prefrontal cortex after sleep deprivation. It focussed on task complexity in terms of
maintenance and manipulation. This research predicted that manipulation would lead to an
increase in parietal and prefrontal activation in case of manipulation when compared to
maintenance states. Simpler tasks are generally expected to be less affected than moderately

complex tasks. This study also proposed to correlate better performance from manipulation
states with an increase in activation of the greater lobe. It utilized PLUS program for
engaging item manipulation in case of verbal working memory. The results highlighted the
dynamic nature of dysfunction in cognitive skills. It gave evidence that suggested better
preservation of performances with respect to complex task. However, when there was a
lesion in the frontal lobe, greater complexities in task attenuated cognitive decline or deficits.
It proved frontal lobe additional engagement after sleep deprivation with sufficiency in task
complexities. Thus, it was successful in establishing a relation between SD and less effect on
tasks that were moderately complex. This was due to the fact that moderate tasks were
associated with better attention engagements. Frontal lobes were shown to exert a top-down
effect on activation of thalamus region in the brain. During wakefulness, PLUS showed
greater activation of thalamus when compared to LTR. Thalamic activation increased for
both tasks after SD. Thus, the fact that some tasks increased prefrontal cortex activity and
some decreased it needs to be explored more before justifying any form of cognitive decline
after SD. Therefore, this theory failed to explain the relation between cognitive decline and
decrease in activity of prefrontal cortex.