State Instability and Prefrontal Cortex Impairment Support

The state instability hypothesis is largely supported by the study, which found that sleep deprivation leads to variable neurobehavioral performances and increased peak signals in cognition control regions. On the other hand, the prefrontal cortex impairment hypothesis is not fully supported as the study did not find a correlation between reduction in activity of prefrontal cortex and severity of lapses.

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 study largely
supports the hypothesis. This study illustrated differences between neural activation during
lapses in sleep deprivation and lapses after a normal night’s sleep. Brain imaging studies of
the participants showed that sleep deprivation resulted in less accuracy and more variability
in the performance. A prominent long right tail was observed after SD in correct trial’s
distribution of response. Task related activation was found to be reduced in SD in comparison
to rested wakefulness. The reduction in peak signal was comparatively small between the
differences in peak signals induced by such lapses in both the states. Increased peak signals in
cognition control regions were associated with SD lapses. This elevation was less pronounced
in SD compared to RW. RW lapses in inferior occipital regions showed no relation to peak
signals. However, in SD they were found to be linked to a reduction in extrastriate peak
signals. On comparing cortical responses, greater bilateral intraparietal sulcus and medial
frontal peak signals were found to be correlate with slow reponses. Fastest responses failed to
create higher activation in the extrastriate visual cortex region. Thus, the study found that SD
attenuated activation in brain during lapses in addition to affecting the overall activation
patterns related to tasks. These findings helped in differentiating SD lapse from other lapses
that occur after a normal sleep. Thus, the findings were completely in line with the theory of
state instability.

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. This
decrease in activity occurs in thalamus and the prefrontal cortex which is involved in
attention and alertness and higher-order cognitive processes. The change in prefrontal cortex
area result of global response slowing effects that are often related to the brain. The
hypothesis also states that short, stimulating PET scans are provide evidence to prove the link
between sleep deprivation in adults with a change in the prefrontal cortex regions. The
principle aim of this study was to establish an association between attention lapses and
delayed behavioural responses during sleep deprivation. It focused on identification of
changes that occur during brain activation related to tasks and their correlation with SD
lapses. It did not correlate reduction in activity of prefrontal cortex with severity in lapses.
The study was motivated by findings which suggested a decrease in BOLD signals in regions
of the brain that take part in visual coordination and processing of sensory information,
related to tasks. However, it did not measure any increase or decrease in the cerebral
metabolic rate in accordance to prefrontal cortex activity. The study did not utilize sufficient
tools that would investigate the effects of sleep deprivation on the performance of the
respondents. For investigating the effect in prefrontal cortical regions, an array of battery
tests should have been employed. Thus, the parameters used in this study failed to support the
hypothesis.