Chee_relayout_US_Neuro 16/02/2010 11:09 Page 94
Imaging
Table 1: Recent Functional Neuroimaging Studies Figure 1: 3D Plots Showing the Results of Trial-by-trial
Involving Sleep Deprivation Modeling of fMRI Signal Associated with Slower and
Faster Responses for a Given Individual
Cognitive Domain Reference
Working memory Bell-McGinty et al., 2004
6
Habeck et al., 2004
10 1
A
0.8
Chee and Choo, 2004
7
0.6
Choo et al., 2005
9 0.4
0.2
Caldwell et al., 2005
11
BOLD signal
0
Mu et al., 2005
12
-0.2
0.4s
0.6s 910
1112
Mu et al., 2005
13 6
1.3s -2-1
0 1
2 3
4 5
7 8
Chee et al., 2006
8
Lim et al., 2007
14
1.2
1
Attention Thomas et al., 2000
17
0.8
Drummond et al., 2001
20
0.6
0.4
Drummond et al., 2005
18 0.2
BOLD signal 0
Tomasi et al., 2009
21
B
-0.2
0.4s
Chee et al., 2008
19 0.6s
1112
3 4
5 6
7 8
910
1.3s -2-1
0 1
2
Short-term memory Chee and Chuah, 2007
30
Chuah and Chee, 2008
57
Logical reasoning Drummond et al., 2004
60
C 0.6
0.4
Inhibition (go/no-go) Chuah et al., 2006
22
0.2
Risky decision making Venkatraman et al., 2007
23
0
Venkatraman et al., 2008
24 BOLD signal
-0.2
Emotional processing Yoo et al., 2007
25
RW SD 0.4s
0.6s
1112
6
8 9
10
Verbal learning Drummond et al., 2000
15 1.3s -2-1 0
1 2
3 4
5
7
Drummond et al., 2005
16
The signal time course at the mean RT is marked in green. A: Medial frontal region; B: Intra-
parietal sulcus; C: Lateral occipital (extrastriate) cortex. Note that peak signal in the fronto-
A small number of studies have found that the magnitude of task-related
parietal control regions increased with slower responses albeit to a lesser extent during sleep
deprivation (SD). By contrast, response slowing was associated with a decrease in extrastriate
activation following a normal night’s sleep can predict an individual’s
19
peak signal during SD. Reproduced with permission from Chee et al., 2008.
resistance to decline in working memory performance following SD,
11,12
harking to a form of ‘cognitive reserve’ in SD-resistant individuals. of loss of top-down biasing of visual processing or whether visual cortex
However, more work needs to be undertaken to evaluate the robustness was transiently ‘shut down’ as a consequence of prolonged
of these data before fMRI can be deployed as a working tool.
14
wakefulness
31
(see Figure 1). Obliquely related to these findings, it has
recently been shown that TMS applied to the left lateral occipital lobe,
The Neural Correlates of Attention Deficits in an area quite consistently affected by SD, can improve working memory
Sleep Deprivation in sleep-deprived individuals.
32
The notion that failure to sustain attention might underlie decrements in
short-term memory was mooted by the finding that increased variability SD results in elevation of task-related activation in the thalamus,
19,21,33
in response time declined more reliably across SD test sessions than which may represent a compensation for the overall lower levels of
memory performance.
14
This hypothesis was tested in a pair of arousal and attenuated fronto-parietal activity that occur when one is
experiments that parametrically varied visual item load and visual short- sleep-deprived. During lapses in attention, the thalamus shows
term memory load in tests conducted following normal sleep and after decrements in activity when under SD but increases in activity after
SD. As expected, capacity-limited visual short-term memory capacity normal sleep.
19,21
The former may represent some form of sensory
was compromised in sleep-deprived persons. Intriguingly, however, SD- gating
34
whereby the flow of sensory information is attenuated, perhaps
related decline in parietal activation occurred well before memory to allow a person to slip into sleep undisturbed by the environment.
capacity was saturated.
30
This finding, together with the attenuation of
extrastriate activation at low levels of perceptual load, suggested that Decision-making and Emotional Processing
deficits in visual attention or visual processing make significant SD can influence decision-making in a manner that resembles deficits
contributions to the reduction of memory capacity observed in SD. arising from an orbitofrontal lesion.
35
Persons subjected to extended SD
for 49 hours continued to make risky, disadvantageous choices despite
Lapses in attention are associated with response slowing. By analyzing sustaining losses.
36
Risky decision-making following even a single night of
cortical responses according to response time, lapses in SD were found total SD was found to elicit greater activation of the nucleus accumbens
to differ from those occurring after normal sleep by showing lesser when the riskier of two choices was selected. This signified a higher
modulation of fronto-parietal activation and profound reduction in anticipation of reward without a change in odds. Concurrently, reduced
extrastriate activation.
19
Thus, visual sensory processing appears to be right insula and lateral orbitofrontal activation followed loss trials signaling
significantly compromised during attentional lapses that occur in SD. At an attenuated reaction to loss that could impair aversive learning. These
present, however, it remains unclear whether this was primarily a result gamble-related brain activation changes did not have the behavioral
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US NEUROLOGY
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