82 BBC SCIENCE FOCUS MAGAZINE COLLECTION
SLEEP5 The combined therapy effectively returned
the insomniacs’ performances on the tasks to
normal levels. Those who received it became
significantly slower on the simple task and
faster on the complex task when tested later.
This outcome suggests that an insomniac’s brain
work s d if ferent ly to ot hers a nd t hat some of t he
cognitive changes associated with insomnia
are at least partly reversible.
In another study, Dr
Altena and her colleagues
found that insomniacs
outperform good sleepers
on a verbal fluency task.
Test subjects had to press
a button whenever a word
belonging to a specified
category was presented.
The performances of the
insomniacs who received
sleep therapy for six weeks
was comparable to that of
the healthy control subjects
when they were tested again.
“Insomniacs suffer from a physiological
condition best described as a light form of
stress, which can be measured in higher
brain activation when trying to fall asleep,”
Dr Altena explains. “This hyper-arousal may
underlie some of the high-performance levels
we observed. It may serve as a compensatory
mechanism of the brain to function relatively
well during the day, despite the sleeping
difficulties.”
Dr Altena’s group has found that insomniacs’
brains are structurally different to those of
good sleepers. They used a brain-scanning
technique called voxel-based morphometry to
measure and compare the volumes of various
brain structures in 24 chronic insomniacs and
13 healthy control subjects. The insomniacs
showed reduced volume of
grey matter in three regions
of their brains. Plus, the
reduced volume of the orbito-
frontal cortex was strongly
related to the severity of the
insomnia – the more severe
a volunteer’s complaints, the
greater the volume reduction.
The results fit well with the
functions of the orbito-frontal
cortex, which is known to be
involved in decision-making
and problem-solving, both
of which are significantly impaired following
sleep deprivation. But it’s unclear whether
these structural changes cause the insomnia
or come after it.
“To draw conclusions about the neural
mechanisms underlying insomnia we need
to investigate which of these effects contribute
to the condition and which are consequences
of it,” says Dr Altena.“Insomniacs
suffer from a
condition that’s
best described
as a light form
of stress”
Scientific studies are trying
to get to the bottom of
what makes for a good
night’s sleepSLEEP AND MEMORY
Quintilian, a famous first-century
Roman teacher of rhetoric, noted the
“curious fact that the interval of a
single night will greatly increase the
s treng th of memor y ”. And it ’s now
well established that sleep enhances
memory consolidation.
Researchers from the University
of Haif a in Jordan have shown that a
daytime nap enhances memory
recall, and that even a short nap
lasting just six minutes is sufficient
to aid the processing of memories.
The slow brainwave oscillations thatoccur during short-wave sleep are
thought to mark the integration of
new information with pre-existing
knowledge. Also, changes in the
pattern of how genes are switched
on or off during REM sleep may
promote the strengthening of
neuronal connectivity that is thought
to underlie memory formation.
One study found that sleep
deprivation promotes the generation
of f alse memories. So using it a s a
technique when interrogating
suspects seems fairly pointless.Don’t forget: beauty sleep is crucial