Key Stage 5 – MRI
The plastic brain
Research Report A
Summary of brief communication in Nature 388 171 – 174 (10 July 1997)
Distinct cortical areas associated with native and second languages
Karl H. S. Kim, Norma R. Relkin, Kyoung-Min Lee and Joy Hirsch
The ability to acquire and use several languages selectively is a unique and essential human capacity. Here
we use fMRI to investigate how multiple languages are represented in the human brain.
Indirect evidence for topographic specialisation within the language-dominant hemispheres of multilingual
subjects has been provided by clinical reports of selective impairments in one or more of several languages
as a result of brain surgery. However, the locations of separate language functions in the brain have not yet
been identified.
Twelve multilingual volunteers were recruited. Six subjects (‘early’ bilinguals) were exposed to two
languages during infancy, and six subjects (‘late’ bilinguals) were exposed to a second language in early
adulthood. Each of the ‘late’ bilingual subjects had lived in the country of the second language, which
assured a high standard for fluency. Each of the early bilinguals was raised in a home where either the
parents spoke one language and siblings and friends spoke another, or the parents spoke two languages.
Ten languages were represented in total, and all subjects reported approximately equal fluency and
frequent usage in each language at the time of testing.
The subjects entered an MRI scanner. They were instructed to use silent internal speech to describe events
that occurred during a specified period of the previous day (morning, afternoon, night) for 10 seconds each
during the 30 second task period. Immediately before each run the subject was told which language he/she
was to imagine speaking.
Figure 1 shows the main findings for a typical ‘late’ bilingual subject. The anterior (front) language area is
highlighted by the green box and shown expanded in the inset. Red indicates significant activity during the
native language task, whereas yellow indicates activity associated with the second language task. Two
distinct but adjacent centres of activation separated by ~7.9 mm were evident, suggesting that two specific
regions served each of the two languages. Figure 2 shows that in the posterior (back) language area of the
same subject, highlighted by the green box and shown expanded in the inset, the same tasks yielded
centroids of activity with a centre-to-centre spacing of 1.1 mm, less that the width of a voxel, suggesting
that similar or identical regions served both languages in this area.
For all six late bilingual subjects, distinct areas of activation were observed for the native and second
languages in the anterior language area of the brain.
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front
back
Figure 1 (Nature 388 171 – 174)
Figure 2 (Nature 388 171 – 174)
Figure 3 illustrates the main findings for a typical early bilingual subject in the anterior language area, in
which the centre-to-centre distance between activity centroids of the two activity patterns was 2.3 mm,
less than 1.5 voxels. This represents the general pattern for all six early bilingual subjects, where the mean
separation was 1.53 mm. In the case of the posterior language area, the mean separation for all early
bilingual subjects was 1.58 mm, similar to the anterior area.
Figure 3 (Nature 388 171 – 174)
Our findings show that activation sites for the two different languages tend to be spatially distinct in the
anterior language area when the second language was obtained late in life and not when acquired in early
childhood. The observation that the anatomical separation of the two languages in this area varies with the
time at which the second language was acquired suggests that age of language acquisition may be a
significant factor in determining the functional organisation of this area of the human brain.
It is possible that representations of languages in the front language area of the brain that are developed
by exposure in early life are not subsequently modified. This could necessitate the utilisation of adjacent
areas for the second language learned as an adult.
The difference between the results of this investigation and a positron emission tomography (PET) study in
which multiple languages were found to generate overlapping regions of activation within the anterior
language area of the brain may be reconciled in part by the higher effective spatial resolution of this fMRI
technique.
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Key Stage 5 – MRI
The plastic brain
Research Report B
Summary of Research article in Neurorehabilitation and Neural Repair 25 (7) 607 – 616 (2011)
Motor practice promotes increased activity in brain regions structurally disconnected after
subcortical stroke
Rosemary A Bosnell, Tamas Kincses, Charlotte Stagg, Valentina Tomassini, Udo Kischka, Saad
Jbabdi, Mark W Woolrich, REsper Andersson, Paul M Matthews and Heidi Johansen-Berg
Repetitive movement practice is an important component of neurorehabilitation after stroke. Clinical
studies have documented performance gains during practice of a motor skill by patients following a stroke.
Imaging studies in healthy individuals have shown that gains in motor performance with practice are
mediated by dynamic changes in brain activation in specific cortical and subcortical regions of the motor
control network. However, the neural correlates of motor performance gains with practice have only
recently begun to be explored in patients after stroke. Defining patterns of functional brain plasticity
associated with motor practice could help doctors to improve therapeutic approaches.
Here, we test the hypothesis that practice-related changes in brain activity are different in patients after
stroke compared with healthy controls.
To do this, we used fMRI to assess changes in task-related brain activity while participants performed a
complex visuomotor tracking task before and after 15 days of practice. Changes in brain activity were
contrasted between patients who had suffered single subcortical left-hemisphere stroke more than 6
months previously and age-matched healthy controls.
Methods
Participants were 10 right-handed patients who had previously suffered a first stroke at least 6 months
previously, and 18 age-matched right-handed controls. The motor function in the right hand of stroke
patients was affected. The patients were without symptoms of any other neurological condition. They had
intact sensation to light touch in affected limbs, and were able to give informed consent. Patients all
demonstrated that they could follow the movement of a visual target on a computer screen, and that their
grip force was sufficient to perform the task.
During fMRI sessions, participants followed on-screen guidance to perform a visuomotor tracking task. They
had to correctly alter the grip force applied to a pressure-sensing device held in their right hand. The
sessions included alternating 38 s blocks of rest and task conditions.
Participants then practised the task at home for 15 days, before returning for repeat fMRI sessions.
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Results and discussion
At baseline, statistical analysis of fMRI data showed that performance of the tracking task versus rest was
associated with activation of contralateral sensorimotor and bilateral premotor and parietal cortical areas,
basal ganglia, thalamus, and cerebellum across all participants. These data defined areas of interest in
which to contrast the voxelwise activity between groups. Patients showed significantly reduced activation
relative to the controls at baseline in the brain regions shown in the diagrams below.
Figure from Neurorehabilitation and Neural Repair 25 (7) 607 – 616 (2011)
After 15 days of task practice at home, fMRI was repeated, and differences from baseline to post-practice
scans were computed and compared across groups. Strikingly different patterns of practice-related brain
activation changes with practice were found between the two groups in cortical regions, including the
inferior frontal gyrus, insular and superior temporal regions, and in the basal ganglia and thalamus
subcortically. Many of these same regions were shown to suffer subtle structural damage in the patients. In
healthy controls, task performance after practice was associated with significantly lower activity in these
brain regions compared to performance of the same task at baseline, consistent with the notion of
increasing efficiency of motor activity for performance of highly practiced movements. However, opposite
trends were seen in patients, who showed an increase in task-related activity in these regions following
practice, consistent with the idea of increased recruitment with practice. This is consistent with the findings
of previous studies.
Conclusion
Our observations provide direct evidence that motor practice promotes functional recovery of brain
regions in which structural integrity is impaired by stroke.
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Key Stage 5 – MRI
The plastic brain
Research Report C
Summary of Research article in Nature communications 10.1038 (2013)
Phantom pain is associated with preserved structure and function in the former hand area
Tamar R Makin, Jan Scholz, Nicola Filippini, David Henderson Slater, Irene Tracey and Heidi
Johansen-Berg
Following arm amputation, individuals often perceive pain in their missing limb. The cause of phantom pain
experience has commonly been attributed to maladaptive plasticity: following loss of sensory input, the
deprived hand area of the primary sensorimotor cortex becomes responsive to inputs from cortical
neighbours (for example, the lips). These inputs are then interpreted as pain arising from the missing hand.
We suggest an alternative explanation for phantom pain. We propose that over the long term, continued
painful inputs, such as those arising from nerve damage at the site of amputation, could preserve local
cortical structure and function in an experience-dependent manner, such that greater chronic phantom
sensation is associated with greater phantom representation. This model will therefore predict that
phantom pain correlates more strongly with maintained phantom representation than with shifted lips
representation.
To revisit the maladaptive plasticity model, we studied the cortical correlates of phantom pain in the area
representing the missing hand itself, rather than the representation of the neighbouring (intact) body parts.
To assess changes in the hand area relating to phantom experiences, we studied 18 individuals with one
arm amputation, 11 individuals who had been born with one arm (one-handers) and had no phantom
sensations, and 22 intact controls. The average time since amputation for the amputees was 18 years.
To functionally localise the cortical representation of the missing hand, participants underwent an fMRI
scan while moving each hand (real or phantom) separately. One-handers were told to imagine moving their
missing hand, as they did not have phantom limbs.
Significant activation was identified in the primary somatosensory cortex contralateral to the phantom
hand in nearly all amputees. Indeed, group activation for phantom movements was similar to that found
during two-handers’ non-dominant hand movements in the primary sensorimotor cortex.
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Activation for movement of phantom hand versus toes in amputees (a) and for imagined missing-hand
movements versus toes in 1-handed controls (b), projected on individuals’ inflated contralateral hemisphere.
Arrows indicate the position of the central sulcus. Amputees are ordered according to their phantom pain
ratings (amputees with greater chronic pain are presented first).
Figure from Nature communications 10.1038 (2013)
Next, we examined the relationship between phantom pain and movement-related fMRI signal in the
phantom hand area. The maladaptive plasticity model predicts increased activity within the phantom
cortex during lip movements. To identify cortical representation of the lips, participants were asked to
perform lip-smacking movements whilst in the fMRI scanner. We were unable to identify significantly
increased activation during lip movements in amputees, compared with the 2-handed controls.
Furthermore, the correlation between activation during lip movements and phantom pain magnitude was
not significant.
We then considered activation during phantom hand movement. Activation during phantom movements
correlated with subjective ratings of chronic phantom pain magnitude in amputees: individuals with a
worse history of phantom pain showed greater activation during phantom movements. This can be seen in
the figure above, where amputees are ordered according to their phantom pain ratings. This correlation
was significantly stronger than that found between phantom pain and activation during lip movement.
We also examined changes in grey matter volume in the phantom hand area. Grey matter volume was
significantly reduced in amputees’ phantom cortex, compared with two-handers’ corresponding hand
cortex, as well as with the intact hand cortex in amputees. This suggests structure degeneration with loss of
sensory inputs. Within the amputee group, grey matter volume was modulated by chronic phantom pain:
grey matter volume was greater in individuals with worse phantom pain. Therefore, while acquired sensory
loss seems generally to precipitate local structural degeneration in the deprived cortex, the experience of
persistent phantom pain sensations appears to maintain local structure.
Conclusion
Taken together, our results prompt a revisiting of the link between phantom pain and brain organisation.
We propose that, contrary to the maladaptive model, cortical plasticity associated with phantom pain is
driven by powerful and long-lasting subjective sensory experience.
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