Maybe you can get something out of this since no one seems to want to make this useable to stroke survivors that need it. On your own once again.
http://journal.frontiersin.org/article/10.3389/fnhum.2017.00332/full
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1Department of Psychiatry, Campus Benjamin Franklin, Charite University Medical School, Germany
The relevance of neuroscience-based treatment for post stroke aphasia
Neuroscience-based
interventions for aphasia are among the most promising approaches
towards successful language rehabilitation. Associated therapeutic
techniques are highly effective in reducing cognitive-behavioural
difficulties resulting from brain damage and can induce neuroplasticity
(Taub et al., 2002; Berthier & Pulvermüller, 2011). However, it is
still not clear how language recovery and reorganisation of language is
reflected by functional changes manifest in human brain activity. In
aphasia research, previous studies addressed the role of the left (LH)
and right (RH) hemisphere across the entire recovery phase. It has been
suggested that brain reorganization in aphasia is a dynamic process, in
which the involvement of perilesional LH regions and RH areas (e.g.
Broca-homologue or RH superior temporal cortex, Musso et al., 1999) is
dependent on the specific phase of language recovery (Saur et al.,
2006). These data highlight the importance to control for time post
stroke when investigating treatment-related changes to avoid the
influence of spontaneous remission.
To date, only few studies have
addressed therapy-induced neuroplasticity in patients with post stroke
aphasia (PSA), and findings are rather inconsistent. The reasons for the
heterogeneity of previous results may be attributed to patient-specific
variables such as lesion size and site, symptom severity, etc. (Crosson
et al., 2005). While patient-specific variables seem to influence
functional recovery, the specific impact of non-patient factors (e.g.
neuroimaging method, language task, therapy method, - intensity, -
amount and – duration) has rarely been addressed. However, to maximize
therapy outcome, it is important to systematically investigate all
possible factors and to identify neurophysiological predictors of
recovery. Focussing on intensive, clinically effective, and short-term
interventions and on suitable language tasks seems promising to achieve
this goal.
Understanding the neuronal mechanisms underlying language recovery by studying treatment-induced changes
Measuring
neuronal correlates of good (or poor) language recovery could help to
identify patients who might benefit (or not) from a specific therapeutic
method and can contribute to the development of effective
neuroscience-based neurorehabilitation techniques. The study of
therapy-induced neuroplasticity in PSA offers the possibility to
systematically control for potentially confounding variables while at
the same time measuring behavioural and neuronal changes following
speech and language therapy (SLT) within a reasonable time frame.
Previous findings do not allow to determine whether any behavioural or
neurophysiological changes were caused by a specific therapeutic
technique or by other factors. This differentiation is only possible by
randomized controlled trials (RCTs) with chronic patients (> 1 year
post stroke), for whom spontaneous remission effects can be excluded.
Only RCTs with at least two active treatment groups and a no-treatment
waiting-list group will ultimately allow to determine the specificity
and amount of therapy-induced changes. Additionally, multiple pre-, and
post-therapy scanning sessions will help to control for repeated
scanning effects (Fridriksson et al., 2006). Although none of the
clinical RCTs conducted in chronic aphasia comprised measurement of
brain correlates before and after therapy, a promising heuristic is
provided by efficient intensive interventions in chronic PSA patients.
In fact, some intensive interventions have proved to lead to significant
and consistent improvements of language performance (Brady et al.,
2016; Breitenstein et al., 2017) and may therefore be good candidates to
study neuroplasticity.
Neuroplasticity after intensive aphasia treatment methods
Within
a short period of time (for example < 4 weeks), spontaneous,
non-therapy-related neuronal changes are highly unlikely in chronic
patients, therefore, one can interpret any changes in behaviour and
brain activity across short-term intervals as treatment-induced. While
intensive training can lead to such changes already within days or weeks
(see Berthier & Pulvermüller, 2011), these effects are unlikely for
non-intensive methods. In fact, several RCTs demonstrated higher
efficacy of intensive SLT compared to non-intensive treatment (Brady et
al., 2016). Although it is not entirely clear yet, which treatment
intensity and duration is required to induce optimal recovery,
meta-analyses suggest a minimum of 1-2 hours a day over a period of 2-4
weeks (Bhogal et al., 2003). This therapy frequency might be regarded as
intensive treatment.
The efficacy of intensive therapies can be
explained by neuroscientific principles of learning and memory: high
intensity and massed practice facilitates and enhances learning and
cortical plasticity by correlated neuronal activity and by strengthening
of synaptic contacts between neurons (Berthier and Pulvermüller, 2011).
From this perspective, any intensive cognitive-behavioural intervention
can maximize the effects of training-induced brain plasticity, which is
ultimately a consequence of effective learning. Similarly, multiple
repetitions of stimuli or tasks applied during language training, as
well as the imitation of language skills modelled by language therapists
will enhance learning and re-structuring of residual language networks.
However, it should be noted that intensity, repetition, or
inter-individual patient characteristics are not the only factors
impacting on learning and language recovery. For example, a recent
cross-over RCT demonstrated a significant influence of the therapy
method used: Communicative-pragmatic and behaviourally relevant language
training in social interactions resulted in significantly better
recovery than equally intensive conventional exercises such as naming
and describing pictures (Stahl et al., 2016). The importance of
behavioural relevance and effective neurorehabilitation techniques for
functional outcome has also been suggested in the context of motor
deficits caused by stroke (e.g. Taub et al., 2002). Behaviourally
relevant therapeutic methods delivered at high intensity could provide
an avenue towards effective treatment in chronic PSA and may help to
increase motivation, engagement and compliance of patients.
Neuroplastic changes in the left and right hemisphere following intensive short-term aphasia therapy
A
recent review (Crinion & Leff, 2015) of neuroplastic changes
following therapy in PSA patients, reported consistent treatment-related
brain activation changes in LH perilesional fronto-temporal regions
and/or in the inferior frontal gyrus in the RH. Unfortunately, due to
the heterogeneity of patient and non-patient variables in these
intervention studies, it is difficult to draw any concise conclusions
about the neuronal mechanisms underlying language recovery. Several
factors might explain this variability of previous findings and could be
relevant for interpreting treatment-related data and for identifying
predictors of recovery. These factors include the phase of PSA (see Saur
et al., 2006), symptom severity (Lazar et al., 2010), or education and
cognitive reserve (Hillis & Tippett, 2014). Also, the degree of
premorbid functional lateralization of language could influence
functional recovery (Knecht et al., 2002), as well the type of aphasia.
Interestingly, language recovery does not seem to be driven by lesion
size (Mattioli et al., 2014), but more likely by lesion location and
load: For example, the structural integrity of subcortical white matter
tracts (i.e. the arcuate fasciculus, Marchina et al., 2011) and specific
left hemispheric cortical regions have been identified to influence
recovery (Fridriksson, 2010; Bonilha et al., 2016). Moreover,
non-patient related factors (e.g. therapy method, intensity, and
language task used during neuroimaging) may strongly influence recovery.
By focusing on intensive and effective interventions with chronic
patients, the number of potential confounds of previous research might
be diminished. To date, very few studies on neuroplastic changes
following intensive, successful SLT have been published. These studies
will be focused on now: Intensive aphasia therapy (a minimum of 1-2h/d,
for at least two weeks, Bhogal et al., 2003) combined with functional or
structural neuroimaging in chronic PSA patients has been reported for
three different methods. The first method, Constraint-Induced Aphasia
Therapy (CIAT, Pulvermüller et al., 2001), also called Intensive
Language Action Therapy (ILAT, Difrancesco et al., 2012) is one of the
most researched SLTs and its clinical effectiveness has been
demonstrated in several RCTs (Pulvermüller et al., 2001; Meinzer et al.,
2005; Berthier et al., 2009; Stahl et al., 2016). The other two
intensive therapy regimes, anomia treatment (Bonilha et al., 2016) and
melodic intonation therapy (MIT, Schlaug et al., 2009) have shown to be
effective, as evidenced by group studies or case series.
CIAT/ILAT-induced
changes in brain activation following two weeks of intensive training
(3h/d) were observed using various neuroimaging methods and language
tasks. A significant body of data was obtained with EEG and MEG and
language tasks applied comprised lexical decisions (Pulvermüller et al.,
2005), passive reading of words (Barbancho et al., 2015) and an
auditory passive listening mismatch negativity (MMN, Näätänen et al.,
1997) design (Mohr et al., 2016; Lucchese et al., 2016). The source
estimates performed on EEG lexical decision data suggested activation
changes in right-frontal and left-temporoparietal areas correlating with
clinical language improvements (Pulvermüller et al., 2005). In an fMRI
study, pre-post-therapy changes in neurometabolic brain activation
brought about by ILAT were reported in RH frontotemporal areas when
patients were auditorily processing complex and semantically ambiguous
sentences (Mohr et al., 2014). A previous fMRI study (Meinzer et al.,
2008) found ILAT-induced metabolic changes in LH perilesional areas
during an overt naming task. Similarly, in an MEG study, ILAT led to
enhancement of LH perilesional neuromagnetic activity evoked by words
presented in a passive auditory MMN paradigm and which correlated with
clinical improvements (Mohr et al., 2016).
Although these intensive
short-term studies were not RCTs, the results of several of them can be
interpreted, because significant correlations between clinical language
improvement and brain activation changes were found. As this therapy
method uses communicative-pragmatic language training, involvement of
residual language regions and neuroplasticity in both hemispheres can be
assumed. Still, the diversity of results across studies of ILAT shows
that the language task and stimulus type might be important factors that
could influence the topography of neuroplastic changes.
While
bi-hemispheric neural recruitment and improvements of naming had
previously been reported in short-term, intensive anomia treatment for
trained items only (Fridriksson et al., 2006), recent studies found
improved naming, and thus generalization effects, also for untrained
items (Fridriksson et al., 2012). However, as this treatment method
specifically focuses on naming, changes in other language domains were
not reported. Neuroplastic changes following anomia treatment showed an
increase of brain activation during picture naming which was observed in
fronto-temporal LH perilesional areas with fMRI (Fridriksson et al.,
2012). These activity changes across the two weeks of intensive training
(also 3h/d) correlated with improvements in naming performance, which
were associated with intact functional connections between preserved
cortical areas of the language network that were responsive to therapy
(Bonhila et al, 2016). Anomia therapy involves training of overt naming
of concrete objects depicted on cards by using either semantic or
phonological cueing and thus, focuses on one specific aspect of aphasia,
namely anomia and linguistic naming excercises, but does not emphasise
behavioural relevance or communicative use of language. Consequently,
training-induced neuroplasticity may specifically tap into
left-hemispheric residual language networks associated with the abilitiy
to name objects.
Using structural DTI before and after intensive
melodic intonation therapy (MIT), an increase in fibre density and
volume of the arcuate fasciculus in the RH was reported (Schlaug et al.,
2009). However, as no correlation was found between language
improvement and structural brain changes after therapy, it is difficult
to interpret these structural data. Interestingly, in another study by
this group, improvements in speech production after MIT correlated with
structural changes in right hemisphere inferior frontal gyrus in
patients with Broca’s aphasia (Wan et al., 2014). Language improvement
in spontaneous speech and re-structuring of the language system in the
RH after MIT could be driven by aspects of this therapy method which
possibly involve right-hemisphere dominant cognitive and motor functions
such as melodic intonation, rhythm, and left hand tapping (Schlaug et
al., 2009). It should be noted though, that while treatment intensity
and duration in ILAT/CIAT and anomia treatment studies were completely
identical (3 h/d for 2 weeks), MIT was applied less intensively (1.5
h/d), but with longer duration (~ 16 weeks), resulting in approximately
three times higher amounts of overall treatment for MIT than for the
other two therapies.
Overall, evidence suggests that intensive
aphasia treatment in chronic PSA leads to reorganisation of the
functional and structural language network in both hemispheres. The
involvement of each hemisphere in neuroplasticity is probably
independent from the neuroimaging method used, but may be strongly
influenced by the therapy method, its intensity, duration and the
language materials and tasks.
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Article Info
Article Info
Bettina Mohr
