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This summary is from a recent issue of Attention Research
Update, edited by David Rabiner of Duke
University
The original journal article appeared in NeuroScience
Letters
Volume
394, Issue 3 , 20 February 2006, Pages 216-221
(#11)
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| Neurofeedback is a popular albeit
controversial intervention used in the treatment of
ADHD. Scientists have known for many years that the
brain emits various brainwaves that are indicative of
the electrical activity of the brain and that different
types of brainwaves are emitted depending on whether the
person is in a focused and attentive state or a
drowsy/day-dreaming state. |
|
Neurofeedback allows a person to view these
brainwaves on a computer screen as they occur. By teaching a
person to produce brainwave patterns that are associated with
a relaxed, alert, and focused state, and having them practice
this skill for many hours of training, neurofeedback
practitioners contend that individuals with ADHD can learn to
maintain this state and that many symptoms of ADHD will
diminish. Many scientists do not believe that such claims have
been sufficiently documented, however.
A typical
clinical session of neurofeedback training for a child with
ADHD involves pasting electrodes (sensors that pick up the
electrical activity of the brain) to the head with conductive
gel. Wires from these electrodes are connected to a device
that amplifies the small signal obtained from the electrodes.
The child sits in a comfortable chair and watches a computer
monitor. The monitor displays a picture such as a moving graph
that indicates the degree to which the child is producing the
desired pattern of brainwave activity. The goal is for the
child to learn to produce the type of brainwave activity that
is associated with a focused and attentive state.
Over
the course of numerous training sessions it may gradually
become easier for the child to achieve this state and to
maintain it for longer periods of time. Proponents of
neurofeedback often describe this training as an exercise
program for the brain, and training continues until the client
demonstrates the ability to consistently achieve and maintain
a pattern of EEG activity indicative of a relaxed and
attentive state. This typically requires 40-60
sessions.
By the conclusion of treatment, neurofeedback
advocates believe that increases in attention and reductions
in impulsivity that are evident during training will transfer
to important areas of the child's life - e.g. home and school
- and there are several published studies (see below) that are
consistent with this position. Critics of neurofeedback,
however, do not believe there is credible evidence to indicate
that such transfer occurs.
** Prior
Neurofeedback Research Reviewed in Attention Research
Update **
 |
In prior issues of Attention Research
Update I have reviewed several neurofeedback studies
that highlight the promise of this approach for helping
individuals with ADHD. In the first study (Monastra et
al., 2001), 101 children and adolescents with AD/HD
received multimodal treatment that included stimulant
medication, behavioral therapy, and school consultation
services. |
Fifty-one of these participants also
received neurofeedback because their parent(s) decided to
include it in their child's overall treatment plan.
Participants in each group (i.e. multimodal treatment vs.
multimodal treatment + neurofeedback) did not differ in the
severity of symptoms before treatment began, and the treatment
provided differed only by whether it included
neurofeedback.
Twelve months later, participants whose
treatment included neurofeedback showed greater improvement
according to parent and teacher behavior ratings, and no
longer demonstrated the brainwave patterns that were
substantially different from children without ADHD. These
gains remained evident a week after medication was
discontinued and suggest that adding neurofeedback to a
multimodal treatment program was associated with important
incremental benefits.
In
a second study (Fuchs et al., 2003), parents of 34 children
with AD/HD between the ages of 8 and 12 chose either stimulant
medication or neurofeedback treatment for their child. The
majority - the parents of 22 children -- opted for
neurofeedback treatment. After 3 months, children in both
groups showed significant and comparable reductions in ADHD
symptoms according to parents and teachers. Laboratory tests
of attention also showed equivalent improvement.
Clearly,
children in both studies who received neurofeedback appeared
to benefit from this treatment. Critics of these studies would
correctly point out, however, that neither employed random
assignment. The absence of random assignment makes it
impossible to rule out other factors the groups may have
differed on - besides whether they received neurofeedback - as
an explanation for the results obtained. This limitation is
found in virtually all studies of
neurofeedback.
Another limitation is the failure to
control for the substantial extra therapist attention provided
to children who received neurofeedback treatment. It is
possible that this extra attention - and not neurofeedback
training per se - is what accounts for children's improvement.
Although this strikes us unlikely given the intractability of
ADHD symptoms to adult attention and support alone, it cannot
be conclusively ruled out as an explanation.
** New Study of Neurofeedback for Treating ADHD **
A recently published study addresses one of these
important concerns, i.e., the absence of random assignment,
and also provides direct evidence of changes in brain activity
for children receiving neurofeedback (Levesque, J.,
Beauregard, M., & Mensour, B. 2006. Effect of
neurofeedback training on the neural substrates of selective
attention in children with AD/HD: A functional magnetic
resonance imaging study. Neuroscience Letters, 394, 216-221.)
Participants were 20 8-12-year-old children
(4 girls and 16 boys) meeting DSM-IV criteria for ADHD;
children who were also diagnosed with learning disabilities or
a psychiatric diagnosis in addition to ADHD were excluded.
Fifteen children were randomly assigned to receive 40
hour-long sessions of neurofeedback training conducted over a
13-week period. More children were assigned to the treatment
group so that a greater number of treated subjects could
participate in the fMRI procedure described
below.
Consistent with what is known about EEG (i.e.,
brainwave) activity in individuals with ADHD, training focused
on reducing the production of lower frequency theta waves and
increasing the production of higher frequency waves that are
associated with a more focused and attentive state. Control
children received no active intervention, nor did they receive
comparable amounts of adult attention. Although children in
both groups had received stimulant medication treatment prior
to the study, no child received medication during the
study.
** STUDY MEASURES **
Both
before and after neurofeedback training, the following
measures were collected on participants in the treatment and
control groups:
1) Parent ratings of ADHD
symptoms;
2) Digit Span Test- This test requires
children to repeat in correct order strings of digits that are
read to them. The strings get increasingly longer until the
child fails 2 trials in succession. After failing 2 successive
trials, the test is repeated with children required to repeat
the digits back in reverse order. Performance on this test
depends on both attention and working memory skills.
3) Continuous Performance Test - This is a computerized
test of sustained attention and the ability to inhibit
impulsive responding. In this test, the child is presented
with a series of auditory and visual stimuli via computer and
must either respond or inhibit responding by pressing
particular keys according to the stimulus that is presented.
To well on this task, children need to sustain careful
attention and refrain from pressing keys impulsively when the
wrong stimulus is presented. This measure is widely used in
the evaluation of attention difficulties.
4) Counting Stroop Task - This is a complex experimental
task that involves both selective attention and the ability to
inhibit a well-learned response. In this task, children are
told that they will see sets of 1-4 identical words appear on
the computer screen. Their job is to indicate how many words
were presented by pressing a button the appropriate number of
times.
On some trials, the words consisted of names of
common animals, e.g., dog, cat, bird, etc.). For example, the
word "cat" would appear 3 times and the child would need to
press the button 3 times. If the word appeared only once, the
child would press the button once. During these "neutral"
trials, the task was thus relatively easy.
On other
trials, however, referred to as "interference" trials, number
words, e.g., "one", "two", "three", appeared on the screen.
For example, the word "one" might be written 3 times,
requiring the child to button press 3 times. This is a more
difficult task, however, because the content of the word - the
number one - conflicts with the number of button presses the
child must make. Because what the child reads interferes with
how he/she must respond, the processing required to do well on
these trials is more complex than when neutral animal words
are presented. Prior research has demonstrated that different
brain areas are activated during these different types of
trials. (Note - This is a variant of the more familiar color
Stroop task, in which it is harder to name the color that
words are printed in when the ink color is different from the
word itself, e.g., when color words are written in green ink,
it takes longer to say the ink is gren when the word written
is "red" than when the word written is "green".
All children completed the Counting Stroop Task both
before and after those in the experimental group received
neurofeedback treatment. A total of 120 "neutral" and
"interference" trials were conducted during each testing
session and children's score was the number of trials they
answered correctly.
An especially important feature of
this study is that children received fMRI scans as while
completing the Counting Stroop Task. FMRI is a technique for
determining which parts of the brain are activated as
individuals perform certain tasks by "imaging" the increased
blood flow to the activated areas of the brain.
The
inclusion of fMRI scans during the Counting Stroop Task
enabled the researchers to examine results on this task in 2
ways. First, they could determine whether treated children
performed better after treatment compared to the control
group. And, second, they could determine via fMRI data whether
patterns of brain activation during the task changed in
neurofeedback treated children. Because neurofeedback is
intended to change the underlying pattern of brain activity,
demonstrating such a change is an important step in
documenting the efficacy of this approach.
** RESULTS **
Results indicated clear improvements
for children receiving neurofeedback treatment. Specifically,
the authors reported the following:
1) For treated
children, parent ratings of inattentive ADHD symptoms declined
significantly - into the normal range - while those of control
children remained clinically elevated.
2) For treated
children, parent ratings of hyperactive/impulsive ADHD
symptoms declined significantly - although not quite into the
normal range - while those of control children showed a modest
increase.
3) On the Digit Span test, scores for treated
children increased significantly from time 1 to time 2; for
control children, no significant increase was found.
4)
On the Continuous Performance Test, scores for treated
children increased significantly from time 1 to time 2; for
control children, no significant increase was found.
5)
On the Counting Stroop Task, treated children performed
significantly better on both neutral and interference trials
at time 2 compared to time 1; for control children, no
increase in the accuracy of their performance was
found.
6) FMRI results showed no difference in patterns
of brain activation between treated and control children at
time 1. At time 2, however, treated children showed a
different pattern of brain activation during the interference
trials, i.e., those that required more complex cognitive
processing. The brain regions that were now activated were
those believed to play important roles in selective attention
and the suppression of inappropriate responses.
** SUMMARY and IMPLICATIONS **
This study provides
important new evidence to support the use of neurofeedback as
a treatment for ADHD. Advantages over several previously
published neurofeedback studies are that participants were
randomly assigned to the treatment vs. control conditions and
the inclusion of fMRI scans to document that neurofeedback
treatment was associated with actual changes in brain activity
during a complex cogntive task.
As with previously
published studies, treatment was associated with a significant
reduction in parent ratings of their child's ADHD symptoms.
Because parents were not blind to condition, however, one can
argue that this finding is confounded by parents' knowledge of
whether or not their child received treatment. In other words,
parents may have reported their child symptoms to improve
simply because they expected this would happen and not because
objective changes actually occurred.
Improvements for
treated children in Digit Span and the Continuous Performance
test - both considered to be objective assessments of
attention and other cognitive skills - are not subject to this
same criticsm, and thus provide a stronger basis for
suggesting the neurofeedback treatment was
helpful.
Most compelling of all, however, is the
finding that neurofeedback treatment was associated with
changes in brain activation detected by fMRI scans during the
Counting Stoop Task. Proponents of neurofeedback treatment
have long suggested that it produces enduring changes in brain
functioning, and it is these changes that cause ADHD symptoms
to diminish. Results from this study provide important initial
evidence consistent with this hypothesis, although the absence
of any long-term follow up makes it impossible to know whether
the changes detected were transient or enduring.
While
these results are encouraging, a balanced review of any study
requires a discussion of it's limitations, and there are
several to note. First, the sample size is relatively small
and replicating the findings with a larger sample would be
important.
Another limitation of the sample is that
children with learning disabilities and diagnoses in addition
to ADHD were excluded. Because many children with ADHD have
one or more co-occurring conditions which can complicate
treatment, it is not clear whether the results obtained would
generalize to a broader and more representative sample of
children with ADHD.
Third, the only behavior measure
obtained fwas rom parents who were not blind to treatment
condition. Because improving children's behavioral and
academic functioning in school is an especially important goal
of ADHD treatment, the absence of such information in this
study is problematic; it should not be assumed that such
changesin the classroom would have occurred. Finally, as the
authors note, the control participants did not receive any
attentional training intervention whatsoever. Thus, although
it is tempting to conclude that specific training in changing
brainwave activity was responsible for the treatment effects,
including changes in the fMRI scans, this conclusion cannot be
made with certainty.
For example, training a different
pattern of EEG activity using neurofeedback, or an attention
training intervention in which no direct feedback on EEG
activity was provided, may have yielded similar results. One
could even argue that the greater contact with researchers
received by children in the treatment group - 40 hours vs. 0
for those in the control group - is what accounted for the
treatment gains and that neurofeedback itself had nothing to
do with it.
Although I do not find this to be a likely
explanation, the study design does not enable this possibility
to conclusively ruled out. In an ideal design, control
children would go through a neurofeedback procedure that
appeared identical to what treated children received, only the
training would provide "sham" feedback that was not linked to
their actual EEG activity. If group differences were found
with this procedure it would be a clear indication that the
specific EEG training received by experimental subjects,
rather than any type of "placebo" effect, is what caused the
improvements.
While these limitations are important to
be aware of, the pattern of findings reported add to the
increasing evidence base for using neurofeedback as a
treatment for ADHD. While many experts would argue that
additional studies are required to clearly demonstrate that
this is an effective intervention - and I personally agree
with this statement - it is also important to recognize that a
number of studies provide converging evidence for the
potential value of this approach.
I will continue to
publish summaries of new studies in this interesting area in
Attention Research Update as they become available.
Thanks again for your ongoing interest in the
newsletter. I hope you enjoyed the above article and found it
to be useful to you.
Sincerely,
David
Rabiner, Ph.D.
Senior Research Scientist
Center for
Child and Family Policy
Duke
University
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