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Articles / Research
ADHD NeuroScience Letters
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)
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. You can find a comprehensive review of this study at www.helpforadd.com/2003/january.htm.
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. A
comprehensive review of this study is available at www.helpforadd.com/2003/april.htm.
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". You can try this for youself at http://faculty.washington.edu/chudler/words.html
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