Wednesday, March 9, 2011

Neurofeedback and Stuttering

Functional magnetic resonance imaging (FMRI) has provided insights into the possible neurological sources of stuttering. FMRI measures the change in blood flow as a result of neural activity in the brain and can document the active regions and functional activity of the brain at work in almost real-time. Evidence for the dopamine hypothesis of stuttering was provided by FMRI studies.

But FMRI has more recently been used to help individuals to control their brains through a neurofeedback mechanism. A cover article on "Understanding Pain," appeared in a recent issue of Time magazine (March 7, 2011). Specifically, subjects were given live access to an image of their brains' functional activity and were taught to control pain when a heat probe was applied to their arms. Their brains were essentially retrained to control the activation of neural pathways by targeting specific brain regions and processes.

The success of neurofeedback to control pain raises the question as to whether stutterers can cultivate the ability to control their brain processes so as to achieve greater fluency. Stuttering, being basically a mind/body problem, could possibly be amenable to such an approach. Dopaminergic pathways in both the motor neuron and the mesolimbic (governing emotions) sections of the brain might be controllable through neurofeedback mechanisms.

Anecdotal evidence that some individuals can control their fluencies to some extent has been discussed in a previous post (i.e., "Endogenously Reducing Dopamine"). It is interesting to speculate that these individuals may be engaging in some sort of neurofeedback at a subliminal level. In addition, certain aspects of speech therapy may informally and implicitly use neurofeedback (as well as biofeedback) approaches.

The exact mechanisms by which this fluency control is accomplished have not been identified. For example, whether dopaminergic activity is actually reduced or merely over-ridden is in question. However, with the use of FMRI, this question might be resolved and approaches developed whereby neurofeedback to improve fluency would be made available to a larger audience.

The use of FMRI has limitations with respect to the expense of the FMRI apparatus and the artificiality of the environment (i.e., lying on one's back and surrounded with noisy machinery) in which the subject would be placed.

A different method to study brain function is electroencephalography (EEG). Benefits of EEG compared to FMRI are that hardware costs are substantially lower, the machinery is less bulky and can be deployed in a wider variety of environments, and greater temporal resolution is enabled (on the order of milliseconds rather than seconds). In addition, the EEG is relatively tolerant of subject movement and is silent.

The limitations of EEG are that it has significantly lower spatial resolution and analyses of EEG results use relatively simple paradigms, compared with FMRI studies. Moreover, the EEG is most sensitive to postsynaptic potentials generated by the superficial layers of the cortex, namely the pyramidal neurons of the cortex because they are well-aligned and fire together. Voltage fields fall off with the square of the distance so activity from deep sources is more difficult to detect than currents near the skull. Thus, neuronal activity that emanates from the dorsal and ventral striata and the amygdala, potentially influencing fluency but deep within the brain, contribute far less to the EEG signal.

However, insofar as dopaminergic pathways and feedback loops exist between the deeper regions and the cortex, the measured EEG signals may contain information about the functioning of these deeper regions. An interesting study found at the URL,

claims to have identified potential EEG markers for stuttering based on comparing the EEGs of 26 children who stuttered with 21 age matched controls. Substantial differences in brain wave patterns exist between the two groups.

In summary, it appears that further explorations of neurofeedback mechanisms to ameliorate disfluency might be warranted, one of the major advantages being the elimination or reduction of the use of drugs.

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