Publisher Summary
This chapter addresses the question of how to classify the neuromodulation effects resulting from widely differing neurofeedback approaches developed over the last four decades. A proliferation of targets and objectives has been observed to which attention is directed in the training. With regard to clinical outcomes, however, one encounters a broad zone of commonality. Why is it that the premises and technological approaches within the neurofeedback network of scholars and clinicians are so disparate, yet they largely achieve common clinical goals? This in-depth analysis may lead one closer to the âessenceâ of neurofeedback and provide focus for further development efforts. This chapter attempts to appraise the âstate of the fieldâ at this moment. The objective is to discern the commonalities among the various approaches on the one hand, and among the clinical findings on the other. This will lead to a codification of a âminimal set of claimsâ that could serve to cover the commonalities among the techniques, and it will lead to a simple classification scheme for the various clinical findings. The evidence in favor of such a minimal set of claims will be adduced largely by reference.
I Introduction
This chapter addresses the question of how to classify the neuromodulation effects resulting from widely differing neurofeedback approaches developed over the last four decades. We have seen a proliferation of targets and objectives to which attention is directed in the training. With regard to clinical outcomes, however, one encounters a broad zone of commonality. Why is it that the premises and technological approaches within the neurofeedback network of scholars and clinicians are so disparate, yet they largely achieve common clinical goals? This in-depth analysis may lead us closer to the âessenceâ of neurofeedback and provide focus for further development efforts.
In its most common applications, EEG feedback typically combines two challengesâone directed to the frequency-based organization of brain communication and one that targets inappropriate state transitions. These two challenges lead to very different rules of engagement. As such rules are unearthed, they must be understood in terms of an appropriate model of brain function. At a more philosophical level, an understanding of this whole process also takes us to the very cusp of the mindâbody problem, the neural network relations that provide the nexus where our thoughts are encoded and interact directly and inseparably with network representations of psychophysiological states.
This chapter will attempt to appraise the âstate of the fieldâ at this moment. The objective is to discern the commonalities among the various approaches on the one hand, and among the clinical findings on the other. This will lead to a codification of a âminimal set of claimsâ that could serve to cover the commonalities among the techniques, and it will lead to a simple classification scheme for the various clinical findings. The evidence in favor of such a minimal set of claims will be adduced largely by reference. Further, the classification of the various clinical findings will serve the objective of a more appropriate or natural language for the field of neurotherapy than is provided in the formalism of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV, APA, 1994).
II Tracing the historical threads of neurofeedback
A. The alpha rhythm and âfelt statesâ
The field of neurofeedback began in two threads of research that concerned themselves with one or another of the primary resting rhythms of the EEG. Here the local synchrony of the neuronal assemblies was such that the EEG amplitude would episodically rise above the ambient into dominant spindle-burst activity. In the case of the alpha rhythm, the feature was so obvious in the record that it became the first identified signature of the EEG in the original discovery of Hans Berger (1929). Joe Kamiya then first studied it in relation to our felt states, the question addressed being whether the human subject is able to have any kind of awareness regarding his own alpha activity (Kamiya, 1968). An affirmative finding eventually led to active reinforcement on alpha spindle incidence getting underway (Hardt and Kamiya, 1976). The preoccupation with subjective states of awareness and of feeling, however, was not consonant with the prevailing Zeitgeist, and Kamiyaâs research found little resonance in the broader field of psychology.
B. The sensorimotor rhythm and behavioral state
The work of Maurice Barry Sterman very consciously took a different tack. First of all, the work utilized animal subjects, so there was no question of inquiring into felt states, but that would not have been Stermanâs inclination in any event. The thrust was to connect the realm of the EEG with that of overt behavior and of behavioral states. The focus became the sensorimotor rhythm, spindle-burst EEG activity localized to the cat sensorimotor cortex that was observable even in the waking state during periods of motoric stillness. It was observed that training the behavior in order to manifest the SMR spindle was not as efficient as rewarding the animal for the appearance of the SMR spindle and having behavioral stillness as the concomitant. Either way, however, the phenomena were coupled (Sterman et al., 1969). (For a review of this early research that ties into later neurofeedback, see Othmer et al., 1999.)
When attention later turned to the use of this simple reinforcement technique for the suppression of seizure susceptibility in humans, the training had to be done under circumstances in which the EEG was often not well-behaved as it had been in the cats. Sterman was the first to install inhibit functions on this account, but the intent was simply to assure that inappropriate triggers of a reward were suppressed. Significantly, the focus of the work remained entirely on the elicitation of an SMR bursting response. A second issue was that the human waking EEG did not manifest SMR spindles that clearly rose above the background activity, as was the case for cats. But the training philosophy carried over, as only extreme SMR amplitude excursions were rewarded. This was expected to either end up in skewing the SMR amplitude distribution or perhaps in moving the entire distribution to higher amplitudes. The focus on seizure management placed this method within the domain of neurology, but it was unlikely then (and remains unlikely now) that the field of neurology would look favorably upon behavioral interventions. (For a review, see Sterman, 2000.)
C. EEG operant feedback and normalcy patterns
Joel Lubar was the first to employ inhibit functions with the overt objective of training toward more normal distributions. This proscriptive aspect of the training imposed its own rules on the training task, and also made for a non-prescriptive appeal to the brain that differed considerably from what was involved in the reward-based training. It also elevated the issue of EEG normalcy as a guiding principle to EEG reinforcement protocols, with profound implications for the emerging field. (For a review of this early work, see Nash, 2000.)
D. Stimulation-based treatment
Paralleling the above developments were various stimulation-based approaches to brain-state alteration, mainly using audio-visual modes. Indeed this work had its earliest precursors in the work of Adrian and Matthews (1934), who evaluated optical stimulation in their replication of Bergerâs rhythm. It therefore preceded EEG feedback by some three decades. But audio-visual stimulation had suffered the same fate as Kamiyaâs work of being taken up by a variety of enthusiasts over the years, which then spoiled it for the attentions of academic researchers. Stimulation-based techniques have since come to be seen as competitive with reward-based feedback in terms of clinical efficacy, and must therefore be included in any comprehensive appraisal of the field. The evidence for this is strongest for ADHD (Siever, 2007). In order to accommodate both neurofeedback and stimulation the more inclusive term of neuromodulation will be used below.
The development of the field subsequent to the early initiatives by Kamiya, Sterman, and Lubar has been modestly evolutionary, but the essential character of the work was laid down during the early days of the field, and threads of continuity carry through to this day. Only the stimulation-based work requires a separate treatment. The subsequent discussion is conducted more at the conceptual level rather than being constructed strictly upon the established empirical basis. Of course empirical data drive the discussion, but it would be premature to make fine distinctions on the basis of the available evidence, or to be too judgmental at this point, for example with respect to the relative efficacy of the various techniques.
Most if not all of the approaches remain in a state of both technical and tactical immaturity. Moreover, the clinical world is not restricted to using only one mode but will likely see the emergence of a multiplicity of techniques and combinations of techniques for synergistic effects. The question of which is best therefore does not even merit a response at this time. And by the time the question can be answered well, it will hopefully no longer be relevant.