Operant control of neural events in humans

Poststroke Cognitive Impairment Research Progress on Application of Brain-Computer Interface

Brain-computer interfaces (BCIs), a new type of rehabilitation technology, pick up nerve cell signals, identify and classify their activities, and convert them into computer-recognized instructions. This technique has been widely used in the rehabilitation of stroke patients in recent years and appears to promote motor function recovery after stroke. At present, the application of BCI in poststroke cognitive impairment is increasing, which is a common complication that also affects the rehabilitation process. This paper reviews the promise and potential drawbacks of using BCI to treat poststroke cognitive impairment, providing a solid theoretical basis for the application of BCI in this area.

Brain-Machine Interfaces: Powerful Tools for Clinical Treatment and Neuroscientific Investigations

Brain-machine interfaces (BMIs) have exploded in popularity in the past decade. BMIs, also called brain-computer interfaces, provide a direct link between the brain and a computer, usually to control an external device. BMIs have a wide array of potential clinical applications, ranging from restoring communication to people unable to speak due to amyotrophic lateral sclerosis or a stroke, to restoring movement to people with paralysis from spinal cord injury or motor neuron disease, to restoring memory to people with cognitive impairment. Because BMIs are controlled directly by the activity of prespecified neurons or cortical areas, they also provide a powerful paradigm with which to investigate fundamental questions about brain physiology, including neuronal behavior, learning, and the role of oscillations. This article reviews the clinical and neuroscientific applications of BMIs, with a primary focus on motor BMIs.

Toward a comprehensive understanding of the neural mechanisms of decoded neurofeedback

Real-time functional magnetic resonance imaging (fMRI) neurofeedback is an experimental framework in which fMRI signals are presented to participants in a real-time manner to change their behaviors. Changes in behaviors after real-time fMRI neurofeedback are postulated to be caused by neural plasticity driven by the induction of specific targeted activities at the neuronal level (targeted neural plasticity model). However, some research groups argued that behavioral changes in conventional real-time fMRI neurofeedback studies are explained by alternative accounts, including the placebo effect and physiological artifacts. Recently, decoded neurofeedback (DecNef) has been developed as a result of adapting new technological advancements, including implicit neurofeedback and fMRI multivariate analyses. DecNef provides strong evidence for the targeted neural plasticity model while refuting the abovementioned alternative accounts. In this review, we first discuss how DecNef refutes the alternative accounts. Second, we propose a model that shows how targeted neural plasticity occurs at the neuronal level during DecNef training. Finally, we discuss computational and empirical evidence that supports the model. Clarification of the neural mechanisms of DecNef would lead to the development of more advanced fMRI neurofeedback methods that may serve as powerful tools for both basic and clinical research.

Electrophysiological CNS-processes related to associative learning in humans

The neurophysiology of human associative memory has been studied with electroencephalographic techniques since the 1930s. This research has revealed that different types of electrophysiological processes in the human brain can be modified by conditioning: sensory evoked potentials, sensory induced gamma-band activity, periods of frequency-specific waves (alpha and beta waves, the sensorimotor rhythm and the mu-rhythm) and slow cortical potentials. Conditioning of these processes has been studied in experiments that either use operant conditioning or repeated contingent pairings of conditioned and unconditioned stimuli (classical conditioning). In operant conditioning, the appearance of a specific brain process is paired with an external stimulus (neurofeedback) and the feedback enables subjects to obtain varying degrees of control of the CNS-process. Such acquired self-regulation of brain activity has found practical uses for instance in the amelioration of epileptic seizures, Autism Spectrum Disorders (ASD) and Attention Deficit Hyperactivity Disorder (ADHD). It has also provided communicative means of assistance for tetraplegic patients through the use of brain computer interfaces. Both extra and intracortically recorded signals have been coupled with contingent external feedback. It is the aim for this review to summarize essential results on all types of electromagnetic brain processes that have been modified by classical or operant conditioning. The results are organized according to type of conditioned EEG-process, type of conditioning, and sensory modalities of the conditioning stimuli.

Effect of a psychoneurotherapy on brain electromagnetic tomography in individuals with major depressive disorder

Recent advances in power spectral analysis of electroencephalography (EEG) signals and brain-computer interface (BCI) technology may significantly contribute to the development of psychoneurotherapies. The goal of this study was to measure the effect of a psychoneurotherapy on brain source generators of abnormal EEG activity in individuals with major depressive disorder (MDD). Thirty participants with unipolar MDD were recruited in the community. The proposed psychoneurotherapy was developed based on the relationship between the localization of abnormal EEG activity and depressive symptomatology. Brain electromagnetic abnormalities in MDD were identified with low resolution brain electromagnetic tomography (LORETA) and a normative EEG database. Localization of brain changes after treatment was assessed through the standardized version of LORETA (sLORETA). Before treatment, excessive high-beta (18-30 Hz) activity was noted in several brain regions located in the fronto-temporal regions. After treatment, only participants who successfully normalized EEG activity in cortico-limbic/paralimbic regions could be considered in clinical remission. In these regions, significant correlations were found between the percentage of change of depressive symptoms and the percentage of reduction in high-beta activity. These results suggest that the normalization of high-beta activity in cortico-limbic/paralimbic regions can be associated with a significant reduction of depressive symptoms.

EEG biofeedback of low beta band components: frequency-specific effects on variables of attention and event-related brain potentials

OBJECTIVE

To test a common assumption underlying the clinical use of electroencephalographic (EEG) biofeedback training (neurofeedback), that the modulation of discreet frequency bands is associated with frequency-specific effects. Specifically, the proposal was assessed that enhancement of the low beta components sensorimotor rhythm (SMR: 12-15 Hz) and beta1 (15-18 Hz) affect different aspects of attentional processing.

METHODS

Subjects (n=25) were randomly allocated to training with either an SMR or beta1 protocol, or to a non-neurofeedback control group. Subjects were assessed prior and subsequent to the training process on two tests of sustained attention. The neurofeedback participants were also assessed on target P300 event-related potential (ERP) amplitudes in a traditional auditory oddball paradigm.

RESULTS

Protocol-specific effects were obtained in that SMR training was associated with increased perceptual sensitivity 'd prime' (d'), and reduced omission errors and reaction time variability. Beta1 training was associated with faster reaction times and increased target P300 amplitudes, whereas no changes were evident in the control group.

CONCLUSIONS

Neurofeedback training of SMR and beta1 band components led to significant and protocol-specific effects in healthy subjects. The data can be interpreted as indicating a general attention-enhancing effect of SMR training, and an arousal-enhancing effect of beta1 training.

Oscillatory brain states and learning: Impact of hippocampal theta-contingent training

Eyeblink classical conditioning is a relatively simple form of associative learning that has become an invaluable tool in our understanding of the neural mechanisms of learning. When studying rabbits in this paradigm, we observed a dramatic modification of learning rate by conducting training during episodes of either hippocampal theta or hippocampal non-theta activity as determined by on-line slow-wave spectral analysis. Specifically, if animals were given trials only when a computer analysis verified a predominance of slow-wave oscillations at theta frequencies (3-8 Hz), they learned in half as many trials as animals trained during non-theta hippocampal activity (58 vs. 115). This finding provides important evidence from awake, behaving animals that supports recent advances in our knowledge of (i) brain sites and neurobiological mechanisms of learning and memory, specifically hippocampus and theta oscillations, (ii) the biological plausibility of current models of hippocampal function that posit important roles for oscillatory potentials, and (iii) the design of interfaces between biological and cybernetic (electronic) systems that can optimize cognitive processes and performance.

Learned self-regulation of EEG frequency components affects attention and event-related brain potentials in humans

Learned enhancement of EEG frequency components in the lower beta range by means of biofeedback has been reported to alleviate attention deficit hyperactivity disorder (ADHD) symptoms. In order to elucidate frequency-specific behavioural effects and neurophysiological mediators, this study applied neurofeedback protocols to healthy volunteers, and assessed impact on behavioural and electrocortical attention measures. Operant enhancement of a 12-15 Hz component was associated with reduction in commission errors and improved perceptual sensitivity on a continuous performance task (CPT), while the opposite relation was found for 15-18 Hz enhancement. Both 12-15 Hz and 15-18 Hz enhancement were associated with significant increases in P300 event-related brain potential amplitudes in an auditory oddball task. These relations are interpreted as stemming from band-specific effects on perceptual and motor aspects of attention measures.

Operant conditioning of left-hemispheric slow cortical potentials and its effect on word processing

This study investigated whether language-related cognitive processes can be modified by learned modulation of cortical activity. Study participants received feedback of slow cortical potentials (SCPs) recorded above left-hemispheric language cortices and were reinforced for producing negative and positive shifts upon two different discriminative stimuli. In all subjects who achieved reliable control of left-hemispheric brain responses, substantial modification of word processing was observed. Behavioral modification could be documented in two experiments in which word probes were presented following discriminative stimuli. When negative shifts of the EEG were required, lexical decisions on words were substantially speeded, while they were slowed during positivity conditions. There was no indication for any performance difference between conditions in control subjects who failed to achieve control over SCPs after feedback training. This result was replicated in an experiment using lateralized-tachistoscopic stimulus presentation. Comparisons of word and pseudoword responses in both experiments indicated that behavioral modification was most pronounced for word responses. It was also not seen in a simple reaction time task not involving language materials. This argues against a global effect related to perception, visuo-spatial attention, or motor processes. We conclude that linguistic processes can be influenced by modification of cortical activity due to operant conditioning. In closing, tentative explanations of the present results based on theories of language and attention processes are being discussed.

EEG operant conditioning (biofeedback) and traumatic brain injury

A review is presented of the currently sparse literature about EEG operant conditioning or biofeedback as a treatment to reduce symptomology and patient complaints following a traumatic brain injury. The paper also evaluates the general use of quantitative EEG (QEEG) to assess traumatic brain injury and to facilitate EEG biofeedback treatment. The use of an age matched reference normative QEEG database and QEEG discriminant function are presented as a method to evaluate the nature or neurological basis of a patient's complaints as well as to individualize an efficient and optimal feedback protocol and to help evaluate the efficacy of the biofeedback therapy. Univariate and multivariate statistical issues are discussed, different classes of experimental designs are described and then a "double blind" research study is proposed in an effort to encourage future research in the area of EEG biofeedback for the treatment and rehabilitation of traumatic brain injury.

Learned changes of brain states alter cognitive processing in humans

Humans can learn to intentionally control their brain states based on information about their own electrocortical activity. Using an operant conditioning technique, twelve healthy volunteers were trained to shift their slow cortical potentials recorded from left-hemispheric language cortices in the positive versus negative direction. After training, six subjects who achieved reliable control of left-hemispheric brain responses showed substantial modification of word processing. During conditioned negative shifts of cortical potentials (activation condition), responses to words were substantially speeded, whereas lexical decisions were slower during positive shifts of slow cortical potentials (inhibition condition). No comparable difference was seen in trained participants who failed to achieve control over slow cortical potentials. Additional data suggest that the effect was not related to perception, attention, or motor processes. Thus, operant conditioning can produce focal cortical activity dynamics and thereby modify specific higher cortical processes such as access to words. This finding may open new perspectives on neuropsychological rehabilitation based on operant conditioning of brain responses.

Applied psychophysiology and biofeedback of event-related potentials (brain waves): historical perspective, review, future directions

This paper reviews the efforts of workers in the 1960s-1980s to demonstrate voluntary control of exogenously evoked (event-related) potentials in visual, somatic sensory, and auditory systems in rats, cats, and humans. The first part of the paper reviews the conceptual foundation and development of the work--it actually arose from traditional sensory coding and neural correlates of behavior studies. The second part summarizes recent applications of the method in the area of pain control. In reviewing these matters, the major effort is directed at revealing how the ideas unfolded in very human, day-to-day, anecdotal terms. There is not much of an attempt to formally review the literature, which is cited for consultation elsewhere. In the same spirit, many possible future experiments are suggested by way of elucidating the key remaining questions in the area.

A fiber tract model of auditory brain-stem responses

The hypothesis that auditory brain-stem responses (ABRs) are generated by action potentials in fiber tracts was tested by recording from frog sciatic nerves in a volume conductor. Far-field recording of the sciatic nerve action potentials confirmed the rule that the initial response of the electrode toward which the action potentials are traveling is positive with respect to the electrode from which they are retreating. This rule explained the initial polarity of response for transverse and longitudinal recordings in humans, and why right and left ear clicks evoke responses of opposite polarity for transverse recording, but the same polarity for longitudinal recording. This result was true for all of the waves evoked, up to 8 msec latency. A later myogenic potential known as the postauricular response did not invert with the ear stimulated. The possibility of a dendritic contribution to the ABR was discussed. It was concluded that the components of the ABR are more satisfactorily explained by action potentials than by somatic or dendritic synaptic activity.

Operant control of auditory brainstem potentials in man

Two studies are described which demonstrate operant conditioning of brainstem auditory evoked response (BAER) component V. Our results show that reinforcement of the cumulative summation of the wave V P8N11 component (20 dB HL stimulus clicks) hastens its summation leading to increased wave V amplitude not associated with trivial mediation factors. The results were interpreted as demonstrating operant control of very early neural events in the brainstem of man.

Operant conditioning of the short-latency cervical somatosensory evoked potential in quadriplegics

Operant conditioning of short-latency cervical somatosensory evoked potentials (CSEP) was demonstrated in five cervical cord injury subjects. Subjects were conditioned to augment the N14 potential, thought to originate from the dorsal column nucleus. Increased N14 potential was associated with an increase in N19 and P22 potentials, and either a decrease (base) or no change (train) in the brachial plexus potential. The N19 potential was correlated with significant reductions in the sensation-twitch (S/T) ratio during conditioning sessions, indexing improved sensation to low-intensity percutaneous stimulation. Moreover, S/T ratios decreased significantly during conditioning sessions, and were reduced significantly relative to initial baseline values. The results do not appear to be associated with trivial mediating influences.

Operant conditioning of trigeminally-evoked cortical potentials: correlated effects on facial nociception

The effects of operant conditioning somatosensory evoked potential (SEP) amplitude on nociceptive sensitivity were studied in albino rats. SEPs were evoked by stimulation to the descending trigeminal tract. Rewarding medial forebrain bundle stimulation (at intensities predetermined to sustain bar pressing) was made contingent upon the animal making the amplitude of the SEP 0.5 standard deviation (S.D.) large (uptraining) or 0.5 S.D. smaller (downtraining) than the predetermined mean value. Nociceptive sensitivity was measured immediately following the conditioning session by heating the rat's face and noting the latency of a defensive face rubbing response directed at that area of the face. Increasing the amplitude of the SEP (uptraining) was associated with a decrease in noxious sensitivity. Decreasing the amplitude of the SEP (downtraining) was associated with an increase in noxious sensitivity.

Effects of frontalis EMG feedback and reinforcement on frontalis EMG level

This experiment employed a between-subjects design (N = 40) to investigate the effects of feedback and reinforcement on the lowering of frontalis electromyographic (EMG) activity. The feedback and reinforcement manipulations were combined in a 2 x 2 factorial design and each subject underwent one baseline and two training sessions on three consecutive days. The analogue feedback signal was a 55 dB tone whose pitch varied as a function of EMG activity, while the reinforcement consisted of points which were exchangeable for money. The training sessions were each divided into 10 2-min baseline periods and 10 2-min trial periods. The results indicated that although analogue feedback did not result in lowered EMG levels, trial period EMG level was significantly lower than baseline level under conditions of reinforcement. These results pose problems for Budzynski and Stoyva's (1972) views concerning the therapeutic usefulness of frontalis EMG feedback training.

Operant conditioning of vertical eye movements without visual feedback in the midpontine pretrigeminal cat

An operant conditioning of vertical eye movements was achieved in the midpontine pretrigeminal cat in total darkness by contingent reinforcement of spontaneous eye movements with lateral hypothalamic (LHT) reward stimulation, when each movement (upward direction was chosen in this experiment) exceeded a preset amplitude. However, the response rates in the dark were lower than those in the light and the time to reach the peak response rate was much longer. Recording of evoked potentials to optic chiasma (OC) stimulation revealed enhancement of late components of the visual cortex (VC) and superior colliculus (SC) responses in relation to eye movements. Sequential records of the averaged evoked responses associated with eye movements indicated that the amplitudes of the late components of the VC and SC waves gradually increased in the course of establishment of the operant conditioning, and decreased gradually during extinction. In a yoked control test, increase in amplitudes of the late components was much less significant during non-contingent reinforcement given independently of the eye movements. These results suggest that 'corollary discharge' may play a critical role as a cue in acquisition of the operant conditioning of vertical eye movements when visual feedback is absent in total darkness.

Biofeedback and self-control of physiological functions: clinical applications

The parameters amenable to biofeedback learning are mentioned, including brainwaves, muscle tension, temperature, the cardiovascular system, and others. A discussion follows of the clinical application of biofeedback in the treatment of such disorders as tension headaches, neuromuscular re-education, epilepsy, "dysponesis," cardiac arrhythmias, blood pressure and migraines. The usefulness of biofeedback has been demonstrated also in the field of psychotherapy for purposes of desensitization, treating anxious patients, encouraging specific personality changes, and indicating stress to patients.

Control of the Ratio of Midline Parietal to Midline Frontal Eeg Alpha Rhythms through Auditory Feedback

The study asks whether voluntary control over the relative appearance of EEG alpha in midline frontal and parietal sites can be achieved with auditory biofeedback training. 16 Ss participated in the training and testing regimen. Ss varied in the number of hour-long single-channel feedback training sessions received. In the test period, dual-channel feedback was given, and Ss were asked to increase the ratio of frontal to parietal alpha and then the reverse. Evidence for small but significant control is presented. Amount of control was correlated with number of practice sessions.

Operant-controlled evoked responses: discrimination of conditioned and normally occurring components

Rats were rewarded for signaling large and small sensory evoked components with appropriate bar presses. Most rats operantly generated large components and correctly signaled only these. Two rats correctly signaled successful and unsuccessful attempts to generate large waves. One rat discriminated component amplitudes without operantly attempting to generate specific wave types.