Although the brain enables us to perceive the external world and our body, it remains unknown whether brain processes themselves can be perceived. Brain tissue does not have receptors for its own activity. However, the ability of humans to acquire self-control of brain processes indicates that the perception of these processes may also be achieved by learning. In this study patients learned to control low-frequency components of their EEG: the so-called slow cortical potentials (SCPs). In particular ''probe'' sessions, the patients (...) estimated the quality of the SCP shift they had produced in the preceding trial. The correspondence between the recorded SCP amplitudes and the subjective estimates increased with training. The ability to perceive the SCPs was related to the ability to control them; this perception was not mediated by peripheral variables such as changes in muscle tonus and cannot be reduced to simple vigilance monitoring. These data provide evidence that humans can learn to perceive the neural activity of their brain. Alternative interpretations are discussed. (shrink)
Brain machine interface (BMI) technology makes direct communication between the brain and a machine possible by means of electrodes. This paper reviews the existing and emerging technologies in this field and offers a systematic inquiry into the relevant ethical problems that are likely to emerge in the following decades.
The ability to imagine objects undergoing rotation (mental rotation) improves markedly with practice, but an explanation of this plasticity remains controversial. Some researchers propose that practice speeds up the rate of a general-purpose rotation algorithm. Others maintain that performance improvements arise through the adoption of a new cognitive strategy—repeated exposure leads to rapid retrieval from memory of the required response to familiar mental rotation stimuli. In two experiments we provide support for an integrated explanation of practice effects in mental rotation (...) by combining behavioral and EEG measures in a way that provides more rigorous inference than is available from either measure alone. Before practice, participants displayed two well-established signatures of mental rotation: Both response time and EEG negativity increased linearly with rotation angle. After extensive practice with a small set of stimuli, both signatures of mental rotation had all but disappeared. In contrast, after the same amount of practice with a much larger set both signatures remained, even though performance improved markedly. Taken together, these results constitute a reversed association, which cannot arise from variation in a single cause, and so they provide compelling evidence for the existence of two routes to expertise in mental rotation. We also found novel evidence that practice with the large but not the small stimulus set increased the magnitude of an early visual evoked potential, suggesting increased rotation speed is enabled by improved efficiency in extracting three-dimensional information from two-dimensional stimuli. (shrink)
euroscience of Rule-Guided Behavior brings together, for the first time, the experiments and theories that have created the new science of rules. Rules are central to human behavior, but until now the field of neuroscience lacked a synthetic approach to understanding them. How are rules learned, retrieved from memory, maintained in consciousness and implemented? How are they used to solve problems and select among actions and activities? How are the various levels of rules represented in the brain, ranging from simple (...) conditional ones if a traffic light turns red, then stop to rules and strategies of such sophistication that they defy description? And how do brain regions interact to produce rule-guided behavior? These are among the most fundamental questions facing neuroscience, but until recently there was relatively little progress in answering them. It was difficult to probe brain mechanisms in humans, and expert opinion held that animals lacked the capacity for such high-level behavior. However, rapid progress in neuroimaging technology has allowed investigators to explore brain mechanisms in humans, while increasingly sophisticated behavioral methods have revealed that animals can and do use high-level rules to control their behavior. The resulting explosion of information has led to a new science of rules, but it has also produced a plethora of overlapping ideas and terminology and a field sorely in need of synthesis. In this book, Silvia Bunge and Jonathan Wallis bring together the worlds leading cognitive and systems neuroscientists to explain the most recent research on rule-guided behavior. Their work covers a wide range of disciplines and methods, including neuropsychology, functional magnetic resonance imaging, neurophysiology, electroencephalography, neuropharmacology, near-infrared spectroscopy, and transcranial magnetic stimulation. This unprecedented synthesis is a must-read for anyone interested in how complex behavior is controlled and organized by the brain. (shrink)
Experiments are described, using electroencephalography (EEG) and simple tests of performance, which support the hypothesis that collapse of a quantum field is of importance to the functioning of the brain. The theoretical basis of our experiments is derived from Penrose (1989) who suggested that conscious decision-making is a manifestation of the outcome of quantum computation in the brain involving collapse of some relevant wave function. He also proposed that collapse of any wave function depends on a gravitational criterion. As different (...) brain areas are known to subserve different functions, we argue that `Penrose collapse' must occur in a particular brain area when performing a task that uses it. Further, taking an EEG from the area should amplify the gravitational prerequisite for collapse, so affecting task performance. There are no non-quantum theories which could lead one to expect that taking an EEG could directly affect task performance by subjects. The results of both pilot and main experiments indicated that task performance was indeed influenced by taking an EEG from relevant brain areas. Control experiments suggested that the influence was quantum mechanical in origin, and was not due to any experimental artefact. The results are statistically significant and merit attempts at replication in an independent laboratory, preferably with more sophisticated equipment than was available to us. (shrink)
Brazilian spiritistic religions have developed along elaborate historical and cultural trajectories with spirit mediumship as a central feature of ritual practice in Candomblé, Umbanda, Kardecismo, and similar groups. In these studies, several Brazilian spiritistic practitioners who worked as mediums were interviewed and, in some cases, tested with psychological measures for dissociation using the Dissociative Experiences Scale, for absorption using the Tellegen Absorption Scale, and for sexual orientation using the Kinsey Scale. Few significant gender differences were noted in these measures. In (...) two cases, psychophysiological measures were employed including electroencephalography, heart rate, skin conductance, and electromyography. In general, the research participants scored highly on measures of dissociation while scoring in the average range on absorption (using U.S. norms). The psychophysiological results indicated that for the two spiritistic practitioners investigated overall peripheral autonomic nervous system activation was negatively associated with sympathetic cortical level deactivation. The data suggested a psychophysiological incongruence between the central nervous system and the peripheral nervous system functioning on the part of the two practitioners. However, the two variables were positively associated and congruent in data obtained from a control subject. Interview data identified five ways in which mediums received their "call to heal," visions, dreams, and unexpected incorporations being the most frequent factors cited. One medium who engages in surgical procedures was observed; tissues were collected from ten clients and were found to be consistent with the site of the surgery. In conclusion, it is apparent that mediumship is a complex phenomenon, one deserving of further investigation by anthropologists, psychologists, and sociologists interested in human consciousness, in indigenous health care, and in the psychophysiology of practitioners who claim to work under the direction of spirit entities. (shrink)
The capacity to stabilize the content of attention over time varies among individuals, and its impairment is a hallmark of several mental illnesses. Impairments in sustained attention in patients with attention disorders have been associated with increased trial-to-trial variability in reaction time and event-related potential deficits during attention tasks. At present, it is unclear whether the ability to sustain attention and its underlying brain circuitry are transformable through training. Here, we show, with dichotic listening task performance and electroencephalography, that training (...) attention, as cultivated by meditation, can improve the ability to sustain atten- tion. Three months of intensive meditation training reduced variability in attentional processing of target tones, as indicated by both enhanced theta-band phase consistency of oscillatory neural responses over anterior brain areas and reduced reaction time variability. Furthermore, those individuals who showed the greatest increase in neural response consistency showed the largest decrease in behav- ioral response variability. Notably, we also observed reduced variability in neural processing, in particular in low-frequency bands, regardless of whether the deviant tone was attended or unattended. Focused attention meditation may thus affect both distracter and target processing, perhaps by enhancing entrainment of neuronal oscillations to sensory input rhythms, a mechanism important for controlling the content of attention. These novel findings highlight the mechanisms underlying focused attention meditation and support the notion that mental training can significantly affect attention and brain function. (shrink)
A general conceptual framework for large-scale neocortical dynamics based on data from many laboratories is applied to a variety of experimental designs, spatial scales, and brain states. Partly distinct, but interacting local processes (e.g., neural networks) arise from functional segregation. Global processes arise from functional integration and can facilitate (top down) synchronous activity in remote cell groups that function simultaneously at several different spatial scales. Simultaneous local processes may help drive (bottom up) macroscopic global dynamics observed with electroencephalography (EEG) or (...) magnetoencephalography (MEG). A local/global dynamic theory that is consistent with EEG data and the proposed conceptual framework is outlined. This theory is neutral about properties of neural networks embedded in macroscopic fields, but its global component makes several qualitative and semiquantitative predictions about EEG measures of traveling and standing wave phenomena. A more general “metatheory” suggests what large-scale quantitative theories of neocortical dynamics may be like when more accurate treatment of local and nonlinear effects is achieved. The theory describes the dynamics of excitatory and inhibitory synaptic action fields. EEG and MEG provide large-scale estimates of modulation of these synaptic fields around background levels. Brain states are determined by neuromodulatory control parameters. Purely local states are dominated by local feedback gains and rise and decay times of postsynaptic potentials. Dominant local frequencies vary with brain region. Other states are purely global, with moderate to high coherence over large distances. Multiple global mode frequencies arise from a combination of delays in corticocortical axons and neocortical boundary conditions. Global frequencies are identical in all cortical regions, but most states involve dynamic interactions between local networks and the global system. EEG frequencies may involve a “matching” of local resonant frequencies with one or more of the many, closely spaced global frequencies. Key Words: binding problem; cell assemblies; coherence; EEG; limit cycles; neocortical dynamics; pacemakers; phase locking; spatial scale; standing waves; synchronization. Footnotes1 The relationship between the synaptic action fields proposed in the target article and cell assemblies is clarified with Figure R1 (p. 416) of the Response. (This figure was not available to Commentators. (shrink)
Psychogenic non epileptic seizures (PNES) are clinical events of psychological nature. Video-electroencephalography monitoring (V-EEGM) is a valuable method for the diagnosis of PNES and may be combined with provocative tests to induce seizures. The use of placebo in provocative tests for the diagnosis of PNES is controversial because of associated deception, and contrasts with the use of truly decreasing epileptogenic threshold techniques such as hyperventilation and photo stimulation. We present a clinical case of a pregnant woman with a past history (...) of refractory epilepsy, admitted in the obstetric department due to unremitting seizures. In this clinical context, non-deceiving provocative tests such as hyperventilation and photo stimulation could be potentially harmful, nevertheless, the use of intravenous saline injection presented as a safer alternative to diagnose PNES and hence obviate an urgent caesarean. This case illustrates a disproportionate risk of causing harm when telling the truth, in comparison with the benefit of avoiding such risk, although deceiving the patient. This is a clinical example of how considerations concerning the use of placebo must be evaluated in an individual basis. (shrink)
activity” has been considered to play a major role in the short-term maintenance of memories. Many studies since then have provided support for this view and greatly advanced our knowledge of the effects of stimulus type and modality on delay activity and its temporal dynamics (Funahashi et al., 1993; Fuster et al., 2000; Romo et al., 1999). In humans, working memory has also been a subject of intense investigation using scalp and intracranial electroencephalography (EEG, iEEG) as well as magnetoencephalography (MEG), (...) which provide estimates of local population activity. The published findings include reports of systematic changes in signal amplitude during working memory in the theta (Raghavachari et al., 2001; Tesche and <span class='Hi'>Karhu</span>, 2000), alpha (Gevins et al., 1997; Working memory has been linked to elevated single Jensen et al., 2002), beta (Tallon-Baudry et al., 1999). (shrink)
Background: Patients in a vegetative state pose problems in diagnosis, prognosis and treatment. Currently, no prognostic markers predict the chance of recovery, which has serious consequences, especially in end-of-life decision-making. -/- Objective: We aimed to assess an objective measurement of prognosis using advanced electroencephalography (EEG). -/- Methods: EEG data (19 channels) were collected in 14 patients who were diagnosed to be persistently vegetative based on repeated clinical evaluations at 3 months following brain damage. EEG structure parameters (amplitude, duration and variability (...) within quasi-stationary segments, as well as the spatial synchrony between such segments and the strength of this synchrony) were used to predict recovery of consciousness 3 months later. -/- Results: The number and strength of cortical functional connections between EEG segments were higher in patients who recovered consciousness (P < .05 – P < .001) compared with those who did not recover. Linear regression analysis confirms that EEG structure parameters are capable of predicting (P = .0025) recovery of consciousness 6 months post-injury, whereas the same analysis failed to significantly predict patient outcome based on aspects of their clinical history alone (P = .629) or conventional EEG spectrum power (P = .473). -/- Conclusions: The result of this preliminary study demonstrates that structural strategy of EEG analysis is better suited for providing prognosis of consciousness recovery than existing methods of clinical assessment and of conventional EEG. Our results may be a starting point for developing reliable prognosticators in patients who are in vegetative state, with the potential to improve their day-to-day management, quality of life, and access to early interventions. (shrink)
: This paper seeks to contribute to the development of a sociological understanding of scientific change. It first presents a conceptual framework for defining and understanding the conditions that give rise to episodes of cumulative change (both as the selective reconstruction of events and as the patterned structuring of innovations over time and across different settings). It argues that one of the most powerful structuring mechanisms is the existence of standardized research technologies. Then, the development of electroencephalography (EEG) is presented (...) as an illustrative case study. The EEG supported a dramatic episode of development in brain science, and did so primarily through technological standardization and reliability. The case shows how standard and manipulable technologies provide a framework for orderly change both in retrospective accounts and in specific historical periods of scientific practice. (shrink)
