Timing in cognition and EEG brain dynamics: discreteness versus continuity

This article provides an overview of recent developments in solving the timing problem (discreteness vs. continuity) in cognitive neuroscience. Both theoretical and empirical studies have been considered, with an emphasis on the framework of operational architectonics (OA) of brain functioning (Fingelkurts and Fingelkurts in Brain Mind 2:291-29, 2001; Neurosci Biobehav Rev 28:827-836, 2005). This framework explores the temporal structure of information flow and interarea interactions within the network of functional neuronal populations by examining topographic sharp transition processes in the scalp EEG, on the millisecond scale. We conclude, based on the OA framework, that brain functioning is best conceptualized in terms of continuity-discreteness unity which is also the characteristic property of cognition. At the end we emphasize where one might productively proceed for the future research.     

Neurophysical substrates of arousal and attention

The study of arousal and attention could be of prominent importance for elucidating both fundamental and practical aspects of the mind–brain puzzle. Defined as “general activation of mind” (Kahnemann in Attention and effort. Prentice-Hall, New Jersey, 1973), or “general operation of consciousness” (Thacher and John in Functional neuroscience: foundations of cognitive processing. Erlbaum, Hillsdale, 1977), arousal can be considered as a starting point of fundamental research on consciousness. Similar role could be assigned to attention, which can be defined by substituting the attributes “general” with “focused”. Concerning the practical applications, the empirically established correlation between neuronal oscillations and arousal/attention levels is widely used in research and clinics, including neurofeedback, brain–computer communication, etc. However, the neurophysical mechanism underlying this correlation is still not clear enough. In this paper, after reviewing some present classical and quantum approaches, a transition probability concept of arousal based on field–dipole quantum interactions and information entropy is elaborated. The obtained analytical expressions and numerical values correspond to classical empirical results for arousal and attention, including the characteristic frequency dependence and intervals. Simultaneously, the fundamental (substrate) role of EEG spectrum has been enlightened, whereby the attention appears to be a bridge between arousal and the content of consciousness. Finally, some clinical implications, including the brain-rate parameter as an indicator of arousal and attention levels, are provided.     

Conscious machines: Memory,melody and muscular imagination

A great deal of effort has been, and continues to be, devoted to developing consciousness artificially (A small selection of the many authors writing in this area includes: Cotterill (J Conscious Stud 2:290–311, 1995, 1998), Haikonen (2003), Aleksander and Dunmall (J Conscious Stud 10:7–18, 2003), Sloman (2004, 2005), Aleksander (2005), Holland and Knight (2006), and Chella and Manzotti (2007)), and yet a similar amount of effort has gone in to demonstrating the infeasibility of the whole enterprise (Most notably: Dreyfus (1972/1979, 1992, 1998), Searle (1980), Harnad (J Conscious Stud 10:67–75, 2003), and Sternberg (2007), but there are a great many others). My concern in this paper is to steer some navigable channel between the two positions, laying out the necessary pre-conditions for consciousness in an artificial system, and concentrating on what needs to hold for the system to perform as a human being or other phenomenally conscious agent in an intersubjectively-demanding social and moral environment. By adopting a thick notion of embodiment—one that is bound up with the concepts of the lived body and autopoiesis (Maturana and Varela 1980; Varela et al. 2003; and Ziemke 2003, 2007a, J Conscious Stud 14(7):167–179, 2007b)—I will argue that machine phenomenology is only possible within an embodied distributed system that possesses a richly affective musculature and a nervous system such that it can, through action and repetition, develop its tactile-kinaesthetic memory, individual kinaesthetic melodies pertaining to habitual practices, and an anticipatory enactive kinaesthetic imagination. Without these capacities the system would remain unconscious, unaware of itself embodied within a world. Finally, and following on from Damasio’s (1991, 1994, 1999, 2003) claims for the necessity of pre-reflective conscious, emotional, bodily responses for the development of an organism’s core and extended consciousness, I will argue that without these capacities any agent would be incapable of developing the sorts of somatic markers or saliency tags that enable affective reactions, and which are indispensable for effective decision-making and subsequent survival. My position, as presented here, remains agnostic about whether or not the creation of artificial consciousness is an attainable goal.     

Brain and mind operational architectonics and man-made “machine” consciousness

To build a true conscious robot requires that a robot’s “brain” be capable of supporting the phenomenal consciousness as human’s brain enjoys. Operational Architectonics framework through exploration of the temporal structure of information flow and inter-area interactions within the network of functional neuronal populations [by examining topographic sharp transition processes in the scalp electroencephalogram (EEG) on the millisecond scale] reveals and describes the EEG architecture which is analogous to the architecture of the phenomenal world. This suggests that the task of creating the “machine” consciousness would require a machine implementation that can support the kind of hierarchical architecture found in EEG.

关于针对最小意识状态患者的促醒综合治疗体系的文献综述

急性脑外伤或非创伤性脑损伤常常导致患者进入一种缺乏意识及思维、对自身及周围的事物缺乏感知的严重意识障碍阶段,过去称之为＂植物状态＂.随着最小意识状态概念的提出,本文在国内外现有参考文献的基础上进行改良并结合自身经验建立了规范的促醒治疗方法,就此促醒治疗方法进行综述,旨在为国内此类患者的评估、诊断、治疗及后续康复提供更多的临床参考.     

Cortical operational synchrony during audio-visual speech integration

Information from different sensory modalities is processed in different cortical regions. However, our daily perception is based on the overall impression resulting from the integration of information from multiple sensory modalities. At present it is not known how the human brain integrates information from different modalities into a unified percept. Using a robust phenomenon known as the McGurk effect it was shown in the present study that audio-visual synthesis takes place within a distributed and dynamic cortical networks with emergent properties. Various cortical sites within these networks interact with each other by means of so-called operational synchrony (Kaplan, Fingelkurts, Fingelkurts, & Darkhovsky, 1997). The temporal synchronization of cortical operations processing unimodal stimuli at different cortical sites reveals the importance of the temporal features of auditory and visual stimuli for audio-visual speech integration.     

Establishing consciousness in non-communicative patients: a modern-day version of the Turing test

In a recent study of a patient in a persistent vegetative state, [Owen, A. M., Coleman, M. R., Boly, M., Davis, M. H., Laureys, S., & Pickard, J. D. (2006). Detecting awareness in the vegetative state. Science, 313, 1402] claimed that they had demonstrated the presence of consciousness in this patient. This bold conclusion was based on the isomorphy between brain activity in this patient and a set of conscious control subjects, obtained in various imagery tasks. However, establishing consciousness in unresponsive patients is fraught with methodological and conceptual difficulties. The aim of this paper is to demonstrate that the current debate surrounding consciousness in VS patients has parallels in the artificial intelligence (AI) debate as to whether machines can think. Basically, (Owen et al., 2006) used a method analogous to the Turing test to reveal the presence of consciousness, whereas their adversaries adopted a line of reasoning akin to Searle's Chinese room argument. Highlighting the correspondence between these two debates can help to clarify the issues surrounding consciousness in non-communicative agents.     

Consciousness: a neurological perspective

Consciousness is a state so essentially entwined with human experience, yet so difficult to conceptually define and measure. In this article, we explore how a bidimensional model of consciousness involving both level of arousal and subjective awareness of the contents of consciousness can be used to differentiate a range of healthy and altered conscious states. These include the different sleep stages of healthy individuals and the altered states of consciousness associated with neurological conditions such as epilepsy, vegetative state and coma. In particular, we discuss how arousal and awareness are positively correlated in normal physiological states with the exception of REM sleep, while a disturbance in this relationship is characteristic of vegetative state, minimally conscious state, complex partial seizures and sleepwalking.     

Recognition of affective prosody in brain-damaged patients and healthy controls: A neurophysiological study using EEG and whole-head MEG

A passive oddball experiment was used in which stimuli were emotional exclamations differing in their affective tone. In both electroencephalography (EEG) and magnetoencephalography (MEG), deviants elicited an N300 component, sometimes accompanied by a slow wave. Both components had a symmetrical distribution, but the former was more posterior than the latter. The same responses to prosodic stimuli were significant in 6 of 27 patients with severe disorders of consciousness (persistent vegetative state and minimally conscious state) and in all 3 of the examined locked-in patients, indicating that the procedure can be applied for testing neurological patients. The occurrence of significant responses depended on the presence or absence of a lesion to the right temporal lobe. Obviously, the N300 depends on the activity of the right temporal cortex but does not originate there. We suggest that the component is related not to the recognition of affective prosody as such, but to the following detection of affective mismatch due to violations of emotional context of stimulation.     

The neural correlate of (un)awareness: lessons from the vegetative state

Consciousness has two main components: wakefulness and awareness. The vegetative state is characterized by wakefulness without awareness. Recent functional neuroimaging results have shown that some parts of the cortex are still functioning in 'vegetative' patients. External stimulation, such as a painful stimulus, still activates 'primary' sensory cortices in these patients but these areas are functionally disconnected from 'higher order' associative areas needed for awareness. Such studies are disentangling the neural correlates of the vegetative state from the minimally conscious state, and have major clinical consequences in addition to empirical importance for the understanding of consciousness.     

Caregiving for Patients in Vegetative and Minimally Conscious States: Perceived Burden as a Mediator in Caregivers’ Expression of Needs and Symptoms of Depression and Anxiety

Involvement of family members is crucial to provide daily informal caring to patients in vegetative state and minimally conscious state. Previous studies showed that perceived burden is a risk factor for informal caregivers as it increases psychophysical distress. This research further investigated the relationship between these factors and aimed at providing a model that thoroughly describes this mechanism of functioning. In the frame of a national survey on people with disorders of consciousness, 487 informal caregivers of children and adult patients in vegetative and minimally conscious state were administered measures of depression, anxiety, caregiver needs, and family strain. Regression models proposed by Baron and Kenny and the Sobel test were adopted to investigate the relationship between depressive and anxiety symptoms, perceived burden and needs expressed. Our study shows that the relation between those symptoms and needs is mediated by burden, where higher burden accentuates and lower burden mitigates the needs expressed by caregivers. Our findings demonstrate that psychosocial components of the burden perceived by caregivers of patients with disorders of consciousness play a key role in shaping those caregivers’ needs, especially their needs for information and communication. We recommend implementation of comprehensive steps to meet the needs of these caregivers, steps that incorporate improved economic and public health programs, social support, and use of psychological interventions to ameliorate caregivers’ psychological distress and decrease their burden.     

Time for consciousness: intention and introspection

We assume that we can act—in at least some cases—by consciously intending to do so. Wegner (2002) appeals to empirical research carried out by Libet et al. (1983) to challenge this assumption. I argue that his conclusion presupposes a particular view of conscious intention. But there is an alternative model available, which has been developed by various writers in the phenomenological tradition, and most recently defended by Moran (2001). If we adopt this alternative account of conscious intention, Wegner’s argument no longer goes through, and we can retain the claim that our conscious intentions can give rise to action.     

Self-consciousness in non-communicative patients

The clinical and para-clinical examination of residual self-consciousness in non-communicative severely brain damaged patients (i.e., coma, vegetative state and minimally conscious state) remains exceptionally challenging. Passive presentation of the patient's own name and own face are known to be effective attention-grabbing stimuli when clinically assessing consciousness at the patient's bedside. Event-related potential and functional neuroimaging studies using such self-referential stimuli are currently being used to disentangle the cognitive hierarchy of self-processing. We here review neuropsychological, neuropathological, electrophysiological and neuroimaging studies using the own name and own face paradigm obtained in conscious waking, sleep, pharmacological coma, pathological coma and related disorders of consciousness. Based on these results we discuss what we currently do and do not know about the functional significance of the neural network involved in "automatic" and "conscious" self-referential processing.     

The global workspace (GW) theory of consciousness and epilepsy

The global workspace (GW) theory proposes that conscious processing results from coherent neuronal activity between widely distributed brain regions, with fronto-parietal associative cortices as key elements. In this model, transition between conscious and non conscious states are predicted to be caused by abrupt non-linear massive changes of the level of coherence within this distributed neural space. Epileptic seizures offer a unique model to explore the validity of this central hypothesis. Seizures are often characterized by the occurrence of brutal alterations of consciousness (AOC) which are largely negatively impacting patients' lives. Recently, we have shown that these sudden AOC are contemporary to non-linear increases of neural synchrony within distant cortico-cortical and cortico-thalamic networks. We interpreted these results in the light of GW theory, and suggested that excessive synchrony could prevent this distributed network to reach the minimal level of differentiation and complexity necessary to the coding of conscious representations. These observations both confirm some predictions of the GW model, and further specify the physiological window of neural coherence (minimum and maximum) associated with conscious processing.     

Intracranial EEG power spectra and phase synchrony during consciousness and unconsciousness

Power density spectra and phase synchrony measurements were taken from intracranial electrode grids implanted in epileptic subjects. Comparisons were made between data from the waking state and from the period of unconsciousness immediately following a generalised tonic–clonic seizure. Power spectra in the waking state resembled coloured noise. Power spectra in the unconscious state resembled coloured noise from 1 to about 5 Hz, but at higher frequencies changed in two out of three subjects to resemble white noise. This boosted unconscious gamma power to a higher level than conscious gamma power. For both gamma and beta passbands, synchrony measurements showed more widespread phase synchrony in the unconscious than the conscious state. We conclude that neither gamma activity per se nor phase synchrony per se are neural correlates of consciousness.     

植物状态的残存脑功能和意识研究

综述了有关植物状态患者对外加刺激脑反应的功能成像研究文献,着重讨论了研究发现的非典型激活的临床价值以及植物状态患者是否存在意识的功能脑成像证据。     

Computational Theories of Conscious Experience: Between a Rock and a Hard Place

Very plausibly, nothing can be a genuine computing system unless it meets an input-sensitivity requirement. Otherwise all sorts of objects, such as rocks or pails of water, can count as performing computations, even such as might suffice for mentality—thus threatening computationalism about the mind with panpsychism. Maudlin in J Philos 86:407–432, (1989) and Bishop (2002a, b) have argued, however, that such a requirement creates difficulties for computationalism about conscious experience, putting it in conflict with the very intuitive thesis that conscious experience supervenes on physical activity. Klein in Synthese 165:141–153, (2008) proposes a way for computationalists about experience to avoid panpsychism while still respecting the supervenience of experience on activity. I argue that his attempt to save computational theories of experience from Maudlin’s and Bishop’s critique fails.     

The brain is both neurocomputer and quantum computer

In their article, Is the Brain a Quantum Computer,? Litt, Eliasmith, Kroon, Weinstein, and Thagard (2006) criticize the Penrose–Hameroff “Orch OR” quantum computational model of consciousness, arguing instead for neurocomputation as an explanation for mental phenomena. Here I clarify and defend Orch OR, show how Orch OR and neurocomputation are compatible, and question whether neurocomputation alone can physiologically account for coherent gamma synchrony EEG, a candidate for the neural correlate of consciousness. Orch OR is based on quantum computation in microtubules within dendrites in cortex and other regions linked by dendritic–dendritic gap junctions (“dendritic webs”) acting as laterally connected input layers of the brain's neurocomputational architecture. Within dendritic webs, consciousness is proposed to occur as gamma EEG‐synchronized sequences of discrete quantum computational events acting in integration phases of neurocomputational “integrate‐and‐fire” cycles. Orch OR is a viable approach toward understanding how the brain produces consciousness.     

Wegner on hallucinations,inconsistency, and the illusion of free will. Some critical remarks

Wegner’s argument on the illusory nature of conscious will, as developed in The Illusion of Conscious Will (2002) and other publications, has had major impact. Based on empirical data, he develops a theory of apparent mental causation in order to explain the occurrence of the illusion of conscious will. Part of the evidence for his argument is derived from a specific interpretation of the phenomenon of auditory verbal hallucinations as they may occur in schizophrenia. The aim of this paper is to evaluate the validity of the evidence on auditory verbal hallucinations as employed by Wegner. I conclude that auditory hallucinations do not provide solid evidence for Wegner’s theory. Moreover, the phenomena in schizophrenia provide, in fact, an argument against part of Wegner’s theory of apparent mental causation.     

Long-term meditation training induced changes in the operational synchrony of default mode network modules during a resting state

Using theoretical analysis of self-consciousness concept and experimental evidence on the brain default mode network (DMN) that constitutes the neural signature of self-referential processes, we hypothesized that the anterior and posterior subnets comprising the DMN should show differences in their integrity as a function of meditation training. Functional connectivity within DMN and its subnets (measured by operational synchrony) has been measured in ten novice meditators using an electroencephalogram (EEG) recording in a pre-/post-meditation intervention design. We have found that while the whole DMN was clearly suppressed, different subnets of DMN responded differently after 4 months of meditation training: The strength of EEG operational synchrony in the right and left posterior modules of the DMN decreased in resting post-meditation condition compared to a pre-meditation condition, whereas the frontal DMN module on the contrary exhibited an increase in the strength of EEG operational synchrony. These findings combined with published data on functional–anatomic heterogeneity within the DMN and on trait subjective experiences commonly found following meditation allow us to propose that the first-person perspective and the sense of agency (the witnessing observer) are presented by the frontal DMN module, while the posterior modules of the DMN are generally responsible for the experience of the continuity of ‘I’ as embodied and localized within bodily space. Significance of these findings is discussed.