Friday June 20, 10:30AM-12:30PM at Alexander Hall
Implicit Processing and Awareness
Implicit processing and awareness are usually concomitant and functioning in harmony for normal cognitive systems. Indeed, understanding implicit processing can provide great insights into the nature of mechanisms underneath awareness, and studies on the relationship between implicit processing and awareness can elucidate the architecture of cognitive processes and the nature of consciousness. This symposium brings together researchers who tackle these issues from electrophysiology, brain imaging, neuropsychology, behavioral measures, and computational modeling. Each speaker would report experimental data taken from non-human animals, normal participants, neuropsychological patients, and neural network models to put forward hypotheses about the interplay between perception, memory, attention, and/or action in uni-sensory and multi-sensory domains.
Chair: Su-Ling Yeh
Department of Psychology
National Taiwan University
Life Sciences Institute and Neural Computation Center
Volodya Yakovlev, Life Sciences Institute & Neural Computation Center, ISRAEL
Sandro Romani, Dip. di Fisiologia Umana Universita di Roma La Sapienza, Roma, ITALY
Daniel Amit, Racah Institute of Physics, Hebrew University, Jerusalem, ISRAEL; Dip. di Fisica, Universita di Roma La Sapienza, Roma, ITALY
Explicit vs. Implicit Perception and Working Memory Processes
When encountering someone on the street, we can often say whether his or her face is familiar, though it may be difficult to identify the same person. Familiarity memory may differ essentially from identification memory, which includes contextual and episodic information and may require conscious scrutiny. We tested macaque monkeys on a delayed-match-to-multiple-sample task, with limited sets of well-trained images or neverbefore- seen images. They performed better with novel images, detecting familiarity vs. novelty, rather than recency of presentation. This implies extremely effective one-shot learning of familiarity, resembling Standing’s (1973) finding that people detect familiarity for 10,000 once-seen pictures. We suggest that with conscious scrutiny delayactivity working memory is used for identifying well-trained stimuli. Novel stimuli do not induce delay-activity, so a different strategy is used, based on modulated responses to repeated images. We present a generic neural network model, quantitatively simulating these behaviors, based on conservative Hebbian synaptic plasticity. Familiarity becomes the first step toward establishing identification.
Interactions between Implicit Processing and Working Memory Revealed through Visual Extinction
In the phenomenon of visual extinction, patients are unaware of a stimulus presented on the side of space contralateral to their lesion when a competing stimulus occurs simultaneously on the ipsilesional side. The phenomenon is classically associated with damage to psoterior parietal cortex. The degree of extinction manifested in patients, however, vary on the basis of whether the contralesional and ipsilesional stimuli group. This is consistent with there being implicit processing of contralesional stimuli, which enables them to enter into grouping relations with ipsilesional events. Recently we have shown that extinction can also be modulated by matches between the contralesional stimulus and items held in working memory, indicating that working memory interacts with implicit processing of items to enable stimuli to enter into awareness. We have examined the neural basis of this interaction using fMRI, with the data revealing that it is dependent on a fronto-thalamic-visual circuit, by- passing posterior parietal cortex. This suggests that deficits in realising awareness can be overcome by recruiting corticalsubcortical circuits that route information to frontal cortex.
The Colavita Effect: An Example of Crossmodal Extinction in Normal Participants?
Colavita (1974) first reported that presenting a light at the same time as a clearly suprathreshold auditory target resulted in many people simply failing to respond to (or be aware of) the sound (a sound that participants were always aware of when presented in isolation). I will describe a number of recent studies on this little-studied, but fascinating, crossmodal phenomenon. I will highlight the spatiotemporal constraints on the Colavita effect and its sensitivity to manipulations of attention/perceptual load. I will also describe the latest research demonstrating that the presentation of a visual stimulus leads to a significant decrease in people’s sensitivity to a simultaneously-presented auditory or tactile stimulus. These results, which contrast with the commonly-held view that multisensory integration always leads to perceptual/performance enhancement, have led us to argue that the Colavita effect can be thought of as a form of crossmodal extinction (experienced by stroke patients) in normal participants.
Coding of Cognitive Control Demand in the Medial Prefrontal Neurons
Resources for top-down attention are limited and therefore allocated to cognitive processes according to demand. While the anterior cingulate cortex is thought to represent such demand for attention allocation, it is unclear what determines the demand represented there. Here we report that neurons in the anterior cingulate cortex showed prominent activities between action completion and visual feedback in an action-learning task. The activities had properties of top-down attention control signals. Their magnitude correlated with the expected size of prediction errors of action values along the action learning in each block. These findings suggest that in the context of action learning the anterior cingulate cortex represents the expected size of prediction errors to indicate how much attention to pay to the action outcome.
Saturday June 21, 10:30AM-12:30PM at Alexander Hall
Basic Neuroscientific and Clinical Approaches to Disorders of CNS Arousal
Chair: Donald Pfaff
Laboratory of Neurobiology and Behavior
Laboratory of Neurobiology and Behavior
The Rockefeller University
Donald Pfaff, Laboratory of Neurobiology and Behavior, The Rockefeller University, USA
Isabel Arrieta-Cruz, Laboratory of Neurobiology and Behavior, The Rockefeller University, USA
Generalized CNS Arousal in Animal and Human Brains
Generalized CNS arousal has been given an operational definition ("Brain Arousal", Harvard Univ. Press, 2006) that is intended to apply to all vertebrate brains. Using a computer-controlled assay that measures the motoric, sensory and emotional components of generalized CNS arousal in mice, we have detected behavioral deficits due to anoxia that did not appear in a 28 point neurological screen ( Experimental Neurology, 2007). Inspired by the success of Schiff et al (Nature, 2007) in using deep brain to improve the functional ability of a patient who had been in a minimally conscious state, we are now using stimulation of the medial thalamus and/or the basal forebrain to elevate arousal-related behaviors in mice. Included in this effort are mathematically defined trains of pulses designed to conform to the likely non-linear character of CNS arousal systems.
Neural and Chemical Substrates of Consciousness across Waking and Sleeping
Waking and sleeping are actively generated by neuronal systems distributed through the brainstem and forebrain with different projections, discharge patterns, neurotransmitters and receptors. Waking is maintained by systems with ascending projections, which by their discharge stimulate cortical activation, necessary for consciousness. It is also stimulated by neurons with descending projections, which by their discharge stimulate behavioral arousal and responsiveness with muscle tone. Together with predominantly glutamatergic and GABAergic long or locally projecting neurons of the central reticular core, other neurons serve to modulate cortical activity and behavior through diffuse projections, state-regulated discharge and use of modulatory neurotransmitters, including acetylcholine, noradrenaline, and orexin (hypocretin). Cholinergic neurons stimulate cortical activation but not behavioral arousal or muscle tone and discharge in association with cortical activation during both Wake and REM sleep. In contrast, many other modulatory systems stimulate both cortical activation and behavioral arousal and discharge selectively during waking. The modulatory neurotransmitters act upon postsynaptic neurons in different manners according to specific receptors associated with excitatory or inhibitory actions and accordingly recruitment or silencing of other wake or sleep neuronal systems. Sleeping is initiated by inhibition of the activating and arousal systems. This inhibition is effected at multiple levels through particular GABAergic neurons that discharge maximally during sleep. Sleep-active GABAergic neurons are inhibited during waking by noradrenaline through α2 adrenergic receptors. Some such GABAergic neurons in the preoptic area and basal forebrain discharge with slow wave activity during slow wave sleep (SWS). Such cortical activity is not consonant with conscious perception or cognitive activity. Other GABAergic neurons discharge at progressively increasing rates during SWS and REM sleep potentially promoting behavioral quiescence and inhibition of responsiveness along with diminishing muscle tone. Such GABAergic neurons likely inhibit noradrenergic and orexinergic neurons. During REM sleep, cholinergic systems become active and stimulate cortical activation, while the noradrenergic and orexinergic systems along with other reticular and motor neurons are held under inhibition such as to prevent responsiveness, motor activity and muscle tone during this ‘paradoxical’ state of sleep, when dreaming and thus a particular state of consciousness occur.
Imaging in Disorders of Conscious
- Learn the difference between coma, vegetative state, minimally conscious state and locked-in syndrome
- Learn the clinical assessment of consciousness
- Learn what is the residual brain function and activation in disorders of consciousness
- Learn about the ethical issues and quality of life measures in these disorders
Financial Disclosure: this presentation will not include discussion of any commercial products or services.
New neuroimaging techniques are giving a better understanding of patients in coma and related conditions. Progress in medical care is increasing the number of people who survive brain damage. We can now save the lives of many patients who suffer trauma or anoxia but if the damage is severe, the victim will slip into a coma. Patients who recover from a coma typically do so within days. Others will die, and still others will awaken but remain unconscious, entering what is called a vegetative state. Even for experts, the vegetative state is very a disturbing condition. It illustrates how the two main components of consciousness can get dissociated: wakefulness remains intact but awareness - encompassing all thoughts and feelings - is abolished. In patients who recover from the vegetative state, the first signs of consciousness are minimal and appear gradually. The patient who starts making non-reflexive movements but remains unable to communicate enters a minimally conscious state. Like the vegetative state, the minimally conscious state may be transient on the way to further recovery, or it may be chronic, sometimes permanent. Making the distinction between vegetative and minimally conscious patients is challenging. Given that conscious awareness is subjective, first-person experience that is inherently difficult to measure in another being; functional neuroimaging offers a unique opportunity to objectively study disorders of consciousness. Positron emission tomography (PET) and functional MRI studies measuring neural activity in brain-damaged patients are disentangling the neural correlates of the vegetative from the minimally conscious state and have major clinical and ethical consequences. More research efforts are awaited so that these new techniques can help in the prognosis and treatment of these devastating medical conditions.
Suggested readings 1-5:
1. Di HB, Yu SM, Weng XC, Laureys S, Yu D, Li JQ, et al. Cerebral response to patient's own name in the vegetative and minimally conscious states. Neurology 2007;68(12):895-9.
2. Di H, Boly M, Weng X, Ledoux D, Laureys S. Neuroimaging activation studies in the vegetative state: predictors of recovery? Clinical Medicine in press.
3. Laureys S, Giacino JT, Schiff ND, Schabus M, Owen AM. How should functional imaging of patients with disorders of consciousness contribute to their clinical rehabilitation needs? Curr Opin Neurol 2006;19(6):520-7.
4. Laureys S. The neural correlate of (un)awareness: lessons from the vegetative state. Trends Cogn Sci 2005;9(12):556-9.
5. Laureys S. Science and society: death, unconsciousness and the brain. Nat Rev Neurosci 2005;6(11):899-909.
Haibo Di, Coma Science Group, University of Liege, Liege, BELGIUM
Steven Laureys, Coma Science Group, University of Liege, Liege, BELGIUM
Eyes Open, Brain Shut: Consciousness in the Vegetative State
Patients in a vegetative state (VS) and minimally conscious state (MCS) continue to pose problems in terms of their diagnosis, prognosis and treatment. Consciousness is a subjective first-person experience which study has remained the field of philosophy for the past millennia. That time has finally changed and empirical evidence from functional neuroimaging is offering a genuine glimpse on the solution to the infamous mind-body conundrum. New technological and scientific advances offer the neurological community unique ways to improve our understanding and management of severely brain damaged patients.
Good medical management starts by making a correct diagnosis. There is an irreducible limitation in knowing for certain whether any other being is conscious. Vegetative patients can move extensively and clinical studies have shown how difficult it is to differentiate reflex or ‘automatic’ from voluntary or ‘willed’ movements. This results in an underestimation of behavioural signs of consciousness and hence a misdiagnosis, estimated to occur in about one third to nearly half of chronically vegetative patients.
PET and fMRI studies have not yet shown to be reliable markers of recovery of consciousness. However, they have permitted to reject the ancient view that vegetative patients are neocortically dead or a-pallic. A succession of neuroimaging data has shown cerebral activation in isolated and disconnected islands of “lower level” cortices or "pallium" in response to auditory, visual, somatosensory and noxious stimuli. Functional neuroimaging studies have also provided scientific evidence that residual brain function in VS is very different from the brain’s integrative capacity in MCS. These studies have confirmed that VS and MCS truly are different physiological entities. However, in the absence of a full understanding of the neural correlates of consciousness, even a normal activation in response to passive sensory stimulation cannot be taken as incontestable proof of consciousness. In contrast, repeated and prolonged activation in response to the instruction to perform a mental imagery task would provide undeniable evidence of voluntary task-dependent brain activity, and hence of consciousness. This ground-breaking approach was recently validated in healthy controls and has been successfully applied to identify conscious perception in a – so far unique - patient behaviourally diagnosed as being in a post-traumatic VS.
Brain computer interfaces (BCI) permit communication via voluntary EEG control, without any motor involvement. Technological improvements in such devices now enable locked-in patients to control their surroundings in ways never possible before. BCI can not only be employed as a communication instrument in LIS but also as a diagnostic tool in disorders of consciousness. It is thrilling to witness the use of this powerful approach in the assessment of possible residual consciousness in patients clinically diagnosed as “VS” or “MCS”. The question of what it feels like to be minimally conscious has not yet been solved but the technology to at least try to answer the issue is now existing.
Death, unconsciousness and the brain, Laureys S Nature Reviews Neuroscience, 11 (2005) 899-909
What is it like to be vegetative or minimally conscious ?, Laureys S and Boly M Current Opinion in Neurology, 20 (2007) 609-13
Self-consciousness in non-communicative patients, Laureys S, Perrin F, Bredart S Consciousness & Cognition, 16 (2007) 722-741?
Eyes open, brain shut: the vegetative state, Laureys S Scientific American, 4 (2007) 32-37
What is it like to be vegetative or minimally conscious ?, Laureys S and Boly M Current Opinion in Neurology, 20 (2007) 609-13
Sunday June 22, 10:30AM-12:30PM at Alexander Hall
Since time immemorial, Jaspers (1963) argued, delusions have been considered the cardinal signs of madness. Yet the nature of these apparent pathologies of misbelief continues to resist satisfactory definition and explanation. In this symposium we present psychological and philosophical approaches to the study of delusions and discuss implications concerning the functional role of consciousness. In order to better understand the unwarranted subjective conviction with which delusional people profess their oft-times fantastic beliefs we consider the interaction of conscious and unconscious processes. In particular, the contribution of discrepant covert and overt self-knowledge to the formation of delusions is discussed with reference to the associated constructs of (non-pathological) defense and self-deception. We also review the current debate concerning the role of conscious perceptual experience in the generation of delusions with reference to relevant patient data.
Jaspers, K. 1963. General psychopathology. Translated J. Hoenig and M. W. Hamilton. Manchester: Manchester University Press.
Chair: Robyn Langdon
Macquarie Centre for Cognitive Science
Are Delusions Pathologies of Consciousness?
On the face of things, delusions seem to be pathologies of consciousness: the delusional patient has a belief which, from his or her own perspective, ought to be rejected, and one of the functions of consciousness is to reject implausible candidates for belief. I examine this proposal in light of accounts of delusions on the one hand and in light of accounts of the functions of consciousness on the other. I argue that despite its intuitive appeal, there is little firm reason to believe that delusions are pathologies of consciousness. Nonetheless, there are important lessons to be learned about the functional role of consciousness by asking whether delusions might qualify as pathologies of consciousness.
Conscious and Unconscious Processes in Persecutory Delusions - Evidence for a Defense Account
Of all delusional themes, delusions of persecution are the most commonly observed clinically and the most vigorously researched empirically. Bentall and colleagues (Bentall & Kaney, 1996; Kinderman & Bentall, 1996, 1997) claim that persecutory delusions are constructed defensively, for the maintenance of self-esteem. A central prediction of their model is that paranoid individuals will demonstrate normal or high self-esteem on overt measures, whereas covert measures will reveal hidden feelings of low self-esteem. Although it is a rather formidable methodological challenge to elicit implicit self-esteem, there have been a number of efforts to empirically test this prediction. I will review these studies, focusing in particular on two recent experiments (McKay, Langdon, & Coltheart, 2007; Moritz, Werner, & von Collani, in press) that have employed a novel and highly influential methodology for eliciting implicit effects, the Implicit Association Test (IAT; Greenwald, McGhee & Schwartz, 1998).
The Misidentification Delusions
The misidentification delusions, once thought rare, are now known to occur frequently in dementia. Although Ellis and Young’s (1990) account of one of these delusions – the Capgras delusion – is perhaps the best model of any delusion, we still understand very little about the cognitive processes implicated in the misidentification delusions or their neural substrates. In this paper I make some suggestions about the neurobiology of the misidentification delusions and their cognitive origins.
The Role of Conscious Experience Differentiates between Received and Reflective Delusions
Maher conceived of delusions as rational explanations of aberrant experience. Two-factor theorists started with and departed from Maher to argue for an additional impairment of belief formation. This was necessary, it was argued, to account for the uncritical adoption of an implausible belief. Maher’s thinking nevertheless continues to impact upon theorizing about the additional impairment of belief evaluation. This is because of the intuitive appeal of his explanationist account of delusion formation. This explanationist account runs into difficulties, however, with explaining the incorrigibility of delusions. The expression, or endorsement, approach fares better and conceives instead of perceptual experience as delivering the delusional content directly to consciousness as the naturally compelling mis-perceived reality. Neither approach, I suggest, satisfactorily accounts for all delusions. I argue instead for different classes of delusion - received versus reflective – and illustrate with reference to two delusional patients.
Sunday June 22, 4:30PM-6:30PM at Alexander Hall
Consciousness and Accessibility
Chair: Ned Block
Department of Philosophy
New York University
Attention and Consciousness: Two Independent Processes
I shall discuss recent psychophysical and functional imaging evidence for the independence of selective attention and consciousness. In particular, a subject can attend to an object or event without being conscious of it or of any of its attributes. Furthermore, a subject can also be conscious of an object or event without directing top-down attention to it. Finally, I shall argue that Block's hypothesized "phenomenal consciousness without cognitive access" correspond to the latter case. Its neuronal correlate may be a coalition of neurons that are consigned to the back of cortex, without access to working memory and planning in frontal cortex.
How Neuroscience Should Attack the Hard Problem
Behavior is considered the gold standard of consciousness: when someone says he is conscious, he is, and when he says not, he isn’t. However, this makes it impossible to find the neural mechanism of conscious experience per se. We will always conflate consciousness with cognition. Therefore, arguments from neuroscience should be allowed to shape a definition of consciousness, together with, yet in some cases overruling behavioral evidence. I will show how such a neuro-behavioral definition of consciousness makes it possible to dissociate consciousness from cognition, explains the key features of conscious experience, and opens up a path towards solving the hard problem.
Unattended and Unaccessible Consciousness: Puzzle or Illusion?
Dissociative approaches to consciousness (phenomenal vs access consciousness; consciousness with vs. without attention) capture much of our intuition about subjective experience. However, such dissociations raise a major methodological puzzle: they are difficult, if not impossible, to demonstrate experimentally. In addition, the empirical evidence "pointing towards" these dissociations does not unequivocally support them. I will provide an overview of several alternative theories, including workspace models and compare them with dissociative approaches. In particular, I will focus on alternative accounts positing that the intuition of a rich phenomenal experience is actually a mere retrospective illusion. I will argue that although dissociative approaches offer a promising way to tackle the hard problem, parsimonious (i.e., non-dissociative) interpretations relying on partial awareness and accessible levels of representation still have as much explanatory power.
Evidence That Phenomenal Consciousness Has a Distinct Neural Basis from Cognitive Access
Evidence will be described that phenomenal consciousness and cognitive access have distinct neural bases. Lamme’s appeal to simplicity and Kouider’s appeal to partial awareness do not challenge this interpretation. The relation to issues of attention will be examined.