Showing papers in "Behavioral and Brain Sciences in 1997"

On a confusion about a function of consciousness. Author's response

Abstract: of the original article: Consciousness is a mongrel concept: there are a number of very different consciousnesses. Phenomenal consciousness is experience; the phenomenally conscious aspect of a state is what it is like to be in that state. The mark of access-consciousness, by contrast, is availability for use in reasoning and rationally guiding speech and action. These concepts are often partly or totally conflated, with bad results. This target article uses as an example a form of reasoning about a function of consciousness based on the phenomenon of blindsight. Some information about stimuli in the blind field is represented in the brains of blindsight patients, as shown by their correct guesses. They cannot harness this information in the service of action, however, and this is said to show that a function of phenomenal consciousness is somehow to enable information represented in the brain to guide action. But stimuli in the blind field are both access-unconscious and phenomenally unconscious. The fallacy is: an obvious function of the machinery of access-consciousness is illicitly transferred to phenomenal consciousness.

What memory is for.

Abstract: Let's start from scratch in thinking about what memory is for, and consequently, how it works. Suppose that memory and conceptualization work in the service of perception and action. In this case, conceptualization is the encoding of patterns of possible physical interaction with a three-dimensional world. These patterns are constrained by the structure of the environment, the structure of our bodies, and memory. Thus, how we perceive and conceive of the environment is determined by the types of bodies we have. Such a memory would not have associations. Instead, how concepts become related (and what it means to be related) is determined by how separate patterns of actions can be combined given the constraints of our bodies. I call this combination "mesh." To avoid hallucination, conceptualization would normally be driven by the environment, and patterns of action from memory would play a supporting, but automatic, role. A significant human skill is learning to suppress the overriding contribution of the environment to conceptualization, thereby allowing memory to guide conceptualization. The effort used in suppressing input from the environment pays off by allowing prediction, recollective memory, and language comprehension. I review theoretical work in cognitive science and empirical work in memory and language comprehension that suggest that it may be possible to investigate connections between topics as disparate as infantile amnesia and mental-model theory.

Sex differences in pain

Abstract: Are there sex differences in pain? For experimentally delivered somatic stimuli, females have lower thresholds, greater ability to discriminate, higher pain ratings, and less tolerance of noxious stimuli than males. These differences, however, are small, exist only for certain forms of stimulation and are affected by many situational variables such as presence of disease, experimental setting, and even nutritive status. For endogenous pains, women report more multiple pains in more body regions than men. With no obvious underlying rationale, some painful diseases are more prevalent among females, others among males and, for many diseases, symptoms differ between females and males. Sex differences in attitudes exist that affect not only reporting, coping, and responses to treatment, but also measurement and treatment. So many variables are operative, however, that the most striking feature of sex differences in reported pain experience is the apparent overall lack of them. On the other hand, deduction from known biological sex differences suggests that these are powerful sex differences in the operation of pain mechanisms. First, the vaginal canal provides an additional route in women for internal trauma and invasion by pathological agents that puts them at greater risk for developing hyperalgesia in multiple body regions. Second, sex differences in temporal patterns are likely to give rise to sex differences in how pain is "learned" and stimuli are interpreted, a situation that could lead to a greater variability and wider range of pains without obvious peripheral pathology among females. Third, sex differences in the actions of sex hormones suggest pain-relevant differences in the operation of many neuroactive agents, opiate and nonopiate systems, nerve growth factor, and the sympathetic system. Thus, while inductive analysis of existing data demonstrate more similarities than differences in pain experience between females and males, deductive analysis suggests important operational sex differences in its production.

The neural basis of cognitive development: a constructivist manifesto.

Abstract: How do minds emerge from developing brains? According to "neural constructivism," the representational features of cortex are built from the dynamic interaction between neural growth mechanisms and environmentally derived neural activity. Contrary to popular selectionist models that emphasize regressive mechanisms, the neurobiological evidence suggests that this growth is a progressive increase in the representational properties of cortex. The interaction between the environment and neural growth results in a flexible type of learning: "constructive learning" minimizes the need for prespecification in accordance with recent neurobiological evidence that the developing cerebral cortex is largely free of domain-specific structure. Instead, the representational properties of cortex are built by the nature of the problem domain confronting it. This uniquely powerful and general learning strategy undermines the central assumption of classical learnability theory, that the learning properties of a system can be deduced from a fixed computational architecture. Neural constructivism suggests that the evolutionary emergence of neocortex in mammals is a progression toward more flexible representational structures, in contrast to the popular view of cortical evolution as an increase in innate, specialized circuits. Human cortical postnatal development is also more extensive and protracted than generally supposed, suggesting that cortex has evolved so as to maximize the capacity of environmental structure to shape its structure and function through constructive learning.

Speed/accuracy trade-offs in target-directed movements.

Abstract: This target article presents a critical survey of the scientific literature dealing with the speed/accuracy trade-offs in rapid-aimed movements. It highlights the numerous mathematical and theoretical interpretations that have been proposed in recent decades. Although the variety of points of view reflects the richness of the field and the high degree of interest that such basic phenomena attract in the understanding of human movements, it calls into question the ability of 'many models to explain the basic observations consistently reported in the field. This target article summarizes the kinematic theory of rapid human movements, proposed recently by R. Plamondon (1993b; 1993c; 1995a; 1995b), and analyzes its predictions in the context of speed/accuracy trade-offs. Data from human movement literature are reanalyzed and reinterpreted in the context of the new theory. It is shown that the various aspects of speed/accuracy trade- offs can be taken into account by considering the asymptotic behavior of a large number of coupled linear systems, from which a delta- lognormal law can be derived to describe the velocity profile of an end-effector driven by a neuromuscular synergy. This law not only describes velocity profiles almost perfectly, it also predicts the kinematic properties of simple rapid movements and provides a consistent framework for the analysis of different types of speed/accuracy trade-offs using a quadratic (or power) law that emerges from the model.

In search of common foundations for cortical computation.

Abstract: It is worthwhile to search for forms of coding, processing, and learning common to various cortical regions and cognitive functions. Local cortical processors may coordinate their activity by maximizing the transmission of information coherently related to the context in which it occurs, thus forming synchronized population codes. This coordination involves contextual field (CF) connections that link processors within and between cortical regions. The effects of CF connections are distinguished from those mediating receptive field (RF) input; it is shown how CFs can guide both learning and processing without becoming confused with the transmission of RF information. Simulations explore the capabilities of networks built from local processors with both RF and CF connections. Physiological evidence for synchronization, CFs, and plasticity of the RF and CF connections is described. Coordination via CFs is related to perceptual grouping, the effects of context on contrast sensitivity, amblyopia, implicit influences of color in achromotopsia, object and word perception, and the discovery of distal environmental variables and their interactions through self-organization. Cortical computation could thus involve the flexible evaluation of relations between input signals by locally specialized but adaptive processors whose activity is dynamically associated and coordinated within and between regions through specialized contextual connections.

Long-term potentiation: What's learning got to do with it?

Abstract: Long-term potentiation (LTP) is operationally defined as a long-lasting increase in synaptic efficacy following high-frequency stimulation of afferent fibers Since the first full description of the phenomenon in 1973, exploration of the mechanisms underlying LTP induction has been one of the most active areas of research in neuroscience Of principal interest to those who study LTP, particularly in the mammalian hippocampus, is its presumed role in the establishment of stable memories, a role consistent with "Hebbian" descriptions of memory formation Other characteristics of LTP, including its rapid induction, persistence, and correlation with natural brain rhythms, provide circumstantial support for this connection to memory storage Nonetheless, there is little empirical evidence that directly links LTP to the storage of memories In this target article we review a range of cellular and behavioral characteristics of LTP and evaluate whether they are consistent with the purported role of hippocampal LTP in memory formation We suggest that much of the present focus on LTP reflects a preconception that LTP is a learning mechanism, although the empirical evidence often suggests that LTP is unsuitable for such a role As an alternative to serving as a memory storage device, we propose that LTP may serve as a neural equivalent to an arousal or attention device in the brain Accordingly, LTP may increase in a nonspecific way the effective salience of discrete external stimuli and may thereby facilitate the induction of memories at distant synapses Other hypotheses regarding the functional utility of this intensely studied mechanism are conceivable; the intent of this target article is not to promote a single hypothesis but rather to stimulate discussion about the neural mechanisms underlying memory storage and to appraise whether LTP can be considered a viable candidate for such a mechanism

The detection and generation of sequences as a key to cerebellar function: experiments and theory.

Abstract: Starting from macroscopic and microscopic facts of cerebellar histology, we propose a new functional interpretation that may elucidate the role of the cerebellum in movement control. The idea is that the cerebellum is a large collection of individual lines (Eccles's "beams": Eccles et al. 1967a) that respond specifically to certain sequences of events in the input and in turn produce sequences of signals in the output. We believe that the sequence-in/sequence-out mode of operation is as typical for the cerebellar cortex as the transformation of sets into sets of active neurons is typical for the cerebral cortex, and that both the histological differences between the two and their reciprocal functional interactions become understandable in the light of this dichotomy. The response of Purkinje cells to sequences of stimuli in the mossy fiber system was shown experimentally by Heck on surviving slices of rat and guinea pig cerebellum. Sequential activation of a row of eleven stimulating electrodes in the granular layer, imitating a "movement" of the stimuli along the folium, produces a powerful volley in the parallel fibers that strongly excites Purkinje cells, as evidenced by intracellular recording. The volley, or "tidal wave," has maximal amplitude when the stimulus moves toward the recording site at the speed of conduction in parallel fibers, and much smaller amplitudes for lower or higher "velocities." The succession of stimuli has no effect when they "move" in the opposite direction. Synchronous activation of the stimulus electrodes also had hardly any effect. We believe that the sequences of mossy fiber activation that normally produce this effect in the intact cerebellum are a combination of motor planning relayed to the cerebellum by the cerebral cortex, and information about ongoing movement, reaching the cerebellum from the spinal cord. The output elicited by the specific sequence to which a "beam" is tuned may well be a succession of well timed inhibitory volleys "sculpting" the motor sequences so as to adapt them to the complicated requirements of the physics of a multijointed system.

Trading spaces: Computation, representation, and the limits of uninformed learning

Abstract: Some regularities enjoy only an attenuated existence in a body of training data. These are regularities whose statistical visibility depends on some systematic recoding of the data. The space of possible recodings is, however, infinitely large - it is the space of applicable Turing machines. As a result, mappings that pivot on such attenuated regularities cannot, in general, be found by brute-force search. The class of problems that present such mappings we call the class of "type-2 problems." Type-1 problems, by contrast, present tractable problems of search insofar as the relevant regularities can be found by sampling the input data as originally coded. Type-2 problems, we suggest, present neither rare nor pathological cases. They are rife in biologically realistic settings and in domains ranging from simple animat (simulated animal or autonomous robot) behaviors to language acquisition. Not only are such problems rife - they are standardly solved! This presents a puzzle. How, given the statistical intractability of these type-2 cases, does nature turn the trick? One answer, which we do not pursue, is to suppose that evolution gifts us with exactly the right set of recoding biases so as to reduce specific type-2 problems to (tractable) type-1 mappings. Such a heavy-duty nativism is no doubt sometimes plausible. But we believe there are other, more general mechanisms also at work. Such mechanisms provide general (not task-specific) strategies for managing problems of type-2 complexity. Several such mechanisms are investigated. At the heart of each is a fundamental ploy - namely, the maximal exploitation of states of representation already achieved by prior, simpler (type-1) learning so as to reduce the amount of subsequent computational search. Such exploitation both characterizes and helps make unitary sense of a diverse range of mechanisms. These include simple incremental learning (Elman 1993), modular connectionism (Jacobs et al. 1991), and the developmental hypothesis of "representational redescription" (Karmiloff-Smith 1979; 1992). In addition, the most distinctive features of human cognition - language and culture - may themselves be viewed as adaptations enabling this representation/computation trade-off to be pursued on an even grander scale.

Peripheral and central hyperexcitability: differential signs and symptoms in persistent pain.

Abstract: This target article examines the clinical and experimental evidence for a role of peripheral and central hyperexcitability in persistent pain in four key areas: cutaneous hyperalgesia, referred pain, neuropathic pain, and postoperative pain. Each suggests that persistent pain depends not only on central sensitization, but also on inputs from damaged peripheral tissue. It is instructive to think of central sensitization as comprised of both an initial central sensitization and an ongoing central sensitization driven by inputs from peripheral sources. Each of these factors, initial sensitization, ongoing central sensitization, and inputs from peripheral sources, contributes to the net activity in dorsal horn neurons and thus influences the expression of persistent pain or hyperalgesia. Since each factor, peripheral inputs and central sensitization (initial or ongoing), can contribute to both the initiation and maintenance of persistent pain, therapies should target both peripheral and central sources of pathology.

Are there nontrivial constraints on colour categorization

Abstract: In this target article the following hypotheses are discussed: (1) Colour is autonomous: a perceptuolinguistic and behavioural universal. (2) It is completely described by three independent attributes: hue, brightness, and saturation: (3) Phenomenologically and psychophysically there are four unique hues: red, green, blue, and yellow; (4) The unique hues are underpinned by two opponent psychophysical and/or neuronal channels: red/green, blue/yellow. The relevant literature is reviewed. We conclude: (i) Psychophysics and neurophysiology fail to set nontrivial constraints on colour categorization. (ii) Linguistic evidence provides no grounds for the universality of basic colour categories. (iii) Neither the opponent hues red/green, blue/yellow nor hue, brightness, and saturation are intrinsic to a universal concept of colour. (iv) Colour is not autonomous.

Real self-deception.

Abstract: Self-deception is made unnecessarily puzzling by the assumption that it is an intrapersonal analog of ordinary interpersonal deception. In paradigmatic cases, interpersonal deception is intentional and involves some time at which the deceiver disbelieves what the deceived believes. The assumption that self-deception is intentional and that the self-deceiver believes that some proposition is true while also believing that it is false produces interesting conceptual puzzles, but it also produces a fundamentally mistaken view of the dynamics of self-deception. This target article challenges the assumption and presents an alternative view of the nature and etiology of self- deception. Drawing upon empirical studies of cognitive biases, it resolves familiar "paradoxes" about the dynamics of self-deception and the condition of being self-deceived. Conceptually sufficient conditions for self-deception are offered and putative empirical demonstra- tions of a kind of self-deception in which a subject believes that a proposition is true while also believing that it is false are criticized. Self- deception is neither irresolvably paradoxical nor mysterious, and it is explicable without the assistance of mental exotica. The key to understanding its dynamics is a proper appreciation of our capacity for acquiring and retaining motivationally biased beliefs.

What memory is for: Creating meaning in the service of action

Abstract: I address the commentators' calls for clarification of theoretical terms, discussion of similarities to other proposals, and extension of the ideas. In doing so, I keep the focus on the purpose of memory: enabling the organism to make sense of its environment so that it can take action appropriate to constraints resulting from the physical, personal, social, and cultural situations.

Colour: An exosomatic organ?

Abstract: Sections R1 to R3 attempt to take the sting out of hostile commentaries. Sections R4 to R5 engage Berlin and Kay and the World Color Survey to correct the record. Section R6 begins the formulation of a new theory of colour as an engineering project with a technological developmental trajectory. It is recommended that the colour space be abandoned.

Central inhibitory dysfunctions : Mechanisms and clinical implications

Abstract: Injury to the central or peripheral nervous system is often associated with persistent pain. After ischemic injury to the spinal cord, rats develop severe mechanical allodynia-like symptoms, expressed as a pain-like response to innocuous stimuli. In its short-lasting phase the allodynia can be relieved with the gamma-aminobutyric acid (GABA)-B receptor agonist baclofen, which also reverses the hyperexcitability of dorsal horn interneurons to mechanical stimuli. Furthermore, there is a reduction in GABA immunoreactivity in the dorsal horn of allodynic rats. Clinical neuropathic pain of peripheral and central origin often cannot be relieved by opiates at doses that do not cause side effects. The loss of sensitivity to opiates may be associated with the up-regulation of endogenous antiopioid substances, such as the neuropeptide cholecystokinin (CCK). CCK and its receptor (CCK-R) protein is normally not detectable in rat dorsal root ganglion cells. After peripheral nerve section, both CCK and CCK-R are up-regulated in the dorsal root ganglia. Furthermore, CI 988, an antagonist of the CCK-B receptor, chronically coadministered with morphine, reduces autotomy, a behavior that may be a sign of neuropathic pain following peripheral nerve section. Thus, opiate insensitivity may be due to the release of CCK from injured primary afferents. Similarly, in the chronic phase of the spinal ischemic model of central pain, the allodynia-like symptom is not relieved by systemic morphine, but is significantly reversed by the CCK-B antagonist. Consequently, up-regulation of CCK and CCK-R in the CNS may also underlie opiate drug insensitivity following CNS injury. Thus, dysfunction of central inhibition involving GABA and endogenous opioids may be a factor underlying the development of sensory abnormalities and/or pain following injury to neural tissue.

Plasticity: implications for opioid and other pharmacological interventions in specific pain states.

Abstract: The spinal mechanisms of action of opioids under normal conditions are reasonably well understood. The spinal effects of opioids can be enhanced or reduced depending on pathology and activity in other segmental and nonsegmental pathways. This plasticity will be considered in relation to the control of different pain states using opioids. The complex and contradictory findings on the supraspinal actions of opioids are explicable in terms of heterogeneous descending pathways to different spinal targets using multiple transmitters and receptors - therefore opioids can both increase and decrease activity in descending pathways. These pathways could exhibit considerable plasticity. There is increasing evidence that delta opioid receptor agonists have the potential to replace morphine as major analgesics with reduced side-effect profiles. The concept of preemptive analgesia, based on preventing the induction of some of the negative plastic influences on opioid controls and the detrimental effects of pain, is sound, but experimental verification in the clinical setting is difficult. For example, a delayed compensatory upregulation of inhibitory systems, particularly in inflammation, may counter persistent painful inputs. Combination therapy with opioids may be beneficial in many pain states where either negative influences are blocked or inhibitory controls are enhanced. Finally, developmental aspects of these systems are discussed in connection with the treatment of pain in young children, where inhibitory systems in the spinal cord are immature.

Schizophrenia as a model of context-deficient cortical computation

Abstract: Phillips & Singer's compelling presentation is weakest in its demonstration of commonalities between sensory plasticity and higher forms of learning and behavior. We propose that available data on schizophrenia can provide such evidence, because of the presence of impairments in a number of functions central to their model, and strong relationships between these dysfunctions and behavior.

Are there fundamental differences in the peripheral mechanisms of visceral and somatic pain

Abstract: There are some conspicuous differences between the sensibilities of cutaneous and visceral tissues: (1) Direct trauma, which readily produces pain when applied to the skin, is mostly without effect in healthy visceral tissue. (2) Pain that arises from visceral tissues is initially often poorly localised and diffuse. (3) With time, visceral pains are often referred to more superficial structures. (4) The site of referred pain may also show hyperalgesia. (5) In disease states, the afflicted viscera may also become hyperalgesic. In this target article, I consider to what extent differences in the physiology, anatomy, and chemistry of peripheral processing systems explain these different sensibilities. In almost every aspect, there are subtle differences in the properties of the processing mechanisms for cutaneous and visceral information. These may arise because of distinct developmental cues operating in the two domains. Many of the differences between visceral and cutaneous afferents are quantitative rather than qualitative. The quantitative differences, for example in the density of afferent innervation, can be large. The quantitative differences in the numbers of afferents alone may be a sufficient explanation for some aspects of the differential sensibility, for example, the poor localisation of sensation and the apparent insensitivity to focal yet tissue-damaging stimuli. In addition, the few clear qualitative differences apparent in the innervations of the two tissue types may be of special importance. That the encoding of visceral nociceptive events may occur by an intensity mechanism rather than a specificity mechanism could be the key difference in viscerosensory and somatosensory processing.

Availability: The cognitive basis of experience

Abstract: Although A-consciousness and P-consciousness are conceptually distinct, a refined notion of A-consciousness makes it plausible that the two are empirically inseparable. I suggest that the notion of direct availability for global control can play a central role here, and draw out some consequences.

Putting knowledge to work

Abstract: Representational redescription (Karmiloff-Smith 1994a; 1994) translates implicit, procedural knowledge into explicit, declarative knowledge. Explicit knowledge is an enabling condition of cognitive flexibility. The articulation and inferential integration of knowledge are important in explaining flexibility. There is an interesting connection to the availability of knowledge for verbal report, but no clear explanatory work is done by the idea of knowledge that is available to consciousness.

Sequences of sensory predictions

Abstract: Braitenberg, Heck and Sultan (BHS ) suggest asingle function for the whole of the cerebellum, thatit generates neural sequences used for motorcommands. I am also tempted by the simplicity ofone function for all regions the cerebellar cortex, butI take issue with them over what that singularoperation might be. I believe that the cerebellum is asensory predictor, responsible for generating pre-dictions about the sensory consequences of motoracts (Miall et al. 1993). Paulin (1989) and Darlot(1993) have suggested similar functions. Sensorypredictions which are available in advance of thenormal delayed reafferent signals can be used tocontrol motor systems (Miall et al. 1993) and forother functions more removed from motor control(Miall & Wolpert 1996). There is a growing bodyof evidence that suggests the cerebellum is more'sensory' than 'motor'. For example, Gao et al.(1996) have demonstrated that the dentate nucleus ishighly activated during sensory discrimination tasks,whether or not the task involves movement. Dieneret al. (1993) and Nawrot & Rizzo (1995) haveshown perceptual deficits in cerebellar patients. Bellet al. (in press) have evidence of the generation ofsensory predictions in 'cerebellum-like' structures infish. The cerebellum is also increasingly implicatedin non-motor behaviours (Leiner et al. 1993),although by itself this does not mean that its outputis sensory.I would suggest that the best predictor of a largecerebellar cortex (relative to body weight) is theecological need for movement-related sensoryanalysis by each species. BHS are puzzled whycattle have such an extended cerebellum in thesagittal axis (BHS Section 9 & Fig. 2); bovines donot appear to have an expanded motor apparatus,and anthropomorphically, its difficult to imagine acow having a need for many more motor sequencesthan other quadrupeds! However, BHS suggest thata major input to the cerebellum is from cutaneousreceptors (Section 27), and if we assume that morecerebellar cortex is required to predict the cutane ousconsequences of movement, then this odd fact andthe relationship given in BHS Figure 4 become moreclear. In Sultan and Braitenberg (1993), they showthat vermal length has a 0.54 power relationshipwith body weight across many species. For aspherical body, surface area scales with mass with apower of 0.66. Thus, vermal length increases withbody surface, but with an exponent of less thanunity: one can imagine that motor actions do notaffect the whole body surface, or that a commonsensory prediction can made for a large number ofcutaneous inputs. But small animals deviate morefrom a spherical shape than larger ones becausetheir weight-bearing limbs can be rela tively slim andlong. Thus the slope of the relation ship between logvermal area and log body weight should beshallower for smaller body weights, and indeed it is(Sultan & Braitenberg 1993, Figure 19). Then inconverting from vermal length to cerebellar width,and plotting against cerebellar area, one achieves thedeclining curve in BHS Fig 4 (see also Sultan &Braitenberg 1993, Figure 15). I agree that thecerebellar width is likely to be related to thecomplexity of the inputs and duration of predictions,and am happy to believe that humans generatesensory predictions that are longer and morecomplex than those of other animals.Finally, I would also point out that although theirsuggestions of a sequence detector system areelegant and are well borne out by Heck's electro-physiological data, there are alternative schemes thatin principle would be equally effective in sequencedetection and yet would look nothing like thecerebellum. For example, Abbott & Blum (1996)have shown that a simulation of overlapping neuronscan both generate and predict motor sequencesbecause of the temporal asymmetry of the rulegoverning LTP, but the neurons need no specialgeometry. Other network models for aspects of

Self-deception vs. self-caused deception: A comment on professor Mele

Abstract: Mele's study of philosophical and psychological theories of self-deception informatively links the conceptual and dynamic aspects of self-deception and explicates it without positing mutually inconsistent beliefs, such as those occurring in two-person deception. It is argued, however, that he does not do full justice to the dissociation characteristic of self-deception and does not sufficiently distinguish self-deception from self-caused deception.

Science [ne] imperialism: There are nontrivial constraints on color naming

Abstract: Saunders & van Brakel's claim that Berlin and Kay (1969) assumed a language/vision correlation in the area of color categorization and disguised this assumption as a finding is shown to be false. The methodology of the World Color Survey, now nearing completion, is discussed and the possibility of an additional language/vision correlation in color categorization is suggested.

Progress toward an understanding of cortical computation

Abstract: The additional data, perspectives, questions, and criticisms contributed by the commentaries strengthen our view that local cortical processors coordinate their activity with the context in which it occurs using contextual fields and synchronized population codes. We therefore predict that whereas the specialization of function has been the keynote of this century the coordination of function will be the keynote of the next.

Sympathetic nervous system and pain: a clinical reappraisal.

Abstract: The target article discusses various aspects of the relationship between the sympathetic system and pain. To this end, the patients under study are divided into three groups. In the first group, called "reflex sympathetic dystrophy" (RSD), the syndrome can be characterized by a triad of autonomic, motor, and sensory symptoms, which occur in a distally generalized distribution. The pain is typically felt deeply and diffusely, has an orthostatic component, and is suppressed by the ischemia test. Under those circumstances, the pain is likely to respond to sympatholytic interventions. In a second group, called "sympathetically maintained pain" (SMP) syndrome, the principal symptoms are spontaneous pain, which is felt superficially and has no orthostatic component, and allodynia. These symptoms, typically confined to the zone of a lesioned nerve, may also be relieved by sympathetic blocks. Since the characteristics of the pain differ between RSD and SMP, the underlying kind of sympathetic-sensory coupling may also vary between these cases. A very small third group of patients exhibits symptoms of both RSD and SMP. The dependence or independence of pain on sympathetic function reported in most published studies seems to be questionable because the degree of technical success of the block remains uncertain. Therefore, pain should not be reported as sympathetic function independent until the criteria for a complete sympathetic block have been established and satisfied.

Making light of keeping color categories in the dark: Some arguments against Saunders and van Brakel's notions of trivial constraints in color nomenclature

Abstract: Saunders & van Brakel prematurely reject the idea of nontrivial constraints in color nomenclature. Their claim that the universality of color naming is caused by Western contact and cultural dominance is inadequate because of the great variety of terminology systems still found in the world. The complex interactions of hue, brightness, and saturation can be studied rigorously. If we discard the standard models of color nomenclature because of some discrepancies and anomalies, we will not be able to explain the vast array of remaining data that is consistent with current theories.

Thinking and believing in self-deception

Abstract: Mele views self-deception as belief sustained by motivationally biased treatment of evidence. This view overlooks something essential, for it does not reckon with the fact that in self-deception the truth is dangerously close at hand and must be repeatedly suppressed. Self-deception is not so much a matter of what one positively believes as what one manages not to think.

Biology versus computation in the study of consciousness

Abstract: The distinction between phenomenal (P) and access (A) consciousness arises from the battle between biological and computational approaches to the mind. If P = A, the computationalists are right; but if not, the biological nature of P yields its scientific nature.

Understanding and explaining real self-deception

Abstract: This response addresses seven main issues: (1) alleged evidence that in some instances of self-deception an individual simultaneously possesses “contradictory beliefs”; (2) whether garden-variety self-deception is intentional; (3) whether conditions that I claimed to be conceptually sufficient for self-deception are so; (4) significant similarities and differences between self-deception and interpersonal deception; (5) how instances of self-deception are to be explained, and the roles of motivation in explaining them; (6) differences among various kinds of self- deception; (7) whether a proper conception of self-deception implies that definitive ascriptions of self-deception to individuals are impossible.