Prior to the twentieth century, theories of knowledge were inherently perceptual. Since then, developments in logic, statis- tics, and programming languages have inspired amodal theories that rest on principles fundamentally different from those underlying perception. In addition, perceptual approaches have become widely viewed as untenable because they are assumed to implement record- ing systems, not conceptual systems. A perceptual theory of knowledge is developed here in the context of current cognitive science and neuroscience. During perceptual experience, association areas in the brain capture bottom-up patterns of activation in sensory-motor areas. Later, in a top-down manner, association areas partially reactivate sensory-motor areas to implement perceptual symbols. The stor- age and reactivation of perceptual symbols operates at the level of perceptual components - not at the level of holistic perceptual expe- riences. Through the use of selective attention, schematic representations of perceptual components are extracted from experience and stored in memory (e.g., individual memories of green, purr, hot). As memories of the same component become organized around a com- mon frame, they implement a simulator that produces limitless simulations of the component (e.g., simulations of purr). Not only do such simulators develop for aspects of sensory experience, they also develop for aspects of proprioception (e.g., lift, run) and introspec- tion (e.g., compare, memory, happy, hungry). Once established, these simulators implement a basic conceptual system that represents types, supports categorization, and produces categorical inferences. These simulators further support productivity, propositions, and ab- stract concepts, thereby implementing a fully functional conceptual system. Productivity results from integrating simulators combinato- rially and recursively to produce complex simulations. Propositions result from binding simulators to perceived individuals to represent type-token relations. Abstract concepts are grounded in complex simulations of combined physical and introspective events. Thus, a per- ceptual theory of knowledge can implement a fully functional conceptual system while avoiding problems associated with amodal sym- bol systems. Implications for cognition, neuroscience, evolution, development, and artificial intelligence are explored.

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Perceptual symbol systems.

Illusions have historically been of great use to psychology for what they can reveal about perceptual processes. We report here an illusion in which tactile sensations are referred to an alien limb. The effect reveals a three-way interaction between vision, touch and proprioception, and may supply evidence concerning the basis of bodily self-identification.

/pdf/rubber-hands-feel-touch-that-eyes-see-4131qmcpv6.pdf

Rubber hands ‘feel’ touch that eyes see

Empathy accounts for the naturally occurring subjective experience of similarity between the feelings expressed by self and others without loosing sight of whose feelings belong to whom. Empathy involves not only the affective experience of the other person’s actual or inferred emotional state but also some minimal recognition and understanding of another’s emotional state. In light of multiple levels of analysis ranging from developmental psychology, social psychology, cognitive neuroscience, and clinical neuropsychology, this article proposes a model of empathy that involves parallel and distributed processing in a number of dissociable computational mechanisms. Shared neural representations, self-awareness, mental flexibility, and emotion regulation constitute the basic macrocomponents of empathy, which are underpinned by specific neural systems. This functional model may be used to make specific predictions about the various empathy deficits that can be encountered in different forms of social and neu...

The functional architecture of human empathy

Do we consciously cause our actions, or do they happen to us? Philosophers, psychologists, neuroscientists, theologians, and lawyers have long debated the existence of free will versus determinism. In this book Daniel Wegner offers a novel understanding of the issue. Like actions, he argues, the feeling of conscious will is created by the mind and brain. Yet if psychological and neural mechanisms are responsible for all human behavior, how could we have conscious will? The feeling of conscious will, Wegner shows, helps us to appreciate and remember our authorship of the things our minds and bodies do. Yes, we feel that we consciously will our actions, Wegner says, but at the same time, our actions happen to us. Although conscious will is an illusion, it serves as a guide to understanding ourselves and to developing a sense of responsibility and morality. Approaching conscious will as a topic of psychological study, Wegner examines the issue from a variety of angles. He looks at illusions of the will -- those cases where people feel that they are willing an act that they are not doing or, conversely, are not willing an act that they in fact are doing. He explores conscious will in hypnosis, Ouija board spelling, automatic writing, and facilitated communication, as well as in such phenomena as spirit possession, dissociative identity disorder, and trance channeling. The result is a book that sidesteps endless debates to focus, more fruitfully, on the impact on our lives of the illusion of conscious will.

The Illusion of Conscious Will

Although phantom-limb pain is a frequent consequence of the amputation of an extremity, little is known about its origin. On the basis of the demonstration of substantial plasticity of the somatosensory cortex after amputation or somatosensory deafferentation in adult monkeys, it has been suggested that cortical reorganization could account for some non-painful phantom-limb phenomena in amputees and that cortical reorganization has an adaptive (that is, pain-preventing) function. Theoretical and empirical work on chronic back pain has revealed a positive relationship between the amount of cortical alteration and the magnitude of pain, so we predicted that cortical reorganization and phantom-limb pain should be positively related. Using non-invasive neuromagnetic imaging techniques to determine cortical reorganization in humans, we report a very strong direct relationship (r = 0.93) between the amount of cortical reorganization and the magnitude of phantom limb pain (but not non-painful phantom phenomena) experienced after arm amputation. These data indicate that phantom-limb pain is related to, and may be a consequence of, plastic changes in primary somatosensory cortex.

/pdf/phantom-limb-pain-as-a-perceptual-correlate-of-cortical-bea2j782yg.pdf

Phantom-limb pain as a perceptual correlate of cortical reorganization following arm amputation

Although there is a vast clinical literature on phantom limbs, there have been no experimental studies on the effects of visual input on phantom sensations. We introduce an inexpensive new device--a 'virtual reality box'--to resurrect the phantom visually to study inter-sensory effects. A mirror is placed vertically on the table so that the mirror reflection of the patient's intact had is 'superimposed' on the felt position of the phantom. We used this procedure on ten patients and found the following results. 1. In six patients, when the normal hand was moved, so that the phantom was perceived to move in the mirror, it was also felt to move; i.e. kinesthetic sensations emerged in the phantom. In D.S. this effect occurred even though he had never experienced any movements in the phantom for ten years before we tested him. He found the return of sensations very enjoyable. 2. Repeated practice led to a permanent 'disappearance' of the phantom arm in patient D.S. and the hand became telescoped into the stump near the shoulder. 3. Using an optical trick, impossible postures--e.g. extreme hyperextension of the fingers--could be induced visually in the phantom. In one case this was felt as a transient 'painful tug' in the phantom. 4. Five patients experienced involuntary painful 'clenching spasms' in the phantom hand and in four of them the spasms were relieved when the mirror was used to facilitate 'opening' of the phantom hand; opening was not possible without the mirror. 5. In three patients, touching the normal hand evoked precisely localized touch sensations in the phantom. Interestingly, the referral was especially pronounced when the patients actually 'saw' their phantom being touched in the mirror. Indeed, in a fourth patient (R.L.) the referral occurred only if he saw his phantom being touched: a curious form of synaesthesia. These experiments lend themselves readily to imaging studies using PET and fMRI. Taken collectively, they suggest that there is a considerable amount of latent plasticity even in the adult human brain. For example, precisely organized new pathways, bridging the two cerebral hemispheres, can emerge in less than three weeks. Furthermore, there must be a great deal of back and forth interaction between vision and touch, so that the strictly modular, hierarchical model of the brain that is currently in vogue needs to be replaced with a more dynamic, interactive model, in which 're-entrant' signalling plays the main role.

Synaesthesia in Phantom Limbs Induced with Mirrors

Touching the phantom limb

Following long-term deafferentation of one upper limb in adult primates, the cortical areas corresponding to that limb become responsive to stimuli applied to the face. To explore this phenomenon, we studied some patients after upper limb amputation. In patient VQ, stimuli applied to the lower face or 7 cm above the stump evoked precisely localized referred sensations in individual digits which were often modality specific. Similarly, in another patient, WK several complete somatotopic representations of the phantom limb were found, on the face, chest and axilla, indicating the emergence of such maps in regions remote from the stump. These effects may be a direct perceptual correlate of the physiological observations of Merzenick et al (1984), Wall (1977) and Pons et al (1991).

https://science.sciencemag.org/content/sci/258/5085/1159.full.pdf

Perceptual correlates of massive cortical reorganization.

The study of phantom limbs has received tremendous impetus from recent studies linking changes in cortical topography with perceptual experience. Systematic psychophysical testing and functional imaging studies on patients with phantom limbs provide 2 unique opportunities. First, they allow us to demonstrate neural plasticity in the adult human brain. Second, by tracking perceptual changes (such as referred sensations) and changes in cortical topography in individual patients, we can begin to explore how the activity of sensory maps gives rise to conscious experience. Finally, phantom limbs also allow us to explore intersensory effects and the manner in which the brain constructs and updates a "body image" throughout life.

/pdf/phantom-limbs-and-neural-plasticity-4amlfk1flt.pdf

Diane Rogers-Ramachandran

Papers

Synaesthesia in Phantom Limbs Induced with Mirrors

Touching the phantom limb

Perceptual correlates of massive cortical reorganization.

Phantom limbs and neural plasticity.

Psychophysical evidence for boundary and surface systems in human vision