Bodily Self-Awareness and Body-Schematic Processes

Ten. Bodily Self-Awareness and Body-Schematic Processes

In this chapter I begin with a review of some of the early writings on notions of body awareness and body schema, specifically the work of the neurologists Hermann Munk and Henry Head. These early writings already reflect the ambiguity, and the often-noted lack of clarity concerning these concepts as they have been developed over the past one hundred thirty years. There are, however, a number of insights to be drawn from these early accounts. In the brief examination of Munk and Head, I identify five significant ideas that I propose to test out by examining a recent experimental study of subjects with deafferentation, involving the absence of proprioceptive, tactile, and other somatosensory input. Deafferentation allows us to see some of the insightful implications that these ideas present concerning body awareness and its relation to motor control. Specifically these studies show how not just neural changes, but also variations in body awareness, and its effect on motor control, along with variations in temporal structure, holistic relations within the body, and ecological factors can all play a role in enacting different capacities for movement.

Here, then, is a brief outline of this chapter. First, I'll provide a brief review of Munk and Head's work on the ideas of body image and body schema, and I'll identify five important insights that can be derived from this work. Second, I'll examine a recent empirical study of two people, IW and KS, who live with significant deafferentation. Third, I'll consider some difficult questions about differences between IW and KS that arise from this research. Finally, I'll return to the five insights from Munk and Head to examine whether or not they align with this recent research.

Ten point one. Two historical sources of the ideas of body image and body schema

The same year that William James wrote about the feelings of 'warmth and intimacy' associated with our bodily awareness, Hermann Munk published the second edition of his Über die Functionen der Grosshirnrinde, where, in terms of brain physiology, he attempts to experimentally discriminate non-conscious processes driven by activity of the spinal cord, from an awareness of active movement, which he calls the 'noetic kinesis of the cerebrum'. If one takes away noetic-kenetic awareness due to damage of the cerebrum, however, the animal will still be capable, in a machine-like way, of moving and avoiding obstacles without complicated deliberation or great effort. According to Munk, however, even with intact motor areas of the cerebrum, it is not possible to generate an isolated image of muscle sensations, although it is possible to generate contact (touch), and pressure images. Tactile and pressure 'sensations combine to provide a distinct image or idea of the actual positions of the different parts of the body, and of the changes in position of the various parts of the body in passive movement'. Awareness of active movement involved two factors: movement perception (one can think of this as one's visual perception of moving body parts) and conscious 'innervation' sensations, a form of proprioception generated by neuronal activation in midbrain and spinal areas as movement is initiated. In the case of haptic exploration, for example, the innervation sensations combine with tactile, pressure and muscle sensations to form an image or representation of the movement that reflects what some psychologists might call an ecological aspect: all of these sensations integrate to form a complex internal representation of bodily movement combined with the 'form and extension of the objects touched by the moving members of the body'. In this process, specific parts of the motor areas of the cortex correlate with various body parts. 'The fibres that carry the skin, muscle and innervation sensations from the body terminate in the perceiving central elements of each area, and within these areas, corresponding parts of the body have their seat and are represented. Accordingly, the independent areas of motor cortex represent corresponding parts of the body'.

From this account, it is not clear that the body image proposed by Munk can be reduced to just a visual image, but this seems to be the way that Henry Head interprets Munk. Oldfield and Zangwill explain:

Munk's conception of the motor cortex as a repository of images of movement was sharply contested by Head, who maintains that the term 'image' strictly refers only to that which can be voluntarily recalled into consciousness. He points out that if we sit immobile, and imagine our fingers touching some object, the only image in consciousness is a visual one. Head then proceeds to adduce clinical evidence from cases of cortical lesion to the effect that appreciation of posture and of passive movement may be impaired or abolished without any loss of power to visualize the position of the affected part of the body.

Nineteen forty-two.

Head recounts an experiment similar to one conducted on the deafferented patient IW. If you ask IW, who has no proprioception or sense of touch below the neck, to hold out his arm in front of him, and then ask him to close his eyes, he will be able to visualize his hand and its position, and use his other hand to point to it. If you then move his arm to the side and ask him to point to it, he will point to where he remembers that hand to be. As Head puts it, 'he will continue to see a picture of the hand in its old position ... The visual image of the limb remains intact, although the power of appreciating changes in position is abolished'. So what Munk calls an Erinnerungsbild, a memory image, is not sufficient to provide a sense of posture or passive movement. Although it is true that some standard based on knowledge of past position is required, the standard cannot be a visual image. Likewise, '"images of movement", by which Head appears to mean kinaesthetic imagery, cannot fulfil this function of supplying postural standards'.

Head thus suggests that the image, 'whether it be visual or motor, is not the fundamental standard against which all postural changes are measured'. He proposes the concept of a schema to solve the problem.

Munk, however, even with an isolated image of muscle and pressure images. Tactile dea (Vorstellung) of the actual position of the various parts ive movement involved two visual perception of moving fühle), a form of propriocep- Is as movement is initiated. In isations combine with tactile, 1 of the movement that reflects :se sensations integrate to form d with the 'form and extension 90: 33). In this process, specific dy parts. "The fibres that carry ninate in the perceiving central arts of the body have their seat cor cortex (Fühlsphäre) represent posed by Munk can be reduced y Head (1920) interprets Munk.

of images of movement was le term 'image' strictly refers ciousness. He points out that some object, the only image to adduce clinical evidence ion of posture and of passive loss of power to visualize the

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the deafferented patient I W, Cole, proprioception or sense of touch. En ask him to close his eyes, he will use his hand to point to it. If you then point to where he remembers that image of the hand in its old position the power of appreciating changes in an Erinnerungsbild, a memory image, movement. Although it is true that some the standard cannot be a visual image. It appears to mean kinaesthetic imagery, 'Oldfield and Zangwill, nineteen forty-two. sual or motor, is not the fundamental. He proposes the con-

Every recognizable change enters into consciousness already charged with its relation to something that has gone before, just as on a taximeter the distance is presented to us already transformed into shillings and pence. So the final product of the test for the appreciation of posture or passive movement rises into consciousness as a measured postural change. For this combined standard, against which all subsequent changes of posture are measured before they enter consciousness, we propose the word 'schema.' By means of perpetual alterations in position we are always building up a postural model of ourselves which constantly changes. Every new posture or movement is recorded on this plastic schema, and the activity of the cortex brings every fresh group of sensations evoked by altered posture into relation with it. Immediate postural recognition follows as soon as the relation is complete.

Nineteen twenty, volume two: six hundred five to six hundred six.

I agree with Oldfield and Zangwill, that this idea fits nicely into Munk's framework insofar as he described an integration of pressure, tactile, muscle and innervation sensations, generated by non-conscious sub-cortical efferent and afferent mechanisms, and not just visual sensation. This combination of proprioceptive and kinesthetic processes constitutes the 'combined standard' which Head calls the schema. This schema forms part of the motor control mechanism and does its work non-consciously. 'the activities on which depend the existence and normal character of the schemata lie for ever outside consciousness; they are physiological processes with no direct psychical equivalent' Nineteen twenty, volume two: seven hundred twenty-three. At the same time these processes may generate an awareness of posture and movement, which, as Head proposes, 'enters into consciousness.' Clearly, proprioception, kinesthesia, vision, and other sensory processes contribute to the workings of the body schema. By the time it enters into consciousness, however, all the work is done. The image or conscious representation of posture and movement is a product of, and, pace Munk, does not contribute to, the motoric process. For Head, the image, which he considers conscious, is insufficient to establish the body schema.

I want to highlight several ideas that result from the analyses by Head and Munk.

* First, recessive body awareness: Head indicates that, in the case of normal everyday action, the body is not in the center field of consciousness; like proprioception, it tends to remain recessive. In this respect, it generally has a prereflective status, which means that body awareness is not the result of reflective attention to the body. The degree of body awareness may vary from prereflective to reflective awareness, however, depending upon circumstances.

· Second, looping effects. It is not clear, and Head provides no evidence on this score, that this prereflective awareness of bodily movement cannot loop back into and contribute to the ongoing motor control processes, perhaps, in a similar way to visual perception or visual proprioception, as part of an afferent monitoring mechanism.

· Third, the temporal structure of body-schematic processes: Head insists on the temporality of the sensory-motoric process, and this implies that our awareness of bodily posture and movement is always relational. As Oldfield and Zangwill explain, for Head, the appreciation of bodily posture and movement 'must necessarily presuppose some background of comparison and relation. In postural recognition, awareness of an altered position is immediate, yet the postural sensations rise into consciousness "charged with the relation to something that has happened before."' Nineteen forty-two: two hundred seventy-three.

Fourth, holistic bodily processes: since proprioception is involved, the body schema involves not just sub-cortical and spinal processes, but the entire peripheral nervous system. It is not just a process in the cortex, both Head and Oldfield and Zangwill mention the peripheral system, but emphasize cortical processes, or what Berlucchi and Aglioti have called 'the body in the brain'; rather, it is more fully defined by processes that happen throughout the body.

· Finally, ecological processes: what I called the ecological aspect of Munk's analysis is not noted by Head. In contrast, we should understand that the body schema is not just a mechanism that tracks bodily posture and movement simpliciter, or in a fashion that is isolated from the environment; rather, it is relational in a second way, insofar as it tracks movement in a way that is always relative to what Munk called the 'form and extension of the objects touched by the moving members of the body' Eighteen ninety: thirty-three. The body schema, we should say, is not just fully embodied, but also embedded in relation to the environment and to the affordances defined by particular situations. It involves a dynamical system of processes that are relationally defined over brain-body-environment. Just as cortical lesions can affect posture and movement, as well as one's awareness of posture and movement, so also can changes in muscular tension, or changes in environment.

In the following sections I'll try to flesh out these ideas and make them more precise by looking at some experiments conducted with subjects who have little or no peripheral input, i.e., cases of deafferentation.