Wednesday, April 28, 2010

Dynamic Touch

Turvey proposes the notion of dynamic touch, based on Gibsonian notion of active touch.
[Turvey, M. T. (1996) Dynamic Touch. American Psychologist.]

We can feel the weight, the size, and the direction of our own limbs through internal senses, even if we close our eyes. In the similar way, we can feel the weight, the size, and the direction of various tools. Baseball bat, tennis racket, umbrella, fishing rod, and so on. Dynamic touch is the perception of properties of one's own body, or the external objects.

When we use tools, we can feel them as a natural part of our body (swinging a racket, driving a car, etc.). We probably extend our proprioception into them through the sense of dynamic touch.

Near and Far

Berti and Frassinetti reports an interesting case of unilateral neglect.
[Berti, A. & Frassinetti, F. (2000) When far becomes near: Remapping of space by tool use. J of Cognitive Neuroscience.]

The patient showed a neglect of the left space, as is seen in other cases of unilateral neglect. In this case, the neglect was seen only in the peripersonal space (near space), not in the extrapersonal space (far space).

But when the patient performed with a stick, the neglect was also extended to the end of the stick. By using a stick, the 'far' space was converted into the 'near' space, as the patient's body schema incorporated the stick into itself.

The distinction between the peripersonal and the extrapersonal, the near and the far, is not something fixed.

motor control

It is said that a human body has nearly 800 to 1000 articulations. And each articulation needs more than two types of muscles to rotate.

How many muscles and articulations should coordinate in movements? A very simple task, holding a cup and drinking the coffee in it, for example, will require the coordination within tens of articulations and muscles.

It is inappropriate to consider the mind as a 'control tower' which dominates the body movements. Body is too complex to be controlled by the mind.

Of course the body moves in accordance with our intention. But this does not mean the mind 'controls' the body. The body must have its own way to coordinate hundreds of articulations and muscles.

But how?

Sunday, April 25, 2010

A phantom sensation

Ramachandran and Blakeslee describe a case of phantom limb;

Tom lost his left arm just above the elbow......In the weeks afterward, even thow he knew that his arm was gone, Tom could still feel its ghostly presence below the elbow. He could wiggle each "finger," "reach out" and "grab" objects that were within arm’s reach. Indeed, his phantom arm seemed to be able to do anything that the real arm would have done automatically, such as warding off blows, breaking falls or patting his little brother on the back. Since Tom had been left-handed, his phantom would reach for the receiver whenever the telephone rang.
[Ramachandran, V. S. & Blakeslee, S. (1998) The Phantoms in the Brain. William Morrow.]

Apparently, the patient’s body still reacted to certain stimuli in a habitual manner. Whenever the telephone rang, his whole body was led to answer it as he used to, and this action involved the movement of the left hand. The sensation of missing limb seems to occur as a part of a habitual action that has been established between the body and a certain situation. The patient need not to represent in his mind the missing part of the body but may feel it immediately, as a need for an embodied action.

Saturday, April 17, 2010

Rubber Hand Illusion

The rubber hand illusion is a well known somatosensory illusion, which was reported by Botvinick and Cohen in 1998. It has become almost classic in the research of body awareness.
[Botvinick, M. & Cohen, J. (1998). Rubber hands 'feel' touch that eyes see. Nature.]

In the experiment, the participant's real hand is hidden out of sight. Instead, a life-sized rubber hand is placed in front of the participant. The experimenter uses two brushes to stroke the real hand and the rubber hand synchronously. After a short period, most of participants start to feel the touch in the position of rubber hand and experience as if the rubber hand is the real hand.


Ehrsson tested the illusion in four conditions to manipulate the feeling of ownership of the rubber hand.
[Ehrsson, H. H., Spence, C., Passingham, R. E. (2004). That's my hand! Activity in premotor cortex reflects feeling of ownership of a limb. Science.]
1. Synchronous and Congruent: stroking synchronously the rubber hand and the real hand,
putting the rubber hand aligned with the real hand.
2. Asynchronous and Congruent: stroking asynchronously, the rubber hand aligned with the real hand.
3. Synchronous and Incongruent: stroking synchronously,
the rubber hand rotated 180 degrees pointing toward the participant.
4. Asynchronous and Incongruent: stroking asynchronously, the rubber hand rotated 180 degrees.

As is expected, the participants felt the most strong illusion in the first condition (synchronous and congruent). The touching stimuli should be synchronous and the orientation of the rubber hand need to be congruent with that of the real hand.

I guess, the position of the rubber hand must be in the circle of possible movements to create the illusion. If the rubber hand is outside the movability of the real hand (very far, rotated conversely, hung upside down, etc.) the participants will not be able to feel the illusion.

Illusion is the possible perceptions, as perception is the possible action.

Sunday, April 11, 2010

The body in Satori

The body image is altered not only in psychotic disorders but also in religious experiences.

Yuasa says;
In satori, there is no distinction between the body of oneself and others, between the body of a person and the Buddha. The body is changed into, as it were, a metaphysical body, and it loses all its objective characteristics found in the everyday dimension.....The distinction between one's own and others' bodies, between being a self and the being of others, completely disappears.
[Yuasa, Y. (1987) The Body: Toward an Eastern Mind-Body Theory. SUNY Press.]

Again, having my own body, is not a matter of course!

Saturday, April 10, 2010

'My' Body

The body image is the image of one's own body in the mind. Thus it has a characteristic of 'my' body. The body image is a kind of body awareness as my own body, not the others.

It is well known that the natural body image is disturbed or even destroyed in Anorexia, Bulimia, or Body dysmorphic disorder. But the nature of body image as one's own body is also altered in psychotic disorders such as Depersonalization or schizophrenia.

In case of depersonalization, patients often feel divorced from their own body. They can intellectually recognize that the body belong to themselves but they can't feel it as theirs. 'My body' is felt like others or a mere physical object. The sense of ownership of the body is disturbed.

In schizophrenia, some patients have delusions of being controlled by an external force. The delusions is sometimes accompanied with body sensations and feelings. They literally feel that they are moved by the force and can visualize it as images. The sense of motor agency is disturbed. Not only the cognition but also the sense of motor agency seems to be affected here.

Having one's own body, is not a matter of course!

being out of body

The phenomenon known as the 'Out-of-Body' experience is related to a failure of integration of multisensory informations from the body, suggests Blanke and Arzy.
[Blanke, O. and Arzy, S. (2005) The Out-of-Body Experience: Disturbed self processing at the Temporo-Parietal Junction. The Neuroscientist.]

In OBE, people often look down their own body from an elevated location like ceiling. The perspective which they look at and the sense of self is located outside the body.

They indicate that the OBE has three characteristics.
1. disembodiment
2. the impression of seeing the world from a distant and elevated visuo-spatial perspective
3. the impression of seeing one's own body from this elevated perspective

OBE--if it really exists--shows that the body image could exist without the sense of self. The experiencing 'I' and the experienced 'my body' are dissociated. Interestingly, the sense of ownership is still functioning (because the body is seemed as 'my body' in OBE), but there is no sense of motor agency.

Saturday, April 3, 2010

Blind Touch

Jacque Paillard says that there is a 'blind touch' (or 'Numbsense') phenomenon which is a tactile equivalent of blind sight.

One of his patients was;

"Unable to detect and to perceive any tactile stimulation delivered at various sites on her right hand when vision was prevented, this patient showed, to her own surprise, a spontaneous ability to point her left finger toward stimulated places on her deafferented right hand.
[Paillard, J.(2005) Vectorial versus configural encoding of body space. in Body Image and Body Schema (ed. Preester and Knockaer).]

This is a very important discovery. Because this phenomena suggests that there is a neural basis for the distinction between body schema and body image, as Paillard also points out.

Mirror and Body Image

When you look at the mirror, you feel that your right hand is the left hand of the mirror-self. You exchange perspectives. But before that, how do you recognize that the person in the mirror is yourself?

You must recognize that the body you feel here through proprioception is equivalent to the body you see there in the mirror.

Animal psychologists say that adult chimpanzees recognizes that the figure in the mirror is him/herself within few hours. It seems that they have their own body image in their mind.

But it is also said that the chimps grown up alone without other chimps don't come to recognize themselves in the mirror.

So, it is possible to speculate that the other individuals body plays a crucial role to create the body image in the mind. Probably we need the other's body to see our own body from third person's perspective and to construct our own body image in the mind.

Body Image

Research literatures on body image in general, stresses too much the unhealthy aspect of them, such as anorexia, bulimia, body dysmorphic disorders, and so on.

It lacks the basic research on body image. For example, how we represent our bodies from the outside of the body, whereas it is impossible. If we have our own body images in the mind, what is it for? Why is it necessary? How we use it? Before stressing the disfunction of the body image, we need to know the ordinary function of it.

Body image is formed with the gaze which represents the body from the outside. In contrast the function of body schema doesn't include this perspective. Neuroscience research on the body seems to ask only the body representation in the brain and doesn't ask the problem of the perspective, which makes the body representation--the perspective from where the body is represented (from within or from outside).

The body image is based on the the perspective of the other person (the third person's perspective).

Body Image and Body Schema

Most of neuroscientists uses the term 'Body Image' and 'Body Schema' indiscriminatingly. But it is important to make clear the difference between them, as is pointed out by Shaun Gallagher.

Body image is the image represented in the mind. It is objectified by the consciousness. We perceive our body, we think about our body, we feel our body as object. And we not only experience our body as an object but also as something belonging to ourselves (the body as my own body). The body image is a source of the sense of body ownership.

In contrast, the body schema is the subject-body and never owned. The sense of motor agency seems to have its origin in body schema but basically its function is anonymous. The body schema works under the conscious reflexion and doesn't have any personhood. It functions unconsciously.

The Body Has a Mind of Its Own

I've read 'The Body has a mind of its own' by Sandra Blakeslee and Matthew Blakeslee.

[Blakeslee, S. & Blakeslee, M. (2007). The Body Has a Mind of Its Own: How Body Maps in Your Brain Help You Do (Almost) Everything Better. Random House.]

The authors are not experts of neuroscience nor cognitive science. But as scientific writers, they encompass a broad range of bodily experiences, from anorexia to yips, from Nintendo game machine to cyborg, from body schema to mirror neurons. All of these topics are written based on the relatively new discoveries in neuroscience. This is a nice book as an introduction to the neuroscience of embodiment.

You can see the online webpage that introduces this book.

Geminoid experiment

I've read the H. Ishiguro's new book, "What is Robot?"(in Japanese, Kodansha, 2009).
[Ishiguro, H. (2009). What is Robot (in Japanese). Kodansha.]

His Geminoid (a humanoid robot that resembles himself!) raises many questions about mind-body relations.

In Ishguro's experiment, 70% of the participants who observed the female android for 2 seconds, noticed that it was not human.

But when they observed the same android with microactions (eye movements, small shoulder movements, etc.) , equally 70% of them believed it to be human.

The appearance of the robot seems very important. Ishiguro gives many other curious examples like this.

Another curious example. When his stuff opened up the geminoid's head to fix it up, he felt 'a curious sensation' as if he was touched and operated.

So, he projected himself to the geminoid's body, in the very similar way in the experiments in rubberhand illusion.

When the robot has the similar appearance to human being and it moves, we can easily project ouselves to the robots.

We can feel touch on the robot's body. The body schema incorporates the robot's body into itself, in the same way as it incorporates tools.

The rubberhand illusion is based on the same principle. We can feel the extended 'touch' on the rubber hand as the body schema incorporates the rubberhand.

Merleau-Ponty's notion of Behavior

Merleau-Ponty's main interest, before he started to be a phenomenologist, were Henri Bergson's philosophy, Gestalt psychology, and neurology.

In his "Structure of Behavior", he denies the notion of reflex. Because it requires one-to-one correspondence between the stimulus and the response.His claim was that the Organisms response to the meanings of the environment or situation, not to the stimuli. Thus the behavior cannot be explained as a complex of reflex acts. He stresses the importance of behavior but it's totally different from that of behaviorist.

Perception as possible actions

Perception is not to receive passively the informations about the object or the environment. Perception is something more active, as Gibson named it 'active touch'.

Perceptions are presentement of actions, so to speak. Through perception we always receive the possibilities of actions which we can take toward the environment. We perceive the action possibilities latent in the environment, what is called affordances.