Motor Imagery

From: Parker, Chris (
Date: Mon Oct 30 1995 - 10:01:46 GMT

>INTENTION AND IMAGERY, by Marc Jeannerod (comments by Chris).
>1. Introduction
>The general idea of this paper is that actions are driven by a represented
>goal rather than directly by the external world. Representations may be
>built from the environment, they may rely, at least partly, on knowledge
>acquired from the outside. Yet, their vehicle is a genuine apparatus which
>pertains to the structure of the brain itself and constrains their
>expression and modalities of functionning.

This seems to be saying behaviourism is much less important than

>Yet, the idea will be defended that motor
>imagery, when properly defined and used, can be a key phenomenon for
>understanding motor representations, and studying the cognitive
>content of actions.

I did not find that motor imagery was well defined! It would have been
helpful if the relationships between: motor imagery, motor actions,
motor preparation, motor learning, motor representations, motor images,
motor rules, motor generation, motor behaviour, motor programs, motor
intention and action planning had been clearly described, perhaps with
a diagram or practical example.

>2. The imagery debate.
> The issue that mental imagery might not be a
>genuine phenomenon but, rather, pertains to the same class of
>representational mechanisms as those which are involved in processing
>ingoing or outgoing information will be developed with examples drawn from
>research on visual and motor images.

This seems to be half saying that mental imagery is an epiphenomenon
(the final article said "..phenomenon but instead pertains to the
representational mechanisms.."

>2.1. A brief look at visual imagery
>One possible explanation for this striking property of visual imagery of
>preserving the metric properties of represented objects is that the image
>is generated within brain areas which are spatially mapped.

Can't metric properties also be represented in a distributed way such
as a coded picture on a floppy disk, where it is the coder/decoder that
preserves the spatial relationships?

>2.2. The case of motor imagery

>The above framework used in the context of visual imagery can also be
>tentatively generalized to mental representations in other modalities, and
>specifically, to motor imagery. Such a generalization implies that motor
>imagery pertains to motor physiology in the same way as visual imagery
>pertains to visual physiology. Accordingly, motor imagery would be part of
>a broader phenomenon (the motor representation) related to intending and
>preparing movements.

I do not think this "tentative generalisation" is reasonable as motor
imagery involves a model of "self", and is more complicated.

>First, the fact that motor imagery and motor preparation are both assigned
>to the same motor representation vehicle has a strong logical consequence,
>namely that motor images cannot be considered as an epiphenomenon of the
>process of motor generation. Instead, in continuity with the claim made in
>the Introduction section, which attributed the motor representation a
>causal role in the generation of movements, motor images must also be
>considered to be functionally related to the imagined movement. This point
>will be extensively discussed in Section 3.

Am I missing the point, I though that in 2., above, it was said that
the idea that motor imagery might not be a genuine phenomenon would be
developed. Can something that isn't a genuine phenomenon have any
causal role?

> According to the
>authors, "there is always a clear link between the effective observed
>movement and that executed by the monkey and, often, only movements
>of the experimenter identical to those controlled by a given neuron are
>able to activate it." This very striking result supports the idea of
>neurons as a common substrate for motor preparation and imagery.

Is this now saying that a link between perception and motor action is
the same as between motor preparation and imagery?

>3. Functional equivalence of motor imagery and motor preparation
>3.1. Effects of motor imagery on motor learning and training.
>If motor preparation and motor imagery are related processes, they must
>interfere at some level: for example, imagining a movement should
>influence the subsequent performance of that movement.

Motor imagery now has a function and seems to be both the wilful
calling up of an imagined movement and also a mental representation (a
correlate of
 motor preparation).

>4. The content of motor representations.
>4.1. Is there a representation of the duration of an action?
>A number of experimental data point to the similarity of the time duration
>needed for mentally and actually performing the same action.

These could be separate processes with the same time clock or standard,
although a single shared mechanism would be a simpler explanation.

>6. Conclusion.

A lot of interesting details and ideas, but as brain death approaches
(this article is the most difficult one to understand that I have ever
read), I am left wondering if this is THE foundation article or is it
simply a subtler relation of Lubinski's one on private states?

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