The Three Structure Model is a model of conscious and unconscious experience which incorporates speech and language. The main aim of the model is to develop a ‘tool’ to help describe consciousness. The diagram above looks a bit messy. The bad news is that it can get even messier. The good news is that it doesn’t have to. The reason for this is that the relationships between the concepts are dynamic and fluid whereas the diagram is an oversimplification of these relationships. There probably isn’t too much too be gained from going into a lot of detail with the arrows. The take home message is that the structures within the model have relationships with each other.
The purpose of this post is to look at the concept of automatic speech a bit more closely and to try to explain how it relates to the other structures. Automatic speech describes the speech arising from absolute unconscious activity. If you recall, absolute unconscious activity can never reach conscious experience. I was thinking along the lines of neuronal activity that happens at a very low level in the nervous system – for example the firing of peripheral sensory nerves. We wouldn’t expect isolated nerves such as the radial nerve to have conscious experience. Conscious experience is generally though to occur at much higher levels of the nervous system and most likely results from the activity of neuronal networks.
Automatic speech in this sense can be thought of as occurring at least at the level of the motor input into the laryngeal muscles and the respiratory muscles. Once the motor instructions pass down the final nerves the instructions are at the point of no return. Regardless of what we might think, we cannot alter that immediate activity that ensues.
The schematic diagram of the Vagus nerve above shows the Laryngeal branch. A significant proportion of the instructions required for speech will pass through the Vagus nerve and via the Laryngeal branch to the muscles of the Larynx. The concept of automatic speech though can still be challenged. How many nerve impulse are needed to pass through the Vagus nerve to produce a single word? How many nerve impulses are needed to pass through the Vagus nerve to produce a single syllable? If many nerve impulse are required are these impulses generated in the motor cortex – in Broca’s area and related areas? Or does Broca’s area generate high level instructions for lower areas to generate batteries of motor impulses?
The answers to these questions provide us with a possible answer to the question of what the largest unit of speech activity is which when initiated is beyond conscious control.
Appendix – Related Resources on the TAWOP Site
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