Continuing with the contrast illusion theme (see Appendix) I created the above picture to illustrate the theme. Thus although all of the filled circles are of the same colour, this colour appears different in the context of the background. Quite accidentally there is a further illusion in the picture. The right side may appear wider than the left side. This is because the theme involves a depth perspective. The images on the left appear closer than those on the right and this interferes with the assessment of the width of the image.
Index: There are indices for the TAWOP site here and hereTwitter: You can follow ‘The Amazing World of Psychiatry’ Twitter by clicking on this link. Podcast: You can listen to this post on Odiogo by clicking on this link (there may be a small delay between publishing of the blog article and the availability of the podcast). It is available for a limited period. TAWOP Channel: You can follow the TAWOP Channel on YouTube by clicking on this link. Responses: If you have any comments, you can leave them below or alternatively e-mail justinmarley17@yahoo.co.uk. Disclaimer: The comments made here represent the opinions of the author and do not represent the profession or any body/organisation. The comments made here are not meant as a source of medical advice and those seeking medical advice are advised to consult with their own doctor. The author is not responsible for the contents of any external sites that are linked to in this blog.
In the previous post I looked at GABA receptors in C.Elegans – the Nematode worm. C.Elegans has been extensively studied and there is a very sophisticated understanding of the organism’s biological machinery. What I found fascinating was that the role of the GABA receptors in C.Elegans has been clarified and has been found to play a role in movement as well as a few other functions. There are only 26 neurons in C.Elegans.
C.Elegans
The Nematode worm moves by contracting the muscles on one side of its body whilst relaxing the opposing muscles. The GABA receptors are involved in the relaxation of the muscles.
Muscle Relaxation and GABA Receptors
When people are anxious this can cause the muscles to tense. Some drugs acting at the GABA receptors in humans can reduce muscle tone. Some drugs which target these receptors can also alleviate anxiety. Which comes first? This is the chicken and egg scenario. Do you have to be anxious to have tense muscles or do you become anxious because your muscles are tense.
The James-Lange and Cannon-Bard Theories
The question of whether emotions or bodily sensations happen first is dealt with by the James-Lange and Cannon-Bard Theories. Essentially the two theories take differing positions on the question. The James-Lange theory states that emotions happen in response to information coming from the body. When the heart races you feel anxious. The Cannon-Bard theory says that emotions and bodily responses occur independently but can be coordinated by the Thalamus.
Nematode Worms, GABA Receptors and Anxiety in Humans
Nematode worms and our ancestors diverged some 800 million years ago. In that space of time Nematodes and our species have continued to evolve. Nevertheless the conservation of the GABA receptors in both Nematodes and our species is evidence of the importance of these receptors. Some simple connections and a narrative can be constructed to account for the above.
1. Nematodes have developed GABA receptors to facilitate movement
2. GABA receptors enable Nematodes to relax muscles to steer and move in certain directions
3. GABA receptors are part of a movement apparatus
4. As species have evolved and become more complex they have become capable of conscious experience
5. The movement apparatus has been conserved but also become associated with other complex phenomenon such as conscious experience
6. In humans muscle groups oppose each other – reciprocal extensor and flexor muscle groups at the elbow are one example.
7. The underlying relationship with GABA receptors remains
8. Action through the GABA receptors relaxes muscle groups and results in accompanying sensory feedback (small variation in the GABA receptor gene may not be related to anxiety but rather it is the physiological effects that the products of these receptor gene variants have in common).
9. This sensory feedback produces an emotional response – lowering of anxiety
While the above supports the James-Lange theory we could argue that there is a bidirectional relationship. For instance a heightened state of anxiety in response to internal stimuli can increase the tension in the muscle groups.
The above is a testable hypothesis. The hypothesis makes a very specific statement about a receptor in adaptive terms. The GABA receptor facilitates movement of the organism. Whilst it may well be wrong it nevertheless contains implicit assumptions which make it testable against the evidence base. The theory in essence states that the GABA receptor function is conserved and associated with increasingly complex phenomenon. If on moving from Nematode worms to humans there was convincing evidence of loss of motor related GABA receptor function in intermediary species this would contradict the hypothesis.
References
Jorgensen, E.M. GABA (August 31, 2005), WormBook, ed. The C. elegans Research Community, WormBook, doi/10.1895/wormbook.1.14.1, http://www. wormbook.org.
Contributors to the Model (links are to the posts in which contributions were made – these links may contain further links directly to the contributors)
Index: There are indices for the TAWOP site here and hereTwitter: You can follow ‘The Amazing World of Psychiatry’ Twitter by clicking on this link. Podcast: You can listen to this post on Odiogo by clicking on this link (there may be a small delay between publishing of the blog article and the availability of the podcast). It is available for a limited period. TAWOP Channel: You can follow the TAWOP Channel on YouTube by clicking on this link. Responses: If you have any comments, you can leave them below or alternatively e-mail justinmarley17@yahoo.co.uk. Disclaimer: The comments made here represent the opinions of the author and do not represent the profession or any body/organisation. The comments made here are not meant as a source of medical advice and those seeking medical advice are advised to consult with their own doctor. The author is not responsible for the contents of any external sites that are linked to in this blog.
In the last post we looked at the a number of images and altered single characteristics to assess the impact on the contrast illusion. The hypothesis generated was that the letter A when compared to a filled circle could with a graded background produce the illusion of heterogeneity within the same shape (i.e within the letter A). The underlying assumption was that the geometry of the letter A would impact on the perception of contrasting colours in the background and foreground to produce the illusion of variegation. The above diagram was created to test this hypothesis. A cursory examination of the diagram suggests that the hypothesis is incorrect. Nevertheless the more general contrast illusion persists. Both the A’s and the solid filled circles appear lighter on the right than on the left.
Index: There are indices for the TAWOP site here and hereTwitter: You can follow ‘The Amazing World of Psychiatry’ Twitter by clicking on this link. Podcast: You can listen to this post on Odiogo by clicking on this link (there may be a small delay between publishing of the blog article and the availability of the podcast). It is available for a limited period. TAWOP Channel: You can follow the TAWOP Channel on YouTube by clicking on this link. Responses: If you have any comments, you can leave them below or alternatively e-mail justinmarley17@yahoo.co.uk. Disclaimer: The comments made here represent the opinions of the author and do not represent the profession or any body/organisation. The comments made here are not meant as a source of medical advice and those seeking medical advice are advised to consult with their own doctor. The author is not responsible for the contents of any external sites that are linked to in this blog.
Intermezzo, Public Domain
