Talk:Perceived location of touch
JB, JM: Our responses are appear after each comment:
I found the article by Brooks and Medina to be interesting and scholarly, and I look forward to it being published as part of the Scholarpedia initiative. The major problem I had with the article was the brevity and the lack of clear connection between the various ideas considered. More details and connections are necessary for the article to be clearly understood by a wide audience. Specific comments follow.
1. I would suggest the authors include an S1 homunculus diagram in the article, and maybe also include a periphery to S1 wiring diagram.
We have included an S1 homunculus diagram. We have not included a periphery to S1 diagram, as we were not sure how it would aid the reader.
2. A longer introduction to numbsense might be useful for those unfamiliar with blindsight. More pressing is that the discussion of numbsense starts by presenting numbsense as providing good evidence for the dissociation of detection and localisation but then veers into a discussion of the weakness of the evidence for numbsense, thus undermining the original point. The authors move too quickly and need to nuance the strengths and weaknesses of the numbsense findings so that they do not annihilate each other on the page.
We have removed any mention of blindsight – but have linked to the Blindsight Scholarpedia section under further reading. The section is now reframed to be upfront about there being two views on numbsense.
3. The discussion of the Harris experiment suffers from similar problems. I think a diagram of the setup might help. Certainly the authors need to make the central issue - that participants can localise without reporting that they felt the touch - more abundantly clear.
We made a flowchart showing why the forced choice method (for detection and localization) is better for evaluating potential cases of numbsense. In healthy individuals it is clear that this is a serial process in which localization is dependent on detection. However, it is unclear in individuals with numbsense. See also changes in the text.
4. The discussion of experiments detailing responses to near-threshold touch stimuli in healthy controls was also challenging. The authors step from mentioning weaker tactile stimuli being localised with more variability straight into weaker touch being localised towards a specific part of the body (the middle of the forearm). That is a confusing step that changes the reader's focus too quickly. Subsequent steps into models and memory biases are also too sudden and need more expansion and connection.
The section has been reorganised to draw upon the similarities of the central biases observed in stroke patients and in healthy individuals (with weak stimuli), and then put forward reasons why this might be so.
5. I struggled to understand how the Pinocchio illusion illustrates the multiple representations of the body integrated with output from S1. S1 provides a relatively fixed body schema, but the nose is felt to elongate immediately. I also struggled to understand the relevance of localisation changing during the illusion.
We have described this in more detail – we suggest that there could be separate processes for representing the body and perceiving location, but that it appears distortions of higher order body representation do influence localization.
6. The discussion of temporal order judgment being challenged by crossed limbs was easier to follow (though it could be made easier with a diagram) but, again, I struggled to find the relevance of the slowed temporal mapping in the crossed situation. In general, the article might benefit from a clearer statement at the start about the gaps in our understanding and what they are aiming to argue for with their article.
See figure 4 and changes to text.
7. In the final section, the authors mention "that most illusions do not have a long lasting effect on pain" (although they miss the "a") but the "illusions" have not been described earlier in the article. Similarly the "conditioning stimulus" is not explained.
See in text. We have removed conditioning stimulus.