tag:blogger.com,1999:blog-26951738.post3189988255403685277..comments2024-03-18T23:49:35.716-07:00Comments on The Splintered Mind: The Spelunker IllusionEric Schwitzgebelhttp://www.blogger.com/profile/11541402189204286449noreply@blogger.comBlogger11125tag:blogger.com,1999:blog-26951738.post-8380531183460812752020-01-05T06:58:11.653-08:002020-01-05T06:58:11.653-08:00I struggled understanding this 'illusion' ...I struggled understanding this 'illusion' for a few years before I came across this blog post. The psyche paper references emboldened me to share my experience with others. <br /><br />I have since discovered that the ability as described is only the beginning. There is actually a fluid-like veil that normally obscures the ability to see through sleep masks. When it thins a little, the ability manifests as described (seeing one's own moving hand). When it thins more, the ability grows to include static and moving objects in the environment as well. When it thins even more, this masked pereception of the surroundings shimmers and waves in a fluid-like manner. <br /><br />Only one time (so far) has the veil fully cleared for me (meditating with binaural beats, hand mudras, and kechari mudra in a home-made sensory deprivation chamber for perhaps an hour). When it did, the room was flooded with a bluish light that could not be sourced and all surroundings were clearly revealed. This only lasted like 30 seconds or so before I saw the veil fall down from the top of my 'vision' in fluid swirls. After it descended, I could not even perceive the weak form of 'my own moving hand'.DocrHuehttps://www.blogger.com/profile/17907413738563528080noreply@blogger.comtag:blogger.com,1999:blog-26951738.post-59100594904786833202011-02-01T11:59:17.293-08:002011-02-01T11:59:17.293-08:00Thanks for all the cool refs, Anon! Yes, I'm ...Thanks for all the cool refs, Anon! Yes, I'm inclined to think some combination of motor efference copy and/or other contributions to the knowledge of one's own limb movements, plus interpretation of ambiguous noise. But it would be interesting to see something rigorous done that tests the various possible explanations.Eric Schwitzgebelhttps://www.blogger.com/profile/11541402189204286449noreply@blogger.comtag:blogger.com,1999:blog-26951738.post-79730816837741184332011-01-26T10:59:05.574-08:002011-01-26T10:59:05.574-08:00Not exactly blindsight, although the sensation is ...Not exactly blindsight, although the sensation is probably not dissimilar judging from various descriptions (Zeki, S., ffytche, D.H. (1998). The Riddoch syndrome: Insights into the neurobiology of conscious vision. Brain 121(1):25–45.). I'd guess the illusion is a consequence of the motor efference copy that's been hypothesized to be important for predicting the consequences of movement (Wolpert, D.M., Miall, R.C. (1996). Forward models for physiological motor control. Neural Networks 9(8):1265–1279.) (Schwoebel, J., Coslett, H.B. (2005). Evidence for multiple, distinct representations of the human body. Journal of Cognitive Neuroscience 17(4):543–553.) (Frith, C.D., Blakemore, S.J., Wolpert, D.M. (2000). Abnormalities in the awareness and control of action. Philosophical Transactions of the Royal Society of London. B. Biological Sciences 355(1404):1771–1788.). Given the tendency of higher brain centers' info to feedback to lower centers and alter primary perception that way (Hansen, T., Olkkonen, M., Walter, S., Gegenfurtner, K.R. (2006). Memory modulates color appearance. Nature Neuroscience 9(11):1367–1368.), it wouldn't surprise me if a motor efference copy signal combined with body schema info leaked back into the visual centers. Cool stuff.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-26951738.post-41671333779220828882010-08-19T16:30:10.311-07:002010-08-19T16:30:10.311-07:00Cool post. I didn't know that this illusion ha...Cool post. I didn't know that this illusion had a name. I used to move my hand in front of my face in the dark before falling asleep at night as a child. I was sure that I could "see" my hand moving (even with my eyes closed) -- or at least just directional movement. I still experiment from time to time at night to see if the illusion persists. It does. Explanations (1) and (2) both seem pretty plausible.<br /><br />A perhaps related illusion that I experienced as a child -- and can still experience -- was a faint tactile tingling between my eyes when I moved my finger toward the bridge of my nose with my eyes closed. Anyone else ever have this experience?Unknownhttps://www.blogger.com/profile/12687447590125870474noreply@blogger.comtag:blogger.com,1999:blog-26951738.post-53040714305593890812010-08-16T13:49:08.052-07:002010-08-16T13:49:08.052-07:00Yes, Norm, that might be a way of thinking about i...Yes, Norm, that might be a way of thinking about it -- though of course it still leaves open the question of the mechanism of that synaesthesia, including at least possibilities 1 and 2 in the post. If we do think of it as synaesthesia, that implies that synaesthesia is not as rare as often assumed.Eric Schwitzgebelhttps://www.blogger.com/profile/11541402189204286449noreply@blogger.comtag:blogger.com,1999:blog-26951738.post-17406441973849514502010-08-16T12:34:42.886-07:002010-08-16T12:34:42.886-07:00Eric, perhaps what is happening is a form of synes...Eric, perhaps what is happening is a form of synesthesia, in which sensations of one's arm and hand movements are "leaking" over into the visual cortex.Norman Nasonhttp://machineslikeus.comnoreply@blogger.comtag:blogger.com,1999:blog-26951738.post-38054241350534408132010-08-14T17:28:33.353-07:002010-08-14T17:28:33.353-07:00Beachjade: That's an interesting thought. My ...Beachjade: That's an interesting thought. My guess is that it will be different, though. My understanding is that blindsight responses still depend upon input into the eyes, but running through different pathways than the main ones leading into primary visual cortex (which is damaged), pathways less associated with consciousness.<br /><br />Dejan: Interesting link! I'll have to read that paper more carefully when I'm back in the office next week.<br /><br />Ken: I really like the idea of trying it with a previously-seen noise-emitting object. That would help pull (1) and (2) apart even more effectively than the passive-hand variation I suggested. If you decide to tinker around with these ideas in your lab, I'd be very interested to hear what you find! And yes, in an fMRI would be great, too. Yuval Nir et al. (2006? 2008?) asked subjects about their visual experience in the dark while in an fMRI scanner, but the questions were so poorly phrased in my view that the results are uninterpretable. (See my discussion in Chapter 8.) It would be nice to try that sort of thing again, but with better introspective prompts.Eric Schwitzgebelhttps://www.blogger.com/profile/11541402189204286449noreply@blogger.comtag:blogger.com,1999:blog-26951738.post-64591709192696622082010-08-13T18:16:18.898-07:002010-08-13T18:16:18.898-07:00This is really interesting and I can picture sever...This is really interesting and I can picture several more very simple experiments to test this out in addition to the ones you mention (might have to see about our visual lab has sometime this year to try this). <br /><br />For example, you could try moving a noise-emitting object that the subject sees previously to determine if the auditory noise causes a visual sensation. A variation of that is if indeed it does, show a noise-emitting object moving in light, and then in the darkness only move the noise but not the object.<br /><br />Also, if there does appear to be definite visual sensations under certain conditions, a far more elaborate experiment might be to involve fMRI and monitor V1 activity. That is, if someone can find subjects not only comfortable with the confines of a MRI unit, but a MRI unit in total darkness.<br /><br />Oh, and to beachjade, the "blindsight" is due to damage to the primary visual cortex, but not to the eyes or alternate nerve pathways. So they still need light to "see", it is just that they do not have any conscious visual experience. The neural activations follow a different path that appears to be unconscious (but does still indirectly feed into other areas so they can detect objects and avoid them without every having a conscious visual experience).Ken Marablehttps://www.blogger.com/profile/11657351442353880984noreply@blogger.comtag:blogger.com,1999:blog-26951738.post-35637403530011822682010-08-13T18:15:37.742-07:002010-08-13T18:15:37.742-07:00This comment has been removed by the author.Ken Marablehttps://www.blogger.com/profile/11657351442353880984noreply@blogger.comtag:blogger.com,1999:blog-26951738.post-17454548424716119152010-08-13T14:23:45.621-07:002010-08-13T14:23:45.621-07:00This is not quite what you want, but it might be h...This is not quite what you want, but it might be helpful - or not.<br /><br />http://www.bsos.umd.edu/psyc/mvsl/papers_posters/Hogendoorn_Neuropsychologia_2009.pdf<br /><br />DejanUnknownhttps://www.blogger.com/profile/03911156882921353735noreply@blogger.comtag:blogger.com,1999:blog-26951738.post-36905953657159394112010-08-13T13:40:45.528-07:002010-08-13T13:40:45.528-07:00Hmmm. Seems like this could be related to the phe...Hmmm. Seems like this could be related to the phenomenon of "blindsight" wherein persons who are physically blind still show remnants of vision. They will report for example that they do not see an object that is presented to them yet later they can identify that object by pointing to it in an array. (At least I think this is how it goes.) They don't think they can identify the object in the array either. They say they are guessing but...their guessing is above chance. So, could the same mechanisms that permit blindsight also be involved in visual experience in lightless environments? I don't know but it might give you some hints.Unknownhttps://www.blogger.com/profile/02786497750159854262noreply@blogger.com