>>7764817 I study a rhythm in the brain called 'gamma oscillations' in the visual system. the stuff I'm working on and about to publish is on the cellular basis of this oscillations, as in these cells connect to each other in this way and therefore the circuit generates this resonant cycle. Hopefully my work will result in understanding how we process visual data into objects and other abstractions.
>>7764955 Listen, I could actually totally do that. No joke. It's just super invasive. Calcium imaging coupled with holographic laser stimulation optogenetics. It's literally going on in my lab right now.
>>7764967 Fairly invasive. No electrodes in the brain though, which is nice.
1. make a window in your skull so we use a microscope to look into your brain 2. inject a virus in your visual cortex containing dna for a calcium indicating protein so that we can see when your neurons fire. 3. inject a virus in your visual cortex containing dna for optogenetic proteins so that we can fire and silence them when we want using light. 4. train software to know what makes each neuron fire (what features of visual space) 5. make neurons fire to replicate what your brain does when it is seeing things
>>7765058 >No it could not be sealed up. You would be attached to a gigantic rig that costs around $250,000. Your head would be locked in place so your brain doesn't move. That makes it rather impractical don't you think? I just want to be able to have a HUD and web browser access direct from my visual field day-to-day. Do you guys have anything that might permit that?
>>7765067 google glass. If you want something that interfaces directly with your brain... you either have to go with the giant expensive immobile rig, OR we have stuff that might work decently today, but is not perfect: http://www.cell.com/neuron/abstract/S0896-6273(14)01005-8?_returnURL=http%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS0896627314010058%3Fshowall%3Dtrue
In case you're wondering, none of this has ever been tested in humans, but based on a priori principles, most people in the field agree that humans would actually be a much better system to work in. The neurons are bigger and code for more explicit visual features. Only problem would be that we couldn't see that many neurons at a time (maybe 5000 or so), which is probably enough to get this to work, but is not perfect. The trade is resolution for greater numbers of neurons.
So answer a couple of questions I've long wondered about.
If you have few or no neurons connecting the two sides of the brain, you have a problem in which you can only identify things to the right. For example, if you stand on main street in your home town, you can identify the stores to your right but not to your left. Go down a block and turn around and you can identify the stores to your right that you could not identify previously when they were on your left and you cannot identify the stores you identified previously that were on your right but are now on your left.
It seems clear that that it is because of the lack of pathways from the right visual cortex (which processes your left field of view) to the left fusiform gyrus.
So here are the questions: 1) Prosopagnosia (face blindness) is apparently the result of a problem with the right fusiform gyrus. Is someone with the same problem above only able to identify people to their left but not to their right? 2) In the case of albinos (and obviously Siamese cats) the optic nerves apparently do not regroup in the optic chiasm so the left visual cortex processes all of the data from the left eye and the right visual cortex processes all of the data from the right eye. How much is an albino affected if they have few or no connections between the left and right brains?
>>7766837 >1) Prosopagnosia (face blindness) is apparently the result of a problem with the right fusiform gyrus. Is someone with the same problem above only able to identify people to their left but not to their right? Yes, if the assumptions are as simple as you stated. In reality you get a little bit of left-eye info to your right brain and vise-versa, making it possible that you might be able to discern a face. That said, there are beautiful studies done by gazzaniga that show interesting effects of showing split-brain people objects in their non-dominant eye-field. Their responses in identification are often correct, but seemingly sub-conscious.
>2) In the case of albinos (and obviously Siamese cats) the optic nerves apparently do not regroup in the optic chiasm so the left visual cortex processes all of the data from the left eye and the right visual cortex processes all of the data from the right eye. How much is an albino affected if they have few or no connections between the left and right brains? Nobody knows. Why do sensory nerves switch sides... I don't know. Is there a benefit I'm unaware of? There must be. That said, I'd guess there would be more poor integration of contrast in the fields of view, due to the bionocular integration that typically takes place at even low visual processes regions in the brain.
>>7766845 Some humans, typically women, are tetrochromats (https://en.wikipedia.org/wiki/Tetrachromacy#Human_tetrachromats).
As far as what the experience would be like... I'm not positive, but if we are talking about a new photoreceptor in a significantly different frequency range than the other ones (say IR or UV), then there are two possible options: 1. We would experience a new color. This is not unthinkable. If we consider how dichromats (color blind people) see the world. In those that are missing the red receptor, they can only see the differences between blue and green. Their green receptor picks up all the red they will see. So, what colors do they experience? They don't associate green with anger and hatred, nor do they associate red with that emotion. (I think this shit if fascinating) In most of these people, that association between RED and RED EMOTIONS is utterly missing. They don't experience it.
Now, this doesn't mean that we would experience new emotions per se, but it might...
2. Normalization of color space; which seems less likely
>>7766983 We know a lot about how it works! We have been able to recompose movies seen by the visual system for years. We are now considerably further along in our understanding. https://www.youtube.com/watch?v=piyY-UtyDZw
>>7765534 Right... this shit is a lot more complicated than you might think. Each electrode would not act as a pixel as you seem to imply. There are really significant nonlinearities that would need to be compensated for. An approach using parallel stimulating electrodes could would for a simple brain machine interface (https://en.wikipedia.org/wiki/Brain%E2%80%93computer_interface) but wouldn't allow the spatial resolution necessary for you to 'experience' images. For that you need something much more nuanced than stim electrodes (ie optical techniques). Take a glance at the paper I posted, it actually has a chance at success (http://www.cell.com/neuron/abstract/S0896-6273(14)01005-8?_returnURL=http%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS0896627314010058%3Fshowall%3Dtrue)
>>7768543 yup. Dario L. Ringach Receptive Fields in Macaque Primary Visual Cortex Spatial Structure and Symmetry of Simple-Cell (2002) J. H. van Hateren and D. L. Ruderman Independent component analysis of natural image sequences yields spatio-temporal filters similar to simple cells in primary visual cortex (2002)
>>7768574 Right. I was just making a quippy rhetorical response. In reality, what matters are the algorithms that were implemented to carry out the computations necessary for that video to be made. About coding for explicit representations... we know a good deal about that too. The term given in the field is 'Sparse Coding' Read this http://www.nature.com/nature/journal/v435/n7045/full/nature03687.html Also skim this http://hubel.med.harvard.edu/book/bcontex.htm
>>7768596 - They are recording from a population of neurons in the visual cortex - They play random video to the animal which recording what on the screen made the neuron fire - They correlate and average what makes each neuron fire - They play a video to the cat - They predict what that video looks like based on the known firing preferences of the neurons
in jargon: They map the STRFs, then reconstruct a movie based on the population activity while a video is played to the animal. This is the bread and butter of visual neuroscience
>>7768642 Right. Those are the building blocks to getting an experiment like that to work. Here's Yang Dan's relevant papers: http://www.nature.com/neuro/journal/v10/n6/full/nn1895.html http://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.0030342
>>7768701 >How does it feel knowing that nonsynaptic plasticity may play a significant role in how the brain operates? Fine... I'm sure it plays a huge role
>How does it feel knowing that we will never be able to properly simulate neurons because computers don't use true real numbers? 'properly'? I'm confident that we'll get close enough. Compete simulations are a long way off, but we'll get there. C. Elegans is about 15 years away, fly is maybe 30, mouse is probably 60, humans maybe 70
>>7769264 I haven't bene on sci in at least a year (used to be very active like 4-6 years ago), and yeah, it's weird. I'll assume there's a decent backstory and I'm just a newfag, but it still seems like a weak insult
Actually, I wasn't really asking about the experience, but if there were any significant difference in the processing. I originally came across this in one of Gordon Shepherd's books on neuroscience but he didn't address this issue.
I assume that for humans, the basic processing might not necessarily be different for the few tetrachromats who exist. But in birds, turtles, ... which are all tetrachromats (I guess there could be a color-blind tetrachromat that was really a trichromat) would there be an area of the brain for processing the extra color?
>>7769345 Color blobs brosef http://cercor.oxfordjournals.org/content/18/3/516.full
They are regions of low orientation selectivity in V1. They are better understood in higher animals like cats and monkeys (I study mice). The ice cube model doesn't really include this, since the blobs go in regions where there is poor orientation selectivity. Think hyper-hyper-icecube model. First hyper is binocular, second for other modalities like color and other esoteric stuff.
Fun fact, in mice, the upper half of their vision is receptive almost entirely to UV, and the lower half to green (like grass and sun). This is actually a really active area of research
>>7769354 In short, yes. I'm not sure how the neuroanatomy differs in other animals, but there have been dooooope ass studies done in mice and monkeys to INDUCE TETROCHROMACY. Yes, new and segregated blobs form in V1 coding just for that new receptor type. This means that there is an activity dependent development mechanism, which is amazing.
>>7769356 Yep. You don't really get into a decent graduate program with less than a proven proficiency is all of these subjects. I didn't take CS as an undergrad, and only took up through calculus in math, but after graduating I took a year off, worked in a lab, and had to teach myself to do some tough signal processing analysis. This was enough for grad schools, as it should it be.
>>7769317 >>7769349 Neuro is not overhyped. Neuro is definitely overcompetitive though. I'm struggling not to get scooped as we speak. I work 60-80hr weeks just to be status quo. Neuro has has had a boom in funding in the last 15 years. It's also produced incredible results that have already begun trickling into medicine. That said, I don't do neuroscience for the medical benefits, I'm in it for the long game: Total brain simulation, brain-machine-interfaces, undercovering general principles related to perception and experience, and uncovering fundamental truths about our thinking machine.
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