Topographical mapping

[@dongyue6934]

thank you so much, extremelty helpful

[@wwmheat]

Hello, Mike, thank you for great explanation! What is the exact value that is colour-coded on topographical maps? I mean, if we're measuring let's say voltage potential, does it show instantaneous value, or some average amplitude, or smth. else? First answer sounds simpler, but I suspect it would be not enough representative, due to great time resolution of EEG, too much dependant on exact choice of time instant at which we plot the map..

[@mikexcohen1]

Hi Valeriy. You can show many different features on topographical maps. In this example, I'm showing voltage values averaged from a time window. Averaging over some 10s or 100s on ms is generally a good idea to reduce the impact of noise, as you also observed.

[@wwmheat]

@@mikexcohen1 thank you, yeah, it makes sense, and I should've guess that myself😅 The source of my original confusion was that for some reason I imagined for myself that signal should always fluctuate about zero level.. In this case I suppose time averaging still wouldn't help. But then I realised that fluctuating about zero is generally not the case.. Anyway, thanks again for the course! I'm already going through ANTS #3

[@wafahabib314]

Hi, after ICA decomposition, I get IC components. What are IC components? I want to get an overall scalp topography of all the channels. Can you please explain how to do that?

[@ananyabadithe663]

Hey, quick question. What does it mean when an area in the brain has more than 1 topographic maps?

[@wafahabib314]

Hi, can you please make a video on how to map scalp topography

[@mikexcohen1]

Hi Wafa. Easiest is to use eeglab's topoplot() function. Or any other EEG analysis program.

[@wafahabib314]

Hi, is ICA topography in EEGlab the same as scalp topography?

[@mikexcohen1]

The term "topography" in general refers to the spatial distribution of some activity over the scalp. Then the question is what variable the topography is showing -- it can be an IC map, the voltage values at some time point, spectral power, etc...

[@aminfakia2756]

can you briefly tell me how the interpolation is done ? are we taking the value of a specific electrode and comparing to the surroundig or what is going exactly ?

[@mikexcohen1]

Hi Amin. I go into more detail about this in my ANTS book, but basically the idea is to do 2D linear interpolation over some grid (e.g., 80x80) given the measured data points (electrode locations). Then that square map is cut into a circle, and black curve lines are added for the ears etc.

[@aminfakia2756]

@@mikexcohen1 oh i see. I have already worked with a similar concept but right now i am trying to plot the heatmap on a 3d model, and i have no clue how to exactly start, there isnt much literature or information about this unfortunatly. Do you have any recommendation or ideas how i can do this ? as for the book recommendation thanks a lot i will order it soon, just came across your content recently in my desprate search for answers to my questions, really love what you are doing :D

[@mikexcohen1]

Headmaps also look great. To be honest, it's best to use eeglab -- they have built-in headmap and topoplot functions. You would only need to supply electrode location information.

[@roseb2105]

what does it mean when there is a photo ( output display) of lines connecting those dots together

[@mikexcohen1]

I'm not sure what lines you are referring to. Sometimes people show inter-electrode synchronization using lines connecting the electrode pairs that have synchronization.

[@roseb2105]

when i sent this stuff to the neurology department in the hospital they had no idea what i was talking about

[@mikexcohen1]

Maybe they should watch some more of the videos on my channel ;)

[@AkankshaSingh-je3nc]

good

[@أبوجابر-ظ7م2و]

Thanks

[@ronliebermann]

I'll tell you something funny. Every city likes to advertise its tax-funded "Green Initiatives." Things like buses powered with natural gas. And a "Sharing Economy" with electric scooters, and beautiful walking areas. But it's all fake. Every bit of it. To understand what these sheisters are doing, first watch the above video. What you'll see are very simple color-coded topographical maps. A topographical map shows the elevation of different parts of town. So a topographical map of San Francisco might display eight main elevations. Only a strong athlete would ride a bicycle in San Francisco because the hills are so steep. For most people it's impossible to handle such major changes in elevation. You'd be exhausted in ten minutes. That's why everyone uses public transportation. There's no alternative. So now bear in mind that public transportation is a giant money-stealing machine. The Unions, the Political Bosses, and the Mafia converge on public transportation to extract as much money as possible. In California, billions of public transportation dollars are stolen in broad daylight. And California public officials don't even care. If you have a government job, then stealing is legal. www.cagw.org/thewastewatcher/californias-100-billion-nightmare-high-speed-rail-project Now, take a look at this San Francisco bicycle route map: www.getyourguide.com/-l61/bike-tours-tc7/? As you can see, the map is offered only as a "vacation guide". It won't generate a bicycle route from your apartment to your office. That's omission is intentional. It would be easy for the San Francisco government to produce a BART topographical bicycle map. That way, you could see all the routes which exist with: No elevation change; or One elevation change; or Two elevations changes. That way you could go on a very easy - no elevation change - bicycle trip with the kids, or Or a slightly more difficult - one elevation change - trip with a friend. Or a more difficult - two elevation change- ride to the office. But as I said, those buses and trains aren't made for helping people, they're made for swindling people. BART is a just Union crime-in-progress. Ridership numbers and revenue are everything. So no city is going to offer useful bicycle maps which encourage people to avoid the bus and the train. Those green "sharing" bicycles you see are offered only as a propaganda stunt. The sharing economy is supposed to fail. It must fail.