Lecture 1: A Walk-through of the Mammalian Visual System
ฝัง
- เผยแพร่เมื่อ 6 ส.ค. 2012
- From the retina to the superior colliculus, the lateral geniculate nucleus into primary visual cortex and beyond, R. Clay Reid gives a tour of the mammalian visual system highlighting the Nobel-prize winning discoveries of Hubel & Wiesel. This is the first lecture of a 12-part series entitled Coding & Vision 101, produced by the Allen Institute for Brain Science as an educational resource for the community.
*Inofficial Outline*
[38:26] TL;DR summary!
[00:00] Organisatorial
[01:23] 12 Lecture series overview
[01:59] What made Clay Reid study the cortex?
[02:21] Listening to the signal of a neuron
- Individual neurons apparently serve functional pattern recognition
- Some neurons specialize on contrast, direction, movement, ...
- How does the brain code its meaning and communicate?
- 1920-1950 sufficiently good amplifiers were constructed to listen to neurons accurately
[06:43] History of brain/connectome studies
- year 1023 AD: first recorded diagram of the brain by ibn al-Haytham (Alhazen)
- year 1902 AD: foundation of neuroscience, (22:09) drawing stained neurons and their information flow by Santiago Ramón y Cajal
[10:37] Modern (simplified) diagram of the brain / visual cortex
[12:46] Retinal layout / photoreceptors / bipolar cells / ganglion cells
- The photosensitive layer of the retina is covered by the processing layer
- This works because neuronal tissue is quite transparent, especially to low freqency light
[17:58] Hubel & Wiesel (1959, 1962) Discovering directional perception in the cortex
[21:16] Key question: how/what do neurons compute?
[28:32] functional categories / Receptive field definition (by Hartline, 1938)
[32:03] Abstrac layout of the primary visual cortex
[33:31] Optogenetics: Watching the brain in action
[35:59] Grandmother neuron?
[38:26] TL;DR summary!
[39:39] Optogenetics: Channel-Rhodopsins, Stimulating cortical neurons with light
[44:28] Q&A: Why is direction computed twice, both in the retina and in the cortex?
[44:04] Q&A: Answer: The spatial receptive field of directionally selective neuons in the cortex is smaller/bigger than their retinal analogon
[47:10] Q&A: Do retinal cells compute more than just direction?
[47:27] Q&A: Answer: yes!, 28 amacrine cell classes, communicating with photoreceptors, relay neurons, horizontal neurons, ganglion cells
[48:32] Q&A: How do know for sure that grandmother neurons do not code anything else?
[49:18] Q&A: Answer: there is controversy about distributed coding vs grandmother neuons, it's probably both
[51:12] Q&A: Do the directional selective neurons @[33:31] receive the same input?
[51:47] Q&A: Answer: Neurons doing different things might receive the same input?
[51:25] Q&A: Can state of the neuronal system be derived from the timing of the signals?
[52:30] Q&A: Answer: Yes, but the optical experiment captured at around one frame per second. Today this would be orders of magnitudes faster. Electric measurements are still more precise, as of today.
[53:51] Q&A: In the optical experiment we were looking near the brain surface?
[54:36] Q&A: Yes. The cortex is only around 1mm deep. We can look already into "layer 2 3" and beyond. Optically capturing data on layer 6 activity might be possible as well in the near future.
This very nice lecture presents excellent visual material and gives a good historical context, explaining the path of modern neuroscience.
very good explanation. very good material. very good presentation. THANK YOU for your preparation and effort!
This is gold.Thanks ...
Thank you for this great lecture.
Really appreciate your work!
Great lectures.
Thanks for this, very very much
Thanks.
was the pupil of the experimented cat kept still during the experiment?
Great lecture, but I have a comment about the reference to Greek philosophers. I don't think the idea of the brain as the central organ of thought was that big around/after the Socratic revolution. Most of the notions of thinking involved it being distributed throughout different parts of the body (e.g., thumos being in the gut).
Everything else was dope though!
There are for example more neurotransmitters in the stomach than the brain.
Very beautiful sweet sir Tq so much
Gyger counter ?? How did you discover the frequency of a neuron ("noise")
Measure stimulating the neurons in different areas and record differences
Never ever not in my mind imagination that happening unless and until in the appropriate scientific settings ect
red light
Wait, are these few crumbs of evidence all that neuroscience has to explain visual processing in the brain? I know this is from 10 years ago, but can't find anything more up to date? Why is this guy presenting as if these few disparate pieces of evidence represent some type of actual flushed out explanation of how the brain works?