-- itt elég későn kezdtem el jegyzetelni -- Oszlopok kimutatása a majom látókérgében tracking visual pathway and detecting columns by injecting dye to thalamic cells Szemidominancia ozslopok a majom és ember látókérgében human equivalent exists to monkey visual cortex pattern (yellow and blue patches) Citokróm-oxidáz oszlopok... You cannot detect column-sensitive cells in 70's it turned out that there is an enzyme that aggregates in a bloby manner (citokróm-oxidáz oszlop=blob) A Magno and Parvo pályák agykérgi kapcsolatai color is in blobs V1 is layer dependent, V2 is not, but columnar in V3 visual input is further processed to detect higher level objects dorsal: top of the brain (green in picture), ventral: sides of brain (pink) V4 is responsible for high level detection as well e.g. faces that are not turned to us directly -- itt most sok kimaradt -- A látókéreg primer input alapvető tulajdonsága: antagonisztikus "center-surround" szerkezet receptive field type: it is divided to central and periferial areas A receptív mező tulajdonságok drasztikusan változnak a látókéregben Experiment: start to sweep with a bar before the eye > Firing pattern in thalamus is independent from direction of the bar >> the receptive field is circularly symmetric > Firing pattern in visual cortex is highly dependent on orientatio A "simple" típusú receptív mező kialakulásának elmélete az elsődleges látókéregben Orientation is extremely important Thalamo-cortical (TC) relay cells project to a "simple" cells > the on-center fields TC cells are aligned to each other along the directions they code together > the "simple" cell that is innervated by them are thus orientation-selective A "complex" típusú erceptív mező kialakulása az elsődleges látókéregben ... A látókérdi receptív mezők szerkezete a Gábor funkció segítségével modellezhető A valóságban nincsenek éles határok In the receptive field there are also no sharp edges > it is rather a Gaussian distribution in firing pattern Gábor function is very simple, can be easily computed by computers, and it can be 100% controlled by parameters Other usage: construct, generate stimuli to investigate visual system > there is no noise or junk, the response is very clear for that stimuli Simple Cell receptive fields: Spatial frequency diagram for with simplified stimuli First figure: small receptive fields does not response well to stimulus, but larger receptive fields does Second figure in first row: here small fields responds better Third row: phase if also effecting whether fields responds well or not Contrast and orientation also metters Az orientáció szelektivitás kialakulásának mechanizmusa I: FEED-FORWARD model there are debates whether the feed-forward (FF) or feed-back (FB) model is more descriptive Predikció: align electrodes > projects output from one to other Subfield of thalamic cells correspond to input in case of 23 cells, but not for n=51 > it is evidence of FF On the right: We measure thalamic input > it corresponds to receptive fields, but just in the direction of cells Kontraszt invariancia: Evidences against FF modell lower the constrast of signal > thalamic cells fires with less intensity Kontraszt invariancia: quantitative model A: preferred and non-preferred cells - does not change within cells ... Az orientáció szelektivitás kialakulásának mechanizmusa I: FEED-BACK model injecting inhibition to inhibitory cells: cells loses their orientation-preference Alapvető sajátságok: general concept is: FB concept says that cortex processes information - FF concept states opposite intracortical mechanism > there is a difference between cortical inhibition and net cortical activity > narrow excitatory input the larger variety can be generated by inhibition, the narrower the excition will be Az orientáció szelektivitás kialakításának alternatív modeljei: offset: mixture of models Az agykéreg globális architektúrája: cortex is not uniform at all studying can be done by staining Látókérgi idejsegtípusok osztályzása: Two big categories