Flashcards
Visual processing
Cards in this deck (13)
- 1optical chiasmFibres from nasal halves decussate at optical chiasm and terminate in contralateral visual centres
- 2lateral geniculate nucleus (LGN)- excitatory synapses release glutamate
- 6 layers:
layer 1-2: -> magno cellular pathway (rods)
-> alpha cells (coarse structure & movement)
layer 3-4: -> parvo cellular pathway
(cones)
-> beta cells (fine details, color vision)
nasal contralateral branch: layers 1,4,6
temporal ipsilateral branch: 2,3,5 - 3filtering of sensory signals- via GABAergic interneurons which project back from layer 6 of V1
- attentive state: exhibit regular spiking activity
- sleepy state: switch into rhythmic burst mode
-> - calcium channels open in response to ipsp and elicit slow depolarization
- threshold is reached, voltage-gated sodium channels open and ignite
burst
- accumulation of calcium finally terminates firing by opening
potassium channels - 4primary visual cortex- 6 cellular layers
- LGN targets to stellate cells in layer 4
-> transfers via pyramidal cells to layer 5 and 6, which feedback to LGN
- most sensitive to bars in different directions - 5simple cells- overlapping receptive fields of stellate cells from layer 4 converge in a target neuron -> linearly aligned on retina
- summation of epsps
- end-inhibition allows discrimination of bar length via feedback inhibition by
pyramidal cells from layer 6 projecting back via GABAergic interneurons - 6complex cells- larger receptive fields
- response characteristics based on innervation pattern they receive from simple cells
- also respond best to borders of different orientations
- independent of simple cell visual fields: edge detection, geometric forms, moving
lines - 7what-pathway- temporal lobe
• object recognition and visual memory
• visual recognition of faces (prosopagnosia) - 8where-pathway-parietal lobe
- depth perception, motion detection, spatial constancy of the visual field
- multisensory integration (hearing, vision, somatic)
- space perception (visual hemineglect) - 9Magnocellular pathway- α-retinal ganglion cells-periphery
• layers 1-2 in the lateral geniculate nucleus
• interblobs in layers 2+3 of the primary visual cortex
• visual field V5 (motion detection) - 10Parvocellular pathway• β-retinal ganglion cells-fovea
• layers 3-6 in the lateral geniculate nucleus
• blobs in layers 2/3 of the primary visual cortex
• visual field V4 (colour vision) - 11Visual cortex (monkey)• V2: subjective shape recognition
• V4: colour vision
• V5: motion detection
• Binding: neurons in V4 and V5 fire synchronously and therefore we perceive e.g. a moving
object in a comprehensive fashion - 12oscular domiance columns- are oriented orthogonally to the orientation columns in visual cortex
- alternately connected to left and right eye
- important for stereoptic vision - 13blobs- agglomerations of cytochrome oxidase
- in layers 2, 3
-> color-sensitive target neurons are grouped together
- parvocellular pathway targeted in blobs
- magnocellular pathway in interblobs
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- Bachelor Sensory Physiology Flashcards on Visual processing, created by Valerie M on 15/06/2016.
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- Valerie M
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