lecture 15 Flashcards
sensory receptors
specialized cellls that transduce sensory energy into neural activity
sensation
registration of physical stimuli from environment by sensory organs
perception
subjective interpretation of sensations by the brain
- visual experience is not an objective reproduction of what is out there: subjective contruction of reality manufactured by the brain
light
electromagnetic energy that we see
range about 400nm-700nm
structure of eye
cornea- clear outer covering
iris- opens and closes to allow more or less light in
lens- focuses light
retina- light energy initiates neural activity
retina
the light sensitive surface at the back of the eye
- consists of neurons and photoreceptor cells to translate light into APs and discriminate wavelengths
fovea
region at hte centre of the eye that is specialized for high acuity
- receptive field at the center of eyes visual field
blind spot
region of retina where axons form the optic nerve and leave the eye
- has no photoreceptors
- dont notice because your brain compensates for it
rods
sensitive to low levels of light, night vision
only one type of pigement
- more numerous than cones
cones
highly responsive to bright light, color
3 types of pigement, concentrated in the fovea
distribution of retinal receptors
more red and green than blue
types of retinal neurons
bipolar: receives input from photoreceptors
horizontal: links photoreceptor and bipolar cells
amacrine: links bipolar and ganglion cells
retinal ganglion: gives rise to optic nerve
magnocellular cells
large, receives input from rods
sensitive to light and movement
parvocellular cell
small, receives input from cones
sensitive to color
visual pathwasy
axons from nasal half cross over to contralateral
axons from temporal half remain in same side
- info from left visual field goes to right vice versa
optic chiasm
junction of the optic nerves from each eye
route 1- geniculostriate system
projections from the retina go to the LGN nucleus to the visual cortex
(LGN–> striate –> other areas)
route 2- tectopulvinar system
projections from retina to superior colliculus to pulvinar (thalamus) to parietal and temporal visual areas
(superior colliculus–> pulvinar–> other areas)
route 3- retinohypothalamic tract
synapses in tiny suprachiasmic nucleus in hypothalamus
- role in regulating circardian rhytms in pupillary reflex
lateral geniculate nucleus
right LGN- input from right half of each retina
left LGN-input from left half of each retina
LGN layers
M cells: layers 1 and 2- movement
P cells: 3 and 6- color and form
striate cortex
primary visual cortex- highly myelinated
two visual paths: one to parietal one to temporal
dorsal visual stream
projects to parietal cortex- the how pathway
- how an object is to be guided
ventral visual stream
projects to temporal cortex- the what pathway
- identifies an object
what cells are in the tectopulvinar path
magnocellular cells from retina project to S.C which sends to pulvinar
medial pulvinar: sends cxns to parietal lobe
lateral pulvinar: sneds cxns to temporal lobe
- provides info about location
- blind sight
occipital cortex
composed of 6 visual regions with varying degrees of complexity
- V1: striate cortex receives input from LGN
- V2-V5: secondary visual cortex
heterogenous layers
blob: V1- regions in the visual cortex that contain color-sensitive neurons
interblob: V1- region that seperates blobs, participates in form and motion
stripes in V1
thick: receive info from movement sensitive interblobs
thin: receive info from color sensitive blobs
pale: receive info from form sensitive interblobs
