sensory receptors transduce
environmental energy to neural energy
retina
light sensitive surface at the back of the eye, consists of photoreceptors and neurons
fovea
densely packed region of photoreceptors at the center of the retina
papilledema
a swollen disk that occurs because that optic nerve is surrounded by cerebral spinal fluid
optic neuritis
inflammation of the optic nerve and another cause of papilledema
first layer of retinal neurons
bipolar
horizontal
amacrine
second layer of retinal neurons
RGCs
magnocellular cells
parvocellular cells
m cells
receive input from rods and sensitive to light not color and moving stimuli
p cells
receive input from cones, sensitive to color and difference in form and color
muller cells (glial cells)
span the retinal inner membrane from front to back
act as optical fibers, channeling light to the buried photoreceptors
melanopsin
a light sensitive protein
the nasal retina
medial path of each retina crosses the opposite side
the temporal path
the lateral path of each retina that travels back to the same side
geniculostriate system
all the p and some of the m ganglion axons
goes from the retina to the lateral geniculate nucleus (LGN) of the thalamus the layer IV of the primary visual cortex (striate (striped) cortex)
tectopulvinar system
formed by the remaining m cells
goes from retina to the superior colliculus sending signals to the pulvinar region of the thalamus
retinohypothalamic system
1-3% of the RGCs are photosensitive
in the tiny superchiasmatic nucleus (SCN) in the hypothalamus
layers 2,3,5 of the LGN
come from the ipsilateral eye
layers 1,4,6
come the the contralateral eye
layers 3-6 of the LGN
responsive to color
fine detail
layers 1-2
responsive to movement
occipital cortex
comprised of six visual regions
V1 (striate (primary visual) cortex)
V2-5 (extrastriata (secondary visual) cortex)
when cut horizontally and strained V1/V2 form
blobs and interblobs
neurons in blobs
take part in color perception
neurons in interblobs
take part in perception of form and motion
thick stripes
input from movement sensitive neurons
thin stripes
input from V1's color-sensitive neurons
pale zones
input from V1's form sensitive neurons
prosopagnosia
damage to regions specialized in facial recognition (fusiform face area (FFE))
principal of proper mass
the amount of neural tissue responsible for a particular function is proportional to the amount of neural processing that function requires
orientation detectors
cells that are maximally excited by bars of light oriented in a particular direction
complex cells
excited by bars of light moving in a particular direction through the visual field
hypercomplex cells
responsive to moving bars but also has a strong inhibitory area at one end of the receptive field
functional columns
cortical structure neurons are organized into this
0.5mm diameter strips of the cortex that include representative neurons and the connections
ocular dominance column
functional column in the visual cortex that is maximally responsive to information coming from the eye
neurons along the ventral stream in the temporal lobe region
excited by complex visual stimuli like faces and hands
stimulus equivalence
recognizing an object as remaining the same despite being viewed from different orientations
opponent processing
cells can be excited by red and inhibited by green
or be excited by blue and inhibited by yellow
or vise versa
homonymous hemianopia
complete cuts of the optic tract, the LGN, or cortical region V1 resulting in blindness of the entire right of left side of the visual field
scotomes
small blind spot in the visual field caused bu migraine or by small lesion of the visual cortex
nystagmus
ting, involuntary movements of the eye
visual form agnosia
an inability to recognize object, real or drawn
achromatopsia
seeing the world in black and white
optic ataxia
deficit in the visual control of reading and other movements bilateral parietal lesion
D.F (ventral stream deficit)
cannot recognize shapes
R.V. (dorsal stream deficit)
object recognition in unimpaired but chooses unstable grasping points