Chapter 10: The Central Visual System Flashcards
() results in perception.
Neural processing
Pathway serving conscious visual perception originates in the ().
retina
Information received by the retina is actually formed as action potential in the ()
retinal ganglion cells (RGC)
RGC axons pass through (3)
- Optic nerve
- Optic chiasm
- Optic tract
optic tract leads to ()
lateral geniculate nucleus (LGN)
Ganglion cell axons from nasal retina cross in () (partial decussation).
optic chiasm
() – all the information from one side
Hemifield
Each optic nerve has 2 parts, each connected to 2 parts of retina: () -> allows each eye to see a part of opposite eye’s hemifield
nasal and temporal
() – in both hemifields; intersection of hemifields that can be perceived by BOTH eyes
Binocular region
Objects in the binocular region of the left visual hemifield will be imaged on the (1) retina of the left eye and on the (2) retina of the right eye
- nasal
- temporal
all info about the left hemifield is directed to the () side of the brain
right
after the partial decussations in the optic chiasm, info from one side of the binocular field (from both hemifields) is merged in each ()
LGN (transmission given to LGN via synaptic transmission)
() – from outside to other part of brain (outside of retina)
Retinofugal
Cutting of () - blindness in left hemifield (not including binocular field)
left optic nerve
Cutting of () – complete blindness to the right side -> signals from right hemifield are not brought to visual cortex
left optic tract
Transection of () – outside of vision field is blinded -> no peripheral vision
optic chiasm
nonthalamic targets of the optic tract: () - role in biological rhythms, including sleep and wakefulness
hypothalamus
Nonthalamic Targets of the Optic Tract: () in the midbrain - control size of the pupil, certain types of eye movement
Pretectum
Nonthalamic Targets of the Optic Tract: () in the midbrain - orients the eyes in response to new stimuli—move fovea to objects of interest
Superior colliculus
In the right LGN, the right eye (ipsilateral) axons synapse on LGN cells in layers (1); the left eye (contralateral) axons synapse on cells in layers (2).
- 2,3, and 5
- 1, 4, and 6
in the LGN, () are between numbered layers
K layers
Receptive fields of LGN neurons: almost identical to the () that feed them
ganglion cells
() LGN neurons: large center-surround receptive fields with transient response
Magnocellular
() LGN cells: small center-surround receptive fields with sustained response
Parvocellular
Within all layers of the LGN, the neurons are activated by (1) and ON-center and OFF-center cells are (2)
- only one eye
- intermixed
() provides 80% of the synaptic input to the LGN—role not clearly identified.
Primary visual cortex
() provide modulatory influence on neuronal activity
Brain stem neurons
other names of the primary visual cortex
- V1
- area 17
- striate cortex
Map of the visual field onto a target structure (seen in retina, LGN, superior colliculus, striate cortex)
retinotopy
Central visual field (fovea) overrepresented in map (retinotopy) because ()
there are many more neurons in the V1 that receive input from the central retina than from the peripheral retina
laminations of the striate cortex
layers I to VI
spiny stellate cells in the striate cortex have (1), and are found in (2)
- spine-covered dendrites
- layer IVC
pyramidal cells in the striate cortex are characterized by (1), and are found in (2)
- spines and thick apical dendrites
- layers III, IVB, V, VI
() in the striate cortex lack spines and are found in all cortical layers -> form local connections
inhibitory neurons
() typically send info to other parts of brain (can do this bc they have long axons/dendrites)
Pyramidal cells
magnocellular LGN neurons project primarily to layer (1), which projects to cells in layer (2)
- IVC-alpha
- 4b
parvocellular LGN neurons project to layer (1), which projects to cells in (2)
- IVC-beta
- layer 3
() LGN axons make synapses primarily in layers I and III
koniocellular
pattern for intracortical connection where in the retinotopic organization established in layer 4 is maintained
radial connections
Interconnections between different radial columns via collateral branches in layer 3 pyramidal neurons
horizontal connections
Hubel and Wiesel injected () into one eye in their experiment
radioactive proline
Hubel and Wiesel’s experiment revealed the action and presence of () -> some neurons are dominated by 1 eye
ocular dominance columns
Ocular dominance column shows () -> receptive field can be dramatically changed
dramatic plasticity
mitochondrial enzyme used for cell metabolism
Cytochrome oxidase
(1): pillars of cytochrome oxidase-rich neurons in V1; usually centered on an ocular dominance column in ()
- Blobs
- layer IV
Multiple center-surround cells generate a () receptive field -> only when many of the cells are stimulated are the upper layer (simple) cells fired
“bar-type”
cells in layer IVC of the striate cortex are similar to ()
LGN celss
cells in layer IVC-alpha of the striate cortex are insensitive to ()
wavelength
cells in layer IVC-beta of the striate cortex have ()
center-surround color opponency
Most neurons in striate cortex layers superficial to IVC are ().
binocular
Most of receptive fields in the retina, LGN and layer IVC are ().
circular
Outside of layer IVC, many neurons in V1 respond best to an ().
elongated bar of light
describe orientation selectivity in striate cortex neurons
responsiveness of neurons (rate of AP firing) is maximum when the object being perceived is in a preferred orientation
Preferred orientation progressively ()
shifts across the layer IVC
() responds to different orientation of bar stimulations
Orientation column
Neuron fires action potentials in ()-dependent response to moving bar of light.
direction
A subset of the orientation-selective cells in V1 shows () -> specialized for the analysis of object motion
direction selectivity
Receptive Field of (): binocular, orientation-selective, elongated ON or OFF area flanked with antagonistic surround
Simple cells
Receptive field may be composed of several LGN inputs from cells with ().
aligned center-surround receptive fields
Receptive Fields of (): binocular, orientation-selective, ON and OFF responses to the bar of light, no distinct ON and OFF regions
Complex cells
Each module capable of analyzing every aspect of a portion of the visual field
cortical modules
beyond the striate cortex: Analysis of visual motion and the visual control of action
dorsal stream
beyond the striate cortex: Perception of the visual world and the recognition of objects
ventral stream
localized below the temporal lobe; highly activated when we see a face and try to recognize it
fusiform face area (FFA)
neurological disorder characterized by the inability to recognize faces.
prosopagnosia
