Visual System - Stanford - Exam 1 Flashcards
A cell with a center-surround antagonistic receptive field responds in one manner when the center of its receptive field (RF) is ___ and in the opposite manner when the surrounding area is illuminated.
Remember, a cell with a center-surround antagonistic receptive field responds in one manner when the center of its receptive field (RF) is illuminated and in the opposite manner when the surrounding area is illuminated.
In addition to contrast, the visual environment has many other features that convey information about its content. For example, the orientation of contrast borders is a critical element for our ability to distinguish form or shape. Furthermore, in the real world, images are not black and white, but in color. In addition, the real world is a dynamic place where things are often in motion. Thus, for every region of visual space multiple neural representations must be present in order to encode the different types of visual information. Because vision is a multifaceted experience, beginning in retina itself, the visual system consists of subsystems specialized to process different aspects of visual information. of retinal ganglion cells.
The essential features of the ____and ___ ganglion cells are:
___ cells: large receptive fields, fast-adapting transient responses, good for detecting motion, sum inputs from all cone types (color insensitive).
____cells: (a) small receptive fields, slow adapting, sustained responses (fine form, texture), some color sensitivity, specialized for analyzing stationary objects in detail; (b) color-opponent receptive fields - color vision *
Within the _____ pathway, fine form (a) and color vision (b) are segregated into subchannels. As we’ll see, each region of visual space is represented in both the magnocellular and parvocellular pathways and these pathways remain anatomically segregated throughout the retinogeniculocortical pathway.
In addition to contrast, the visual environment has many other features that convey information about its content. For example, the orientation of contrast borders is a critical element for our ability to distinguish form or shape. Furthermore, in the real world, images are not black and white, but in color. In addition, the real world is a dynamic place where things are often in motion. Thus, for every region of visual space multiple neural representations must be present in order to encode the different types of visual information. Because vision is a multifaceted experience, beginning in retina itself, the visual system consists of subsystems specialized to process different aspects of visual information. of retinal ganglion cells.
The essential features of the magnocellular (M) and parvocellular (P) ganglion cells are:
M-ganglion cells: large receptive fields, fast-adapting transient responses, good for detecting motion, sum inputs from all cone types (color insensitive).
P-ganglion cells: (a) small receptive fields, slow adapting, sustained responses (fine form, texture), some color sensitivity, specialized for analyzing stationary objects in detail; (b) color-opponent receptive fields - color vision *
Within the parvocellular pathway, fine form (a) and color vision (b) are segregated into subchannels. As we’ll see, each region of visual space is represented in both the magnocellular and parvocellular pathways and these pathways remain anatomically segregated throughout the retinogeniculocortical pathway.
This schematic summarizes the ascending visual pathways from retina to primary visual cortex. The axons of the retinal ganglion cells exit the retina and form the__ __. The optic nerve partially decussates (crosses) in the__ __ to form the__ ___.
The primary termination site of retinal ganglion cells is the ____ ____ ____ of the thalamus.
Axons of LGN cells form the optic (or visual) radiations and project to ___ ___ ___ located both above and below the ____ fissure.
A subset of retinal projections go to midbrain structures, the___ and the__ ___.
This schematic summarizes the ascending visual pathways from retina to primary visual cortex. The axons of the retinal ganglion cells exit the retina and form the optic nerve. The optic nerve partially decussates (crosses) in the optic chiasm to form the optic tract.
The primary termination site of retinal ganglion cells is the lateral geniculate nucleus (LGN) of the thalamus.
Axons of LGN cells form the optic (or visual) radiations and project to primary visual cortex located both above and below the calcarine fissure.
A subset of retinal projections (See magnified view) go to midbrain structures, the pretectum and the superior colliculus.
This slide shows that visual space is represented _____ in the brain.
In other words, cells in LGN and visual cortex of the ____ side of the brain represent the ____ half of visual space and vice versa.
Underlying this organization is the partial _____ of ganglion cell axons in the__ ___.
Axons from ganglion cells in the ____ hemi-retina, which receive light from ____ visual space, cross in the optic chaism to reach the _____ LGN.
Conversely, ganglion cells in the ____ hemi-retina, which receive light from contralateral space do not cross, but instead project to the LGN of the ____side.
Although each LGN receives input from both retinas, input from the contralateral and ipsilateral retina remains segregated. Contralateral retina projects to layers ___ (magno), __ & ___ (parvo), whereas the ipsilateral retina projects to layers __ (magno), ___ & ___ (parvo).
As we’ll see (below), this segregation is maintained via the ocular dominance columns of primary visual cortex.
This slide shows that visual space is represented contralaterally in the brain. In other words, cells in LGN and visual cortex of the right side of the brain represent the left half of visual space and vice versa. Underlying this organization is the partial decussation of ganglion cell axons in the optic chiasm. Axons from ganglion cells in the nasal hemi-retina, which receive light from ipsilateral visual space, cross in the optic chaism to reach the contralateral LGN. Conversely, ganglion cells in the temporal hemi-retina, which receive light from contralateral space do not cross, but instead project to the LGN of the same side.
Although each LGN receives input from both retinas, input from the contralateral and ipsilateral retina remains segregated. Contralateral retina projects to layers 1 (magno), 4 & 6 (parvo), whereas the ipsilateral retina projects to layers 2 (magno), 3 & 5 (parvo). As we’ll see (below), this segregation is maintained via the ocular dominance columns of primary visual cortex.
___ ____ - the part of the optic radiations that bulges laterally into temporal cortex. These fibers course around the inferior horn of the lateral ventricle and carry information deriving from the inferior temporal retina of the ipsilateral eye (uncrossed retinal projection) and from the inferior nasal retina of the contralateral eye (crossed retinal projection) and thus represent the superior quadrant of contralateral space.
Meyer’s loop - the part of the optic radiations that bulges laterally into temporal cortex. These fibers course around the inferior horn of the lateral ventricle and carry information deriving from the inferior temporal retina of the ipsilateral eye (uncrossed retinal projection) and from the inferior nasal retina of the contralateral eye (crossed retinal projection) and thus represent the superior quadrant of contralateral space.
