chapter 10 Flashcards
what are Neurons in the Visual System
Neural processing in the visual system leads to perception, with parallel pathways originating in the retina, progressing through the lateral geniculate nucleus (LGN), primary visual cortex, and higher-order visual areas
what is The Retinofugal Projection
The optic nerve, optic chiasm, and optic tract are involved in conveying visual information from the eyes to the brain. Ganglion cell axons from the nasal retina cross, while temporal retinal axons stay ipsilateral, resulting in specific visual deficits from lesions in this pathway.
what is The Lateral Geniculate Nucleus (LGN)
The LGN receives inputs segregated by eye and ganglion cell type, with magnocellular and parvocellular cells exhibiting different receptive field properties. It also receives inputs from the primary visual cortex and brainstem neurons.
what is the Anatomy of the Striate Cortex
exhibits retinotopy and laminar organization, with different layers receiving inputs from different types of LGN neurons. Ocular dominance columns are present, and outputs from the striate cortex project to other cortical areas, the superior colliculus, and the LGN
what is the Physiology of the Striate Cortex
contains neurons with monocular and binocular receptive fields, exhibiting properties such as orientation and direction selectivity. Cortical modules analyze various aspects of the visual field, and parallel pathways like the magnocellular, koniocellular, and parvocellular pathways are involved in visual processing.
what is Beyond Striate Cortex
The dorsal and ventral streams process visual information for different functions. The dorsal stream is involved in visual motion analysis and action control, while the ventral stream is responsible for visual perception and object recognition.
Define neural processing in the visual system and its relationship to perception.
Neural processing in the visual system refers to the series of steps by which visual information is received, transmitted, and interpreted by the brain. This process ultimately leads to perception, allowing individuals to understand and interpret the visual world around them.
Explain the significance of parallel pathways in visual processing.
Parallel pathways in the visual system refer to the multiple streams of visual information processing that occur simultaneously. These pathways serve different functions, such as analyzing visual motion and controlling action (dorsal stream) or perceiving the visual world and recognizing objects (ventral stream).
Describe the components involved in the retinofugal projection.
The retinofugal projection involves the transmission of visual information from the retina to various brain regions. It includes components such as the optic nerve, optic chiasm (where nasal retinal fibers decussate), and optic tract. Ganglion cell axons from the nasal retina cross over at the optic chiasm, while temporal retinal axons remain ipsilateral.
What are the visual deficits that can occur from lesions in the retinofugal projection?
Lesions in the retinofugal projection can result in specific visual deficits, depending on the location of the lesion. For example, damage to the optic nerve can lead to partial or complete blindness in the corresponding eye, while damage to the optic tract can result in visual field defects in the contralateral visual field.
How are inputs to the LGN segregated? Describe the receptive field properties of magnocellular and parvocellular cells in the LGN.
Inputs to the LGN are segregated by eye and ganglion cell type. Magnocellular LGN neurons have large, monocular receptive fields with transient responses, while parvocellular LGN cells have small, monocular receptive fields with sustained responses.
Discuss the nonretinal inputs to the LGN and their influence on neuronal activity.
Nonretinal inputs to the LGN include synaptic inputs from the primary visual cortex, which provide 80% of the synaptic input to the LGN. Brainstem neurons also provide modulatory influence on LGN neuronal activity, accounting for the remaining 20% of inputs.
Explain the concept of retinotopy in the striate cortex.
Retinotopy in the striate cortex refers to the orderly mapping of the visual field onto the cortical surface. This mapping ensures that adjacent points in visual space are represented by adjacent neurons in the striate cortex. The central visual field is overrepresented in the striate cortex, while the peripheral visual field is underrepresented.
What is the significance of ocular dominance columns in the striate cortex?
Ocular dominance columns in the striate cortex are columns of neurons that respond preferentially to input from one eye. These columns alternate between inputs from the left and right eyes, facilitating binocular vision and depth perception.
Differentiate between monocular and binocular receptive fields in the striate cortex.
Monocular receptive fields in the striate cortex are similar to those observed in the LGN, with center-surround organization and sensitivity to contrast and wavelength of light. Binocular receptive fields exhibit properties such as orientation selectivity, direction selectivity, and binocularity.
