Volume and neuron number of the lateral geniculate nucleus in schizophrenia and mood disorders
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Parvocellular cell
Lateral geniculate nucleus
Magnocellular cell
1. Visual abilities decline during normal aging, and many of these declines are due to neural changes in the retina or central visual pathways. We have begun studies of the primate visual system to investigate the location and nature of these changes as well as to answer general questions about the effects of aging on neural function. We began with the dorsal lateral geniculate nucleus (LGN) because it is the main structure through which visual information passes on the way to cortex and because the parallel parvocellular and magnocellular pathways, which may be affected differently by aging, are anatomically distinct there. 2. Single -cell recordings were made in the LGN of young adult (5–16 yr) and old (25–28 yr) rhesus monkeys. We made quantitative measures of a wide variety of response properties for a large number of parvocellular (n = 257) and magnocellular (n = 113) neurons in the two groups of animals. As a result, in addition to studying the effects of aging, we were able to make quantitative comparisons between parvocellular and magnocellular neurons using larger samples than have been studied previously and for some properties that have not been studied before. 3. We found that magnocellular neurons have significantly higher maximal response rates and signal -to -noise ratios than parvocellular neurons. However, response latencies to visual stimulation were similar for neurons in the two types of layers. In agreement with previous studies, magnocellular neurons had higher maximal contrast sensitivity and higher contrast gain than parvocellular neurons. However, the sensitivity difference occurred because nearly all of the neurons with low sensitivities (< 10) were in the parvocellular layers, not because neurons in the magnocellular layers had the highest sensitivities. 4. Neurons with the smallest receptive-field centers, the highest spatial-frequency resolutions, and the highest optimal spatial frequencies were found in the parvocellular layers. However, the overall distributions of each of these properties overlapped substantially for neurons in the two types of layers, and the mean values were not significantly different. The mean high temporal-frequency cutoff was significantly higher for magnocellular than parvocellular neurons, but the difference was small (only 3 Hz), and it occurred because many parvocellular neurons had lower cutoffs than any seen in the magnocellular layers, not because magnocellular neurons had the highest temporal-frequency cutoffs. Parvocellular neurons also had narrower temporal-frequency tuning than magnocellular neurons. However, there was no significant difference in optimal temporal frequency.(ABSTRACT TRUNCATED AT 400 WORDS)
Parvocellular cell
Lateral geniculate nucleus
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Geniculate
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Parvocellular cell
Magnocellular cell
Lateral geniculate nucleus
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Lateral geniculate nucleus
Neurofilament
Magnocellular cell
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Parvocellular cell
Magnocellular cell
Lateral geniculate nucleus
Geniculate
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Abstract Five lagged cells were recognized by extracellular recording in the lateral geniculate nucleus of an awake, behaving macaque monkey. Previous reports of lagged cells were all in the anesthetized cat. Both parvocellular and magnocellular lagged cells were observed. Response timing was distributed continuously across the population, and both sustained and transient responses were seen in the magnocellular subpopulation. Cortex thus receives signals with a wide range of timing, which can mediate direction selectivity across multiple dimensions.
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As a basis for studies of the histologic effect of visual deprivation, cell section areas were determined in all six laminae from the anterior, central, and posterior regions of both lateral geniculate nuclei (LGN) from a normal macaque monkey. No significant cell size variations existed between the right and left LGN's, between the contiguous parvocellular and magnocellular laminae of the same LGN, and between parvocellular sizes in varous regions of the LGN's. In the magnocellular laminae, cell section areas increased in an anteroposterior direction.
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1. This study investigated the functional specificity of the lateral geniculate mucleus (LGN) of the rhesus monkey using microelectrode-recording techniques. 2. The parvocellular laminae of the LGN receive input predominantly from medium-conduction-velocity optic tract fibers, while the magnocellular laminae receive fast-conducting axons from the retina. 3. Cells projecting from the parvocellular layers to area 17 have medium-conduction velocities, while those from the magnocellular layers are fast conducting. 4. The majority of cells in the parvocellular layers have a concentric color-opponent receptive-field organization. The receptive fields of magnocellular layers cells are also concentrically organized, but their center-surround organization is independent of wavelength. 5. Responses in the parvocellular layers are more sustained than in the magnocellular layers. 6. Cells in the dorsal pair of parvocellular layers are predominantly on-center. In the ventral pair of parvocellular layers, most cells are off-center. 7. Blue-selective cells are found predominantly in the ventral pair of parvocellular layers. All of these found gave on-responses to blue stimuli.
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Parvocellular cell
Lateral geniculate nucleus
Magnocellular cell
Geniculate
Stereology
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We tested color and contrast sensitivity in the magnocellular and parvocellular subdivisions of the lateral geniculate body and in layers 2, 3, 4B, and 4C alpha of visual area 1 to obtain physiological data on the degree of segregation of the 2 pathways and on the fate of the color and contrast information as it is transmitted from the geniculate to the cortex. On average, magnocellular geniculate cells were much less responsive than parvocellular cells to shifts between 2 equiluminant colors. Nevertheless, many magnocellular cells (though not all) continued to give some response at equiluminance. As expected from previous studies, luminance contrast sensitivity differed markedly between magnocellular and parvocellular layers. In V-1, the properties of cells in the magnorecipient layers 4C alpha and 4B faithfully reflected the properties of magnocellular geniculate cells, showing no evidence of any parvocellular input. Like magnocellular geniculate cells, they showed high contrast sensitivity, and with color contrast stimuli they showed large response decrements at equiluminance. In the interblob regions of cortical layers 2 and 3, which anatomically appear to receive most of their inputs from parvorecipient layer 4C beta, contrast sensitivities of some of the cells were compatible with a predominantly parvocellular input. Other interblob cells had sensitivities intermediate between magno- and parvocellular geniculate cells, suggesting a possible contribution from the magnocellular system. Many cells in cortical layers 2 and 3 responded to color- contrast borders equally well at all relative brightnesses of the 2 colors, including equiluminance. We recorded from many direction- and disparity-selective cells in V-1: most of the direction-selective and all of the clearly stereo-selective cells were located in layer 4B.
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Lateral geniculate nucleus
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Parvocellular cell
Lateral geniculate nucleus
Magnocellular cell
Geniculate
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