Central projections of cat retinal ganglion cells

Abstract

The central projections of different groups of cat retinal ganglion cells were studied following small iontophoretic injections of horseradish peroxidase (HRP) into physiologically characterized sites. Analysis was restricted to labeled cells in the upper periphery of the nasal retina, contralateral to the injection site. Injections were made to the A lamina and C lamina of the dorsal lateral geniculate nucleus (LGNd-A,C), the geniculate wing (LGNd-W), the ventral lateral geniculate nucleus (LGNv), the pretectum (PT), and the superior colliculus (SC). The dendritic fields of alpha, beta, and epsilon cells were well labeled by the procedures we employed. A group, termed "g1," had somal sizes within the range of the smaller beta and epsilon cells, but dendritic morphologies distinct from either class. The g1 group may consist of a number of types, but our material provided no basis for further distinguishing them. Many cells were observed that had smaller somas; all had thin axons, and few had dendritic fields that labeled to any significant extent. We were not able to further distinguish these cells, and refer to this group, which may include a number of types, as "g2" cells. From the peripheral nasal retina, alpha cells project to LGNd-A, LGNd-C, PT, and SC. Beta cells project to LGNd-A, LGNd-C, and PT. Epsilon and g1 cells project to the LGNd-C, LGNd-W, LGNv, PT, and SC. We determined the total spatial density of cells in the region of the retina analyzed, using a Nissl-stained preparation. We then estimated the relative fraction of cells in each of the above groupings by injecting HRP throughout a cross section of the optic tract. Multiplying this relative fraction by the total spatial density gave an estimate of the spatial density of each of these groupings. From the spatial density of cells labeled from the injection site, we were able to estimate the fraction of cells of each retinal grouping that project to each of the zones investigated. By these calculations, almost all alpha cells from the upper nasal retina project to LGNd-A and LGNd-C; most project to SC, and about a third to PT. Beta cells, by contrast, project almost exclusively to LGNd-A, with about 10% going to LGNd-C, and about 1% to the PT. The great majority of epsilon cells, if not all, project to LGNd-W, and up to half of this population also project to the other zones noted above.(ABSTRACT TRUNCATED AT 400 WORDS)

The role of spatial frequency information for ERP components sensitive to faces and emotional facial expression

“…Selective activation from LSF stimuli is consistent with anatomical evidence that these brain areas receive substantial magnocellular inputs [9,42,61], possibly as part of a phylogenetically old route specialised for the rapid processing of fear-related stimuli [21,41,50,56,59].…”

Learning to see the trees before the forest: Reversible deactivation of the superior colliculus during learning of local and global visual features

“…Neither of these types of ganglion cells is responsible for high-acuity vision, which would seem to be essential for the discrimination of local visual features (30). Higher-acuity vision is associated with beta ganglion cells (31,32), which project exclusively to the lateral geniculate nucleus (27,28). Therefore, the anatomical and physiological characteristics of the midbrain pathway support the finding that global, but not local, feature processing is disrupted by bilateral deactivation of the SC.…”

“…This view is supported by the types of visual signals that are transmitted through the midbrain, en route to the extrageniculate thalamus and extrastriate cortex. Alpha and gamma-type retinal ganglion cells provide the dominant, if not the only, retinal input to the superficial layers of the SC (25)(26)(27)(28)(29). Neither of these types of ganglion cells is responsible for high-acuity vision, which would seem to be essential for the discrimination of local visual features (30).…”

Enhanced extrastriate visual response to bandpass spatial frequency filtered fearful faces: Time course and topographic evoked‐potentials mapping

“…Furthermore, LSF fearful faces, relative to LSF neutral faces, can also produce a greater activation of fusiform cortex [Winston et al, 2003], as previously found for broadband images [Morris et al, 1998;Vuilleumier et al, 2001], whereas no such effect was found for HSF fearful faces, suggesting that an enhanced response in visual cortex for fearful expressions might also be primarily driven by LSF cues. Importantly, neurophysiological data indicate that LSF visual information is mainly carried by magnocellular channels, projecting to the dorsal parietal stream and subcortical structures more than to the ventral temporal stream [Leventhal et al, 1985], and is processed faster than HSF information transmitted by parvocellular pathways to the ventral stream [Bar, 2003;Bullier, 2001;Merigan and Maunsell, 1993]. Taken together, these results raise the hypothesis that LSF components in fearful face expressions might benefit from rapid processing and early access to the amygdala, either through a direct subcortical pathway involving visual pulvinar [Morris et al, 1999;Vuilleumier et al, 2003] or through an initial feedforward sweep of inputs within the visual system [Bullier, 2001;Foxe and Simpson, 2002], allowing a rapid enhancement of ventral temporal activations for fearful stimuli through extensive feedback projections from the amygdala to posterior brain areas [Amaral et al, 2003;Morris et al, 1998;Vuilleumier et al, 2001.…”