Sources of subcortical GABAergic projections to the superior colliculus in the cat

Abstract

The goal of this study was to identify GABAergic input to the cat superior colliculus from neurons located in the caudal diencephalon, mesencephalon, pons and medulla. Cells efferent to the superior colliculus were labeled retrogradely with the tracer horseradish peroxidase, and an antibody to gamma-aminobutyric acid was used to label GABAergic neurons in the same sections. The results indicate that neurons in several distinct areas of the caudal diencephalon and brainstem are both immunocytochemically labeled for GABA and retrogradely labeled with horseradish peroxidase. These areas include zona incerta, nucleus of the posterior commissure, anterior and posterior pretectal nuclei, nucleus of the optic tract, superior colliculus, cuneiform nucleus, subcuneiform area, substantia nigra pars reticulata and pars lateralis, periparabigeminal area, external nucleus of the inferior colliculus, the area ventral to the external nucleus of the inferior colliculus, mesencephalic reticular formation, dorsal and ventral nuclei of the lateral lemniscus, and the perihypoglossal nucleus. The role that such diverse inhibitory input to the superior colliculus might play, particularly in influencing eye movements, is discussed.

Different roles for GABAA and GABAB receptors in visual processing in the rat superior colliculus

“…External sources of GABA arise from several areas including the zona incerta, substantia nigra, pretectum and contralateral SC (Araki, McGeer & McGeer, 1984;Ficalora & Mize, 1989;Appell & Behan, 1990). Of these, the projections from the substantia nigra and zona incerta are non-visual and terminate in the deeper layers of the SC and thus are GABA and vision in rat superior colliculus J. Physiol.…”

Comparison of the ultrastructure of cortical and retinal terminals in the rat superior colliculus

“…However, the superficial layers of the SC contain a wide variety of cell types, including interneurons and cells that project to the parabigeminal nucleus, contralateral SC, pretectum, ventral and dorsal lateral geniculate nuclei, and lateral posterior nucleus (for reviews, see Huerta and Harting, 1984;May, 2006). SC interneurons, tectopretectal, and tectotectal neurons have been found to be GABAergic (Appell and Behan, 1990;Mize, 1992;Schmidt et al, 2001, Baldauf et al, 2003. Thus, these cell types may be ruled out as the primary targets of area 17 terminals.…”

Effects of callosal lesions in a model of letter perception

“…Another possibility, given past experimental evidence that brainstem and thalamic regions substantially influence cortical functionality, is that hemispheric specialization and asymmetries in function (readily produced in earlier models having transcallosal inhibition, but not excitation) and the postlesion changes of cerebral diaschisis (readily produced in past models having transcallosal excitation, but not inhibition)could both be accounted for if excitatory callosal influences are complemented by a subcortical mechanism for cross-midline competition/rivalry in afferent pathways. The existence of cross-midline inhibitory influences is well established in biological subcortical afferent pathways (Appell & Behan, 1990;Hilgetag, Kotter, & Young, 1999;Popper & Fay, 1992), may be viewed as consistent with findings in visual cuing effect studies of attentional mechanisms in human callosotomy subjects (Berlucchi, Aglioti, & Tassinari, 1997;Mangun et al, 1994), and has also in the past formed a central part of some computational models of paradoxical lesion effects and visuospatial neglect (Hilgetag et al, 1999). We thus recently hypothesized that excitatory callosal influences plus subcortical cross-midline inhibitory mechanisms might provide the best fit to experimental data in a single model (Reggia, Goodall, & Levitan, 2001;Reggia, Goodall, Shkuro, & Glezer, 2001).…”