Functional anatomy of the avian centrifugal visual system.
Although first described over a century ago, the centrifugal visual system (CVS) projecting to the retina still remains somewhat of an enigma with regard to its functional role in visually-guided behavior. The highly developed avian CVS has been the most extensively investigated and the anatomical organization of its two component centrifugal structures, the n. isthmo-opticus (NIO) and ectopic neurons (EN), including its afferent brainstem projections is reviewed. The results of double-labeling studies combining axonal tracing techniques and immunohistofluorescence have demonstrated GABA immunoreactivity (-ir) of interneurons within the neuropilar zone of the NIO, choline acetyltransferase (ChAT)-ir and nitric oxide synthase (NOS)-ir in the centrifugal cells of the NIO and EN as well as in the afferent projection neurons of layers 9/10 of the optic tectum. The data are discussed in terms of neurochemical and excitatory/inhibitory mechanisms within the different components of the avian CVS in relation to hypotheses which have implicated this system in visual attention and ground-feeding behavior.
Miceli
D
D
Département de psychologie, Université du Québec, Trois-Rivières, Canada.
Repérant
J
J
Bertrand
C
C
Rio
J P
JP
D000818:Animals; D001288:Attention; D001522:Behavior, Animal / Q000502:physiology*; D001717:Birds / Q000033:anatomy & histology* / Q000502:physiology*; D001921:Brain / Q000033:anatomy & histology / Q000502:physiology; D018377:Neurotransmitter Agents / Q000502:physiology; D014795:Visual Pathways / Q000033:anatomy & histology* / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*
D018377:Neurotransmitter Agents