Science Topics - 91

Expression of immediate-early genes reveals ocular dominance domains in New World owl monkeys
Toru Takahata (Jon H. Kaas)

 Neuronal computation circuits are represented by brain structures. Ocular dominance columns (ODCs) have been well studied in the striate cortex (V1) of macaques, as well defined arrays of columnar structure. When ODCs were first identified in 1960’s, researchers thought that this structure represents circuit of stereoscopic depth coding. However, ODC expression seems obscure in some New World primate species, although they are all capable of stereopsis. Then, studies of depth coding through ODCs have been turned down. Previously, ODCs have been investigated by means of eye injections of transneuronal transporters and examination of cytochrome oxidase (CO) activity patterns after monocular enucleation. Here, we used the expression of immediate-early genes (IEGs), c-Fos and Zif268, after monocular inactivation (MI) to identify ODCs in New World owl monkeys. Using IEGs, we not only revealed apparent ODCs in owl monkeys but also discovered a number of unique features of their ODCs. These ODCs sometimes bridged to other columns in layer 4. The ODC pattern continued into V2. Finally, border strips were observed along ODC borders after only brief MI. Our data suggest that apparent species differences of ODCs were due to technical limitations, not fundamental nature, and revive debate over the functions, variability and development of ODCs.

 Takahata et al., Identification of ocular dominance domains in New World owl monkeys by immediate-early gene expression. Proc Natl Acad Sci USA(2014) 111 (11): 4297-4302

Figure. A: In situ hybridization for c-Fos in a tangential section of flattened V1 of an owl monkey that was subjected for MI. Apparent ODCs were represented by the staining pattern.B: ODCs are not revealed by cytochrome oxidase (CO) staining that was commonly used to reveal ODCs. Adjacent sections were stained for c-Fos or CO. While c-Fos staining shows significant difference in relative optical density (ROD) between pale and dark columns, CO staining does not. Circles represent identical radial blood vessels of adjacent sections. 

 Department of Psychology, Vanderbilt University, USA