Table 2. Nomenclature of the adult telencephalon.

For the medaka brain research, two brain atlases of adult medaka have been used (Anken and Bourrat, 1998; Ishikawa et al., 1999). Because performing three-dimensional reconstruction from brain slices is difficult, some inconsistencies in nomenclature were observed among references. To overcome this difficulty, we performed a three-dimensional imaging of the nuclei-stained adult medaka telencephalon, which allowed us to analyze the anatomical boundaries in more accuracy. The number in the name of anatomical regions (such as Dm1, Dm2, Dm3) was defined by the order of the emergence in the anterior to posterior axis. Here, the table shows the nomenclature of the anatomical regions of the adult telencephalon and the description of cellular organization in the anatomical regions, which we used to define the names.

Abbreviation of anatomical region	Name of subregion	Name of anatomical region	Cellular distribution
Dc		The dorso-central telencephalon	In most teleostean species, cells in Dc have larger size of cell body (Cichlid fish Burmeister et al., 2009, sea bass Cerdá-Reverter et al., 2001) and are sparsely distributed. According to the medaka brain atlas of Ishikawa et al., 1999, Dc is defined in the center of the pallium as well. However, in the other brain atlas of medaka fish (Anken and Bourrat, 1998), multiple subregions are separately defined as Dcs. In our atlas, we defined the center region of the pallium that has less dense cell populations as Dc.
Dcpm		The posterior medial nucleus of the dorso-central telencephalon	The aggregates of cells in the posterior medial center of dorsal pallium (Dcpm) were found.
Dm		The medial part of the dorsal pallium	Small cell-body neurons with high density were observed. In the horizontal optic sections, we found several linearly aligned cells on the dorsal surface of the telencephalic hemispheres which correspond to the boundaries of Dm subregions.
	Dm1		Densely packed with small cells.
	Dm2		Dm2 is packed with cells more densely than Dm1.
	Dm3
	Dm4
Dl		The dorsal lateral pallium	In the previous medaka brain atlas, the anterior region of dorsal lateral pallium is simply named as Dl (Anken and Bourrat, 1998). But here we named this anterior part of dorso-lateral telencephalon the Dla because the nuclear density is less than Dld, Dlv, and Dlp. We also divided Dl into the dorsal and ventral part since the nuclear density is different between the dorsal and ventral parts.
	Dla	The anterior part of the dorso-lateral telencephalon	In the horizontal sections, we found that the density of nucleuses are more sparse in Dla than Dld and Dlv.
	Dld	The dorsal part of the middle and posterior part of the dorso-lateral telencephalon	The dorsal part of the middle and posterior part of the dorso-lateral telencephalon (Dld) (Anken and Bourrat, 1998) is next to Dla and the cell density is more than that of Dla.
	Dlv	The ventral part of the middle and posterior part of the dorso-lateral telencephalon	The boundary between Dld and Dlv is not clear. But the cells are more densely distributed in Dlv than Dld. The ventral part of the middle and posterior part of the dorso-lateral telencephalon (Dlv)(Anken and Bourrat, 1998) is highly packed with cells.
	Dlp	The posterior regions of the dorso-lateral telencephalon	Higher DAPI signal density in Dlp than Dld and Dlv were detected. There is no clear boundary among the posterior regions of the dorso-lateral telencephalon (Dlp), the posterior of dorsal telencephalon (Dp), Dld, and Dlv. But we observed that Dlp was highly dense with a small nucleus and the cell distribution pattern was different from neighboring regions.
Dd		The dorso-dorsal telencephalon	In the previous report (Anken and Bourrat, 1998), Dd is subdivided into two regions, Dd1 and Dd2. In the other report (Ishikawa et al., 1999), only Dd is defined which corresponds to Dd2 of Anken and Bourrat, 1998. Since the boundary between Dd1 and Dd2 was visible in DAPI staining, we followed the definition of Ralf H Anken, 1998.
	Dd1
	Dd2		Dd2 is clearly demarcated in the telencephalon. As observed with the horizontal sections, Dd2 can be subdivided into two regions, Dd2a (anterior part of Dd2) and Dd2p (posterior part of Dd2). Dd2p is surrounded by cells, and the cell density is relatively higher than Dd2a.
Dp		The posterior part of dorsal telencephalon	The posterior part of dorsal telencephalon (Dp) (Anken and Bourrat, 1998) is remarkably denser with the cell nucleus than other posterior anatomical regions.
Vd		The dorsal medial part of the subpallium	Cells in the dorsal medial part of the subpallium are called Vd. We also observed some cell clusters that are located laterally and inside the pallium. Those cell clusters correspond to the Vc region in some references. But according to the cell density and some gene expression, we define those regions also as Vd.
Vs		The supracommissural part of ventral telencephalon	The supracommissural part of ventral telencephalon (Vs) is located ventral to Vd. But there is no clear boundary between Vs and Vd.
Vv		The ventral part of the subpallium
ECL		The external layer of the olfactory bulb	In the anterior part of the telencephalon, the external (ECL) and internal (ICL) cellular layer of the olfactory bulb and the glomerular layer of the olfactory bulb (GL) are clearly found.
ICL		The internal layer of the olfactory bulb