Figure 23.

Schematic drawing of the ascending auditory pathways at the brainstem, midbrain, and thalamic levels. A part of the drawing at the brainstem and midbrain levels was previously published in Wang and Karten (2010). The dorsal auditory brainstem sends three separate pathways (green, red, and blue) upon three distinct subdivisions of MLd and then upon three distinct subdivisions of the Ov proper. The blue pathway also integrates information from the red pathway at the midbrain level. Filled circles and lines indicate neurons and connections in each pathway, respectively. At the level of brainstem projection upon the midbrain, solid and dashed lines indicate connections issued from the left and right sides of the midbrain, respectively. For the purpose of the clarity, the red and blue pathways in A are not illustrated; the organization of these connections is the same as demonstrated in B and C. The NA-recipient zone in MLd and Ov, shown as black cells, receives information from both red and blue pathways. This drawing demonstrates strong innervations in the pathways; light or sparse projections are not included, such as ipsilateral projections from NL and NA upon MLd, the light projection from NA upon the NL-recipient zone of MLd, and the connections between the NA-recipient zones of two side. The potential projections from MLd upon SPO and cOv are not unambiguously determined, thus they were not included in the drawing. Abbreviations: see table of abbreviations.