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. Author manuscript; available in PMC: 2014 May 1.
Published in final edited form as: Neurobiol Learn Mem. 2013 Aug 30;106:163–176. doi: 10.1016/j.nlm.2013.08.010

Figure 1.

Figure 1

Auditory pathway and electrode placements. A. Schematic of auditory pathway, lateral part, in the songbird brain (Jarvis et al., 2005). Only the most prominent and/or most studied connections are indicated. Most of the hindbrain connectivity is extrapolated from non-songbird species. Not indicated are reciprocal connections in the pallial auditory areas. Shown for landmark purposes are song nuclei HVC, RA and NIf. B. Bird 5 during an experiment. The headstage is visible to the top left. The elastic suspension of the cable makes it light enough for the bird to hold its head normally. C. Electrode array from Bird 2, inside the skull after dissection. The electrodes are numbered from rostral to caudal (G=ground electrode). D. DiI and DiO labeled electrode tracts in a sagittal section (same orientation as in A through the auditory forebrain of Bird 6. The fluorescently labeled tracts of five electrodes (7, 6, 5, 4, and 3; alternating red and green) aimed at pallial auditory areas are visible in this section, as well as the edges of the tract of electrode 1, aimed at the auditory striatum CSt. DiI (red) spreads more and is more visible than the DiO (green) signal. The dyes leave a trace along the tract of the electrode as the electrode array is lowered into the brain during surgery. Electrode position is marked down the midline of the fluorescent signal, where the track can be seen. The outlines of the anatomical regions are based on adjacent sections, which were stained with cresyl violet and hybridized with a radio-active probe against egr-1 mRNA (see text). E. An example autoradiogram of an in-situ hybridization for the mRNA of egr-1 in the forebrain of Bird 5. Note the strong signal in the auditory pallium, bisected by the light diagonal line of Field L2 (arrow), which has low expression of egr-1. F. and G. examples of tips of cresyl violet-stained gliosis scars in the forebrain of Bird 5 (electrode 6 (L2; F) and 8 (NCM; G)). Abbreviations: Cb-Cerebellum; CM-Caudal Mesopallium; CSt-Caudal Striatum; HA-Hyperpallium apicale; HF-Hippocampal Formation; NCM-Caudal Medial Nidopallium.