Night-time neuronal activation of Cluster N in a day- and night-migrating songbird - PubMed (original) (raw)

Night-time neuronal activation of Cluster N in a day- and night-migrating songbird

Manuela Zapka et al. Eur J Neurosci. 2010 Aug.

Free PMC article

Abstract

Magnetic compass orientation in a night-migratory songbird requires that Cluster N, a cluster of forebrain regions, is functional. Cluster N, which receives input from the eyes via the thalamofugal pathway, shows high neuronal activity in night-migrants performing magnetic compass-guided behaviour at night, whereas no activation is observed during the day, and covering up the birds' eyes strongly reduces neuronal activation. These findings suggest that Cluster N processes light-dependent magnetic compass information in night-migrating songbirds. The aim of this study was to test if Cluster N is active during daytime migration. We used behavioural molecular mapping based on ZENK activation to investigate if Cluster N is active in the meadow pipit (Anthus pratensis), a day- and night-migratory species. We found that Cluster N of meadow pipits shows high neuronal activity under dim-light at night, but not under full room-light conditions during the day. These data suggest that, in day- and night-migratory meadow pipits, the light-dependent magnetic compass, which requires an active Cluster N, may only be used during night-time, whereas another magnetosensory mechanism and/or other reference system(s), like the sun or polarized light, may be used as primary orientation cues during the day.

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Figures

FIG. 1

FIG. 1

Autoradiographs showing ZENK brain activation during (A) daytime and (B) night-time in day- and night-migrating meadow pipits. During night-time (B) high neuronal activity, indicated by ZENK expression, occurred in Cluster N, whereas during the day (A) Cluster N does not show increased neuronal activity. Instead, during the day, brain regions, comprising parts of MV, N and St known to be active during movement and to process day vision (lateral to this section) are highly active. ZENK expression indicating neuronal activity: black dots. (C) GluR1 staining for anatomical characterization. (D) Anatomical profile of a parasagittal section; red and blue lines indicate the regions quantified for Fig. 2. (E) Higher magnification of GluR1 staining in and around Cluster N. (F) Detailed anatomical profile of Cluster N (parasagittal brain sections are shown). Dorsal is up; anterior is right; scale bar = 1.5 mm. Abbreviations: Gp, globus pallidus; St, striatum; N, nidopallium; MD, dorsal mesopallium; MV, ventral mesopallium; H, hyperpallium; Hf, hippocampal formation; IH, interstitial layer of the hyperpallium; DNH, dorsal nucleus of the hyperpallium.

FIG. 2

FIG. 2

Quantification of ZENK expression expressed as pixel density on a 256 grey scale (white = 0, black = 255). (A) Relative ZENK expression in Cluster N (i.e. the posterior dorsal parts of the H, IH, MD) minus the anterior ventral part of the H, IH and MD) was significantly higher in meadow pipits during night-time and dim-light conditions compared with meadow pipits exposed to bright light during the day. (B) Differences in absolute ZENK expression between birds tested during day and night were highly significant in Cluster N but not in the rest of H+MD or in the globus pallidus. ***P < 0.001; n.s = not significant. Abbreviations: MD, dorsal mesopallium; H, hyperpallium; IH, interstitial layer of the hyperpallium.

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