Emotion and Stress

Abstract

The avian archistriatum has been implicated in fear behaviour. However, most tests of fear also involve social separation and it has proved difficult to distinguish between fear and social reinstatement (SR) behaviour. The duration of the tonic immobility (TI) response is a robust and relatively unambiguous measure of fear in domestic birds and treadmill behaviour is a reliable measure of SR. In quail, selection for TI responses weighted for independence from SR behaviour and vice versa, reveals that the expression of TI and SR can be separated at the genetic level. Thus, divergent selection for TI responses and SR behaviour provides a powerful tool for investigating the neural basis of fear and SR behaviour. Day-old, straight run offspring (F19 generation) of quail lines selected for long (LTI) or short duration of TI, or high or low SR behaviour, were anaesthetised and given bilateral electrolytic archistriatal lesions (ARCH) or shamoperation (SHAM). A third group of chicks was untreated (U). On day 3 post-hatch, the chicks were given open-field and hole-in-the-wall box timidity tests and on day 8 post-hatch they underwent a treadmill test for SR and a TI test. ARCH chicks were then killed and their brains processed for lesion site verification. In the LTI line only, ARCH chicks showed significantly shorter (@ 60%) TI durations than SHAM + U chicks (F 1,192 = 5.59; p = 0.01).