Subdivisions of the Arcopallium/posterior Pallial Amygdala Complex Are Differentially Involved in the Control of Fear Behaviour in the Japanese Quail

Growing evidence suggests that the arcopallium/posterior pallial amygdala plays a major role in the control of fear behaviour in birds. This brain region comprises several subdivisions, but no direct evidence is available about its functional parcellation. The aim of the present study was to investigate the relative involvement of two subdivisions of the arcopallium/posterior pallial amygdala complex in four classical tests of fear in quail: the presentation of a novel object, the 'hole-in-the-wall', 'open-field' and tonic immobility tests. Bilateral electrolytic lesions damaging the posterior part of the arcopallium/posterior pallial amygdala resulted in an increase in fear behaviour in the 'open-field' test, whereas quail with lesions damaging the anterior part of the arcopallium displayed a decrease in an 'overall fear score', compared to quail with bilateral nidopallium or sham lesions. The differential involvement of the anterior and posterior parts of the arcopallium/posterior pallial amygdala in fear behaviour is discussed in view of the known connections between the arcopallium/posterior pallial amygdala complex and brain regions considered to be limbic in nature.