Pharmacological manipulation of GABA activity in nucleus subpretectalis/interstitio-pretecto-subpretectalis (SP/IPS) impairs figure-ground discrimination in pigeons

• Published in: Behavioural brain research 2018-05, Vol.344, p.1-8
• Main Authors: Acerbo, Martin J., Lazareva, Olga F.
• Format: Article
• Language: English
• Subjects: Figure-ground segregation; Inhibitory regulation; Nucleus rotundus; SP/IPS; Visual processing
• ISSN: 0166-4328; 1872-7549
• DOI: 10.1016/j.bbr.2018.01.033

[Display omitted] •Conducted pharmacological manipulation of the SP/IPS in figure-ground task.•The SP/IPS is a thalamic nucleus regulating activity of nucleus rotundus in birds.•Bicuculline and muscimol impaired accuracy in a dose-dependent manner.•CNQX had no consistent effect across birds.•Figure-ground segregation in birds may occur at a thalamic level. Figure-ground segregation is a fundamental visual ability that allows an organism to separate an object from its background. Our earlier research has shown that nucleus rotundus (Rt), a thalamic nucleus processing visual information in pigeons, together with its inhibitory complex, nucleus subpretectalis/interstitio-pretecto-subpretectalis (SP/IPS), are critically involved in figure-ground discrimination (Acerbo et al., 2012; Scully et al., 2014). Here, we further investigated the role of SP/IPS by conducting bilateral microinjections of GABAergic receptor antagonist and agonists (bicuculline and muscimol, respectively) and non-NMDA glutamate receptor antagonist (CNQX) after the pigeons mastered figure-ground discrimination task. We used two doses of each drug (bicuculline: 0.1 mM and 0.05 mM; muscimol: 4.4 mM and 8.8 mM; CNQX: 2.15 mM and 4.6 mM) in a within-subject design, and alternated drug injections with baseline (ACSF). The order of injections was randomized across birds to reduce potential carryover effects. We found that a low dose of bicuculline produced a decrement on figure trials but not on background trials, whereas a high dose impaired performance on background trials but not on figure trials. Muscimol produced an equivalent, dose-dependent impairment on both types of trials. Finally, CNQX had no consistent effect at either dose. Together, these results further confirm our earlier hypothesis that inhibitory projections from SP to Rt modulate figure-ground discrimination, and suggest that the Rt and the SP/IPS provide a plausible substrate that could perform figure-ground segregation in avian brain.