1. Effect of pharmacological manipulation of nucleus subpretectalis/interstitio- pretecto-subpretectalis (SP/IPS) on figure-ground discrimination in pigeons Hannah E. Moses 1, Erin N. Scully 1, Martin Acerbo 2, and Olga F. Lazareva 1 Acknowledgments This research was supported by the A&S Drake University Faculty Development Research grant to OFL. We thank all members of CoPAL research team for their help with running experiments. References Acerbo, M. J., Lazareva, O. F., McInnerney, J., Leiker, E., Wasserman, E. A., & Poremba, A. (2012). Figure-ground discrimination in avian brain: Nucleus rotundus and its inhibitory complex. Vision Research, 70, 18-26. Lazareva, O. F., Castro, L., Vecera, S. P., & Wasserman, E. A. (2006). Figure-ground assignment in pigeons: Evidence for a figural benefit. Perception and Psychophysics, 68 (5), 711-724. Shimizu, T., & Watanabe, S. (2012). The avian visual system: Overview. In O. F. Lazareva, T. Shimizu & E. A. Wasserman (Eds.), How animals see the world: Comparative behavior, biology, and evolution of vision. New York, NY: Oxford University Press. Wang, Y. C., Jiang, C., & Frost, B. J. (1993). Visual processing in pigeon nucleus rotundus: Luminance, color, motion, and looming subdivisions. Visual Neuroscience, 10(1), 21-30. Background  Collothalamic visual pathway is a major source of visual information (90%; Shimizu & Watanabe, 2012)  N. rotundus (Rt) is the largest midbrain nucleus in birds  Rt receives inhibitory input from nucleus subpretectalis/interstitio- pretecto-subpretectalis (SP/IPS) Goal : Investigate the modulatory role of SP in figure-ground discrimination by conducting pharmacological blockade of specific neurotransmitter receptors Method Stimuli  Target presented in one of four locations, equally often on figure or ground region (see left) Subjects  9 pigeons, kept at 85% of free-feeding weight Procedure  Trained until 80% correct or better on both figure and background trials Surgery  Bilateral implantation of cannuli into SP (n = 9)  Four-day recovery Intracranial injections  Alternating injections of drug and baseline (artificial cerebrospinal fluid)  Bicuculline (GABA antagonist), muscimol (GABA agonist), CNQX (glutamate antagonist)  Two doses for each drug (12.75 and 25.5 ng for bicuculline, 0.5 and 1 ng for muscimol, 0.3 and 0.6 ng for CNQX)  Order and dose of drugs randomized across birds  Has to maintain high levels of performance to proceed to next drug injection (modified from Lazareva et al., 2006) Preliminary results  All three drugs produced a deleterious effect on figure-ground discrimination  Both muscimol and CNQX produce a dose-dependent impairment on figure trials but not on background trials  Bicuculline produces a dose-dependent effect on background trials  The effect of CNQX suggests that excitatory input from optic tectum is critical for accurate performance on figure trials but not on background trials  The increased inhibitory activity in SP produced by muscimol impairs discrimination on figure trials, possibly due to imbalance of modulation of Rt by SP  It is possible that the decreased inhibitory activity in SP primarily affects background trials  Large individual differences may be due to the precise location of the cannula  Future work will include determining the exact location of the cannuli via histological analysis 1 Drake University, 2 Iowa State University SP connectivity Excitatory connections from optic tectum  Affected by CNQX Inhibitory connections within SP and from SP to Rt  Affected by both bicuculline and muscimol  7 out of 9 birds injected o Complete absence of any behavioral responses during first 30 min or even 90 min for some of the birds  Dose-dependent effect on figure trials  Non-dose-dependent effect on figure-trials  Large individual differences (e.g., background trials ranges from +0.11 to -0.28) Results: Bicuculline  8 out of 9 birds injected o Complete absence of any behavioral responses during first 30 min for most of the birds o Concentrated on 90-mi data  Non-dose-dependent effect on background trials  Dose-dependent effect on figure trials Results: Muscimol  7 out of 9 birds injected o Complete absence of any behavioral responses during first 30 min for only in a few birds  Relatively short-lasting effect  Non-dose-dependent on background trials  Dose-dependent effect on figure trials  Very large individual differences (e.g., background trials range from +0.05 to -0.21) Results: CNQX  Earlier study (Acerbo et al., 2012) demonstrated higher activity of Rt and SP/IPS after figure-ground discrimination, but not after color or shape discrimination  We also found significant impairment of figure-ground discrimination after lesion of SP/IPS complex (Scully, Acerbo, & Lazareva, in prep.)