Every moment of their lives, organisms from pigeons to people are bombarded by a wide array of visual stimuli. Some of these stimuli are relevant to current circumstances and goals, whereas others are not. How does the visual system distinguish relevant from irrelevant stimuli?
One adaptive strategy may be to establish which visual regions are figures and which are backgrounds. Figures correspond to objects that should be attended to, recognized, and acted upon, whereas backgrounds correspond to the spaces between objects, and should be ignored.
We have developed a behavioral task in which pigeons were trained to discriminate whether a target spot appeared on a colored figural shape or on a differently colored background (Lazareva, Castro, Vecera, & Wasserman, 2006). Using this task, we found that the birds were faster to detect the target, to report its location, and to learn the correct response on figure trials than on background trials. We also found that this figural benefit is more pronounced when the figural region was smaller (Castro, Lazareva, Vecera, & Wasserman, 2010).
In collaboration with Martin Acerbo (Iowa State University), we have also established that figure-ground segregation is regulated by the avian midbrain nucleus called nucleus rotundus and its inhibitory control center, nucleus subpretectalis / isthmi-pretecto-subpretectalis (SP/IPS; Acerbo et al., 2012; Scully, Acerbo, & Lazareva, 2014; Acerbo & Lazareva, 2018).
We are currently exploring metabolic activity associated with figure-ground discrimination in entopallium (a higher-level visual nucleus) and in nucleus isthmi (a regulatory center for deep layers of optic tectum). This work will help us establish potential involvement of other brain areas located upstream or downstream from nucleus accumbens.
Acerbo, M. J., & Lazareva, O. F. (2018). Pharmacological manipulation of GABA activity in nucleus subpretectalis/interstitio-pretecto-subpretectalis (SP/IPS) impairs figure-ground discrimination in pigeons: Running head: SP/IPS in figure-ground segregation. Behavioural Brain Research, 344, 1-8. https://doi.org/10.1016/j.bbr.2018.01.033
Scully, E. N., Acerbo, M., J., & Lazareva, O. F. (2014). Bilateral lesions of nucleus subpretectalis/interstitio-pretecto-subpretectalis (SP/IPS) selectively impair figure-ground discrimination in pigeons. Visual Neuroscience, 31, 105-110.
Acerbo, M. J., Lazareva, O. F., McInnerney, J., Leiker, E., Wasserman, E. A., & Poremba, A. (2012). Figure–ground discrimination in the avian brain: The nucleus rotundus and its inhibitory complex. Vision Research, 70, 18-26. doi: 10.1016/j.visres.2012.07.023
Castro, L., Lazareva, O. F., Vecera, S. P., & Wasserman, E. A. (2010). Changes in area affect figure-ground assignment in pigeons. Vision Research, 50,497-508. doi:10.1016/j.visres.2009.12.016
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, 711-724.