The Neural Signature of Visual Learning Under Restrictive Virtual-Reality Conditions

Abstract

Honey bees are reputed for their remarkable visual learning and navigation capabilities. These capacities can be studied in virtual reality (VR) environments, which allow studying performances of tethered animals in stationary flight or walk under full control of the sensory environment. Here, we used a 2D VR setup in which a tethered bee walking stationary under restrictive closed-loop conditions learned to discriminate vertical rectangles differing in color and reinforcing outcome. Closed-loop conditions restricted stimulus control to lateral displacements. Consistently with prior VR analyses, bees learned to discriminate the trained stimuli. Ex vivo analyses on the brains of learners and non-learners showed that successful learning led to a downregulation of three immediate early genes in the main regions of the visual circuit, the optic lobes (OLs) and the calyces of the mushroom bodies (MBs). While Egr1 was downregulated in the OLs, Hr38 and kakusei were coincidently downregulated in the calyces of the MBs. Our work thus reveals that color discrimination learning induced a neural signature distributed along the sequential pathway of color processing that is consistent with an inhibitory trace. This trace may relate to the motor patterns required to solve the discrimination task, which are different from those underlying pathfinding in 3D VR scenarios allowing for navigation and exploratory learning and which lead to IEG upregulation.

Efficient visual learning by bumble bees in virtual‐reality conditions: Size does not matter

“…, 2021; Lafon et al. , 2022). Fixation time (s) was defined as the time spent by each cylinder at the center of the screen (± 2.5 mm) where it was brought by the bee's actions (Lafon et al.…”

“…, 2022; Lafon et al. , 2022), among others. The full control offered by VR allows referring neural and molecular events recorded under these circumstances to the specific problem being solved by the insects.…”

“…In this sense, research on visual cognition has faced the same problem as that experienced for many decades by studies on this topic in honey bees, namely the impossibility of developing invasive analyses of neural activity in freely flying animals. Yet, bumble bees may offer advantages for research under VR conditions compared with honey bees (Buatois et al, 2017;Rusch et al, 2017;Schultheiss et al, 2017;Buatois et al, 2018;Zwaka et al, 2018;Lafon et al, 2021;Rusch et al, 2021;Geng et al, 2022;Lafon et al, 2022). For instance, bumble bees seem to be more resilient to the potential stress induced by the tethering condition, and thus more disposed to engage in the VR experiments than honey bees.…”

Involvement of octopamine in conditioned visual flight orientation in honeybees

“…Recently, a series of behavioral studies of honeybees involving two-or three-dimensional VR conditions have reported that walking bees on a treadmill ball could learn to associate a visual stimulus with the location of the sucrose reward, similar to the free-ying bees in the Y-maze (Buatois et al 2017(Buatois et al , 2018Lafon et al 2021Lafon et al , 2022Geng et al 2022). In addition, the involvement of the mushroom body of the brain in visual learning under VR conditions has been suggested by electrophysiological recordings from mushroom body extrinsic neurons (Paffhausen et al 2020) and analyses of immediate early gene expression (Lafon et al 2022;Geng et al 2022). However, in all these previous studies, the bees did not y but walked on the treadmill ball, even though the honeybees y foraging.…”

“…This experimental setup allows us to present a stimulus more precisely than a free-ying condition and to easily investigate neural correlates of the learning behavior as the animal is tethered and moves stationary in the setup. Recently, a series of behavioral studies of honeybees involving two-or three-dimensional VR conditions have reported that walking bees on a treadmill ball could learn to associate a visual stimulus with the location of the sucrose reward, similar to the free-ying bees in the Y-maze (Buatois et al 2017(Buatois et al , 2018Lafon et al 2021Lafon et al , 2022Geng et al 2022). In addition, the involvement of the mushroom body of the brain in visual learning under VR conditions has been suggested by electrophysiological recordings from mushroom body extrinsic neurons (Paffhausen et al 2020) and analyses of immediate early gene expression (Lafon et al 2022;Geng et al 2022).…”