Visual associative learning in wood ants

Abstract

Wood ants are a model system for studying visual learning and navigation. They can forage for food and navigate to their nests effectively by forming memories of visual features in their surrounding environment. Previous studies of freely behaving ants have revealed many of the behavioural strategies and environmental features necessary for successful navigation. However, little is known about the exact visual properties of the environment that animals learn or the neural mechanisms that allow them to achieve this. As a first step towards addressing this, we developed a classical conditioning paradigm for visual learning in harnessed wood ants that allows us to control precisely the learned visual cues. In this paradigm, ants are fixed and presented with a visual cue paired with an appetitive sugar reward. Using this paradigm, we found that visual cues learnt by wood ants through Pavlovian conditioning are retained for at least 1 h. Furthermore, we found that memory retention is dependent upon the ants' performance during training. Our study provides the first evidence that wood ants can form visual associative memories when restrained. This classical conditioning paradigm has the potential to permit detailed analysis of the dynamics of memory formation and retention, and the neural basis of learning in wood ants.

Visual Classical Conditioning in Wood Ants

“…Train ants through either a ( C ) paired or ( D ) unpaired training. This figure has been modified from Fernandes et al 16 . Please click here to view a larger version of this figure.…”

“…( E ) Ants undergoing paired training ( N = 51) perform a full extension with movement (FEM; dark brown), an FE (mid-brown) or a PE (light brown). This figure has been modified from Fernandes et al 16 . Please click here to view a larger version of this figure.…”

“…Note: For analysis, a statistical test that takes individual ants into account is recommended, thereby accounting for variability within individuals. When classifying ants’ responses during training in a binary manner (1 for positive responses and 0 for no response), logistic regression with mixed effects is advisable 16 19 . For comparing the proportion of ants responding in each training trial or test, a G -test or Fisher’s exact test is recommended, depending on the number of ants analysed 16 20 .…”

“…The main goal of the protocol we describe here is to provide a way to perform classical conditioning experiments using a visual conditional stimulus with a widely studied ant species, Formica rufa . It is issued from our study of visual learning in wood ants 16 , which is also an adaptation of visual classical conditioning paradigms.…”

Are ants botanists? Ant associative learning of plant chemicals mediates foraging for carbohydrates

“…extrafloral nectar and honeydew) of different qualities. Because ants also use visual landmarks and tactile cues when navigating (Seidl & Wehner, 2006;Steck et al, 2011), future studies should test whether associative learning of multiple cues in combination mediates ant foraging for plant-associated resources (Fernandes et al, 2018).…”