Pheromones as modulators of cognitive tasks
Our basic hypothesis is that appetitive pheromones (i.e. pheromones signalling valuable resources) exert an incremental effect on appetitive learning and a decremental effect on aversive learning. By contrast, we posit that aversive pheromones (i.e. pheromones signalling potentially noxious situations) exert an incremental effect on aversive learning and a decremental effect on appetitive learning. Pheromones would thus provide contextual information rendering subsequent learning more or less relevant for the context signalled. Testing this hypothesis requires a combination of pheromone exposure and conditioning protocols in both modalities, appetitive and aversive.
Pheromone exposure and biogenic amines
We study the mechanisms of pheromone modulation by focusing on octopaminergic and dopaminergic circuits, which in many insects signal appetitive and aversive events, respectively. We hypothesize that appetitive pheromones will mainly activate octopaminergic circuits that may prone insects to learn about reward, whilst aversive pheromones will mainly activate dopaminergic circuits that may prone animals to learn about punishment. We are testing this hypothesis using a combination of behavioural and pharmacological approaches. We use a pharmacological approach to specifically block/activate different aminergic systems potentially involved in the modulation of associative learning. In this way, we will elucidate the influence of aminergic signalling in this form of modulation.
The effect of pheromones on odour coding in the brain
As odour coding in the brain changes after appetitive learning in several insect species, we are investigating whether pheromone exposure modifies per se the odour code in the antennal lobe (the first olfactory relay in the brain) in the three species. We hypothesize that pheromone exposure will position the animal in an appetitive or aversive context that may exert a significant modification of subsequent brain processing of stimuli relevant for the cognitive tasks considered. A combination of pheromone/neutral odour exposure and in vivo calcium imaging recordings of antennal lobe activity is used to this end. We compare neural activity patterns at the level of the antennal lobe of naive and conditioned insects before and after pheromone exposure, for the same set of neutral odorants in all three species.
