Learning and memory in Rhodnius prolixus: habituation and aversive operant conditioning of the proboscis extension response

Abstract

SUMMARYIt has been largely accepted that the cognitive abilities of disease vector insects may have drastic consequences on parasite transmission. However, despite the research effort that has been invested in the study of learning and memory in haematophagous insects, hitherto few conclusive results have been obtained. Adapting procedures largely validated in Drosophila, honeybees and butterflies, we demonstrate here that the proboscis extension response (PER) of the haematophagous insect Rhodnius prolixus can be modulated by non-associative (habituation) and associative (aversive conditioning) learning forms. Thermal stimuli were used as both unconditional stimulus (appetitive temperatures) and negative reinforcement (thermal shock). In the first part of this work, the PER was habituated and dishabituated to thermal stimuli, demonstrating the true central processing of information and discarding motor fatigue or sensory adaptation. Habituation was revealed to be modulated by the spatial context. In the second part, bugs that were submitted to aversive operant conditioning stopped responding with PER to thermal stimulation more quickly than by habituation. They were able to use their training experience when tested up to 72h later. Our work constitutes the first demonstration of PER habituation and conditioning in a blood-sucking insect and provides reproducible experimental tools for the study of the mechanisms underlying learning and memory in disease vectors.

Circadian modulation of learning abilities in a disease vector insect,Rhodnius prolixus

“…This represents an advantage in comparison with mosquitoes or biting flies, as it makes it possible to adapt experimental tools and paradigms developed in classical models, e.g. honeybees or fruit flies, for the study of learning (Chabaud et al, 2006;Giurfa, 2007;Carcaud et al, 2009;StrubeBloss et al, 2011), as we have recently demonstrated (Vinauger et al, 2013). In addition, as mentioned above, these bugs exhibit a high temporal organisation of their behaviour (Lazzari, 1992).…”

“…We carried out aversive operant conditioning experiments, as described in Vinauger et al (2013). First, the PER was elicited by exposing each insect to an appetitive thermal stimulus (a Peltier element at 35°C), upon which the extended proboscis was subjected to an aversive stimulus (i.e.…”

“…We carried out aversive conditioning experiments as described in Vinauger et al (2013). Insects were first offered an appetitive stimulus (35°C stimulation), which evoked the PER, and then subjected to a 50°C thermal shock, which inhibited the PER.…”

“…However, until recently, such abilities had not been clearly experimentally evinced, to the extent of making some authors wonder whether haematophagous insects could learn anything from their hosts (Alonso et al, 2003). In recent years, the number of studies devoted to analysing the learning ability of disease vector insects has increased regarding mosquitoes (McCall and Eaton, 2001;McCall and Kelly, 2002;Kaur et al, 2003;Alonso and Schuck-Paim, 2006;Tomberlin et al, 2006;Chilaka et al, 2012;Menda et al, 2013;Vinauger et al, 2014), tsetse flies (Bouyer et al, 2007) and triatomine bugs (Vinauger et al, 2011a(Vinauger et al, ,b, 2012(Vinauger et al, , 2013. These studies provided direct or indirect evidence of learning ability, but as far as we know none of them dived deeper into the characterisation of how learning and memory could be modulated by endogenous factors.…”

A Proboscis Extension Response Protocol for Investigating Behavioral Plasticity in Insects: Application to Basic, Biomedical, and Agricultural Research

“…PER experiments with fruit flies have provided many insights into the molecular signaling cascades involved in chemosensation and learning 34 . And PER has recently been used to study habituation in the flea (Rhodnius prolixus) 35 , an important disease vector.…”