Proboscis extension reflex (PER) is the extension by an insect with an extendable proboscis (e.g. a bee or fly) of her

proboscis A proboscis () is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In invertebrates, the term usually refers to tubular arthropod mouthparts, mouthparts used for feeding and sucking. In vertebrates, a pr ...

(sticking out of her tongue) as a

reflex In biology, a reflex, or reflex action, is an involuntary, unplanned sequence or action and nearly instantaneous response to a stimulus. Reflexes are found with varying levels of complexity in organisms with a nervous system. A reflex occurs ...

to antennal

stimulation Stimulation is the encouragement of development or the cause of activity in general. For example, "The press provides stimulation of political discourse." An interesting or fun activity can be described as "stimulating", regardless of its physic ...

. It is evoked when a sugar solution is touched to a bee's antenna.

Use

The proboscis extension reflex is part of an insect's feeding behavior. When the taste receptors on the antenna or tarsi are stimulated by sugar water, the proboscis automatically sticks out to drink. This reflex response can be used to study insect learning and memory in the context of foraging. The PER paradigm is most commonly used in associative

learning Learning is the process of acquiring new understanding, knowledge, behaviors, skills, value (personal and cultural), values, Attitude (psychology), attitudes, and preferences. The ability to learn is possessed by humans, non-human animals, and ...

experiments in honeybees and bumblebees because it is easy to use for simple Pavlovian conditioning.Bitterman et al. 1983. Classical Conditioning of Proboscis Extension in Honeybees (''Apis mellifera''). J. Comp. Psych. 97: 107-119. It can also be used as a taste behavior assay in fruit flies to measure taste preferences and better understand feeding behaviors.

How the PER learning paradigm works

There are two steps in a PER experiment. The first step trains the individual to associate a conditioned stimulus (CS), such as an odor with an unconditioned stimulus (US) such as a sugar. For example, the bee is presented with an odor (CS) and an application of the sugar (US) solution to its antennae, upon which she reflexively extends her proboscis. In some variations, the bee is immediately fed with sugar at this point; this constitutes an operant reinforcement which would tend to establish the odor as a discriminative stimulus. After some number of pairings of the CS and US, the second step in the PER paradigm tests whether or not the association has been learned. The odor (CS) is presented to the bee in the absence of the sugar solution (US), and the association is confirmed if the bee extends her proboscis to this CS alone.

In honeybees

The PER paradigm has been successfully used to investigate olfactory learning in

honeybees A honey bee (also spelled honeybee) is a eusocial flying insect within the genus ''Apis'' of the bee clade, all native to mainland Afro-Eurasia. After bees spread naturally throughout Africa and Eurasia, humans became responsible for the cur ...

. It was first introduced by Kimihisa Takeda in 1961. Experiments by Bitterman used first-order classical conditioning to associate an odor with a sugar reward. Individual bees were placed in a tube with their head sticking out. Then a stream of odorant blown towards the bee's head was immediately followed by touching the antenna with a sugar droplet. After only three such trials, the odor alone caused the bee to extend its proboscis approximately 90% of the time. Bees also showed second-order conditioning, learning to associate a second odor with the original odor. The PER paradigm has also been used in honeybees to study motion learning, thermal learning, color learning,

habituation Habituation is a form of non-associative learning in which an organism’s non-reinforced response to an inconsequential stimulus decreases after repeated or prolonged presentations of that stimulus. For example, organisms may habituate to re ...

, and reversal learning. Abramson et al 2004 use this technique to investigate their sensation of and response to tebufenozide and diflubenzuron.

In bumblebees

Although the majority of PER studies are performed on honeybees, there is at least one successful study of using PER on bumblebees. After they were exposed to a conditioning procedure like that used with honeybees (see above) they gave a conditioned PER response to odor alone PER response 85% of the time after 10 trials.Riveros and Gronenberg. 2009. Olfactory learning and memory in the bumblebee, ''Bombus occidentalis.'' Naturwissenschaften 96:851-856.

Learning laterality

Recently, interesting findings in PER studies show

laterality The term laterality refers to the preference most humans show for one side of their Human body, body over the other. Examples include Handedness, left-handedness/right-handedness and left/right-footedness; it may also refer to the primary use of ...

in olfactory learning in the two antennae i.e., one antenna is better at associative learning than the other antenna. In honeybees, individuals had either their right or their left antenna covered with a silicone sleeve, leaving the other antenna exposed. The bees that had their right antenna exposed were better at associating an odor with a food reward than bees that had their left antenna exposed.Letzkus et al. 2006. Lateralization of Olfaction in the Honeybee ''Apis mellifera.'' Current Biology 16:1471-1476. The same study also found that the right antenna has more olfactory receptors than the left antenna, a possible cause for this lateralized PER learning. However, other causes such as internal differences in the actual olfactory pathway or the central nervous system must not be ruled out just yet.

References

External links

Video of PER on a honeybee

Picture diagram of PER on a honeybee

Picture of a honeybee sticking out her proboscis

Article on using PER in detecting illicit drugs and explosives
{{DEFAULTSORT:Proboscis Extension Reflex Reflexes Bees Beekeeping

Use