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 mouthparts used for feeding and sucking. In vertebrates, a proboscis is an elon ...

(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 occur ...

to antennal

stimulation Stimulation is the encouragement of development or the cause of activity generally. 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 of PER

The proboscis extension reflex is part of an insect's feeding behavior. When the antenna is 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, values, attitudes, and preferences. The ability to learn is possessed by humans, animals, and some machines; there is also evidence for some kind of le ...

experiments in honeybees and bumblebees because it is easy to use for simple

Pavlovian Classical conditioning (also known as Pavlovian or respondent conditioning) is a behavioral procedure in which a biologically potent stimulus (e.g. food) is paired with a previously neutral stimulus (e.g. a triangle). It also refers to the lear ...

conditioning.Bitterman et al. 1983. Classical Conditioning of Proboscis Extension in Honeybees (''Apis mellifera''). J. Comp. Psych. 97: 107-119.

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.

PER 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 Afro-Eurasia. After bees spread naturally throughout Africa and Eurasia, humans became responsible for the current cosmop ...

. 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 innate (non-reinforced) response to a stimulus decreases after repeated or prolonged presentations of that stimulus. Responses that habituate include those that involve the intact or ...

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

tebufenozide Tebufenozide is an insecticide that acts as a molting hormone. It is an agonist of the ecdysone receptor that causes premature molting in larvae. It is primarily used against caterpillar pests. Because it has high selectivity for the targeted ...

and

diflubenzuron Diflubenzuron is an insecticide of the benzoylurea class. It is used in forest management and on field crops to selectively control insect pests, particularly forest tent caterpillar moths, boll weevils, gypsy moths, and other types of moths. ...

PER 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.

PER and 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 body over the other. Examples include left-handedness/right-handedness and left/right- footedness; it may also refer to the primary use of the left or right he ...

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