Shock avoidance by discrimination learning in the shore crab (Carcinus maenas) is consistent with a key criterion for pain

Abstract

SUMMARYNociception allows for immediate reflex withdrawal whereas pain allows for longer-term protection via rapid learning. We examine here whether shore crabs placed within a brightly lit chamber learn to avoid one of two dark shelters when that shelter consistently results in shock. Crabs were randomly selected to receive shock or not prior to making their first choice and were tested again over 10 trials. Those that received shock in trial 2, irrespective of shock in trial 1, were more likely to switch shelter choice in the next trial and thus showed rapid discrimination. During trial 1, many crabs emerged from the shock shelter and an increasing proportion emerged in later trials, thus avoiding shock by entering a normally avoided light area. In a final test we switched distinctive visual stimuli positioned above each shelter and/or changed the orientation of the crab when placed in the chamber for the test. The visual stimuli had no effect on choice, but crabs with altered orientation now selected the shock shelter, indicating that they had discriminated between the two shelters on the basis of movement direction. These data, and those of other recent experiments, are consistent with key criteria for pain experience and are broadly similar to those from vertebrate studies.

Operant avoidance learning in crayfish, Orconectes rusticus: Computational ethology and the development of an automated learning paradigm

“…Crayfish are tuned to distinguishing tactile cues (Bouwma & Hazlett, 2001) and several crustaceans learn to avoid environmental cues that are paired with electric shock (Denti et al, 1988;Magee & Elwood, 2013). Although widely used as a punishment in learning studies, the application of electric shock may also constitute a confound where electromagnetic stimulation may, in itself, impact neuronal/synaptic function (Kling et al, 1990;Misanin et al, 1984).…”

Electric shock causes physiological stress responses in shore crabs, consistent with prediction of pain

“…The crabs to be shocked then had the other end of each wire attached to a Grass S9 electric stimulator (West Warwick, RI, USA). The left and right legs had wires randomly attached to the positive and negative terminals of the stimulator and, following Magee & Elwood [11], shock was set to deliver at 10 V and 180 Hz for 200 ms with 10 s intervals for 2 min. The wires for the control group were not attached to the stimulator but the crabs were otherwise treated the same.…”

Animal Consciousness

“…Other scientists have suggested however, that the presence of a centralised nervous system that is protected by a blood-brain interface, and particularly, the rather complex behavioural reactions in octopuses and in mollusc cephalopods in general to various situations, including injury, would suggest at least the possibility of the presence of some degree of a negative affective experience in response to a nociceptive stimulation (Barr et al, 2008). Similarly, the behaviours of crustaceans present a certain complexity and some scientists interpret their reactions to nociceptive stimuli as indicative of at least some degree of a negative affective experience associated with nociception (Magee and Elwood, 2013;Elwood and Adams, 2015).…”