title: Abnormal strategies during visual discrimination reversal learning in ephrin-A2(-/-) mice.
abstract: Eph receptors and ephrins are involved in establishing topographic connectivity in primary sensory brain regions, but also in higher order structures including the cortex and hippocampus. Ephrin-A2(-/-) mice have abnormal topography in the primary visual system but have normal visual and learning performance on a simple visual discrimination task. Here we use signal detection theory to analyse learning behaviour of these mice. Wild-type (WT) and ephrin-A2(-/-) (KO) mice performed equally well in a two-stimulus visual discrimination task, with similar learning rates and response latencies. However, during reversal learning, when the rewarded stimulus was switched, the two genotypes exhibited differences in response strategies: while WTs favoured a win-stay strategy, KOs remained relatively neutral. KOs also exhibited a stronger lateralization bias in the initial stages of learning, choosing the same arm of the maze with high probability. In addition, use of a Bayesian "optimal observer" revealed that compared to WT, KO mice adapted their decisions less rapidly to a change in stimulus-reward relationship. We suggest that the misexpression of ephrin-A2 may lead to abnormal connectivity in regions known for their involvement in reversal learning and perseverative behaviours, including thalamic-prefrontal cortical-striatal circuitry and particularly orbitofrontal cortex. The implication is that topographic organisation of higher order brain regions may play an important role in learning and decision making.
authors.affiliation: School of Animal Biology, University of Western Australia, Crawley, WA 6009, Australia.
authors.forename: S
authors.initials: S
authors.lastname: Arnall
authors.forename: L Y
authors.initials: LY
authors.lastname: Cheam
authors.forename: C
authors.initials: C
authors.lastname: Smart
authors.forename: A
authors.initials: A
authors.lastname: Rengel
authors.forename: M
authors.initials: M
authors.lastname: Fitzgerald
authors.forename: J P
authors.initials: JP
authors.lastname: Thivierge
authors.forename: J
authors.initials: J
authors.lastname: Rodger
mesh_terms: D000818:Animals; D001499:Bayes Theorem; D001522:Behavior, Animal / Q000502:physiology; D002755:Choice Behavior / Q000502:physiology*; D004193:Discrimination Learning / Q000502:physiology*; D036383:Ephrin-A2 / Q000172:deficiency*; D005508:Food Deprivation / Q000502:physiology; D007839:Functional Laterality / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010775:Photic Stimulation / Q000379:methods; D012193:Reversal Learning / Q000502:physiology*; D012201:Reward; D012680:Sensitivity and Specificity; D013647:Task Performance and Analysis; D014796:Visual Perception / Q000235:genetics*
chemical_list: D036383:Ephrin-A2