Emotional & Spatial Learning in goldfish is dependant on different telencephalic pallial systems M. Portavella & J. Vargas European Journal of Neuroscience Vol. 21, pp. 2800-2806, 2005 Morris 1981 Rodrigo 2002 Portavella et al 2004 a, b

How big of a nerd am I?

Objectives Test the effects of specific lesions on different learning capacities and explore the existence of differentiated learning and memory systems in fish Establish homologies between pallial areas of both fish and other vertebrates

Which part of the telencephalon are you? Hippocampus Spatial, relational, contextual learning Amygdala Emotional learning, ‘nose brain’ Mammals, birds and reptiles Not so clear if the divisions exist so clearly in the fish Most lesion studies are entire telencephalon Impairs aggressive and reproductive behaviors

DG Entorhinal Cortex CA3 Damage to any One specific area Mossy fiber Entorhinal Cortex CA3 Schaffer collateral Damage to any One specific area Can affect new memory Acquisition CA1 Sub

Development of the Telencephalon Eversion in teleost fishes Evagination in land vertebrates

Lateral Telencephalic Pallium LP Ablation of LP impairs spatial learning in T-maze

Medial Telencephalic Pallium MP Ablation of MP impairs two way avoidance conditioning Ablation of MP and LP negatively affect trace conditioning

Learning: process by which new information is used to modify subsequent responses Memory: using processed information to modify subsequent behavioral responses Not directly measurable, inferred from changes in Behavior over time enter the behavioral models….

Spatial Learning Navigate through space to a discrete goal Cartographic Strategy: navigation based on cognitive map Integration of positional information derived from different views of environment at different times Positioning vectors Egocentric- specify landmarks in a body-centered coordinate system (relative to me) Geocentric- specify my location in earth centered coordinates

The animal’s geocentric position vector is computed by the dead-reckoning mechanism. The egocentric position vector for the landmark – its direction (or bearing, β) and distance from the animal–is computed by the animal’s perceptual system. Rotating the egocentric vector by the animal’s geocentric orientation (its heading, η ) gives a vector of the same length with orientation η+β (heading+bearing). Adding that vector to the animal’s geocentric position vector ag gives the landmark’s position in the geocentric coordinate framework

Morris Water Maze 1980 ish

Way Cool Michael Jordan Poster Use landmarks and extra-maze cues to find platform located underwater Perform worse if cues are mixed up No effect if some cues are removed No effect if maze is rotated Learning is based on spatial relationships between landmarks

Spatial Learning Task used in this study Pre exposure to box with all doors open Acquisition phase = 25-trials/session daily Error scored if fish bumped into glass plate Correct choice scored if fish swims into correct exit 80% correct choices in 25 trials = learning criteron

Once learning criteria were met, fish were exposed to reversal training, where goal was moved to other side Of the tank. Same criteria for learning, 80% correct/25 trials

The Shocker

2-Way Avoidance: shuttlebox 3 days of pre exposure, with no shock or lights Daily session of 10 trials separated by 1-2 min for 20d 5 mins pre and post session acclimation CS (discriminative stimulus; green light) for max 15 s If fish escapes within 10 s, no shock delivered If no response within 10 s, shock for a max of 5 seconds Thus, 10 s of temporal separation btwn shock and CS

Responses classified in 2 categories Avoidance response: escape within 10 s Escape response: escape between 10-15 s

Subjects 24 pet shop grade goldfish 3 experimental groups LP (lateral pallium ablation) n=8 MP (medial pallium ablation) n=8 Control Surgery but no ablation n=4 No surgery n=4

Surgery Fish were anaesthetized and placed in surgical chamber, with constant flow or doped water over gills Skull was opened and offending brain tissue was sucked out with a micro pipette driven by a vacuum 5 days recovery in home tank Following experiments all brains were removed to verify ablation

Timeline Spatial task 2 way avoid 5 days rest Death. Brains fixed and Checked for albation accuracy Surgery 4 surgery controls 4 non-surgery controls 8 LP 8 MP

Results: Avoidance Task No diff between non-treated and sham controls, so they were grouped MP group show lower level of avoidance responses compared to LP & Control

Results MP lesion group show escape LP and control groups show avoidance

Results: Spatial Learning Task No diff between groups in # of trials it takes to acquire spatial task During reversal, LP lesion group requires more sessions to reach learning criteria, compared to original acquisition phase P< .07 compared to MP group session #

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Results No diff between groups in # of errors scored in initial learning phase During reversal, LP lesion group had significantly more errors than it did in the first learning trials

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Discussion Lesions of the Medial Pallium impair acquisition of an avoidance conditioning response Similar to whole telencephalic lesion Amygdalar lesions in land vertebrates produces same result No effect on spatial learning or reversal

Cause deficits in spatial learning however Lesions of the Lateral Pallium have no effect on acquisition of an avoidance conditioning response Cause deficits in spatial learning however More sessions necessary during reversal More errors accrued during reversal Less efficient in reversal But they still did reverse It was pretty easy

Differences in learning systems? Cartographic vs Taxon Learning system Taxon- can not detect changes in an environmental cue set, learn each time de novo LP lesion fish using taxon system? Cartographic- detect changes in the relations between environmental cues, facilitates re- learning of a task MP and Control using cartographic system I think this is bogus Incomplete ablation Help from other regions

MP lesion and pain MP fish show escape from shock behavior in two way avoidance, but swim out within .5 to 1s after shock onset The shock still hurts No effect of MP lesion on pain tolerance Or locomotion

Importantly, these results support the existence of different telencephalic based learning systems in a teleost Support the homology hypothesis on functional features between mammalian and fish models