Feature Analysis in Toads Flashcards
Quick visual classification of predators and prey
Predator-like stimulus → toad turns away and jumps to safety
Prey-like stimulus → series of motor actions that are part of the FAP
Prey FAPs
Orient (o)
Approach (a)
Fixate (f)
Snap (s)
Does not have to start at orient, can also repeat steps
Ewert & colleagues lab experiment with different stimuli
Used dummy stimulus and measured turns per minute
3 conditions: fake worm (horizontal rectangle), fake “anti-worm” (vertical rectangle), and square (could represent shadow of predator)
Preference for worm-like stimulus → high releasing value (turns/min increased as stimulus became longer)
Turns/min decreased as stimulus became taller (“anti-worm”)
Turned towards square if small (prey), turned away from square if large (predator)
Property of invariance
Stimulus contrast and velocity were not important
Configural property
Shape of stimulus and direction of movement were most important
Neural mechanisms of prey detection
Contralateral projections from retina to the optic tectum (OT)
Parallel projections to OT and thalamic pretectum (TP)
Topographic map of visual space in OT (retinotopy)
Visual electrophysiology
Specific regions of the retina map onto the contralateral optic tectum and pre-tectum (systematic one-to-one map of visual space)
Feature detection in tectal T5 cells and thalamic-pretectal area (TH3) cells
T5(2) cells could be considered an integrator of T5(1) cells and TH3 cells → T5(1) cells excite T5(2) cells when a worm-like stimulus is presented, TH3 cells inhibit T5(2) cells when an anti-worm stimulus is presented