PSY352H5 Lecture Notes - Lecture 5: Superior Colliculus, Striking Distance, Preoptic Area
Lecture 5
One step beyond simple reflexes: Prey capture in the frog
Prey capture: A five step process that is triggered by particular visual stimuli
• 1.Orienting towards the visual stimulus
• 2.Approach to be within striking distance
• 3.Tongue strike to capture prey
• 4.Swallow prey
• 5.Mouth wipe
What is an appropriate prey: systematic analysis of prey characteristic
Horizontal, long objects elicit the best prey catching response
How does the toad “decide” about whether the object is an appropriate prey?
• Stimulus filtering and feature detectors
• It recognizes long things as potential prey
•
The structure and major connections of the visual stimulus processing pathway in toads
• It doesn’t have columnar organization but it does have layer
• The stimulus processing starts at the retina
• Wherever the light shines in the receptive field, the surrounding cells get hyperpolarized (they
get inhibited)
• the retina is trying to provide a more clearer image of what it is looking at
Multiple levels of processing: Stimulus filtering starts in the retina
• the optic nerve to the thalamus and eventually the cortex
• in the cortex due to the layered organization there are particular stimuli
• there are all kinds of feedback loops and connections
•
Teasing apart the filtering: T5 cells of the optic tectum respond most specifically to prey-like visual
stimuli
• the t 5 cells makes it easier to associate simpler versions of the image
• so the animal is able to recognize the prey and catch it
• the multiple layers of feedback loops allow the recognition of the prey
TP3 cells Thalamic pre-tectum, TP5 cells Tectum
Prey capture circuit in the frog: numerous brain areas are involved
• Key: AT - anterior dorsal thalamus; CT - caudal dorsal thalamus; OT - optic tectum; T -
telencephalic nuclei; EY - eye; HY - hypothalamus; MP - medial pallium; PA - preoptic
area; ST - striatum
• Figure 2a shows connections that have been derived from physiological experimental
data
• Figure 2c shows the anatomically identified connections.
• Note that in these figures, the pathways for both the predatory-avoidance and the prey-
capture are included
find more resources at oneclass.com
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So what’s the principle here?
• Feature detector (T5(2)) cells are at the end of a long chain of neurons.
• Multiple steps of filtering allows detection of very simple features of the visual stimulus at every
step
• Eventually, very complex images can then be analyzed this way
Heritability, Genetic Determinism, IQ, Sex, Criminality & Racism
• When behavior genetics is mixed with the dark side of the political motivation
• The story of Glayde Whitney and James Watson
o Discovered the structure of the DNA and how it can store information about proteins and
replicate itself
• James Watson suggested that people from Africa are not smart due to genetic factor and as a
result we should not support Africa financially
o Was removed from the University and face a lot of backlash
• Glayde also made a similar racist comment
• 60-70% of IQ is based on heritability
• Genetic predispositions:
• There are specific preferences that we have such as a favourite temperature
o This is because we have a common ancestor that comes from Africa so we like this
temperature
• There are many things in our biology and genes that are universal
• If there is very long selection pressure there is no variance in the genome
• Parental investment theory: how males and females behave based on evidence from humans and
animals
o There is a difference between male and females in their nature of reproduction
o Men try to mate with different women as they want to increase their reproductive success
o Our societal attitudes also evolve based on our genetic instincts
Problems with racism: a scientific perspective
• 1.Major racial groups are not genetically well defined
o If someone is called African American it is unclear how much percent of their genetics
comes from African descent
▪ Eg. 50 or 25%
o About 70% of the genome contributes to IQ
o The genes that are used to identify a part of someone’s ethnic background (only 100
genes )
o The genes that are linked to ethnic background are not all linked to intelligence
▪ Thus we cannot assume that ethnic background is solely related to intelligence
there is a lot of other factors that are also influencing IQ
• 2.Larger genetic variability within as compared to between racial groups
o there is a genetic bottle neck because only a few people left Africa
o and 100,000-150,000 years is not enough to create significant differences between genes
o those that stayed in Africa evolved by separate tribes that lived far apart that didn’t allow
them to mix
▪ these groups evolved in complete isolation from each other
• 3.Phenotypical recording techniques are biased (IQ)
o it gives the highest score to Caucasian males
o because the creator of the test was Caucasian
• 4.Environmental effects are not parsed out
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
One step beyond simple reflexes: prey capture in the frog. Prey capture: a five step process that is triggered by particular visual stimuli: 1. orienting towards the visual stimulus, 2. approach to be within striking distance, 3. tongue strike to capture prey, 4. swallow prey, 5. mouth wipe. What is an appropriate prey: systematic analysis of prey characteristic. Horizontal, long objects elicit the best prey catching response. How does the toad decide about whether the object is an appropriate prey: stimulus filtering and feature detectors. The structure and major connections of the visual stimulus processing pathway in toads. It doesn"t have columnar organization but it does have layer: the stimulus processing starts at the retina. Wherever the light shines in the receptive field, the surrounding cells get hyperpolarized (they get inhibited) the retina is trying to provide a more clearer image of what it is looking at.
