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Innate visual recognition
E
• Wolf decoy for geese (plenty in New England).
• Why are these decoys efficient?
• Geese do not have pictures to teach their young ones what
animals to avoid…
• … and so they must be born with images of predators
engraved in their brain
• Why are we surprised to observe innate
predator recognition in visual domain?
• For us innate predator recognition in the
olfactory domain is much more intuitive.
• Rats are born knowing the smell of cats.
• Even humans are born with innate aversion to
certain smells (such as smell of rotten eggs).
Frogs
• Frogs can recognize prey stimuli—worm-like objects—immediately
after metamorphosis. (Although the accuracy of this recognition
improves during ontogeny)
• Lesion studies: bilateral ablation of both telencephalic
hemispheres and removal of the dorsal thalamus 
Frogs readily responded to moving visual stimuli with prey
orienting and snapping.
• Lesions to the optic tectum (superior colliculus homologue) cause
a total loss of responses to moving predator and prey objects.
• In amphibian species, there are no telencephalic components
that correspond to the visual cortex of mammalian species.
• Conclusion: optic tectum includes all the neurons frogs need for
visual recognition of predators and prey.
Birds
• Naive turkey chicks respond with escape behaviors to the
overhead presentation of moving birdlike silhouettes.
• Newly hatched chicks will peck at small objects shortly
after birth and show definite preferences for certain types,
colors and shapes of objects, even when these objects
produce no reward.
• Complete bilateral hemispherectomy performed in early
life spares many behaviors that require stimulus
discrimination, such as pecking at food objects, flying and
cleaning feathers with beak
Birds
• Right after hatching chicks have the innate predisposition to
approach stimuli that resemble their own species, both in their
shape and color, and in the way they move.
• Telencephalic ablation does not change preference for their own
species.
• The process of imprinting involves the learned recognition of a
particular stimulus object, which becomes ‘mother’ for the chicks.
• This imprinting is stored in telencephalon. Telencephalic ablation
erases the imprinted memory.
• Conclusion: same pattern as in frogs, chicks are born with
neurons (in optic lobe = tectum) necessary for visual recognition
of predators and food objects. Telencephalon is only necessary
for memory.
Rats
• Naïve rats (laboratory born and raised) exposed to a cat respond
with freezing behavior, and wild running and jumping.
• Complete bilateral lesion of visual cortex  same behavior.
• Rodents without visual cortex pursue objects that move in a
naturalistic fashion. As in the case of prey recognition in frogs, the
precise shape of the stimulus object is not overly important, and
recognition is primarily based on the characteristics of the
movement of the object.
• Conclusion: As in frogs and birds, recognition of predator and
prey can be mediated primarily by optic tectum (superior
colliculus).
Primates
• Snakes are oldest predators of monkeys.
• The infant monkeys raised in isolation respond to the pictures of
threatening monkeys with alarm vocalizations.
• Wild-reared adult monkeys are afraid of both live snakes and
snake models. Monkeys respond by moving to the back of the
cage, jumping in the cage, etc.
• Laboratory-reared adult monkeys react to the snakes with much
milder avoidance responses. For example, of the juveniles that had
been exposed to snakes as infants, six out of seven emitted alarm
calls, while only one out of seven inexperienced subjects emitted
an alarm call.
• But no monkeys approached the snake and almost all of them
oriented to the snake.
Vervet
monkey
• Vervet monkey select correct calls for four classes of predators (a
leopard, an eagle, a snake, a baboon).
• A young vervet can mistakenly produce the raptor call to hawks
(which resemble the true predator), produce the snake call to
inappropriate snakes, and the leopard call to inappropriate ground
animals.
• It corrects these errors, learning to confine the call to the correct
member of each category, and to respond more quickly.
• However, even when the vervet produces its first calls, it does not
make between-category errors, for example, issue the snake call to
a bird, and so on.
• That means they have innate representation of these classes in
their brain.
Humans
• Human neonates at only 9 minutes from birth track a
slowly moving schematic face stimulus with their head
and eyes significantly further than they follow scrambled
faces or blank stimuli.
• As in frogs, birds, and monkeys, mediated by superior
colliculi.
• The tendency to orient to face-like stimuli continues into
the second month, and thereafter decays to be replaced
by learned recognition of individual faces, starting at
approximately 3 months of age.
• The learned response is mediated by the cortex.
Conclusions: Innate visual recognition
• Almost all vertebrates are capable of recognizing
the classes of biologically relevant stimuli
(prey vs. predator) at or shortly after birth.
• In some phylogenetically ancient species (frogs) visual object
recognition even in adulthood is exclusively innate.
• In rodent species the innate sensory recognition systems
function throughout ontogeny. In adulthood it is acting in
parallel with the cortical recognition systems.
• In primates the structures involved in innate stimulus
recognition are essentially the same as those in rodents, but
innate recognition is only present in very early ontogeny, and
after a transition period gives way to learned object
recognition mediated by cortical structures.
• After the transition period, primate superior colliculi still
function to provide unconscious innate stimulus recognition
of the object’s class (prey vs. predator), and this recognition
can still generate orienting and emotional response!
• stop
1
4.5 BILLION
years ago
The Earth forms
2
1.5
3
Vertebrates
originated about 525
million years ago
(Cambrian explosion:
twice complete
genome duplication)
4
Dinosaurs originated
~230 million years ago
6
Primates originated
~70 million years ago
5
7
Human line split from
chimpanzee line
Modern humans:
~0.1 million YA
1. Hydra (relative of jellyfish)
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“…consciousness arises as a solution to one of the most
fundamental problems facing any nervous system: Too much
information constantly flows in to be fully processed. The brain
evolved increasingly sophisticated mechanisms for deeply
processing a few select signals at the expense of others…
consciousness evolved gradually over the past half billion years
and is present in a range of vertebrate species”
“Even before the evolution of a central brain, nervous systems
took advantage of a simple computing trick: competition.
Neurons act like candidates in an election, each one shouting
and trying to suppress its fellows. At any moment only a few
neurons win that intense competition, their signals rising up
above the noise and impacting the animal’s behavior. This
process is called selective signal enhancement, and without it,
a nervous system can do almost nothing.”
When selective signal enhancement first evolved?
“The hydra, a small relative of jellyfish, arguably has the
simplest nervous system known—a nerve net. If you poke the
hydra anywhere, it gives a generalized response. It shows no
evidence of selectively processing some pokes while
strategically ignoring others. The split between the ancestors
of hydras and other animals, according to genetic analysis, may
have been as early as 700 million years ago. Selective signal
enhancement probably evolved after that.”
1cm
2. Arthropod compound eye
• “The arthropod eye, on the other hand,
has one of the best-studied examples of
selective signal enhancement. It
sharpens the signals related to visual
edges and suppresses other visual
signals, generating an outline sketch of
the world.”
• “Selective enhancement therefore
probably evolved sometime between
hydras and arthropods—between about
700 and 600 million years ago.”
• “Selective signal enhancement is so
primitive that it doesn’t even require a
central brain. The eye, the network of
touch sensors on the body, and the
auditory system can each have their own
local versions of attention focusing on a
few select signals.”
3. Tectum - the centralized
controller of attention
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“The next evolutionary advance was a centralized
controller for attention that could coordinate among all
senses. In many animals, that central controller is a brain
area called the tectum. (“Tectum” means “roof” in Latin,
and it often covers the top of the brain.)
Tectum coordinates attention – aiming the satellite dishes
of the eyes, ears, and nose toward anything important.
All vertebrates (evolved 525 million years ago)—fish,
reptiles, birds, and mammals—have a tectum; Tectum is
absent from all invertebrates.
Tectum “simulates the current state of the eyes, head, and
other major body parts, making predictions about how
these body parts will move next and about the
consequences of their movement. For example, if you
move your eyes to the right, the visual world should shift
across your retinas to the left in a predictable way. The
tectum compares the predicted visual signals to the actual
visual input, to make sure that your movements are going
as planned. ... In fish and amphibians, the tectum is the
pinnacle of sophistication and the largest part of the brain.
A frog has a pretty good simulation of itself.”
Human brainstem with
thalamus on top
Cerebral cortex
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“The cortex is like an upgraded tectum. We
still have a tectum buried under the cortex
and it performs the same functions as in fish
and amphibians. If you hear a sudden sound
or see a movement in the corner of your eye,
your tectum directs your gaze toward it
quickly and accurately. The cortex also takes in
sensory signals and coordinates movement,
but it has a more flexible repertoire. ”
Unlike the tectum, which models concrete
objects like the eyes and the head, the cortex
can model something much more abstract.
”We say we have consciousness because deep
in the brain, something quite primitive is
computing that semi-magical self-description.
… and self-models become models of others.”
“…consciousness arises as a solution to one of
the most fundamental problems facing any
nervous system: Too much information
constantly flows in to be fully processed. The
brain evolved increasingly sophisticated
mechanisms for deeply processing a few select
signals at the expense of others…
consciousness evolved gradually over the past
half billion years and is present in a range of
vertebrate species”