Evolution of the brain
Brain volume increased gradually (geleidelijk) and later
with jumps
Brain volume started to increase only with Homo
erectus. Largest brain is in the late Neanderthals.
There is little evolution of brain volume within species,
but between different species there is large evolution of
brain volume
Increase of brain volume is correlated with decrease of
prognathism (positional relationship between mandible or maxilla to skeletal base)
Evolution of skull shape:
1. High-vaulted (Homo sapiens)
2. Backwards elongated (Homo neanderthalensis)
Brain volume is related to body size in mammals
o Due to a logarithmic scale it becomes linear but in
real it is not linear
o If brain volume increases by factor of 2 than body
size increase by factor lower than 2
o Big animals have relative small brain volume
o Small animals have relative big brain volume
Allometric (relationship between 1 thing of an animal and body
weight) relationship between brain volume and body mass
(weight)
o Due to a logarithmic scale it becomes linear but in real it
is not linear
o Slope is 0,6 (2/3) – brain volume increase with the
surface of body not with the volume (body mass) and the surface is related to
the volume with power of 2/3
The brainis a surface
Develops from 5 vesicles at the end of neural tube
1. Prosencephalon (forebrain)
a. Telencephalon – develops into 2 hemispheres (left and right part)
b. Diencephalon
2. Mesencephalon (midbrain)
3. Rhombencephalon (hindbrain)
a. Metencephalon
b. Myelencephalon
Cerebral isthmus separates the hindbrain from the midbrain
Brain is a hollow structure the neural network is in the cortex
Encephalization quotient (EQ)
Correlation for allometric relationship with body mass
EQ = brain volume / 0,12W^0,67 – W= body mass
, Gorilla (EQ =1,61): means that the brain volume of a Gorilla is 1,61 times greater
than the brain volume of a mammals with the body size of a Gorilla.
Homo Sapiens (EQ=8,07): means that the brain volume of a Human is 8,07 times the
brain volume that you would expect if you were a mammal with body size of 70 kg.
EQ = 1, you are an average mammal. So, gorilla has bigger brain volume than
average mammal. Higher EQ means bigger brain volume
Conclusion:
o EQ = 1, you are an average mammal. So, gorilla has bigger brain volume than
average mammal.
o Higher EQ means bigger brain volume
o Increase of encephalization through evolutionary history
o Higher EQ in predators (carnivors) compared to herbivores
Neocortex/cerebellum/brainstem
o (Neo)cortex
o Lobus frontalis (constitutes 1/3 of
neocortex): prefrontal cortex is the
last part of neocortex that develop
Medial prefrontal cortex:
control of basic drives
Lateral prefrontal cortex:
temporal organization of
behaviour
2 tracks in prefrontal cortex – has to do with human reasoning and
making decisions
1. From ventro-medial to dorso-medial
Probabilistic inferences (gevolgtrekkingen) about the reliability of
ongoing behaviour
Judge whether I should adjust the behaviour with something from
long-term memory
2. From central to lateral
Probabilistic inferences (gevolgtrekkingen) about the reliability of 2
or 3 alternative strategies
Judge whether I should further exploit (benutten) one of the
alternatives
o Lobus temporalis
o Lobus parietalis
o Lobus occiptalis
o Cerebellum
o Brainstem
Neocortex (infolding by sulci (groeve) and gyri) (cerebral hemispheres) enlarges and
in neocortex especially the prefrontal cortex enlarges
Brain volume increased gradually (geleidelijk) and later
with jumps
Brain volume started to increase only with Homo
erectus. Largest brain is in the late Neanderthals.
There is little evolution of brain volume within species,
but between different species there is large evolution of
brain volume
Increase of brain volume is correlated with decrease of
prognathism (positional relationship between mandible or maxilla to skeletal base)
Evolution of skull shape:
1. High-vaulted (Homo sapiens)
2. Backwards elongated (Homo neanderthalensis)
Brain volume is related to body size in mammals
o Due to a logarithmic scale it becomes linear but in
real it is not linear
o If brain volume increases by factor of 2 than body
size increase by factor lower than 2
o Big animals have relative small brain volume
o Small animals have relative big brain volume
Allometric (relationship between 1 thing of an animal and body
weight) relationship between brain volume and body mass
(weight)
o Due to a logarithmic scale it becomes linear but in real it
is not linear
o Slope is 0,6 (2/3) – brain volume increase with the
surface of body not with the volume (body mass) and the surface is related to
the volume with power of 2/3
The brainis a surface
Develops from 5 vesicles at the end of neural tube
1. Prosencephalon (forebrain)
a. Telencephalon – develops into 2 hemispheres (left and right part)
b. Diencephalon
2. Mesencephalon (midbrain)
3. Rhombencephalon (hindbrain)
a. Metencephalon
b. Myelencephalon
Cerebral isthmus separates the hindbrain from the midbrain
Brain is a hollow structure the neural network is in the cortex
Encephalization quotient (EQ)
Correlation for allometric relationship with body mass
EQ = brain volume / 0,12W^0,67 – W= body mass
, Gorilla (EQ =1,61): means that the brain volume of a Gorilla is 1,61 times greater
than the brain volume of a mammals with the body size of a Gorilla.
Homo Sapiens (EQ=8,07): means that the brain volume of a Human is 8,07 times the
brain volume that you would expect if you were a mammal with body size of 70 kg.
EQ = 1, you are an average mammal. So, gorilla has bigger brain volume than
average mammal. Higher EQ means bigger brain volume
Conclusion:
o EQ = 1, you are an average mammal. So, gorilla has bigger brain volume than
average mammal.
o Higher EQ means bigger brain volume
o Increase of encephalization through evolutionary history
o Higher EQ in predators (carnivors) compared to herbivores
Neocortex/cerebellum/brainstem
o (Neo)cortex
o Lobus frontalis (constitutes 1/3 of
neocortex): prefrontal cortex is the
last part of neocortex that develop
Medial prefrontal cortex:
control of basic drives
Lateral prefrontal cortex:
temporal organization of
behaviour
2 tracks in prefrontal cortex – has to do with human reasoning and
making decisions
1. From ventro-medial to dorso-medial
Probabilistic inferences (gevolgtrekkingen) about the reliability of
ongoing behaviour
Judge whether I should adjust the behaviour with something from
long-term memory
2. From central to lateral
Probabilistic inferences (gevolgtrekkingen) about the reliability of 2
or 3 alternative strategies
Judge whether I should further exploit (benutten) one of the
alternatives
o Lobus temporalis
o Lobus parietalis
o Lobus occiptalis
o Cerebellum
o Brainstem
Neocortex (infolding by sulci (groeve) and gyri) (cerebral hemispheres) enlarges and
in neocortex especially the prefrontal cortex enlarges
