Neurons are about 100 billions, the connections between
each neuron are between 1000 and 10,000.
It’s estimated that the number of permutations and combinations
of a single brain exceeds the number of elementary particles of the universe.
(It’s surely the structure more complex we know.)
Longer arm departing from the nucleus.
It transmits the information in centrifugal direction.
Arms departing from the nucleus.
They gather information moving in centripetal direction.
Structure that permits a neuron to pass an electrical or chemical signal to another neuron.
It has been often asserted that a lot of the connections (synapses)
depend on the genetic, they spoke about the gene of jealousy,
the gene of mathematic, the passion for chocolate, etc.
However this is not demonstrated anywhere and would make the DNA almighty.
It’s enough to see the behaviour of two monozygotic twins, where the genetic is identical.
Besides the some of genetic nature, synapses are generated:
OF THE EXTERNAL
IT’S THE MOMENT
The first months of life are fundamental for visual areas,
if the brain of a child doesn’t receive the necessary external stimuli
those synapses will never create.
After 25 weeks the brain is already very similar to what it would be in adult age.
Humans are the only animals born without an instict.
Spiders know how to weave a net, cat know how to hunt without lessons, etc..
Intellettive skills are ready at the beginning of the adolescence, but the emotions
are completely ready only after 20-22 years.
Humans’ maturation process is very slow and requires learning phases:
Theory of Paul MacLean of the three brains,
controverse because too simplificatory.
Feel - Remember
Interact with other
Survive - React - Repeat
Talk - Think - Move
Create - Learn
THE THREE BRAINS
Portion of the lymbic system (2nd brain) with the of an almond.
Here are the emotive responses and the fear.
It’s where pleasure for food and sex are elaborated.
Through a TAC has been demonstrated how the amygdala reacts to a face which induce fear
and how it calms down as soon as the face smiles.
For men the hypothalamus
switches on during the
orgams, so for it it’s enough
only the second brain.
For women instead also part
of the cortex is activated
during the orgams.
VISUAL AREAS OF THE BRAIN
Named with the letter V they are over 40 in humans.
Squirrels have 4, cats 12, monkey 20
Given by a damage to V4, area which takes care of the colour.
The world is seen in black and white.
A damage to V5 prevents the elaboration of the movement
and the world appears as a series of frames in succession.
People affected by cortical blindness have no vision.
However if they are asked to touch a bright point in front of them
they will always manage in the task.
They might believe it’s just luck, but it’s not. Indeed their brain is damaged, but their eyes work perfectly.
Ways to see the brain (TAC, PET, NMR)
LOOKING AT THE BRAIN
Saying the world walking we can see motor neurons activate.
Math is in the old part of the brain.
Birds know how to count till 5. They would soon notice if a chick is missing from the nest.
Same is for the elephant which however can count only till 3, after that they perceive many.
VENTRAL PATHWAY the “what” pathway
shape, colour and identity of things
space, environment and movementDORSAL PATHWAY the “where” pathway
If we try to grab the two orange dots, as the fingers get closer
the dorsal pathway (where pathway) adjusts the aim and calibrates
the grabbing so that the hand is not deceived by the optical illusion.
Color is perceived before than the shape.
Shape before the movement.
Between colour and movement there are about 60-80 milliseconds.
We’re not conscious about that because the neuroal times are very quick
compared to our consciousness.
All the mammals have an area which elaborates the luminosity,
but only the primates have an area for the colours.
The older pathway (the where pathway) is blind to the colour,
this means that the spatial elaboration thinks only in terms of quantity
of reflected light (so in greyscale).
That’s why if we add a colored item on a background of a different colour but of the same luminosity,
the image tends to flicker.
RED TEXT ON GREEN BACKGROUND
RED TEXT ON GREEN BACKGROUND
The flickering is given by two information crossing from a pathway to the other.
So the brain answers to two signals apparently contradictory.
The use of vibrant colours is a classic in graphic design, especially between the complimentary cold
and warm colours. It increase the attention although the readability is obviously quite low.
“They asked me why the ice-cream
on the book cover is pistachio, chocolate
The reason - both technical and
aesthetic - is that those three colours
once converted into black and white
correspond to the same “grade of grey”
(equiluminant tints) and, since our eyes
read the light difference independently
from the colour, in this way the lettering
is always more readable in every point.
There are two harmonic layers: the one
of the figure and the one of the text.
Furthermore, chocolate and strawberry
are a playful and unscrupulous match,
very United States”.
the lettering lays on an unique
grade of grey
lettering is not very readable
Classic exercise in arts schools is to portrait a model before in greyscale
and then using only tints, but of the same luminosity.
In this way the brain trains itself to differentiate the tonal values from the chromatic ones,
taking advantage of the functional segregation in the brain.
Differentiate tonal and chromatic values is important for whoever works
with visual languages.
Like one of the best Hollywood costume designer of the last century, Edith Head (1897-1981)
Part of a body which cause the reaction a neuron when stimulated.
On the retina these fields are not sitting side by side,
but they overlap each other.
So the perception is given by the combination of hundreds of bodies.
Visually every cell has its own receptive field which corrisponds
to a specific part of the scene.
For the on-center cell, whatever goes in the centre activates it,
whatever goes in the surrounding center inhibits it.
For the off-center cell is obviously the opposite.
ON-CENTER, OFF-SURROUND OFF-CENTER, ON-SURROUND
On-off cells are sensitive to lines of borders of things.
End-stop are more sensitive to corners, sharp edges, dashed lines, etc.
All the cells are more sensitive to brightness discontinuity
than to the light quantity.
In general, light quantity, is not that important in biology and neurons
answer better to net jumps than to gradients.
The brain did not evolve to appreciate absolute tonal values, but to survive in a world where scene changes are cru-
I.E. DIGITAL IMAGES
More an image is compressed less are the colour used and so
the gradients, there is only a drastic change of colour which however
allow us to recognise the figure.
ACTUAL LUMINANCE DISTRIBUTION
PERCEIVED LUMINANCE DISTRIBUTION
In the gradient passages from light to dark (and opposite),
the brain sees the reinforce bands before darker and then lighter.
In classic painting they used to teach that when portraing the real
three things must be included:
A) THE BODIES OWN SHADOW
B) THE SHADOW BROUGHT BY THE BODIES
C) A DARKER LINE AS REINFORCEMENT IN THE SHADOW PASSAGES
Without knowing it they were painting a product of the brain rather than a quality of light.
A black flickering is perceived in the corners, but only in periferic area,
in fact the flickering disappears when fixing the corner.
Cells on the intersection receive the inhibition on 4 sides, producing a weaker answer (and so less white)
than the one obtained when inhibited only on two sides.
THE HERMANN GRID
In the environment the gradual fadings are almost always characteritics
of the illuminating light and not of the things themselves.
Parthenon original colours.
They wanted the colours to change as less as possible during the day.
Verticality and horizontality are the most simple orientations
to recognise by the brain.
Surely it depends also on the fact that we stand up on the Earth, that we feel the gravity
and that we have two eyes horizontally aligned.
EACH EYE HAS A VISUAL FIELD OF ABOUT 90º
Having more than one eye is needed for two things:
- enlarge the visual field
- to see in three dimensions
Some animals have visual field which don’t overlap each other,
so they can’t see the depth.
Have an almost 360º field which allows them to check
on every side if a predator is approaching.
Can see the distance to the prey.
Crossing the eyes you can make overlap the border of a tile seen by the right eye,
with the border of another tile (just next to it) seen by the left eye.
Being the tiles perfectly identical, the brain is deceived and tries to rebuild the tridimensionality although
starting from altered data - like if the distance between the two eyes was different from the human one.
The resulting perception is to feel physically smaller, feeling very close to the wall.
Basically seeing the tiles from the point of view of a fly.
BRAIN DECEPTION ON THE TRIDIMENSIONALITY
SPACE BETWEEN TILES
(the wall looks closer)
If you try to overlap the two images crossing the eyes the result will be a
series of moving and intermittent spots, due to the binocular antagonism.