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In an auto associative memory you don't have to have the entire pattern you want to  retrieve in order to retrieve it.

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The auto-associative memory can retrieve the correct pattern, as it was originally stored, even though you start with a messy version of it.

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With a sequence of patterns, similar to a portion of a melody, the auto associative memory can remember the entire melody.

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People learn practically everything as a sequence of patterns.

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A neuron collects inputs from  its synapses,    and combines these inputs together    to decide when to output a spike    to other neurons.

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A typical neuron can cycle its functions and reset itself in about 5 ms, or around 200 times per second.

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The brain is a parallel “computer. “   It has billions of cells    all computing at the same time.

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The brain does not compute the answers to problems.    It retrieves the answers    from memory.

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The neocortex is not like a computer,    parallel or otherwise.    Instead of computing answers to problems,    the neocortex uses stored memories    to solve problems and produce behavior.

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Neocortex stores sequences of patterns.

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Neocortex    recalls patterns    auto-associatively.

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Neocortex    stores patterns    in an invariant form.

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Neocortex    stores patterns    in a hierarchy.

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A story    is stored in your head    in a sequential fashion    and can only be recalled    in the same sequence.

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It's almost impossible    to think of anything complex    that isn't a series of events or thoughts.

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All memories are like this.    You have to walk through the temporal sequence    of how you do things.

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Your memory    of the alphabet    is a sequence of patterns.

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All memories    are stored in the synaptic connections    between neurons.

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An adult human neocortex    has an incredibly large memory capacity    but we can only remember a few    at any time    and can only do so    in a sequence of associations.

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An autoassociative memory    is one that can recall complete patterns    when given only a partial    or distorted input.

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Autoassociative memory can work    for both spatial    and temporal patterns.

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During conversation    we often can't hear all the words    we are in a noisy environment.    Our brains fill in    what they miss    with what they expect to hear.

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Some people    complete of the sentences    of others aloud,    but in our minds    all of us    are doing this constantly.

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When you see, feel, or hear something,    the cortex takes the detailed highly specific input   and converts it    to an invariant form.

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Memory storage,    memory recall,    and memory recognition    occur at the level of invariant forms.

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An important function    of the neocortex    is to use its memory    to make predictions.

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Your brain does this    by combining a memory    of the invariant structure of her face    with the particulars of your immediate experience.

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The combining    of invariant representations    and current input    to make detailed predictions    is exactly what is happening.

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This combining    is a ubiquitous process    that happens in every region of  cortex.

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Three properties of cortical memory    (storing sequences,    autoassociative recall,    and invariant representations)    are necessary ingredients to predict the future    based on memories of the past.

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The predictions    are made in parallel    and will just as readily detect    an odd texture,    a misshapen nose,    or an unusual motion.

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What we perceive    is a combination    of what we sense    and of our brain's memory=derived predictions.

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Visual areas make predictions about edges,    shapes,    objects,    locations,    and motions.

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Auditory areas make predictions about tones,    direction to source,    and patterns of sound.

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somatosensory areas make predictions about touch,    texture,    contour,    and temperature.

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Correct predictions result in understanding.

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Prediction    is the primary function of the neocortex,    and the foundation of intelligence.

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Rodolfo Llinas, I of the Vortex, the capacity to predict the outcome of future events is most likely, the ultimate and most common of all global brain functions.

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There is an entire subfield of mathematics devoted to Bayesian networks.

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Bayesian networks use probability theory to make predictions.

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When listening to people speak,    you often know what they're going to say     before they finished speaking.

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People tend to use     common phrases or expressions    in much of their conversation.

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Prediction   is not always exact.    Rather, our minds work to make probabilistic predictions    concerning what is about to happen.

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In Western music,    the brain automatically predicts    beats,    repeated rhythms,    completion of phrases,    and end of songs.

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Intelligence    is measured by the capacity to remember and predict    patterns in the world    including language,    mathematics,    physical properties of objects,    and social situations.

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To recall the appropriate memories,    the brain has to retrieve patterns    by their similarity to past patterns (auto associative recall).

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Memories have to be stored in an invariant form    so that the knowledge of past events    can be applied to new situations    that are similar but not identical    to the past.

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As many if not more feedback connections in visual cortex as there are feedforward connections.

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Patterns received by the first auditory area    can vary widely.    A word can be spoken    with different accents,    and different pitches, or at different speeds.

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Higher up in the cortex,     those low level features don't matter;     a word is a word    regardless of the acoustic details.

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We see the same kind of feedback,    prediction,    and invariant recall    in auditory cortex    as we see in the visual system.

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The downward flow    fills in the current input    and makes predictions   about what we will experience next.

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These predictions    can only come about    by massive coordination    of patterns streaming up and down    the cortical hierarchy.

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We have an overarching sensory system,    sights,    sounds,    touch,    and more    combined,    all flowing up and down    a single multi-branched hierarchy.

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You are not born with    any of this knowledge;    you learned it through the incredibly large capacity    of your cortex    to remember patterns.

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The way the cortex processes    downward-flowing sensory predictions    is similar to    how it processes    downward-flowing motor commands.

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Sensory patterns    simultaneously flow in anywhere and everywhere,    and then flow back down    in any area of the hierarchy,    leading to predictions or motor behavior.

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Seeing,    hearing,    touching,    and acting    are profoundly intertwined.

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V1,V2, and V4,    each is a collection    of many smaller subregions.

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The largest region by far    is V1,    the primary visual area.

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Next would be V2.    They are large    compared to most regions.

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V1 is made up of numerous separate little cortical areas     that are only connected to their neighbors indirectly,    through regions higher up in the hierarchy.

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The cortex    now looks similar    everywhere.

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Pick any region    and you will find many lower regions    providing converging sensory input.

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The receiving region    sends projections back    to the input regions,    telling them what patterns    they should expect to see next.

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Higher association areas    unite information    from multiple senses    such as vision and touch.

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The most important result    of this depiction of cortical hierarchy    is that every region of cortex    forms invariant representations.

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Now we can say that invariant representations are ubiquitous.    Invariant representations are formed in every cortical region.

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Association regions    above IT    form invariant representations    of patterns from multiple senses.

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All regions of the cortex    form invariant representations    of the world beneath them in the hierarchy.

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The real world's nested structure   is mirrored    by the nested structure of the cortex.

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The cortex has a clever learning algorithm     that naturally finds    whatever hierarchical structure exists    and captures it.

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Higher regions of the cortex    are keeping track of the big picture    while lower areas are actively dealing with the fast-changing small details.

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If the patterns are related    in such a way    that the region can learn to predict    what pattern will occur next,    the cortical region    forms a persistent representation,   or memory,    for the sequence.

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As information moves up    from primary sensory regions    to higher levels,    we see fewer and fewer    changes over time.

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In primary visual areas like V1,    the set of active cells    is changing rapidly    as new patterns fall on the retina    several times each second.

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In visual area IT,    self firing patterns    are more stable.

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Each region of cortex    has a repertoire    of sequences it knows.

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Each cortical region    has a name    for each sequence    it knows.

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The "name"    is a group of cells    whose collected firing    represents the set of objects    in the sequence.

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These cells remain active    as long as the sequences playing,    and it is this “name”    that is passed up    to the next region in the hierarchy.

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We can imagine region IT    at the top of the visual hierarchy    relaying to an association area above it, "I am seeing a face."

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One region    might recognize a sequence of sounds    that comprise phonograms.

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The next higher region    recognizes sequences the phonems    to create words.

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The next higher region    recognizes sequences of words    to create phrases,    and so on.

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By collapsing predictable sequences    into named objects    at each region in the hierarchy,    we achieve more and more stability    the higher we go.

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This creates invariant representation.

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The opposite effect happens    as a pattern moves back down the hierarchy:    stable patterns    get unfolded into sequences.

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At this point the unfolding pattern splits    and travels down both the auditory section of cortex    and the motor section of cortex.

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In the final bottom region,    each phonem is unfolded    into a sequence of muscle commands    to make sounds.

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The lower you look in the hierarchy,    the faster the patterns are changing.

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A single constant pattern    at the top of the motor hierarchy    eventually leads to    a complex and lengthy sequence    of speech sounds.

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The bottom-up inputs to a region of cortex    are input patterns    carried on thousands or millions of axons.

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The number of possible patterns    that can exist on even 1000 axons    is larger than    the number of molecules in the universe.

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Both steps,    classification and sequence formation,    are necessary    to create invariant representations,     and each region of cortex    does them.

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You use the context of known sequences    to resolve ambiguity

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Most of the time    you are aware    that you are filling in    ambiguous or incomplete information    from your memories or sequence  

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By recognizing a sequence of patterns,    a cortical region will predict its next input pattern    and tell the region below    what to expect.

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A region of cortex    not only learns familiar sequences,    it also learns how    to modify its classifications.

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In cortical regions,    bottom-up classifications    and top-down sequences    are constantly interacting,    changing throughout your life.

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Forming new classifications    and new sequences    is how you remember the world.

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Another part of the cortical job    is to relay the “name,”  of the sequence you are seeing    to the next level up.

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The hierarchy of the cortex    ensures that memories of objects are distributed over the hierarchy;    they aren't located in a single spot.

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Because each region of the hierarchy    forms invariant memories,    what a typical region of cortex learns is sequences of invariant. representations,    which are themselves sequences of invariant memories

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Cortical regions    vary greatly in size,    the largest being the primary sensory areas.

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Let's assume that a typical cortical area    is the size of a small coin.

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The density and shape    of the cells in the cortex    vary as you move from top to bottom.

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These differences    define the layers.

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Layer 1, the top layer    is the most distinct of the six layers.    It has very few cells    consisting primarily of a mat of axons    running parallel to the cortical surface

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Layers 2 and 3 looks similar.    They contain many,    tightly packed. pyramidal cells.

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Layer 4 has a type of star-shaped cell.

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Layer 5 has regular pyramidal cells    as well as a class of extra big pyramidal-shaped cells.

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Layers 6,  the bottom layer   also has several types of unique neurons.

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Columns of cells    run perpendicular to the layers.    You can think of columns    as being vertical units of cells    that work together.

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The layers within each column    are connected by axons    that run up and down,    making synapses along the way.

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Columns do not have clear boundaries    but their existence can be inferred    from several lines of evidence.

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The cells within each column    are strongly connected.

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Activity spreads up and down    within a column of cells.

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In an embryo,    single precursor cells    migrate from an inner brain cavity    to where the cortex takes take shape.

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Each of these cells    divides    to create about 100 neurons,    called a microcolumn.

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The human cortex    has an estimated several hundred million    microcolumns.

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Imagine a single microcolumn is the width of a human hair.

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The brush like mat    is a simplistic model    of the coin size cortical region.

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And information flows    mostly in the direction of the hairs:    horizontally in layer 1    and vertically in layers 2 through 6

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At least 90% of the synapses    on cells within each column    come from places outside the column itself.

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Some connections    arrived from neighboring column.

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Other connections    come from halfway across the brain.

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Vernon Mountcastle argued there is a single cortical algorithm,    he also proposed a cortical column is the basic unit of computation in the cortex.

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It is believed that the column is the basic unit of prediction.

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Converging inputs from lower regions always arrive at layer 4, the main input layer.

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Layer 4 cells then send projections up to cells in layer 2 and layer 3    within their column.

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Layer 6 cells are the downward projecting output cells    from a cortical column    and project to layer 1    in the region hierarchically below.

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The sum of all these mechanisms    allows the cortex to learn sequences,    make predictions,    and form constant representations,    or "names," for sequences.

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The neocortex is responsible for all complex motor sequences    and can directly control your limbs.

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Connections between the hippocampus and the neocortex    suggest that the hippocampus is the top region of the neocortex.

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The hippocampus occupies the peak of the neocortical pyramid.

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The hippocampus not only sits at the top of the cortical pyramid,    but it still connects directly to many older parts of the brain.

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Think about the information flowing from     your eyes,    ears,    and skin    into the neocortex.

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Each region of the neocortex    tries to understand the input    in the in terms of the sequences it knows.

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If it does understand the input    it does not pass on the details    to higher levels of the hierarchy.

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If a region does not understand the current input,    it passes it up the hierarchy    until some higher region    does understand it.

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A pattern that is truly novel    will escalate further and further up the hierarchy   until some higher region    does understand it.

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The net effect is that when you get to the top of the cortical pyramid,    what you have left is information that can't be understood    by prior experience.

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You are left with    the part of the input    that is truly new and unexpected.

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It is these unexplained and unanticipated remainders,    the new stuff,    that enters the hippocampus    and is stored there.

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This new, fresh information    won't be stored forever.    Either it will be transferred into the cortex    or it will eventually be lost.

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The hippocampus has a heterogeneous structure    with several specialized regions.    It's good at the unique task of quickly storing    whatever pattern it sees.

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You can instantly remember a novel event in the hippocampus,    but you will permanently remember something in the cortex   only if you experience it over and over,    either in reality or by thinking of it.

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The cortex has a second major pathway    for passing information    from region to region,    up the hierarchy.

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The alternate path starts with cells in layer 5    which project to the thalamus    and then up to the next higher region    of cortex.

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As we move up the cortical hierarchy,    there is a direct path    between two regions    and an indirect path    through the thalamus.

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The alternate pathway    through the thalamus    is likely the mechanism    by which we attend to details    that normally we would not notice.

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It bypasses the grouping of sequences    in layer 2,    sending the raw data to the next higher region    of cortex.

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In this way unusual events    quickly rise    to your attention.

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This is why   we can't avoid focusing on deformities    and other unusual patterns.

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Often however, errors aren't strong enough    to open the alternate pathway.    This is why we sometimes don't notice    if a word is misspelled as we read it.