Materialistic Brains
definition of brains o Brains are something made of neurons (a type of cell) o Plus all the associated brain chemistry (e.g., neurotransmitters) Materialist definition of neurons o Long cells that connect to each other and also to sensory cells and motor cells o Sensory cells Cells that react to activity in the environment o Motor cells (muscles) Groups of cells that can contract, allowing for movement
Functionalist definition of brains o The function of brains is to connect knowledge about the world to actions in the world, such that the actions promote our survival Functionalist definition of neurons o The function of neurons is to transmit information in such a way that knowledge about the world leads to effective behavior in the world Different types of (functionalist) brains
Brains without neurons o Plants Can follow the sun Catch flies
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Single cell organisms
! Single Eelao rganiAms eba (lives i n our intestines) c x l mpSe: s mell organisms o l ingle c o Example: Amoeba (lives in our intestines) ! Canmove ! Example: Amoeba (lives in our intestines) ! ! ! ! ! !
Can s ov e i an s vironheir t Can mense theCr enense tmenenvironment Can ense heiCan nd onprey and catch it y a sense m n Can ssensetprer envircatcheitt
Can move
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CansenIss t pran cer a ca m ells ct ocally, there is no network for Can senn ehese gand ntdtchoiveaawlay e d ey ases he c t In !heCacasencoordinationndocalvy, away is no network for coordination t se n sesste e anglerac t l mo l e there h d cel s a
In these cases the cells act locally, there is no network for coordination
Can sense danger and move away
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Brains without thought
! wmple ho ni ht Brains Siithoutotrgaugsms ! Examporganis ra ! Simple le: Hydms(very tiny, lives in ponds)
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Exa! pNeuronsatr(ansly ttensy,nsvtis nninto movement in a very direct way m le: Hydr ver a i e li ae o i ponds) ! Hyd on transl en ory at lls int movement cel s very di uro w ! Neurra:smore satessensceionando movement inla than nerectns ay
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Huma : orp o n mr t l e l 00, d 0 cve nectt ce l e t r an or ons Hydra:nmape rsexisoayecyl1s an00moonmening lns uhonsnfeurevery sensory neuron Human: approximately 100,000 connecting neurons for every sensory neuron
Brains without thought o Simple organisms o Example: Hydra (very tiny, lives in ponds) Neurons translate sensation into movement in a very direct way Hydra: more sensory cells and movement cells than neurons Human: approximately 100,000 connecting neurons for every sensory neuron
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Human brains
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Possibly tPe most cohe lex thinomplex phing on the planet o h ossibly tmp most cg on the tlanet
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Human brains can: Plan
o I t a coordina o c movement and ovement and p n brains can: In additionn o ddition tingoordinating mperception, humaerception, human brains
Be creative Be self aware Think Solve problems Manipulate and/or assist other human brains Self medicate Fall in love Etc.
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Brains without biology
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Robots use electronic circuitry to connect sensation (and knowledge) to behavior, in a meaningful way
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Bra nsBrains wtithout biology i withou biology
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o e elect use c circuitr c to conno c sensa ion (and ( now edge) to Robots usRobots ronielectronic yircuitry tectonnect tsensation kand klnowledge) behavior, to behavior, in fa mway in a meaning ul eaningful way
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How neurons work o Dendrites pick up chemical signals from neural transmitters o If enough signals are picked up the cell fires an electric charge o The charge travels down the axon to the presynaptic terminals (or buttons) that release neural transmitters into synaptic cleft o The neural transmitters are detected by dendrites at the synaptic cleft and the process begins again
Some facts
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Neurons are binary (i.e. they have two states): they either fire or they dont
Some facts o There are numerous different types of neurons but they are all the same at a certain level All are excited by neurotransmitters and this leads to firing a charge down the axon, which released neural transmitters o Neurons are binary (i.e. they have two states): they either or fire they dont This is similar to computers, which are also binary o Human knowledge is not believed to be stored in individual neurons e.g. the grandmother neuron Instead it is believed to reside in the pattern of connections and activation between neurons o Speed of transmission down the axon ranges from approximately 1 mile an hour to 270 miles per hour This is much slower than a computer o There are estimated to be approximately 100 billion neurons and 100 trillion synapses this is much much more capacity than any computer o The power of the brain comes from massive computing power massive parallel processing o The brain stores information by Changing the electrical patterns Fast Growing new connections and letting old ones die off Slow Growing new neurons Mainly in infants and children Now known to occur somewhat in adults Biological complications o Electrical synapses smaller and faster, can directly stimulate using electrical charge o Dendrites may be able to boost or attenuate signals backpropagating action potentials may play a role o Glial cells Neurons and glia make up the two chief cell types of the central nervous system Glia outnumber neurons by as many as 10:1, some estimate 50:1 Traditionally glia cells have been viewed as a support mechanism for neurons Now known that glia can act and react to neural transmitters
o Quantum computing Roger Penrose has argued that the brain can compute things at the quantum level using particle states isolated in the microtubules of the neurons o Question These exist but are they used for information processing? Or do they just provide support? The neural cognitive gap o We know a lot about our cognitive abilities and a lot about neurons, but But we do not know how neurons function together to produce cognitive abilities such as memory attention and perception o Methods Dissecting brains Good for finding the connections between areas Single cell recording Not so usable on humans (requires implanting) Limited to single cells Neural imaging fMRI, EEG, CAT scan, etc. shows relatively large areas associated with specific functions Not good for looking at the workings of specific neural circuits Assumes modularity Models Build models using simulated neurons on a computer See what kind of information processing they can do o Methods are (ideally) used in combination o Must also be guided by cognitive theory Knowing what areas are active during a task does not explain what the brain is doing To make sense of imaging data we need to know what the brain is doing during the imaging the functions it is carrying out If we have a wrong view of the functions we will interpret the imaging data wrongly
Brain plasticity o if a part of the brain is destroyed (e.g., by a stoke) those functions can be taken on by other parts of the brain o this shows all of the information needed is not stored within the area different brain areas can do different things makes sense, they are all made of the same stuff neurons they are not like different organs in the body o Examples of plasticity Deaf people Have better o Peripheral vision o Motion detection Because these are also processed in auditory cortex Blind people Better at o Reading brail o Verbal memory Because these are also processed in visual cortex Also use it to process language o The brain adapts over time to normalize changes Drugs at first a drug will have a strong effect but over time the brain will adapt to the drug so you need the drug just to feel normal if the drug is stopped then the brain needs time to adapt back to normal functioning Stress chronic stress causes you to internally manufacture chemicals that were never meant to be used so much this can also cause long lasting effects on the brain sometimes drugs are given to try to get the brain into a more normal state e.g., anti anxiety drugs Money studies show that people who win the lottery are no happier a year later The brain adapts to training if we do something a lot the brain assumes it's important and increases its ability to process along those lines