Francis Crick; Astonishing Hypothesis
Book	Page		Topic
Crick; Astonishing Hypothesis	3		"You" are the behavior of a vast assembly of nerve cells and their associated molecules.
Crick; Astonishing Hypothesis	6		Not all neuroscientists believe that the idea of the soul is a myth -- Sir John Eccles is the most notable exception -- but certainly the majority do.		3
Crick; Astonishing Hypothesis	7		Many educated people, especially in the Western World, share the belief that the soul is a metaphor    and that there is no personal life either before conception or after death.    They may call themselves atheists, agnostics, humanists, or just lapsed believers,    but they all deny the major claims of the traditional religions.		1
Crick; Astonishing Hypothesis	10		Evolution is not a clean design.  As Francis Jacob the French molecular biologist has written, "Evolution is a tinkerer."  It builds, mainly in a series of smallish steps, on what was there before.		3
Crick; Astonishing Hypothesis	11		The mature brain is the product of both Nature and Nurture.		1
Crick; Astonishing Hypothesis	11		The ability to handle complex language fluently appears to be unique to human beings.		0
Crick; Astonishing Hypothesis	11		Much of the behavior of the brain    is emergent --    i.e. behavior does not exist in its separate parts,    such as the individual neurons.		0
Crick; Astonishing Hypothesis	11		Scientific meaning of emergent -  The whole may not be the simple sum    of the separate parts.    The whole can be understood from (1)  behavior of the parts      plus    (2) knowledge of how all the parts interact.		0
Crick; Astonishing Hypothesis	15		In the behaviorist movement,    all behavior had to be explained in terms of the stimulus and the response.		4
Crick; Astonishing Hypothesis	15		Behaviorism was especially strong in the United States,    where was started by John B. Watson    and others before World War I.		0
Crick; Astonishing Hypothesis	15		Behaviorism flourished    in the 1930s and 1940s    when B. F. Skinner    was its most celebrated exponent.		0
Crick; Astonishing Hypothesis	15		Neurobiologists David Hubel and Torsten Wiesel    in the late 1950s    found that nerve cells in the visual cortex of the brain of an anesthetized cat    showed a whole series of interesting responses    when light was shown on the cat's opened eyes,    even though it's brain waves showed it to be more asleep them awake.    For this and subsequent work they were awarded a Nobel Prize in 1981.		0
Crick; Astonishing Hypothesis	20		It is better to avoid a precise definition of consciousness.    Until the problem is understood much better,    a formal definition is likely to be misleading or overly restrictive.		5
Crick; Astonishing Hypothesis	21		A language system    of the type found in humans    is not essential    for consciousness.		1
Crick; Astonishing Hypothesis	21		Not profitable to argue about whether lower animals (octopus) are conscious.    It is probable that consciousness correlates    to some extent with complexity of any nervous system.		0
Crick; Astonishing Hypothesis	22		Attention involves some form of short term memory.    Global unity of shape, color, movement, location, etc, may be expressed by the correlated firing of the neurons involved.    Neurons that respond to the properties of a particular object fire in synchrony.    Other active neurons    do not fire in synchrony.		1
Crick; Astonishing Hypothesis	30		Necker cube.		8
Crick; Astonishing Hypothesis	36		Gestalt psychology -- started in Germany at around 1912. When the Nazis came to power all three left Germany for India and the United States.		6
Crick; Astonishing Hypothesis	37		Gestalt laws of grouping    include proximity,    similarity,   continuation,    and closure.		1
Crick; Astonishing Hypothesis	37		Gestalt law of proximity    states that we tend to group things together    that are close to one another,    and more distant from    other (similar) objects.		0
Crick; Astonishing Hypothesis	39		Gestalt law of similarity    means that we group things together    if they have some obvious visual property in common,    such as color or direction of movement.		2
Crick; Astonishing Hypothesis	41		Gestalt laws of perception    should not be regarded as rigid laws    but as useful heuristics.		2
Crick; Astonishing Hypothesis	41		An important operation in vision,    as the Gestaltists recognized,    is to separate figure from ground.		0
Crick; Astonishing Hypothesis	54		"Everyone likes to show that philosophers are wrong."		13
Crick; Astonishing Hypothesis	59		Psychology distinguishes between "arousal" (or alertness) and "attention."		5
Crick; Astonishing Hypothesis	60		All forms of attention    are likely to have both reflex    and willed components.		1
Crick; Astonishing Hypothesis	60		Attention filters out unattended events.		0
Crick; Astonishing Hypothesis	82		The cortex    consists of two separate sheets of nerve cells,    one on each side of the head.    The sheet varies somewhat in thickness but is typically 2 to 5 millimeters thick.		22
Crick; Astonishing Hypothesis	82		About 100,000 neurons per square millimeter in the cortex.		0
Crick; Astonishing Hypothesis	83		The hippocampus stores, probably for a few weeks or so, new long-term episodic memories before the information is established more permanently in the cortex.		1
Crick; Astonishing Hypothesis	84		The thalamus is divided into about two dozen regions,    each of which is concerned with some particular subdivision of the neocortex.    Each thalamic area also receives massive connections from the cortical areas to which it sends information.    These neocortical areas can also connect directly to other parts of the brain.		1
Crick; Astonishing Hypothesis	88		The hypothalamus has many small subregions    whose functions are to regulate      hunger,    thirst,    temperature,    sexual behavior,    and similar body operations.		4
Crick; Astonishing Hypothesis	89		The inactivity of the locus ceruleus during REM sleep may help explain why we are unable to recall the majority of our dreams.		1
Crick; Astonishing Hypothesis	92		When nothing much is happening,    a neuron usually sends spikes down its axon at a background rate between 1 and 5 Hz.		3
Crick; Astonishing Hypothesis	92		When a neuron becomes excited,    because it receives many excitatory signals,    its firing rate increases to 50-100 Hz or more.		0
Crick; Astonishing Hypothesis	92		For short intervals,    a neuron's firing rate    may reach 500 Hz.		0
Crick; Astonishing Hypothesis	93		Neuron firing rates - background rate;    average rate;    as fast as it can  -  (illustration)		1
Crick; Astonishing Hypothesis	103		Neurons of the brain stem    that project to the cortex    use transmitters such as serotonin, norepinephrine, and dopamine.     Other neurons in the brain use acetylcholine.		10
Crick; Astonishing Hypothesis	111		In REM sleep,    brain waves are similar to awake brain,    hence the name paradoxical sleep,    since the person is asleep    but the brain appears to be awake.		8
Crick; Astonishing Hypothesis	115		Two types of brain scan:    (1) those that respond to some aspect of the static structure of the brain    and (2) those that detect activity.    CAT scan uses X-rays.     MRI records the density of protons,    especially sensitive to water,    static,    do not register activity.		4
Crick; Astonishing Hypothesis	130		Six layers of LGN of a macque monkey. - (diagram). Each layer gets input from only one eye.		15
Crick; Astonishing Hypothesis	131		Inhibitory neurons in the reticular nucleus of the thalamus.		1
Crick; Astonishing Hypothesis	131		Reticular nucleus of the thalamus is a thin sheet of cells surrounding much of the thalamus.  It's neurons are all inhibitory.		0
Crick; Astonishing Hypothesis	131		Neurons of the reticular nucleus of the thalamus receive excitation from most of the axons passing to and from the neocortex.  Their output is mapped onto the underlying part of the thalamus immediately beneath them.		0
Crick; Astonishing Hypothesis	131		If the thalamus can be described as the gateway to the cortex,    the reticular nucleus looks like the guardian of the gateway.		0
Crick; Astonishing Hypothesis	131		LGN neurons also get input coming back from the visual cortex.     Many more axons coming back from the cortex than going to it.		0
Crick; Astonishing Hypothesis	131		Inputs from the brainstem    that modulate the behavior of the thalamus    and especially its reticular nucleus.		0
Crick; Astonishing Hypothesis	135		Major pathways within cortical layer V1 -  (illustration)		4
Crick; Astonishing Hypothesis	137		Parts of cortical layer V1 show heavy striations. (hence the name 'striate cortex') -  (photo)		2
Crick; Astonishing Hypothesis	139		Albert Einstein, "We should make things as simple as possible, but not simpler."		2
Crick; Astonishing Hypothesis	145		Area V1 develops so that broad features,    such as which region corresponds to the fovea,    are probably laid down by genes.    Finer details are likely to be modifications made during input from the eyes, perhaps by whether the firing of neurons are correlated.		6
Crick; Astonishing Hypothesis	149		Almost as many neurons project backward from V2 as project forward from V1.    The forward projection goes heavily into layer 4 of V2,    whereas the backward projection to V1    avoids layer 4 altogether.		4
Crick; Astonishing Hypothesis	149		At least twenty    distinct visual areas have been identified,    plus about seven more that are partly visual.		0
Crick; Astonishing Hypothesis	156		Many connections between visual areas;    RGC, retinal ganglion cells; LGN of thalamus; V1, V2, . . . ER, entorhinal cortex; HC, hippocampus; each line in the diagram symbolizes millions of axons running in both directions -  (diagram)		7
Crick; Astonishing Hypothesis	157		There are many cross-connections     between cortical areas  at the same level.		1
Crick; Astonishing Hypothesis	157		Connections between areas in the cortex are almost always reciprocal.		0
Crick; Astonishing Hypothesis	157		Adjacent areas    in the cortex    almost always connect to each other.		0
Crick; Astonishing Hypothesis	158		The general pattern from LGN to hippocampus    is that each area    receives several inputs    from lower layers.		1
Crick; Astonishing Hypothesis	158		Back pathways -- urgently need more study; may help to synchronize neuronal oscillations.		0
Crick; Astonishing Hypothesis	159		Whole system does not look like a one-shot static response mechanism. Likely to operate by many transient, dynamic interactions, conducted at a fairly fast rate.		1
Crick; Astonishing Hypothesis	159		Although there are many different visual regions,    each of which analyzes visual input in different and complex ways,    we can locate no single region in which the neural activity corresponds exactly    to the visual picture of the world we see in front of our eyes.		0
Crick; Astonishing Hypothesis	159		We can see how the brain takes the picture apart, but do not yet understand how it puts it together.    How does it construct the well-organized and detailed visual awareness of all the objects, and the behavior of these objects, in our visual fields?		0
Crick; Astonishing Hypothesis	161		A remarkable degree of functional specialization in the cortex.		2
Crick; Astonishing Hypothesis	161		Living cortex has the texture of a rather soft jelly.  Bits of it can easily be removed by sucking on a pipette.		0
Crick; Astonishing Hypothesis	171		"Blindsight" -- even with a badly damaged V1,    the brain can detect some fairly simple visual stimuli    and act on them,    although the patient will firmly deny his awareness of them.		10
Crick; Astonishing Hypothesis	174		Hippocampus and its closely associated cortical areas are not necessary for visual awareness.		3
Crick; Astonishing Hypothesis	178		Typical firing rate of active neurons is in the range of 100 spikes/sec.		4
Crick; Astonishing Hypothesis	179		Functionality of the individual neurons are subject to much variability.     Neurons are subjected to signals that can modulate their behavior,    and some neuron properties can change while the neurons are active.		1
Crick; Astonishing Hypothesis	179		Typical neuron can have anywhere from a few hundred to many tens of thousands of inputs,    and its axon projects as multitudeinously.		0
Crick; Astonishing Hypothesis	179		A brain does not look even a little bit like a general-purpose computer.		0
Crick; Astonishing Hypothesis	179		Different parts of the brain,    even different parts of the neocortex,    specialize, at least to some extent,    in handling different sorts of information.		0
Crick; Astonishing Hypothesis	179		Most memory    appears to be stored in the very same locations    that carry out current operations.		0
Crick; Astonishing Hypothesis	183		In 1949, Canadian psychologist Donald Hebb published a book called Organization of Behavior.  In the process of learning,    one of the key factors is a modification of the strength    of the neuronal connections -- the synapses.		4
Crick; Astonishing Hypothesis	183		Donald Hebb's rule -- "When an axon of cell A is near enough to excite a cell B, and repeatedly and persistently takes part in firing it, some growth process or metabolic change takes place in one or both cells such that A's efficiency, as one of the cells firing B, is increased." Such a mechanism, or one somewhat resembling it, is called "Hebbian."		0
Crick; Astonishing Hypothesis	184		Memory is "content addressable."    Any appreciable part of the input pattern    will act as an address.		1
Crick; Astonishing Hypothesis	184		Memory is embedded in the pattern of weights --    the strength of the connections    between all the various neurons.		0
Crick; Astonishing Hypothesis	184		Any one memory    is distributed    over many connections.		0
Crick; Astonishing Hypothesis	184		Memory is superimposed,    because any one connection    can be involved in several memories.		0
Crick; Astonishing Hypothesis	184		Memory is robust,    since altering a few connections    will usually not alter its behavior very much.		0
Crick; Astonishing Hypothesis	185		Connections of a region of the hippocampus    called CA3    do in fact look like a content-addressable network.		1
Crick; Astonishing Hypothesis	207		Consciousness will correspond to a particular type of activity in a transient set of neurons    that are a fraction    of a much larger set.  [dynamic core]		22
Crick; Astonishing Hypothesis	208		Awareness is likely to involve some form of attention -- we should study the mechanism the brain uses    to attend to one visual object    rather than another.		1
Crick; Astonishing Hypothesis	208		Awareness is likely to involve some form a very short-term memory.		0
Crick; Astonishing Hypothesis	208		It seems probable that, at any moment,    any particular object In the visual field    is represented by the firing    of a set of neurons.		0
Crick; Astonishing Hypothesis	208		Any object will have different characteristics (form, color, motion, etc.)    that are processed in several different visual areas.		0
Crick; Astonishing Hypothesis	208		Seeing any one object    often involves neurons in many different visual areas.		0
Crick; Astonishing Hypothesis	208		How the neurons in different areas    temporarily become active    as a unit is often described as the "binding problem."		0
Crick; Astonishing Hypothesis	208		An object seen is often also heard, smell, or felt. This binding must also occur across different sensory modalities.		0
Crick; Astonishing Hypothesis	209		Brain can sometimes be tricked into making an incorrect binding,    as when you hear the voice coming not from the ventriloquist but from his dummy.		1
Crick; Astonishing Hypothesis	211		Attentional mechanism makes use of correlated firing.  -- what matters is not just the average rate of firing of a neuron, but the exact moments at which each neuron fires.		2
Crick; Astonishing Hypothesis	211		Correlated firing -- spikes arriving at a neuron at the same moment    will produce a larger effect    than the same number of spikes    arriving at different times.		0
Crick; Astonishing Hypothesis	211		Theoretical requirement    is that the firing of the neurons    in each set    should be strongly correlated with each other,    while at the same time    firing of neurons in different sets    should be weakly correlated,    or not at all.		0
Crick; Astonishing Hypothesis	212		Necker cube -- bistable vision -- visual information coming into the eyes remains the same, but the percept changes.		1
Crick; Astonishing Hypothesis	220		Cortical area MT is that area mainly concerned with movement, but largely indifferent to color.		8
Crick; Astonishing Hypothesis	227		Thalamus ("gateway to the cortex") has many fairly distinct regions, some of which are interested in vision.		7
Crick; Astonishing Hypothesis	227		Superior colliculus is closely involved with the control of eye movements,    another form of visual attention.		0
Crick; Astonishing Hypothesis	228		"anesthetize a patient during an operation    in such a way that he is unaware of what is going on,    partly to spare the patient pain    and partly to prevent him from suing them."		1
Crick; Astonishing Hypothesis	228		"unwise to embark on experiments on consciousness on alert people until he had obtained the security of academic tenure."		0
Crick; Astonishing Hypothesis	229		In the somatosensory system,    a weak or brief signal can influence behavior    without producing awareness,    while a stronger or longer signal of the same type can make awareness occur.		1
Crick; Astonishing Hypothesis	234		Awareness may involve reentrant pathways    as Gerald Edelman has suggested.		5
Crick; Astonishing Hypothesis	234		Hippocampus is reentrant, since it gets most of its input from the entorhinal cortex and sends most of its output back there.		0
Crick; Astonishing Hypothesis	234		Theoretical arguments about reentrant pathways to give it an air of intellectual respectability.		0
Crick; Astonishing Hypothesis	235		By the cortical system I mean the cerebral cortex and such regions as the thalamus and claustrum that are very closely associated with it.		1
Crick; Astonishing Hypothesis	236		Although the dendrites and axon of a neuron    often extend over several layers,    the layer in which its soma (the cell body) is located is probably determined genetically during normal embryonic development.		1
Crick; Astonishing Hypothesis	236		Hippocampal system involved in the temporary storage, or coding, of episodic memory.		0
Crick; Astonishing Hypothesis	239		Long-term changes in synaptic strength.		3
Crick; Astonishing Hypothesis	240		Temporary maintenance of reverberating circuits.		1
Crick; Astonishing Hypothesis	240		Reverberation -- associated with active short-term memory.		0
Crick; Astonishing Hypothesis	240		Circuit from the thalamus to the type of pyramidal neuron in cortical layer 6,    which sends signals back to the same part of the thalamus.		0
Crick; Astonishing Hypothesis	240		Back pathway, from layer 6 to the LGN    has perhaps five or ten times as many axons    as the major forward connections    from LGN to layer 4.		0
Crick; Astonishing Hypothesis	240		Neural pathways from the brainstem can alter the activity of the LGN    during slow wave sleep.		0
Crick; Astonishing Hypothesis	241		It is mainly the lower cortical layers whose activity correlates with consciousness in general,    and with visual awareness in particular.		1
Crick; Astonishing Hypothesis	242		One example where short-term memory involves the continued firing of neurons.    Working memory for visual spatial location.		1
Crick; Astonishing Hypothesis	250		Claustrum - thin sheet of neurons next to lower cortical layers,    project very widely over the cortex.		8
Crick; Astonishing Hypothesis	258		Philosophers have had such a poor record    over the last two thousand years    that they would do better to show a certain modesty    rather than the lofty superiority that they usually display.		8
Crick; Astonishing Hypothesis