about> going inside
Here is a chapter by chapter description of Going Inside, my big book
about how the brain works and how to think about consciousness as a
property of brains.
ONE - RELUCTANT BEGINNINGS
The 1990s were meant to be the decade of great discovery in
neuroscience. There were new brain scanning techniques like PET and
f-MRI and a new theoretical boldness from the likes of Francis Crick.
At last, it seemed, the secrets of consciousness would be laid bare.
But it turned out that what had to be unlearnt became as important as
what was learnt. Researchers found they were entering the hunt for the
secrets of the mind with too many wrong assumptions.
TWO - DISTURBING THE SURFACE
One of these key assumptions was that the brain was much like a
computer. The brain had a hierarchical design so that sensory input
entered at the bottom and was transformed by stages into conscious
output. Cognitive scientists went even further in believing that
particular brain modules would "do" specific functions such as memory
recall, speech generation and perhaps self-awareness itself.
But as
soon as researcher began using PET to scan real brains it became
obvious that their circuits reacted in a much more globally coherent
way. There was something structured about the brain - it did have a
hierarchical organisation of mapping areas. But equally, it was dynamic
and adaptive in its processing flows.
Experiments by Harvard's Stephen
Kosslyn to discover how humans generate mental images illustrated the
problem. When his subjects were scanned, individual modules did not
light up. Instead, as he says, the brain's response was more like
watching pebbles tossed into a pond. Ripples spread across the brain
spinning complex feedback patterns.
[features Stephen Kosslyn, Roger Tootell, cognitive science woes,
brain-scanning hopes]
THREE - UGLY QUESTIONS ABOUT CHAOS
The dynamism that Kosslyn and other neuro-imagers were seeing at the
whole brain level was just as troublesome at the level of individual
brain cells. Researchers had assumed that like a computer, the brain's
circuitry would deal in a stream of bits. Neurons would signal to one
another to create an accumulating pattern of processing. But it was
being found that the output of a cell could be wildly variable. A spike
might or might not cross a particular junction depending on whether the
brain was interested in the message.
It was as if consciousness were
controlling the spikes rather than the spikes adding up to produce a
state of consciousness! This sounded spooky but the mystery was easily
explained by a dynamical view of the brain. If neural states of
representation had to evolve, then the firing of any cell needed to
strike some sort of feedback-based balance with activity in the rest of
the brain. The spiking of a neuron did not have meaning until it had
developed to fit a context. The problem was that neuroscientists found
it hard to accept just how deeply this changed the traditional
conception of the brain.
[features Donald Hebb, Warren McCulloch, neural networks bandwagon,
discomforting implications of chaos theory]
FOUR - THE HUNT FOR THE NEURAL CODE
The finding that really set the cat among the pigeons was Robert
Desimone's 1985 report of attention effects in V4, the "colour filter"
of the visual cortex. If a monkey had to pay attention to a green bar
and ignore a red bar, then red-coding neurons would be damped within
half a second - a conscious-level intention could feed back to control
the firing response of an individual brain cell. The idea that neurons
coded pixel-like for discrete bits of information could no longer be
sustained.
And yet apart from this, the computational view seemed to be
telling the story so well. Neuroscientists were finding that neurons
lined up to form topographically organised mappings - images were
literally painted across the visual cortex in twinkling neural
outlines. And these mappings then stacked up to form complex processing
pathways with each map refining the information captured in the level
below. With new discoveries like population voting and synchronised
firing, neuroscientists even seemed close to cracking the neural code -
an exact understanding of how brain cells encoded messages to each
other in their complex packets of spikes.
[features Robert Desimone, David Hubel and Torsten Wiesel, Wolf Singer,
cortex maps, population coding, synchronous cell firing]
FIVE - A DYNAMICAL COMPUTATION
Despite the continuing attempts to see neurons as simple input-output
units, by the mid-1990s this position was crumbling fast. Not only was
the behaviour of cells dynamic on a sub-second timescale - they
responded to the attentional needs of the moment - but other work was
showing how they could fluidly adapt their receptive fields over
minutes, days and months. A hand coding cell could become a face coding
cell if the local balance of feedback changed sufficiently.
Eventually,
younger neuroscientists like Karl Friston - who knew about non-linear
maths and complex systems - began to see how the actions of individual
cells could not be divorced from the activity of the brain as a whole.
Patterns of firing would settle as different levels of brain processing
fell into temporary agreement. This quite different view of brain
activity demanded new methods of measurement such as Friston's idea of
the neural transient.
[features Francis Crick, Michael Merzenich, Karl Friston, the paradox
of fluid structure]
SIX - BENJAMIN LIBET'S HALF SECOND
Reluctantly, neuroscientists were being forced to give up their simple
computational view of the brain. But one startling finding of the 1960s
should already have given pause for thought. Indeed, even the work of
the very first psychologists - 19th Century researchers like Helmhotz
and Wundt - should have been a warning. Because consciousness seems
instant and effortless, it is tempting to assume it is actually so. But
careful reaction time experiments had already suggested that awareness
develops slowly and in stages.
Then a San Francisco researcher,
Benjamin Libet, stuck stimulating electrodes in people's heads during
brain surgery and showed that it seemed to take a full half second for
a person to evolve a state of consciousness for a new experience. The
time it takes to settle a fully-tuned spread of neural representation
means that we must constantly run half a second behind reality -
although for some reason we never notice the fact.
The critical
response to Libet's experiments over the following 30 years tells much
about why science has struggled so hard to find the right path to an
understanding of the human mind.
[features Wilhelm Wundt, Wilder Penfield, Benjamin Libet, Bernard
Baars, mental chronometry, pre-consciousness and automatic actions, the
freewill issue]
SEVEN - A MOMENT OF ANTICIPATION
The big sticking point with Libet's results was that half a second
seemed such a long time. If consciousness was the result of activity in
the brain, then everyone knew it had to lag reality simply because of
the time it took for signals to travel across its maze of billions of
connections. But while most researchers could stomach a "barely
noticeable" delay of, say, a tenth of a second, Libet's half a second
posed too many uncomfortable questions - especially for the standard
cognitive science view of brain processing.
Again, the answer had
already been discovered by 19th Century psychologists. But the rise of
sports psychology in the 1980s brought the matter into sharp focus. A
tennis player or baseball batter has to contact the ball within a
window measured in milliseconds and millimetres. The only thing that
makes such accuracy possible is anticipation. And as a few cognitive
psychologists such as Ulric Neisser and Bernard Baars realised,
anticipation must lead the way into every moment of consciousness.
We
begin each "perceptual cycle" with a set of plans and expectations that
allow us to deal with the moment smoothly and skillfully. Consciousness
does not lag. Instead it grades from strong prediction to settled
resolution. But the question was how the brain might actually generate
states of expectation? A dynamic view of the brain's pathways gave an
obvious answer - and again, experiments carried out in Robert
Desimone's lab held vital clues.
[features sports psychology studies, Ulric Neisser, Bernard Baars,
Robert Desimone, Keiji Tanaka]
EIGHT - THE NEEDS THAT SHAPE THE BRAIN
The dynamism of the neuron and the stretched-out cycle of processing
needed to arrive at a state of settled awareness were two key
realisations. But there were a number of other essential ingredients
for a new view of consciousness.
For instance, there was the idea that
the brain's purpose would be clear in its design. Early in the 1990s,
it was recognised that the sensory cortex was divided by a what-where
logic - activity headed for the temporal lobe was most concerned with
questions of object identity and object meaning while activity headed
for the parietal lobe focused on the question of location and spatial
relationships.
There also seemed to be a similar division of the
cerebral hemispheres with the left half of the brain having a "narrow"
attentional focusing style and the right processing the same
information in a broad or holistic way. Another point that became
obvious was that the brain had to have a pathway for evaluating the
moment - for deciding what particular aspect to promote to the eye of
consciousness - and that the need to squeeze in this valuing step might
be one reason for the delays observed by Libet. A large body of
psychophysics research - especially Evgeny Sokolov's work on the
orientation response and a EEG wave known as the P300 - seemed now to
tell a story.
Then the first really important discovery to come out of
PET scanning began to hit home. Research at Washington University and
Hammersmith Hospital was revealing the "practice effect" - what
happened in the brain as a mental skill went from being in the eye of
consciousness to become a pre-conscious, unthinking habit.
[features Gerald Edelman, Evgeny Sokolov, hidden logic of the cortex
sheet, aha! feelings, the P300 oddball response, the practice effect]
NINE - CONSCIOUSNESS'S TWIN PEAKS
The idea of a dynamic perceptual cycle, with anticipations paving the
way for the quick and graded assimilation of sensation, made sense of a
lot of puzzling data. But the more astute realised that there was a
step further still. Sensation could not be meaningful until it had
begun to inspire a response - until the motor cortex had become woven
into the evolving state of mental representation to provide at the
least the inklings of an output intention.
The frontal lobes were
discovered to have the same kind of hierarchical organisation as the
sensory cortex, except the logic worked top-down with high-level
thoughts being translated by stages into a concrete set of muscle
commands. The essence of the moment - whatever aspect was turning out
to matter most and so forming the centre of attention - would be
"loaded" into the working memory buffers of the prefrontal lobe.
From
there, associative connections would direct traffic down through the
rungs of motor mapping to rouse a suitable state of response. Seeing a
coffee cup would automatically inspire thoughts about what could or
should be done with a coffee cup.
The motor hierarchy was actually only
one leg of the brain's output machinery. Equally substantial was a
hierarchy for orientation - for thinking about where to look next - and
in humans, a language hierarchy. The focus of each cycle of processing
also automatically became the potential jumping off point for some
voiced, or merely thought, comment. The need to wait for the brain to
become fully orientated to the moment - to reach a state poised for
meaningful output - seemed another reason why the full perceptual cycle
might take as long as half a second or more.
[features frontal motor hierarchy, prefrontal organisation, the complex
role of the hippocampus]
TEN - OF SUB-CORTICAL BOTTLENECKS
Having described the general cycle of processing that takes place
during every moment of consciousness, and then how this cycle develops
across the cortex, this chapter looks at the role played by two
sub-cortical organs, the thalamus and basal ganglia. The thalamus is
used by the cortex as a lens to focus its own activity while the basal
ganglia allow for the controlled (willed) development of thoughts and
reactions.
[features David LaBerge, Chris Passingham, Patricia Goldman-Rakic, Ann
Graybiel]
ELEVEN - THE BRAIN'S FORKING PATHWAY
This chapter finishes the "systems level" review of the brain by
zeroing in on the key decision the brain has to make during every
moment - what to escalate to focal consciousness? The brain has to have
a mechanism for choosing whether to stick with its planned and
anticipated point of focus, or whether to break to take notice of an
interruption or a surprise.
[features Jeffrey Gray, Joseph LeDoux, Michael Posner, the cingulate
cortex, amygdala, and nucleus accumbens]
TWELVE - GETTING IT BACKWARDS
The conclusion begins. This chapter draws together the many strands of
evidence to show what it means to see the mind as a dynamic brain
process - an adaptation that takes place in the blink of an eye, but
also one that is continuous with a recent history of working memories
and expectations, a lifetime's history of habits and learnt perceptual
skills, and even a genetic legacy of evolved neural structure.
THIRTEEN - THE APE THAT SPOKE
But there is still the puzzle of exactly how the human mind is
different from an animals. This chapter looks at how language allows
for the extra mental abilities of humans. In particular, it shows how
language-based habits of thought sink in to become part of the very
structure of the brain and also how anticipation solves the traditional
riddle of how we know what we are going to say or think before we the
words are uttered (either audibly, or to ourselves using our inner
voice).
[features evidence of Hominid evolution, Lev Vygotsky, scanning studies
of language areas, learning the skills of recollective memory and
self-awareness].
FOURTEEN - ANSWERING THE HARD QUESTION
The sign-off chapter considers how close we can come to an
intellectually-satisfying account of consciousness - one that balances
the computational and dynamic approaches - and why some deeply rooted
assumptions have led many to expect completely the wrong kind of answer.
Going Inside - a tour around a single moment of consciousness, by John
McCrone, published March 1999 by Faber & Faber in London (ISBN
0 571 17319 5, price £17.99).