Consciousness & Neuroscience
Francis Crick & Christof Koch
Consciousness is a scientifically tractable
problem and can be approached using the
modern tools in neurobiology.
Christof Koch’s website http://www.klab.caltech.edu/
Koch’s video lectures for undergrads at CalTech
papers available for download:
Main Points of the Paper don’t
want to make it too long
• Who are these guys and why should we take them seriously?
• That consciousness and its different aspects (pain, visual awareness &
self-consciousness, etc) employ basic mechanisms that we all have
• The neuronal correlate of consciousness or NCC
• The idea of visual consciousness and visual representation
• How this relates to machine consciousness
• Two hard problems: the problem of qualia & the problem of meaning &
problems omitted in the paper
Brief Background on Crick &
• Christof Koch neuroscientist & prof. of biology & engineering at
CalTech. Wrote, „The Quest for Consciousness”
„To understand how consciousness is linked to the brain, how the flickering activity
of myriad of nerve cells leads to ineffable experiences, of seeing blue, of being
warmed by the sun, or of being scared by exposure on a climb” (Koch 2005)
• Francis Crick molecular biologist & physicist. Co-discoverer of
the DNA molecule in 1953—subsequently jointly won Nobel Prize
• His later research centered on theoretical neurobiology and attempts to
advance the scientific study of human consciousness.
What is this NCC all About?
• constitute the minimal set of neuronal events and mechanisms
sufficient for a specific conscious percept (Koch 2004)
• A scientific study of consciousness must explain the exact
relationship between subjective mental states and brain
states, the nature of the relationship between the conscious mind
and the electro-chemical interactions within your body.
• NCC may be viewed as its causes and consciousness thought of
as a state-dependent property of an undefined type of
complex, adaptive, and highly interconnected biological system
What was focused on in the
Note: in a paper from 2003 by Krick & Koch: „We propose that conscious awareness
for vision is a series of static snapshots with motion „painted on them”
• They chose visual consciousness for an initial scientific attack into
understanding consciousness in a scientific manner. We are extremely visual
and our visual precepts are strong & rich in information
• Nature of Visual Representation is multifaceted
o Psychologically different levels that correspond to for example, lines and faces
o Physiologically our brain has to construct a multilevel, explicit, symbolic
interpretation of a visual scene
o Neurologically-- there are differing levels in the visual hierarchy
IMPORTANT! EXPLICIT REPRESENTATION = small group of neurons that
employ coarse coding to represent some aspect of the visual scene.
o Where is this stuff? its likely this is distrubuted in the cerebral cortex and maybe
some areas of the subcortical structures
Visual Systems con’t:
• Normal vivid experience which encompasses a variety of processes.
• Iconic memory is essential for visual consciousness (working memory
for expanding the time frame of consciousness & as a mechanism for
• Visual attention is consciously directed and in order for us to interpret
the visual input our brain must arrive at a coalition of neorions whose
firing best represents the interpretation of the visual scene
• There were many studies done, I will summarize the most important (to
NCC): BISTABLE PRECEPTS
• Perceptual multistability can be evoked by visual patterns that are too
ambiguous for the visual system to recognise with one unique
interpretation ex. Necker cube
• Study the behavior of single neurons when a monkey is looking at a
bistable precept. Why? the visual input (other than eye movement) is
constant; but the subjects perception can take one of two alternative
• Which neurons are following the precept? The NCC neurons can be
elsewhere. BUT! Where are they? In what way do they fire? And
WHERE DO THEY PROJECT?
• These questions are important to understand neural nature of
The Cliffnotes Version of the Problem of Qualia & the Meaning
Problem (plus what issues were put aside for purposes of this
• Qualia the greeness of green, the sadness of sad. How can you
possibly argue explain consciousness by the behavior of the brain?
(vivid, rich visual scene=firing of neurons(?!)
• Visual consciousness can be a result of the way the brain works. Your
preception of blue and my preception of blue may turn out to be the
same neural correlate of blue in both our brains—in essence then we
see blue the same.
• Problem of Meaning How is meaning generated by the brain? How do
other parts of the brain know that the firing of a set of neurons produces
the conscious precept of a face? How is meaning expressed in neural
terms? And how does this expression of meaning arise? The neurons
may be part of a larger network, for example: the firing of neorons to
see a face activates the neurons firing to remember the name, to her/his
voice/ and memories. A chain reaction.
What was omitted in the Paper:
• A semantic discussion and deliberation of what it means to be
conscious & a precise definition of consciousness.
• That whether simple animals and plants are
conscious(octous, fruit flies, plant).
• There are different forms of consciousness (we focused on
visual) & self-consciousness is special—but we cannot study
self-consciousness in a moneky.
• Some species, especially higher mammals possess essential
features of consciousness and studies on monkeys to finding the
mechanism underlying consciousness.
All this Neuroscience & Consciousness...great, what
does this have to do with us in this class?
• Well, basically if our conscioussness has
biological and neurological underpinnings
then conscioussness is not a
nebulous, ephermeal concept but a definable
and transferable idea that can be applied to a
• My consciousness is biological fact in
functional terms so in extension a computer
can be conscious
• Implications for people?
A parting thought: From Christof
Koch’s personal website:
• I'm also interested in a theory of consciousness, a formal
framework - formulated using the idiom of information theory -
that explains what consciousness is, which system can have
subjective experiences and why in functional terms. Such a
theory would imply that a computer, properly programmed as to
mimic the functional connectivity of the human brain, could be
consciousness. Together with Giulio Tononi, a neuroscientist at
the University of Madison in Wisconsin working on such a theory
of Integrated Information, I recently surveyed what we can learn
about biological consciousness and apply to machine sentience
(and how we can teach a machine to truly understand the movie
Blade Runner). (Koch 2010)