Consciousness and Neuromorphic Chips: A Case for Embodiment
Introduction
The philosopher John Searle is often cited for his Chinese Room argument against strong-AI
in which he states that a nonbiological medium, such as a computer, is not conscious. Searle’s
argument rests on the belief that specific biological mechanisms within human brains cause
conscious perception to occur (Searle, 1984). Proponents of whole brain emulation (WBE) and
“mind uploading”, on the other hand, do not view nonbiological reproductions of human brain
structure and function as limiting factors for consciousness.
In this paper we propose that embodiment is a necessary condition for any emulated,
nonbiological brain to be conscious. Such an argument is not as adverse to strong-AI as Searle’s
critique, yet holds to the ontological notion of consciousness requiring a minimal level of biological
brain-like structure in the computer’s hardware/software. We will first address the
neurobiological aspects of embodied human consciousness from both a functional and structural
standpoint, and then present the counterexample, which states that a simulated, biophysically
accurate software reconstruction of the human brain is sufficient for “virtual” consciousness. Lastly,
we discuss the limitations of current von Neumann-based computers and propose neuromorphic
chip technology as an alternative method for achieving embodied, human brain-like consciousness.
The importance of embodiment
Unless you are a floating head from the television show, Futurama, chances are that you
possess both a brain and a body. For obvious reasons, the one requires the other. Our brain wires
itself, and rewires itself, based not solely on our genetic makeup but also our interactions with the
external world. This notion of embodiment is well accepted in the field of biology and is also
popular among robotics researchers such as Rodney Brooks, who believes that a robot can only
learn and update its behavioral state by way of actuator and sensor feedback (Brooks, 2003). Why,
then, is embodiment important for replicating human consciousness in a nonbiological system?
What capacity is missing from our current computers that we currently have inside our own heads?
Hypothetically speaking, let us imagine a supercomputer in 2010 containing a software
program that has generated an accurate replica of Daniel Dennett’s brain. On this very day, the
research team responsible for collecting and organizing this daunting amount of data decides to
“turn on” the simulation in front of the entire world. Would the virtual, multi-realizable Dennett
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Version 1.0 be capable of speaking (given that we had supplied the proper output devices) with us
or giving us a qualitative report of what it’s like to reside in a new physical form? We would reply
“no”. Dennett Version 1.0 may meet the requirements for weak-AI whereby he shows signs of
intelligence yet, as Searle contends, cannot describe the qualia of his new environment. In other
words, Searle argues that the biology of information transfer is just as important as the information
itself.
Hardware requirements aside, how can we even know other humans are conscious? Giulio
Tononi has written extensively on methods for quantifying conscious experience, relying on 1)
observable reports and 2) oral reports from subjects (Tononi and Koch, 2008). Were these the only
requirements for consciousness in a computer, it would probably be sufficient to say our current
computers can indeed be conscious. Unfortunately, a third prerequisite is needed: observed and
measurable brain activity. Isolated regions of activity, synchrony, oscillations, and trace networks of
activity are items measured outside of the agent. We are not privy to the synchrony and oscillatory
behavior of our own mental states, yet we are now able to observe these states using numerous
recording methods. This leads to the obvious question: if a researcher was able to probe the inner
workings of a computer, would she see, for example, oscillations which are known to be required
for conscious perception?
In order to distinguish between conscious and unconscious states in the human brain, an
analysis of experimental work targeted at characterizing brain activity in various states of
consciousness must be performed. These states range from attentive waking behavior, often
referred to as “conscious” behavior in the neuroscience literature, to sleep and pathological states
such as schizophrenia, autism, and coma. Experimental studies have begun to unveil the
electrophysiological correlates of brain states associated with consciousness…and the absence of it.
Electroencephalograph (EEG) recordings of cortical and thalamic nuclei (a subcortical nuclear
complex that relays sensory information to the cortex and reciprocally links cortical areas) have
shown that slow, large, and regular frequency neural oscillations are the signatures of anesthesia
and dreamless sleep. The waking state, as well as the dream state, is usually labeled as conscious
and is associated with fast, small, and irregular oscillations (Steriade et al., 1993a,b). Furthermore,
the classes of brain oscillations associated with specific behaviors tend to be the same across
different mammals (Destexhe and Sejnowski, 2003). These oscillations are what a measuring tool
such as EEG can tell us about the interactions of billions of neurons in a large-scale network of
excitatory and inhibitory cells during a specific brain state. Ultimately, these interactions determine
what is processed, giving rise to the resulting qualia, introspectively associated with a conscious or
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unconscious state. What gives conscious states, or dreams, their peculiar status in our personal
experience yet makes dreamless sleep and anesthesia a “psychological vacuum” that is devoid of
the richness of conscious experience? Steve Esser and colleagues have researched the neural basis
of consciousness via sleep function using transcranial magnetic stimulation (TMS) and draws on
information theory to show there is a breakdown of information integration during sleep (Esser et
al., 2009). If this theory were to be true, breakdown of information during sleep would coincide
with regularity in neural oscillations.
One would be tempted to claim that fast oscillations, often labeled as beta and gamma
frequency, are functional to “produce” conscious states (Uhlhaas et al., 2009). This argument is
simply shifting the problem to why the brain that expresses fast oscillation frequency produces
conscious experience, and the brain that expresses low frequency oscillations does not. What makes
fast oscillations special? In a fast oscillatory regimen, for instance when reading an article or
listening to a talk, neurons tend to discharge, or spike, at a fast rate, which has been shown to
promote propagation of information across the cortical hierarchy and promote synaptic plasticity,
or learning. In these states, neurons in various brain areas experience highly non-uniform pattern
of activations, which eventually leads to the typical beta and gamma oscillatory activity as recorded,
for instance, in EEG. These physically embedded patterns of activations are the qualia, or the
perceptual correlate, of our conscious experience. What turns subconscious (or unconscious) states,
then, into conscious ones? Networks of biological neurons do not cease to discharge during sleep or
within a coma. To the contrary, oscillations caused by neuronal spikes are often more pronounced,
but they tend to be slower and more synchronized. In other words, during sub- or un-conscious
states, many neurons tend to spike together, which eventually produces powerful, slow, and
synchronized oscillations. Slow frequency oscillations have also been shown to express weaker
learning in both brain recordings and computational modeling work (Wespatat et al., 2004;
Grossberg and Versace, 2008). On the microscopic level, large scale synchronized oscillations mean
that neurons tend to process, and broadcast, uniform information over time. There is no pattern. Or
better – the pattern is uniform.
What changes between these two states is the content of what is processed. During sleep,
for instance, neurons tend to discharge in sync: all neurons communicate “the same message” to the
next information processing stage. Uniform messages have a peculiar effect on the nervous system,
as a simple but powerful experiment can demonstrate. In the 1930s, psychologist Wolfgang
Metzger described the ganzfeld experiment (from the German for “entire field”) as part of his
investigation into gestalt theory. In a typical visual ganzfeld experiment, the subject is presented a
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uniform visual field by wearing translucent, monochromatic and completely homogeneous goggles
(simply ping-pong balls halves), whereby the subject experiences a “loss of vision,” often
accompanied with altered states of consciousness. Why is vision “lost”? The eyes are open and light
impinges on the photoreceptors, causing neural discharges on the retina, which propagate to the
cerebral cortex and higher association areas. Nevertheless, a brain function is “lost”, at least by
introspective accounts of subjects (Metzger, 1930).
The ganzfeld experiment is a simple, easily reproducible protocol that points out how an
altered brain state, such as the loss of a brain function as important as vision, can be caused by
uniform stimulation. What determines the subjective label of conscious and unconscious experience
is the content of this processing, where lack of consciousness has been mistaken by states where
uniform information is processed. Figure 1 provides an illustration of how conscious and
unconscious states might be generated by the activity of an underlying neural network, linking
single neuron activation and EEG recording.
Figure 1. Left: conscious states might be generated by the non-uniform activity of large-scale neural networks. The
activation of each cell, depicted as a round gray circle, is proportional to its gray level (top). The activation in time is also
non-uniform (middle), causing the characteristic irregular shape of a “conscious state” EEG. Right: during states
commonly labeled “unconscious”, cells are express uniform patterns of activation (top), which in time (middle) result in
the typical slow, large-scale, synchronized oscillations observed in sleep, anesthesia and coma (Steriade et al., 1993a,b).
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From this brief overview of oscillatory networks, it becomes evident that the physical
transmission of electrical and chemical activity from neuron to neuron within large networks is
required for various conscious or unconscious states to emerge. Such states can be analyzed by way
of EEG or other such techniques required by our third stipulation for consciousness: observable and
measurable “brain” activity. Thus, from the above segment we can state that oscillations within the
brain are necessary but not sufficient for conscious experience; they are the signature of the
underlying physical interaction in biological brains. Such a statement would preclude large-level
simulation work currently being explored by proponents of whole brain emulation, which we will
now explain in more depth.
Counterexample: whole brain emulation
Whole brain emulation (WBE) posits that consciousness can in fact arise from computer
simulations or software replications of the brain. A technical report1 by Anders Sandberg and Nick
Bostrom at the Future of Humanity Institute, Oxford University, presented a 130-page roadmap for
WBE. This detailed account of one-to-one modeling of the human brain lays out economic, scientific,
technological, and ethical WBE concerns that will assuredly arise as computational neuroscientific
research progresses. Even though WBE strives to achieve consciousness in their brain uploading
activities, it is unclear as to whether this effort will be able to pass our third test for embodiment;
there must observed and measurable activity within the physical medium. In fact, given the current
technological status of the computer industry, it is almost a guarantee that WBE would not be able
to pass this test. Traditional von Neumann architectures would not be able to support brain
activities like those described in the previous section including, but not limited to oscillations,
localized regions of activation, networks of distributed activity, and self-organization of activity.
Despite these limitations in the approach, several researchers have attempted to construct
future plans for simulating and emulating the human brain from within the confines of a computer
program. One recent example comes from IBM’s Almaden Research Center which recently
simulated a fully connected large scale network with the number of elements on the order of those
found in a cat brain (Ananthanarayanan et al., 2009). This feat garnered a lot of attention for its
computational methods and visually stunning results. However, many critics pointed out that this
was little more than a pretty show and had little to do with neural physiology, and much less with
1
URL: www.fhi.ox.ac.uk/reports/2008‐3.pdf
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cognitive functioning2. Thus, if either the WBE proposal or the IBM project is to have any future
success, they should focus more on relating high-level functional theory to low-level neural activity.
Even if the simulation performed by IBM contained faithful adherence to the biology (i.e. neural
structure, connectivity, etc.), there is still no established causation of consciousness or any other
form of coherency in neural processing output.
WBE and other mind uploading proposals assume that a computer will be able to faithfully
run a model of our own brain once the "mind upload" is complete. Our simulated mind, running on
a sophisticated computer of the future, should, to all intents and purposes, be a working version of
our conscious selves - only virtual. The question is whether or not such a simulation could indeed
be our conscious doppelganger. We suspect that the software/hardware distinction must collapse
into a sort of embodied hardware for conscious perception and cognitive action to be enabled from a
computer. Furthermore, the embodied hardware must be able to pass our third criterion for
measuring consciousness by being able to observe and measure its activity.
Embodiment in a neuromorphic chip
From a philosophical standpoint, computers send commands to the CPU via numeric
computations, a sort of metaphysical representation of an ontological representation of the mental
state. The actual electrical processing of that numeric code is separate from what the human brain
processes. In other words, a traditional computer's physical state change involves electrical activity
alteration on a chip for memory storage and retrieval; this electrical activity does not correlate well
with the activity seen during an active brain state, but rather the current sequence state for
interpreting that brain state. For the computer to be conscious, both the hardware and software
should be the same so as to eliminate a distinction between numeric interpretation and the
physical, electrical CPU response.
As a result, an embodied neuromorphic chip would be different than a von Neumann-based
chip and, it would be able to generate observable and measurable activity. Such a neural chip would
be built to adhere to neurobiological principles of neural structure, organization, and connectivity.
A von Neumann chip was not designed to adhere to these biological principles but rather to achieve
computational efficiency. Thus, the electrical activity of the actual neuromorphic chip should show
2
URL: http://spectrum.ieee.org/tech-talk/semiconductors/devices/blue-brain-project-leaderangry-about-cat-brain
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some correlation to activity in the human brain. It should be able to self organize into localized
regions of activation and show coherent, meaningful oscillations.
Is a speculative neuromorphic chip such as the one described above sufficiently embodied
in order to be conscious? Yes, however, were we to completely transfer biological Dennett over to
its neuromorphic twin, Dennett Version 1.0, the new iteration of Professor Dennett would quickly
become his own identity with a very unique sort of conscious perception that would most probably
vary exponentially from “ordinary” human consciousness. The millisecond that a researcher
uploads Dennett’s mind to the neural chip, his experience will become very different based on the
change in physical systems. Human minds are wired by their embodied experience, thus whatever
device an individual’s mind has been uploaded to will determine what the contents of this new
mind will be. This is similar to Thomas Nagel’s argument in “What Is It Like To Be a Bat?” (Nagel,
1974).”
Such a chip is not purely hypothetical. In fact, Defense Advanced Research Projects Agency
(DARPA) of the United States government is currently funding a project aimed at creating such
chips. This project, Systems of Neuromorphic Adaptive Plastic Scalable Electronics (SyNAPSE)3,
aims “to develop electronic neuromorphic machine technology that scales to biological levels.” In
other words, the program goal is to develop nano-scale chips capable of functioning in a similar
manner to the synapse between two neurons in a brain in the way in which electric signals are
passed from one to the other. Not only could these chips adhere to neurobiological architecture
and functional constraints, but they will also be required to perform useful behaviors including
learning and navigation in virtual environments. It seems then that the hypothetical embodied
neuromorphic chip that we have proposed may still be a thing of the future, but its development
will be completed sooner than one may think.
Conclusion
Although Searle has argued for biological embodiment as a necessity for causation of
consciousness, this paper puts forth the argument that biological embodiment is not the only
embodiment that can produce consciousness. Instead, we argue that the brain is an optimal form of
embodiment giving rise to consciousness because it can produce observable reports, oral reports,
and observed and measured activity. The first two qualifications of consciousness can be replicated
3
URL: http://www.darpa.mil/dso/thrusts/bio/biologically/synapse/index.htm
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with computer simulations as discussed by the proponents of WBE. However, the third qualification
requires a unique stipulation for embodiment that is able to self organize and generate unique
global and local patterns of activities within its constituent elements. At this point in time, this is
only achievable within brain tissue. However, with the advancement of neural chip development,
we would argue that embodiment necessary for consciousness would be achievable in a new
medium, the neuromorphic chip.
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