Progress in Brain Research, Vol. 150
ISSN 0079-6123
Copyright r 2005 Elsevier B.V. All rights reserved
CHAPTER 4
Global workspace theory of consciousness: toward a
cognitive neuroscience of human experience?
Bernard J. BaarsÃ
The Neurosciences Institute, 10640 John Jay Hopkins Dv., San Diego, CA 92121, USA
Abstract: Global workspace (GW) theory emerged from the cognitive architecture tradition in cognitive
science. Newell and co-workers were the first to show the utility of a GW or ‘‘blackboard’’ architecture in a
distributed set of knowledge sources, which could cooperatively solve problems that no single constituent
could solve alone. The empirical connection with conscious cognition was made by Baars (1988, 2002). GW
theory generates explicit predictions for conscious aspects of perception, emotion, motivation, learning,
working memory, voluntary control, and self systems in the brain. It has similarities to biological theories
such as Neural Darwinism and dynamical theories of brain functioning. Functional brain imaging now
shows that conscious cognition is distinctively associated with wide spread of cortical activity, notably
toward frontoparietal and medial temporal regions. Unconscious comparison conditions tend to activate
only local regions, such as visual projection areas. Frontoparietal hypometabolism is also implicated in
unconscious states, including deep sleep, coma, vegetative states, epileptic loss of consciousness, and
general anesthesia. These findings are consistent with the GW hypothesis, which is now favored by a
number of scientists and philosophers.
Introduction
Shortly after 1900, behaviorists attempted to purge
science of mentalistic concepts like consciousness,
attention, memory, imagery, and voluntary control.
‘‘Consciousness,’’ wrote John B. Watson, ‘‘is
nothing but the soul of theology.’’ But as the facts
accumulated over the 20th century, all the traditional
ideas of James (1890) and others were found
to be necessary. They were reintroduced with more
testable definitions. Memory came back in the
1960s; mental imagery in the 1970s; selective
attention over the last half century; and consciousness
last of all, in the last decade or so.
It is broadly true that what we are conscious of,
we can report with accuracy. Conscious brain events
are therefore assessed by way of reportability. We
now know of numerous brain events that are
reportable and comparable ones that are not. This
fact invites experimental testing: why are we
conscious of these words at this moment, while a
few seconds later they have faded, but can still be
called to mind? Why is activity in visual occipitotemporal
lobe neurons reportable, while visually
evoked activity in parietal regions is not? Why does
the thalamocortical system support conscious experiences,
while the comparably large cerebellum
and basal ganglia do not? How is waking consciousness
impaired after brain damage? These are all
testable questions. The empirical key is to treat
consciousness as a controlled variable.
A growing literature now compares the brain
effects of conscious and unconscious stimulation.
Precise experimental comparisons allow us to ask
what conscious access does ‘‘as such.’’ Many
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
33
35
37
39
41
43
45
47
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
33
35
37
39
41
43
45
47
3B2v8:06a=w ðDec 5 2003Þ:51c
XML:ver:5:0:1
PBR : 50004 Prod:Type:
pp:45254ðcol:fig::NILÞ
ED:
PAGN: SCAN:
ÃCorresponding author. Tel.: 925-283-2601;
Fax: 925-283-2673; E-mail: baars@nsi.edu
DOI: 10.1016/S0079-6123(05)50004-9 45
techniques are used for this purpose. In visual
backward masking, a target picture is immediately
followed by a scrambled image that does not block
the optical input, but renders it unconscious
(Dehaene et al., 2001). Binocular rivalry has been
used for the same reason: it shows that when two
competing optical streams enter the two eyes, only
one consistent interpretation can be consciously
perceived at any given moment (Leopold and
Logothetis, 1999). Most recently, several studies
have demonstrated inattentional blindness, in
which paying attention to one visual flow (e.g., a
bouncing basketball) blocks conscious access to
another one at the very center of visual gaze (e.g.,
a man walking by in a gorilla suit) (Simons and
Chabris, 1999). These studies generally show that
unconscious stimuli still evoke local feature
activity in sensory cortex. But what is the use of
making something conscious if even unconscious
stimuli are identified by the brain? More than a
score of studies have shown that although
unconscious visual words activate known wordprocessing
regions of visual cortex, the same
stimuli, when conscious, trigger widespread additional
activity in frontoparietal regions (e.g.,
Dehaene et al., 2001).
A rich literature has arisen comparing conscious
and unconscious brain events in sleep and waking,
general anesthesia, epileptic states of absence, very
specific damage to visual cortex, spared implicit
function after brain damage, attentional control
(also see Posner, this volume), visual imagery,
inner speech, memory recall, and more (Crick and
Koch, 2003). In state comparisons, significant
progress has been made in understanding epileptic
loss of consciousness (Blumenfeldt and Taylor,
2003; Blumenfeld, this volume), general anesthesia
(Fiset et al., 2001; John et al., 2001; Alkire and
Fiset et al., this volume) and sleep1
(Steriade, 2001;
Maquet, this volume).
The global access hypothesis
The idea that consciousness has an integrative
function has a long history. Global workspace
(GW) theory is a cognitive architecture with an
explicit role for consciousness. Such architectures
have been studied in cognitive science, and have
practical applications in organizing large, parallel
collections of specialized processors, broadly
comparable to the brain (Newell, 1994). In recent
years, GW theory has been found increasingly
useful by neuroscientists. The theory suggests a
fleeting memory capacity that enables access
between brain functions that are otherwise separate.
This makes sense in a brain that is viewed as a
massive parallel set of specialized processors. In
such a system, coordination and control may take
place by way of a central information exchange,
allowing some processors — such as sensory
systems in the brain — to distribute information
to the system as a whole. This solution works in
large-scale computer architectures, which show
typical ‘‘limited capacity’’ behavior when information
flows by way of a GW. A sizeable body of
evidence suggests that consciousness is the primary
agent of such a global access function in humans
and other mammals (Baars, 1988, 1997, 2002). The
‘‘conscious access hypothesis’’ therefore implies
that conscious cognition provides a gateway to
numerous capacities in the brain (Fig. 1). A
number of testable predictions follow from this
general hypothesis (Table 1).
A theater metaphor and brain hypotheses
GW theory may be thought of as a theater of
mental functioning. Consciousness in this metaphor
resembles a bright spot on the stage of
immediate memory, directed there by a spotlight
of attention under executive guidance. Only the
bright spot is conscious, while the rest of the
theater is dark and unconscious. This approach
leads to specific neural hypotheses. For sensory
consciousness the bright spot on stage is likely to
require the corresponding sensory projection areas
of the cortex. Sensory consciousness in different
modalities may be mutually inhibitory, within
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
33
35
37
39
41
43
45
47
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
33
35
37
39
41
43
45
47
PBR : 50004
1
At the level of cortical neurons, bursting rates do not change
in deep sleep (Steriade, 2001). Rather, neurons pause together
at o4 Hz between bursts. Synchronous pausing could disrupt
the cumulative high-frequency interactions needed for waking
functions such as perceptual continuity, immediate memory,
sentence planning, motor control, and self-monitoring. It is
conceivable that other unconscious states display similar
neuronal mechanisms.
46
approximately 100 ms time cycles (Baars and
Franklin, 2003)QA :1 . Sensory cortex can be activated
internally as well as externally, resulting in the
‘‘internal senses’’ of conscious inner speech and
imagery. Once a conscious sensory content is
established, it is distributed widely to a decentralized
‘‘audience’’ of expert networks sitting in the
darkened theater, presumably using corticocortical
and corticothalamic fibers. The transfer of information
from conscious visual episodes to the
(unconscious) hippocampal system is a clear
example of such distribution of conscious information
in the brain (Moscovitch, 1995). This is the
primary functional role of consciousness: to allow
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
33
35
37
39
41
43
45
47
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
33
35
37
39
41
43
45
47
PBR : 50004
Fig. 1. A schematic diagram of GW theory, viewed metaphorically as a theater of mind. Conscious contents correspond to the bright
spot on the stage of working memory. Once conscious, they activate many unconscious regions of the brain, including interpreters,
memories, language capacities, and automatisms. In brain terms, those would be involved in certain cortical regions, hippocampus, and
basal ganglia, which are believed not to directly support conscious experiences. However, conscious cognitions themselves are always
shaped by unconscious contexts. Executive functions (self) may be considered as one set of such contexts (Adapted from Baars, 1997).
Table 1. Theoretical claims: brain capacities enabled by conscious events
1. Conscious perception enables access to widespread brain sources; unconscious sensory processing is much more limited
2. Conscious perception, inner speech, and visual imagery enable working memory functions; there is no evidence for unconscious
access to working memory
3. Conscious events enable almost all kinds of learning: episodic and explicit learning, but also implicit and skill learning
4. Conscious perceptual feedback enables voluntary control over motor functions, and perhaps over any neuronal population and even
single neurons
5. Conscious contents can evoke selective mechanisms (attention) and be evoked by it
6. Consciousness enables access to the ‘‘observing self’’ — executive interpreters, involving parietal and prefrontal cortex
47
a theater architecture to operate in the brain, in
order to integrate, provide access, and coordinate
the functioning of very large numbers of specialized
networks that otherwise operate autonomously.
All the elements of GW theory have
reasonable brain interpretations, allowing us to
generate a set of specific, testable brain hypotheses
about consciousness and its many roles in the
brain. Some of these ideas have now received
considerable empirical support (Baars, 2002; Baars
et al., 2003).
The theory has been implemented in computational
and neural net models and bears a family
resemblance to Neural Darwinist models (Edelman,
2003). Franklin and colleagues have implemented
GW theory in large-scale computer agents,
to test its functionality in complex practical tasks
(Franklin, 2001). IDA (for ‘‘intelligent distributed
agent’’), the current implementation of the extended
GW architecture directed by Franklin, is
designed to handle a very complex artificial
intelligence task normally handled by trained
human beings (also see Aleksander on machine
consciousness in this volume). The particular
domain in this case is interaction between U.S.
Navy personnel experts and sailors who move
from job to job. IDA negotiates with sailors via email,
and is able to combine numerous regulations,
sailors’ preferences, time, location and travel
considerations into human-level performance.
While it has components roughly corresponding
to human perception, memory, and action control,
the heart of the system is a GW architecture that
allows the content or meanings of the messages to
be widely distributed, so that specialized programs
called ‘‘codelets’’ can respond with solutions to
centrally posed problems. Franklin writes that
‘‘The fleshed out global workspace theory is
yielding hopefully testable hypotheses about human
cognition. The architectures and mechanisms
that underlie consciousness and intelligence in
humans can be expected to yield information
agents that learn continuously, adapt readily to
dynamic environments, and behave flexibly and
intelligently when faced with novel and unexpected
situations.’’ (http://csrg.cs.memphis.edu/). Similar
architectures have been applied to difficult problems
like speech recognition. While such autonomous
agent simulations do not prove that GW
architectures exist in the brain, they give an
existence proof of their functionality. It is worth
noting that few integrative theories of mind or
brain show functional utility in applied settings.
Sensory consciousness as a test case
Visual consciousness has been studied in depth, and
there is accepted evidence that visual features that
become conscious are identified by the brain in the
ventral stream of visual cortex. There, featuresensitive
cells support visual experiences of light,
color, contrast, motion, retinal size, location, and
object identity; small lesions can selectively abolish
those conscious properties without affecting other
aspects of conscious vision (Zeki, 2001; Naccache,
in this volume).
However, to recollect the experience of a human
face, we need the hippocampal system. To respond
to it emotionally, neurons in amygdala may be
activated. But hippocampus and amygdala do not
seem to support conscious contents directly
(Moscovitch, 2001) QA :2. Thus, the ventral visual
stream, which is needed for specific conscious
contents, seems to influence regions that are not.
Dehaene and colleagues have shown that backward-masked
visual words evoked brain activity
confined to the well-known visual word recognition
areas of cortex (Dehaene et al., 2001).
Identical conscious words triggered higher levels
of activity in these areas, but more importantly,
they also evoked far more widely distributed
activity in parietal and prefrontal cortex. That
result has now been replicated more than a dozen
times, using different brain imaging techniques
and different methods for comparing conscious
and unconscious input. Such methods have
included binocular rivalry (Sheinberg and Logothetis,
1997), inattentional blindness (Rees et al.,
1999), neglect and its extinction (Rees et al., 2002),
and different sense modalities, such as audition
(Portas et al., 2000), pain perception (Rosen et al.,
1996), and sensorimotor tasks (Haier et al., 1992;
Raichle et al., 1994). In all cases, conscious sensory
input evoked wider and more intense brain activity
than identical unconscious input.
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
33
35
37
39
41
43
45
47
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
33
35
37
39
41
43
45
47
PBR : 50004
48
Complementary findings come from studies of
unconscious states. In deep sleep, auditory stimulation
activates only primary auditory cortex
(Portas et al., 2000). In vegetative states following
brain injury, stimuli that are ordinarily loud or
painful activate only the primary sensory cortices
(Laureys et al., 2000, 2002). Waking consciousness
is apparently needed for widespread of inputdriven
activation to occur. These findings support
the general notion that conscious stimuli mobilize
large areas of cortex, presumably to distribute
information about the input.
Inner speech, imagery, and working memory
Both auditory and visual consciousness can be activated
endogenously. Inner speech is a particularly important
source of conscious auditory-phonemic events, and
visual imagery is useful for spatial memory and
problem-solving. The areas of the left hemisphere
involved in outer speech are now known to be involved
in inner speech as well (Paulesu et al., 1993). Likewise,
mental imagery is known to involve visual cortex
(Kosslyn et al., 2001). Internally generated somatosensory
imagery may reflect emotional and motivational
processes, including feelings of psychological pain,
pleasure, hope, fear, sadness, etc. (Damasio, 2003). Such
internal sensations may communicate to other parts of
the brain via global distribution or activation.
Prefrontal executive systems may sometimes
control motor activities by evoking motivational
imagery, broadcast from the visual cortex, to
activate relevant parts of motor cortex. Parts of
the brain that play a role in emotion may also be
triggered by global distribution of conscious
contents from sensory cortices and insular cortex.
For example, the amygdala appears necessary to
recognize visual facial expressions of fear and
anger. Thus, many cortical regions work together
to transform goals and emotions into actions
(Baars, 1988).
The attentional spotlight
The sensory ‘‘bright spot’’ of consciousness
involves a selective attention system, the ability
of the theater spotlight to shine on different actors
on the stage. Like other behaviors like breathing
and smiling, attention operates under dual control,
voluntary, and involuntary. Voluntary attentional
selection requires frontal executive cortex, while
automatic selection is influenced by many areas,
including the brain stem, pain systems, insular
cortex, and emotional centers like the amygdala
and peri-aqueductal grey (Panksepp, 1998) QA :3. Presumably,
these automatic attentional systems that
allow significant stimuli to ‘‘break through’’ into
consciousness, as when a subject’s name is
sounded in an otherwise unconscious auditory
source.
Context and the first-person perspective
When we step from a tossing sailboat onto solid
ground, the horizon can be seen to wobble. On an
airplane flight at night passengers can see the cabin
tilting on approach to landing, although they are
receiving no optical cues about the direction of the
plane. In those cases unconscious vestibular
signals shape conscious vision. There are numerous
examples in which unconscious brain activities
can shape conscious ones, and vice versa. These
unconscious influences on conscious events are
called ‘‘contexts’’ in GW theory (Fig. 1). Any
conscious sensory event requires the interaction of
sensory analyzers and contextual systems. In
vision, sensory contents seem to be produced by
the ventral visual pathway, while contextual
systems in the dorsal pathway define a spatial
domain within which the sensory event is defined.
Parietal cortex is known to include allocentric and
egocentric spatial maps, which are not themselves
objects of consciousness, but which are required to
shape every conscious visual event. There is a
difference between the disorders of content systems
like the visual ventral stream, compared to
damaged context systems. In the case of ventral
stream lesions, the subject can generally notice a
missing part of normal experience; but for damage
to context, the brain basis of expectations is itself
damaged, so that one no longer knows what to
expect, and hence what is missing. This may be
why parietal neglect is so often accompanied by a
striking loss of knowledge about one’s body space
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
33
35
37
39
41
43
45
47
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
33
35
37
39
41
43
45
47
PBR : 50004
49
(Bisiach and Geminiani, 1991). Patients suffering
from right parietal neglect can have disturbing
alien experiences of their own bodies, especially of
the left arm and leg. Such patients sometimes
believe that their left leg belongs to someone else,
often a relative, and can desperately try to throw it
out of bed. Thus, parietal regions seem to shape
contextually both the experience of the visual
world and of one’s own body. Notice that neglect
patients still experience their alien limbs as
conscious visual objects (a ventral stream function);
they are just disowned. Such specific loss of
contextual body information is not accompanied
by a loss of general intelligence or knowledge.
Vogeley and Fink (2003) suggest that parietal
cortex is involved in the first-person perspective,
the viewpoint of the observing self. When subjects
are asked to adopt the visual perspective of
another person, parietal cortex became differentially
active.
Self-systems
Activation by of visual object regions by the sight
of a coffee cup may not be enough to generate
subjective consciousness of the cup. The activated
visual information may need to be conveyed to
executive or self-systems, which serve to maintain
constancy of an inner framework across perceptual
situations. When we walk from room to room
in a building, we must maintain a complex and
multileveled organization that can be viewed in
GW theory as a higher-level context. Major goals,
for example, do not change when we walk from
room to room, but conscious perceptual experiences
do. Gazzaniga (1996)QA :4 has found a number of
conditions under which split-brain patients encounter
conflict between right and left hemisphere
executive and perceptual functions. He has proposed
the existence of a ‘‘narrative self’’ in the left
frontal cortex, based on split-brain patients who
are clearly using speech output in the left hemisphere
to talk to themselves, sometimes trying to
force the right hemisphere to obey its commands.
When that proves impossible, the left hemisphere
will often rationalize the sequence of events so as
to repair its understanding of the interhemispheric
conflict. Analogous repairs of reality are observed
in other forms of brain damage, such as neglect.
They also commonly occur whenever humans are
confronted with major, unexpected life changes.
The left-hemisphere narrative interpreter may be
considered as a higher-level context system that
maintains expectations and intentions across many
specific situations. Although the inner narrative
itself is conscious, it is shaped by unconscious
contextual influences.
If we consider Gazzaniga’s narrative interpreter
of the dominant hemisphere to be one kind of selfsystem
in the brain, it must receive its own flow of
sensory input. Visual input from one-half of the
field may be integrated in one visual hemicortex, as
described above, under retinotopic control from
area V1. But once it comes together in late visual
cortex (presumably in inferotemporal object regions),
it needs to be conveyed to frontal areas on
the dominant hemisphere, in order to inform the
narrative interpreter of the current state of
perceptual affairs. The left prefrontal self system
then applies a host of criteria to the input, such as
‘‘did I intend this result? Is it consistent with my
current and long-term goals? If not, can I
reinterpret it to make sense in my running account
of reality?’’ It is possible that the right hemisphere
has a parallel system that does not speak but that
may be better able to deal with anomalies via
irony, jokes, and other emotionally useful strategies.
The evidence appears to be good that the
isolated right prefrontal cortex can understand
such figurative uses of language, while the left does
not. Full consciousness may not exist without the
participation of such prefrontal self systems.
Relevance to waking, sleeping, coma, and general
anesthesia
Metabolic activity in the conscious resting state is
not uniformly distributed. Raichle et al. (2001)
reported that mesiofrontal and medial parietal
areas, encompassing precuneus and adjacent
posterior cingulate cortex, can be posited as a
tonically active region of the brain that may
continuously gather information about the world
around, and possibly within, us. It would appear
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
33
35
37
39
41
43
45
47
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
33
35
37
39
41
43
45
47
PBR : 50004
50
to be a default activity of the brain. Mazoyer et al.
(2001)QA :5 also found high prefrontal metabolism
during rest. We will see that these regions show
markedly lower metabolism in unconscious states.
Laureys (1999a, b, 2000) and Baars et al. (2003)
list the following features of four unconscious
states, that are causally very different from each
other: deep sleep, coma/vegetative states, epileptic
loss of consciousness, and general anesthesia under
various agents. Surprisingly, despite their very
different mechanisms they share major common
features. These include: (i) widely synchronized
slow waveforms that take the place of the fast
and flexible interactions needed for conscious
functions; (ii) frontoparietal hypometabolism;
(iii) widely blocked functional connectivity, both
corticocortical and thalamocortical; and (iv) behavioral
unconsciousness, including unresponsiveness
to normally conscious stimuli. Fig. 2 shows
marked hypofunction in the four unconscious
states compared with conscious controls, precisely
where we might expect it: in frontoparietal regions.
In a related study, John and co-workers showed
marked quantitative electroencephalogram
(EEG)2
changes between conscious, anesthetic,
and post-anesthetic (conscious) states (John et al.,
2000)QA :6 . At loss of consciousness, gamma power
decreased while lower frequency bands increased
in power, especially in frontal leads. Loss of
consciousness was accompanied by a significant
drop in coherence between homologous areas of
the two hemispheres, and between posterior and
anterior regions of each hemisphere. However,
there was hypersynchronous activity within anterior
regions. The same basic changes occurred
across all six anesthetics,3
and reversed when
patients regained consciousness (see John, in this
volume).
From the viewpoint of globalist theories, the
most readily interpretable finding is the coherence
drop in the gamma range after anesthetic loss of
consciousness. It suggests a loss of coordination
between frontal and posterior cortex, and between
homologous regions of the two hemispheres. The
authors also suggest that the anteriorization of low
frequencies ‘‘must exert a profound inhibitory
influence on cooperative processes within (frontal)
neuronal populations. This functional system then
becomes dedifferentiated and disorganized’’ (p.
180). Finally, the decoupling of the posterior
cortex with anterior regions suggests ‘‘a blockade
of perception’’ (p. 180). These phenomena appear
to be consistent with the GW notion that widespread
activation of nonsensory regions is required
for sensory consciousness.
The role of frontoparietal regions in conscious
contents and states
Could it be that brain regions that underlie the
contextual functions of Fig. 1 involve frontal and
parietal regions? In everyday language, the ‘‘observing
self’’ may be disabled when those regions
are dysfunctional and long-range functional connectivity
is impaired. Frontoparietal association
areas have many functions, but several lines of
evidence suggest that they could have a special
relationship with consciousness, even though they
do not support the sensory contents of conscious
experience directly. (i) Conscious stimulation in
the waking state leads to frontoparietal activation,
but unconscious input does not; (ii) in unconscious
states, sensory stimulation activates only sensory
cortex, but not frontoparietal regions; (iii) the
conscious resting state shows high frontoparietal
metabolism compared with outward-directed cognitive
tasks; and (iv) four causally very different
unconscious states show marked functional decrements
in the same areas. Although alternative
hypotheses must be considered, it seems reasonable
to suggest that ‘‘self’’ systems supported by
these regions could be disabled in unconscious
states. From the viewpoint of the narrative
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
33
35
37
39
41
43
45
47
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
33
35
37
39
41
43
45
47
PBR : 50004
QA:7
2
Although the spike-wave EEG of epileptic seizures appears
different from the delta waves of deep sleep and general
anesthesia, it is also synchronized, slow, and high in amplitude.
The source and distribution of spike-wave activity varies in
different seizure types. However, the more widespread the
spike-wave pattern, the more consciousness is likely to be
impaired (Blumenfeldt and Taylor, 2003). This is again marked
in frontoparietal regions.
3
There is a debate whether ketamine at relatively low doses
should be considered an anesthetic. All anesthetic agents in this
study were used at dosages sufficient to provide surgical-level
loss of consciousness.
51
observer, this would be experienced as subjective
loss of access to the conscious world. Unconscious
states might not necessarily block the objects of
consciousness; rather, the observing subject might
not be at home.
Conclusion
GW theory suggests that consciousness enables
multiple networks to cooperate and compete in
solving problems, such as retrieval of specific items
from immediate memory. Conscious contents may
correspond to brain processes that work much like
brief memories whose contents activate widespread
regions in the brain. Physiologically such
interactions seem to involve multiple high-frequency
oscillatory rhythms. The overall function
of consciousness is to provide widespread access,
which in turn may serve coordination and control.
Consciousness is the gateway to the brain.
Uncited References
Fiset et al. (1999); Frackowiak et al. (2004); Franklin
(2000); Freeman (2003); Tononi and Edelman (1998).
Acknowledgments
I gratefully acknowledge support from the Neurosciences
Institute and the Neurosciences Research
Foundation (10640 John Jay Hopkins
Drive, San Diego, CA 94549, USA). I thank
Steven Laureys, Gerald M. Edelman, Stan Franklin,
Bjorn Merker, Anil Seth, Douglas Nitz,
E. Roy John, and Walter Freeman for helpful
discussions.
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
33
35
37
39
41
43
45
47
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
33
35
37
39
41
43
45
47
PBR : 50004
Fig. 2. Neural activity in four types of unconscious states, subtracted from conscious controls. Positron emission tomography scans
showing regional decreases in metabolism or blood flow when unconscious states are compared with resting consciousness. Coma,
persistent vegetative state, sleep, and general anesthesia all show regional decreases in frontoparietal association cortices. Column 1:
the right lateral aspect of the brain; column 2: the left lateral aspect; column 3: a medial view of the left hemisphere. Abbreviations: F,
prefrontal; MF, mesiofrontal; P, posterior parietal cortex; Pr, posterior cingulate/precuneus (from Baars et al., 2003).
52
References
Baars, B.J. (1988) A cognitive theory of consciousness. Cambridge
University Press, New York.
Baars, B.J. (1997) In the theater of consciousness: The
workspace of the mind. Oxford, New York.
Baars, B.J. (2002) The conscious access hypothesis: origins and
recent evidence. Trends Cogn. Sci., 6: 47–52.
Baars, B. J., Ramsoy, T., Laureys, S. (2003). Trends in
Neurosci., 26, 671–675.QA :8
Baars, B.J. and Franklin, S. (2003) How conscious experience
and working memory interact. Trends Cogn. Sci., 7: 166–172.
Bisiach, E. and Geminiani, G. (1991) Anosognosia related to
hemiplegia and hemianopiaQA :9 . In: Prigatano G.P. and Schacter
D.L. (Eds.), Awareness of Deficit After Brain Injury: Clinical
and Theoretical Issues. Oxford University Press.
Blumenfeldt, H. and Taylor, J. (2003) Why do seizures cause
loss of consciousness? Neuroscientist, 9: 1–10.
Crick, F. and Koch, C. (2003) A framework for consciousness.
Nat. Neurosci., 6: 119–126.
Damasio, A. (2003) The feeling of knowing. Basic Books, New
York.
Dehaene, S., et al. (2001) Cerebral mechanisms of word
masking and unconscious repetition primingQA :10 . Natl. Neurosci.,
4: 752–758.
Edelman, G.M. (2003) Naturalizing consciousness: a theoretical
framework. Proc. Natl. Acad. Sci. USA, 100: 5520–5534.
Fiset, P., Paus, T., Daloze, T., Plourde, G., Meuret, P.,
Bonhomme, V., et al. (1999) Brain mechanisms of propofolinduced
loss of consciousness in humans: a positron emission
tomographic study. J. Neurosci., 19(13): 5506–5513.
Frackowiak, et al. (2004) Human brain function (2nd ed.).
Elsevier, London.
Franklin, S. (2000) Deliberation and voluntary action in ‘conscious’
software agents. Neural Network World, 10: 505–521.
Franklin, S. (2001) Automating human information agents. In:
Chen Z. and Jain L.C. (Eds.), Practical Applications of
Intelligent Agents. Springer-Verlag, Berlin.
Freeman, W.J. (2003) The wave packet: an action potential for
the 21st century. J. Integr. Neurosci., 2(1): 3–30.
Haier, R.J., et al. (1992) Regional glucose metabolic changes
after learning a complex visuospatial motor task: a positronemission
tomographic study. Brain Res., 570: 134–148.
James, W. (1890) The principles of psychology. Holt, New
York.
John, E.R., Prichep, L.S., Kox, W., Valdes-Sosa, P., BoschBayard,
J., Aubert, E., et al. (2001) Invariant reversible
QEEG effects of anesthetics. Conscious Cogn., 10(2):
165–183.
Kosslyn, S.M., Ganis, G. and Thompson, W.L. (2001) Neural
foundations of imagery. Natl. Rev. Neurosci., 2(9): 635–642.
Laureys, S., et al. (2000) Restoration of thalamocortical
connectivity after recovery from persistent vegetative state.
Lancet, 355: 1916.
Laureys, S., et al. (1999a) Cerebral metabolism during
vegetative state and after recovery to consciousness. J.
Neurol. Neurosurg. Ps., 67: 121.
Laureys, S., et al. (1999b) Impaired functional connectivity in
vegetative state: preliminary investigation using PET. Neuroimage,
9: 377–382.
Laureys, S., et al. (2000) Auditory processing in the vegetative
state. Brain, 123: 1589–1601.
Laureys, S., et al. (2002) Cortical processing of noxious
somato–sensory stimuli in the persistent vegetative state.
Neuroimage, 17: 732–741.
Mazoyer, B., et al. (2001) Cortical networks for working
memory and executive functions sustain the conscious resting
state in man. Brain Res. Bull., 54: 287–298.
Moscovitch, M. (1995) Recovered consciousness: a hypothesis
concerning modularity and episodic memory. J. Clin. Exp.
Neuropsychol., 17(2): 276–290.
Newell, A. (1994) Unified theories of cognition: The William
James lectures. Harvard University Press, Cambridge, MA.
Panksepp, J. (1998) Affective Neuroscience. Oxford University
Press, New York.
Paulesu, E., Frith, D. and Frackowiak, R.S.J. (1993) The neural
correlates of the verbal component of working memory.
Nature, 362: 342–345.
Portas, C.M., et al. (2000) Auditory processing across the
sleep–wake cycle: simultaneous EEG and fMRI monitoring
in humans. Neuron, 28: 991–999.
Raichle, M.E., et al. (1994) Practice-related changes in human
brain functional anatomy during non-motor learning. Cereb.
Cortex, 4: 8–26.
Raichle, M.E., et al. (2001) A default mode of brain function.
Proc. Natl. Acad. Sci. USA, 98: 676–682.
Rees, G., Russell, C., Frith, C.D. and Driver, J. (1999)
Inattentional blindness versus inattentional amnesia for
fixated but ignored words. Science, 286(5449): 2504–2507.
Rees, G., Wojciulik, E., Clarke, K., Husain, M., Frith, C. and
Driver, J. (2002) Neural correlates of conscious and
unconscious vision in parietal extinction. Neurocase, 8(5):
387–393.
Rosen, S.D., Paulesu, E., Nihoyannopoulos, P., Tousoulis, D.,
Frackowiak, R.S., Frith, C.D., et al. (1996) Silent ischemia as
a central problem: regional brain activation compared in
silent and painful myocardial ischemia. Ann. Int. Med.,
124(11): 939–949.
Sheinberg, D.L. and Logothetis, N.K. (1997) The role of
temporal cortical areas in perceptual organization. Proc.
Natl. Acad. Sci. USA, 94(7): 3408–3413.
Simons, D.J. and Chabris, C.F. (1999) Gorillas in our midst:
sustained inattentional blindness for dynamic events. Perception,
28(9): 1059–1074.
Steriade, M. (2001) Active neocortical processes during
quiescent sleep. Arch. Ital. Biol., 139: 37–51.
Tononi, G. and Edelman, G. (1998) Consciousness and
complexity. Science, 282: 1846–1851.
Vogeley, K. and Fink, G.R. (2003) Neural correlates of the
first-person perspective. Trends Cogn. Sci., 7: 38–42.
Zeki, S. (2001) Localization and globalization in conscious
vision. Annu. Rev. Neurosci., 24: 57–86.
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
33
35
37
39
41
43
45
47
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
33
35
37
39
41
43
45
47
PBR : 50004
53
AUTHOR QUERY FORM
ELSEVIER
Progress in Brain Research
Queries and / or remarks
JOURNAL TITLE: PBR
ARTICLE NO: 50004
Query
No
Details required Author's response
AQ1 Please confirm the change in the year of publication.
AQ2 Please provide the reference.
AQ3
Please confirm the change in the year of publication.
AQ4
Please provide the reference.
AQ5
Please confirm the change in the year of publication.
AQ6
Please provide the reference.
AQ7 Please check the citation of 'notes' 1 and 2 in the text.
AQ8 Please check the insertion of initials.
AQ9
Please provide the place of publication.
AQ10
Please provide the names of remaining authors where 'et al' is
refered in the ref. list.
UC. ref.
If uncited references are appear under the section 'uncited references,' please cite
them at relevant places in the text.