two views of consciousness

[Stephen Grossberg]

CONSCIOUSNESS AND COMPLEXITY
OR
CONSCIOUSNESS AND RESONANCE?

Stephen Grossberg and Rajeev D.S. Raizada
Department of Cognitive and Neural Systems
Boston University
677 Beacon Street
Boston, MA 02215
Phone: 617-353-7858 or-7857
Fax: 617-353-7755
Email: steve at cns.bu.edu, rajeev at cns.bu.edu


In their recent article in Science, Tononi and Edelman (1) suggest
that "conscious experience is integrated ... and at the same time it
is highly differentiated", that "integration [occurs] ... through
reentrant interactions", and that "attention may increase
.. conscious salience". They also note that "cortical regions ...
for controlling action ... may not contribute significantly to
conscious experience".

An alternative theory unifies these several hypotheses into a single
hypothesis: "All conscious states are resonant states" (2), and suggests
how resonant states enable brains to learn about a changing world
throughout life (3). Resonance arises when bottom-up and top-down, or
"reentrant", processes reach an attentive consensus between what is
expected and what is in the world. Because resonance dynamically regulates
learning of sensory and cognitive representations, this theory is called
adaptive resonance theory, or ART.

ART implies all the properties noted by Tononi and Edelman, but also
clarifies their critical link to learning, and explains why only a certain
type of excitatory top-down matching can stabilize learning (4): When
top-down attentional signals match bottom-up sensory input, their mutual
excitation strengthens and maintains existing neural activity long enough
for synaptic changes to occur. Thus, attentionally relevant stimuli are
learned, while irrelevant stimuli are suppressed and hence prevented from
destabilizing existing memories. Recent experiments support these
predictions during vision (5), audition (6), and learning (7).

Why dorsal cortical circuits that control action do not support
consciousness now follows easily: Such circuits use inhibitory matching.
For example, after moving your arm to an expected position, movement
stops (viz., is inhibited) because "where you want to move" matches "where
you are" (8). Inhibitory matches do not resonate, hence are not conscious.

A detailed model of how the laminar circuits of neocortex use resonance to
control cortical development, learning, attention, and grouping of
information has recently been proposed (9), and suggests new experiments
to test the predicted linkages between learning, attention, and
consciousness.

REFERENCES

1. G. Tononi and G.M. Edelman, Science 282, 1846 (1998).

2. S. Grossberg, Psychol. Rev. 87, 1 (1980); S. Grossberg, Studies of Mind
and Brain (Kluwer/Reidel, Amsterdam, 1982); S. Grossberg, The Adaptive
Brain, Vol I. (Elsevier/North-Holland, Amsterdam, 1987); S. Grossberg,
Amer. Scientist 83, 438 (1995). S. Grossberg, Consciousness and Cognition,
8, 1, 1999.

3. C. D. Gilbert, Physiol. Rev. 78, 467 (1998); D. V. Buonomano and M. M.
Merzenich, Ann. Rev. Neurosci. 21, 149 (1998).

4. G. A. Carpenter and S. Grossberg, Computer Vis., Graphics, and Image
Proc. 37, 54.

5. A. M. Sillito, H. E. Jones, G. L. Gerstein, D. C. West, Nature 369,
479; J. Bullier, J. M. Hupe, A. C. James, P. Girard, J. Physiol. (Paris)
90, 217 (1996); V. A. F. Lamme, K. Zipser, H. Spekreijse, Soc. Neurosci.
Abstr. 23, 603.1 (1997).

6. Y. Zhang, N. Suga, J. Yan, Nature 387, 900 (1997).

7. E. Gao and N. Suga, Proc. Natl. Acad. Sci. USA 95, 12663 (1998); E. R.
Ergenzinger, M. M.  Glasier, J. O. Hahm, T. P. Pons, Nature Neurosci. 1,
226 (1998); J. P. Rauschecker, Nature Neurosci. 1, 179 (1998); M. Ahissar
and S. Hochstein, Proc. Natl. Acad. Sci. USA 90, 5718 (1993).

8. D. Bullock, P. Cisek, S. Grossberg, Cereb. Cortex 8, 48 (1998).

9. S. Grossberg, Spatial Vision, 12, 163 (1999); S. Grossberg and J. R.
Williamson, Soc. Neurosci. Abstr. 23, 227.9 (1997); R. D. S. Raizada and
S. Grossberg, Soc. Neurosci. Abstr. 24, 105.10 (1998).