Reporter: 蕭百娸 2005/12/19

1. Bernard J. Baars (2002).The conscious access hypothesis: origins and recent evidenceTrends in Cognitive Science, 6, 47-52. Reporter: 蕭百娸2005/12/19

2. What is conscious access hypothesis (CAH)? • Csns helps tomobilize and integrate brain functionsthat are otherwise separate and independent. • It was described in a framework called ‘Global Workspace Theory’

3. Other Senses Inner Senses Ideas Conscious Access Hypothesis Global Workspace Theory

4. CAH from the past 20 years...

5. Philosophical questions… • How does private experience relate to the physical world? (mind-body problem) • Why do the brain states which mobilize and integrate brain functions become consciousness?(the hard problem)

6. Scientific questions about evidences • Relevant evidences for conscious functions was indirect. • Brain image technology is used for more apparent answer of conscious functions. • Today, scientists used ‘contrastive analysis’.

7. General criticisms of the theory • Integrative theories were often viewed as untestable. • GWT was mistakenly thought to be a ‘Cartesian theater’.

8. Cartesian Theater We seem to imagine that there is some place inside “my” mind or brain where “I” am. The homunculus problem: an infinite regress

9. Seven Predictions (1) Conscious perception involves more than sensory analysis; it enables access to widespread brain sources, whereas unconscious input processing is limited to sensory regions.

10. Visible Words Masked Words Dehaene, S. et al., 2001 • enables widespread access • unconscious input processing is limited

11. Tononi, G. et al., 1998 Binocular rivalry • Conscious visual input evokes more intense and coherent MEG responses. • Activity in many MEG channels shows 50-80% greater power for conscious input.

12. (2) Consciousness enables comprehension of novel information, such as new combinations of words. • Relative evidences: The cases about subliminal priming,unattended processing, and anesthesia condition, are worse than conscious cases. • Rarely used to describe csns functions. • Those researches focus on unconscious processes.

13. (3) Working memory (WM) depends on conscious elements, including conscious perception, inner speech and visual imagery, each mobilizing widespread functions.

14. (4) Conscious information enables many types of learning, using a variety of different brain mechanisms. • Hippocampusseems specialized for learning conscious events. (Kosslyn 1994, Standing 1973) • Even implicit learning requires conscious information.(Rebers 1989)

15. (5) Voluntary control is enabled by conscious goals and perception of results. • There are evidence (Evans, Simard) shows that conscious feedback training help voluntary control, but no evidence of unconscious feedback.

16. (6) Selective attention enables access to conscious contents, and vice versa. • Attention and consciousness are distinct. (Barrs 1999, 1997) • According to GWT, many attentional mechanisms exist, whose function is to bring different events to consciousness, leading global distribution of information.

17. (7) Consciousness enables access to ‘self’: executive interpretation in the brain. • Fugue, Hypnosis: ‘time loss’ report • loss of one executive interpreter’s reported access to conscious events while another is dominant. • Split-brain: what they reports depended on the hemisphere’s executive system received conscious input. (Gazzaniga)

18. Possible mechanisms of global access

19. Conclusions • Consciousness might be a gateway to brain integration, enabling access between otherwise separate neuronal functions. • More studies are needed to explore the hypothesis.