Phenomenology and Workspace Interaction

I question Block’s final step towards establishing the modular independence of phenomenal consciousness from workspace activity. He relies on insufficient behavioral data to make a conclusion about an underlying neural mechanism. His argument goes something like this: (1) There is evidence suggesting that workspace is located in the prefrontal cortex; (2) It is established that visual experience correlates with activity in the back of the head; (3) Computational models seem to represent well the interactions between these two areas suggesting that there is competition between coalitions of neurons in the back of the head for the activating of coalitions of neurons in the front of the head. There also seems to be competition for dominance in the frontal area and feedback signaling that may affect the success of given coalitions in the back; (4) Sergent & Dehaene’s 2004 experiments show that subjects tend to ignore completely one of a couple of target stimuli when they have already detected the first; (5) Therefore even though there were two coalitions of neurons that were active in the back of the head only one succeeded in the activating of a coalition of neurons in the front of the head. This is to say that even though the subjects had phenomenal experience of two stimuli they only had cognitive access to one of them. As I see it (5) does not follow from the premises. Block ignores an alternative interpretation of the data that is consistent with what is assumed in (3). One of the options suggested by the computational model is that there is a feedback mechanism from the front to the back of the head. Given that the subjects tended to report having seen the first stimulus and not the second, it is possible that once a perception was detected in the front of the head, signals were sent to the back of the head that blocked perception and not just attention to the second target stimulus.