no-go control

24/04/2010 by admin.

A recent paper, Unconscious Activation of the Prefrontal No-Go Network, by S Van Gaal and others, has results that may mean that I will have to revise my thinking. Unfortunately only the abstract (here) is available to me and so I have not been able to judge what this should do to my ideas.

Cognitive control processes involving prefrontal cortex allow humans to overrule and inhibit habitual responses to optimize performance in new and challenging situations, and traditional views hold that cognitive control is tightly linked with consciousness. We used functional magnetic resonance imaging to investigate to what extent unconscious “no-go” stimuli are capable of reaching cortical areas involved in inhibitory control, particularly the inferior frontal cortex (IFC) and the pre-supplementary motor area (pre-SMA). Participants performed a go/no-go task that included conscious (weakly masked) no-go trials, unconscious (strongly masked) no-go trials, as well as go trials. Replicating typical neuroimaging findings, response inhibition on conscious no-go stimuli was associated with a (mostly right-lateralized) frontoparietal “inhibition network.” Here, we demonstrate, however, that an unconscious no-go stimulus also can activate prefrontal control networks, most prominently the IFC and the pre-SMA. Moreover, if it does so, it brings about a substantial slowdown in the speed of responding, as if participants attempted to inhibit their response but just failed to withhold it completely. Interestingly, overall activation in this “unconscious inhibition network” correlated positively with the amount of slowdown triggered by unconscious no-go stimuli. In addition, neural differences between conscious and unconscious control are revealed. These results expand our understanding of the limits and depths of unconscious information processing in the human brain and demonstrate that prefrontal cognitive control functions are not exclusively influenced by conscious information.

What the authors seem to be saying, to my understanding, is that there are two no-go systems: conscious and unconscious. The conscious one actually works to stop an action. The unconscious one only slows the action and does not actually stop it.

If by conscious control, the authors mean control that we are conscious of, I find nothing disturbing. If by conscious control, they mean control that relies on a prior conscious process to come into existence, I find that very disturbing. If they are saying that a signal that is strong enough to stop an action will also be strong enough to enter our conscious awareness, then great. But I am not sure that this is what they mean. If they are saying that there are two paths and a signal enters the one or the other (for some unknown reason) and so it can either be conscious and successful in controlling action along the one path or it can be unconscious and only slow the action down on the other path, then I find it completely unconvincing.

Posted in will | 1 Comment »