Phenomenal Consciousness without Cerebral Cortex?

Contrary to what many doctors apparently assume, there is overwhelming evidence (cf. here and here) that hydranencephalic children, who lack a cerebral cortex, are creature conscious in a robust sense.  That is, they have a sleep-wake cycle, they respond appropriately to some features of stimuli, and they express emotions and preferences.  But are they phenomenally conscious?  Since they can’t give linguistic reports, it’s hard to tell.

I suggested the following test:  if hydranencephalic children exhibit differences between sleep phases similar to the differences between REM and non-REM sleep, then that is evidence that they are phenomenally conscious. 

Lynne Trease is the mother of Nikki, an eight-year-old hydranencephalic girl.  You can read Nikki’s story in a five-part story by the Omaha World-Herald.  Lynne wrote me as follows: “I believe that Nikki does have REM sleep cycles as she has noticeable rapid eye movements frequently while sleeping”.  It would be interesting to know if there are any rigorous studies on this matter, and if not, it’s time for some neuroscientists to look into it.  For if Lynne is right, the burden of proof starts shifting to anyone who denies that these children are phenomenally conscious.


  1. Nigel Pedersen

    That is an interesting idea. I would like to explain why I think your point demonstrates well the importance of brainstem and subcortical structures in processes that we commonly associate with consciousness, but first some examples:

    -Decorticate animals groom, and feed quite well, in fact they are difficult to distinguish from intact ones. This is less the case in humans who are more dependent on the cortex for the execution of bipedal locomotion and fine motor control, of course not to mention language and communicable conscious awareness.

    -Another common example is the way in which anencephalic babies smile and cry, sleep and wake and startle to unexpected sounds. They reject unpleasant food and become agitated with hunger. (See WW Blessing, 1997). But such children never go on to develop higher cognitive function, language, or theory of mind, nor any other features of consciousness. It is quite clear to me that they are not conscious, and that those things that they can do ought instead be conceived of as part of the vegetative brain, including the sleep-wake circuitry. Thus wakefulness supports consciousness as a necessary, not a sufficient condition. Of course here the word wakefulness is not being used in the phenomenal sense, but instead as it is usually employed to describe a neurologic vigilance state.

    -Comatose patients rarely stay in an unresponsive sleep like state for long, instead emerging into a ‘coma vigil’ whereby sleep-wake cycles again establish themselves, even with widespread cortical damage. (See the classic, Plum and Posner’s Diagnosis of Stupor and Coma).

    -As you know, the REM state is defined by its characteristic EEG, muscle atonia and eye movements, which may or may not be present in your example case, where the EEG is likely to be very abnormal, and the frontal eye fields may not be fully intact. Muscle atonia may still be present. Overall, I’m not sure that having a sleep cycle that includes something akin to REM demonstrates the presence of phenomenal consciousness, and I instead think the burden of proof would be upon those who suggest the contrary.

    Interestingly, the cortex is perhaps relatively less important than is often made out, but I would suggest that this is medical perspective, and I feel that the excessive attention given the cortex is more common amongst other groups, not doctors. I look forward to hearing more about subcortical structures in discussions of consciousness.

  2. I´ve been cautious in not commenting in this post for the serious implications to those suffering this clinical picture ( e.g. anenchepalic individuals) and their families, but neverthles i would like to point that is needed to shift the current philosophical framework that always is focused in those aspects of higher levels of consciousness, when in fact many considered lower levels mechanisms are of the highest importance in supporting life, physical well-being, and the possibility of the normal expressions of feelings, emotions and consciousness.

    I´m referring to the autonomic nervous system and all of the visceral afferent neurons pathways and its three branches (parasympathetic, sympathetic and enteric)that are represented in the central nervous system within the brainstem and hypothalamus all of them outside the cerebral cortex.

    Without them we cannot have a coherent self and body, a unified being, and they don´t belong to the higher parts of the brain.

    In this issue i would like to be aligned with those philosphers that recognized the importance of the body for ones own like and a meaningful interaction with the enviroment (for example, Jose Luis Bermudez)

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