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In the context of PVS or Locked-In Syndrome I cannot think about life being worth living without considering "The Diving Bell and the Butterfly" by Jean-Dominique Bauby, (1997), translation published by Fourth Estate. From clinical experience I also believe that memory plays a very important role in subjective consciousness, and that we cannot say that experiences are not important simply because they cannot be remembered.

Perhaps the highly significant distinction made by Block (1994, 1995): access consciousness and phenomenal consciousness, doesn´t fit well for clinical cases like the one you discuss (and you acknowledge that), because this distinction principally latched onto the top-down/bottom-up axis of controlling mechanisms in cognitive functions, that in the case of PVS due to the only recognize activity within the hippothalamus and brain stem discard other cortical sites known to be the putative centers of the so called higher functions, thoght to be revolving around accessibility (top down and bottom up processes).

Speculating a bit, the role play by "interneurons", and their effects hysteresis and accomodation processes, that is, persistent neural activitation even if they lack stimuli (hysteresis), and on the other hand, failure to show activation because of higher concentrations of inhibitors, maybe is plausible to account theoretically for PVS.
What is clear, as demonstrated by Owen et al. is that in PVS patients islands of neural activity exist, because lack of connection with other association areas does not mean turning the lights off in a given area that can function in their own. Quite so, is possible to find weak patterns of activity (or just simply spontaneous activity resembling organized activity) but this is not to say structured and organized human consciousness someone might say.

Even if the studies commented describe activity in some brain regions in a PVS patient usually active also in the healthy brain when they are conscious of something, and some other paradigms in conciousness research (e.g. visual masking, psychology of automatic behaviours) are pointing to the possibility of this duality of domains of being conscious but without access (i don’t grab if the converse is truly possible: being in an accessible state for no content to access); what evidence could contribute to the brute fact that truly human consciousness involve both access and phenomenal consciousness blended in a undifferentiated manner (in the normal spectrum).

The Big issue, morally speaking, is that the consciousness debate cannot be put in terms of all or none (there are instances of degrees in consciousness: minimally conscious states, stupor, lock-in-syndrome, pseudocomas…) but maintaining the life of an individual with only residual signs of consciousness suppose a big economic burden for our health systems when after all the existence of no optimal prognosis or rehabilitation turn the problem worse.

My own conviction is to sustain life-treatment procedures because if our best scientists discover the possibility of residual consciousness in PVS patients, why not to be OPTIMISTIC and think that they can discover in the future effective ways to reverse the damage done by the clinical condition to neural tissue (cell transplantation, stimulation, for example).

P.S.: To be honest, Block´s distinction is supported by empirical data. In a disconnection syndrome known as alexithymia, individuals have a diminished ability to identify their emotions which in fact are present.

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