Hi, gavintaylor. Thanks for your comment. Research in patients with vegetative or minimally consciousness states –different from dementia or delirium, which should be better described as acute disturbances in consciousness– would probably shed some light on this matter. However, this area of research might be challenging by itself.
Disorders of consciousness are heterogeneous, and judging the level of actual awareness has proved a complicated process. Traditional tests and observations have been criticized since they require some level of subjective interpretation –such as deciding whether a patient’s movements are purposeful or not. In fact, recent research has revealed that about 40% of vegetative state diagnoses is incorrect.
We know, for instance, that some vegetative patients and other individuals in a minimally conscious state are capable of simple learning (i.e., classical conditioning). In a study, it was observed that the amount of learning correlated with the degree of cortical damage and was a good indicator of future recovery. But none of these effects were found in control subjects under the effect of anesthesia.
Furthermore, integrative brain processing, a proposed prerequisite of awareness, has been observed in minimally conscious state patients as well. Previous neuroimaging work has shown that some vegetative patients, when asked to imagine performing physical tasks such as playing tennis, still had activity in premotor areas. In other patients, verbal cues sparked language sectors.
Hence, these results have two interpretations. First, individuals with disorders of consciousness may have partially preserved conscious processing, which cannot be exhibited clearly via voluntary movement or verbal responses. Or, a second interpretation is that conditioning, for example, can indeed be acquired in the absence of consciousness.
Given that (i) individuals in a pharmacologically controlled unconscious state were incapable of displaying signs of learning, and (ii) learning was a good predictor of recovery, researchers consider that the first interpretation is more likely. However, this comparison must be made cautiously and complementary evidence about these processes–including neuroimaging studies–should also be taken into account.
As you suggest, more research in this field may pave the way for more definitive and accurate assessments of consciousness in humans, and probably, in non-human individuals as well.
Hi, gavintaylor. Thanks for your comment. Research in patients with vegetative or minimally consciousness states –different from dementia or delirium, which should be better described as acute disturbances in consciousness– would probably shed some light on this matter. However, this area of research might be challenging by itself.
Disorders of consciousness are heterogeneous, and judging the level of actual awareness has proved a complicated process. Traditional tests and observations have been criticized since they require some level of subjective interpretation –such as deciding whether a patient’s movements are purposeful or not. In fact, recent research has revealed that about 40% of vegetative state diagnoses is incorrect.
We know, for instance, that some vegetative patients and other individuals in a minimally conscious state are capable of simple learning (i.e., classical conditioning). In a study, it was observed that the amount of learning correlated with the degree of cortical damage and was a good indicator of future recovery. But none of these effects were found in control subjects under the effect of anesthesia.
Furthermore, integrative brain processing, a proposed prerequisite of awareness, has been observed in minimally conscious state patients as well. Previous neuroimaging work has shown that some vegetative patients, when asked to imagine performing physical tasks such as playing tennis, still had activity in premotor areas. In other patients, verbal cues sparked language sectors.
Hence, these results have two interpretations. First, individuals with disorders of consciousness may have partially preserved conscious processing, which cannot be exhibited clearly via voluntary movement or verbal responses. Or, a second interpretation is that conditioning, for example, can indeed be acquired in the absence of consciousness.
Given that (i) individuals in a pharmacologically controlled unconscious state were incapable of displaying signs of learning, and (ii) learning was a good predictor of recovery, researchers consider that the first interpretation is more likely. However, this comparison must be made cautiously and complementary evidence about these processes–including neuroimaging studies–should also be taken into account.
As you suggest, more research in this field may pave the way for more definitive and accurate assessments of consciousness in humans, and probably, in non-human individuals as well.