Brain stem may be key to consciousness:
From MindHacks
An article in this week’s Science News discusses whether the brain stem may play a more central role in consciousness than it’s usually given credit for.
It focuses on children with hydranencephaly, a where the cortex fails to develop in children and instead, the space is filled with cerebral spinal fluid.
Typically, affected children survive only a few months after birth, but those that do survive seem to remarkably more conscious than you would guess based on theories that suggest the cortex is where all the action happens to support consciousness.
Swedish neuroscientist Bjorn Merker wrote an article [pdf] in February’s Behavioural and Brain Sciences journal arguing that these cases suggest we need to rethink our ideas about how the brain supports conscious thought, and perhaps, even consciousness itself.
Merker argues that the brain stem supports an elementary form of conscious thought in kids with hydranencephaly. It also contains auditory structures capable of preserving hearing in someone without a cortex. In contrast, optic nerve damage in hydranencephaly frequently impairs vision, regardless of what the brain stem does.
Self-awareness and other “higher” forms of thought may require cortical contributions. But Merker posits that “primary consciousness,” which he regards as an ability to integrate sensations from the environment with one’s immediate goals and feelings in order to guide behavior, springs from the brain stem.
If he’s right, virtually all vertebrates—which share a similar brain stem design—belong to the “primary consciousness” club. Moreover, medical definitions of brain death as a lack of cortical activity would face a serious challenge. At the very least, physicians could no longer assume that individuals with hydranencephaly don’t need pain medication or anesthesia during invasive medical procedures.
Link to Science News article ‘Consciousness in the Raw’.
pdf of BBS article ‘Consciousness without a cerebral cortex’.
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Pingback by arbitrarymarks.com » Blog Archive » Linkdump 09.18.07 — September 18, 2007 @ 1:28 pm
Before we try to determine what are the causes of consciousness it might be helpful to accept that we are not collectively clear about what we mean by it.
However, it ought to be obvious that a sufficient metabolic turnover fueling the firing of excitatory signals from certain basal brainstem ‘reticular activating type’ neurons with excitatory synaptic efferent influences on, other in turn excitatory superposed neurons within the actention selection serving system, is how any level or mode (or aspect) of consciousness is being energized.
We ought to be able to accept that it is a continuum of self-regulatory capacity that include both a vigilant and reflexive autonoumous sensorymotor type modular actention selection serving system (~ up to an amphibian style system for “paying actention”), up to a emotion effecting, or feeling, such system; and a cognitive (including ‘abstractly aware’) mode of being “actentive” or “paying {metabolically, i.e.) actention”.
Comment by Peter F — September 24, 2007 @ 12:39 am
I´m also inclined to think that brainstem functions are vital for human conciousness. The “reticular activating system” seems crucial for arousal, an integral component of conciousness, and the brainstem is similar to a relay-station of input to mayor telencephalic areas.
Another issue of mayor importance is that many neurologists specialized in the determination of brain death (e.g. Bernat) are reluctant to consider the neocortical formulation of brain death (in the worst case, the whole formulation), and have to exclude thereby congenitally decorticated infants or vegetative patients from being alive.
Comment by Anibal — October 9, 2007 @ 7:17 am
i think the buddhists have been saying something similar for 2000 years. the dismissal of consciousness that has characterized science until recently is going to be the thread that unravels neuropsychology in the way that quantum theory undid physics.
Comment by carl k — November 28, 2007 @ 10:34 am