Show Reference: "Consciousness without a cerebral cortex: A challenge for neuroscience and medicine"

Consciousness without a cerebral cortex: A challenge for neuroscience and medicine The Behavioral and Brain Sciences, Vol. 30, No. 1. (February 2007), pp. 63-81, doi:10.1017/s0140525x07000891 by Björn Merker
@article{merker-2007,
    abstract = {A broad range of evidence regarding the functional organization of the vertebrate brain - spanning from comparative neurology to experimental psychology and neurophysiology to clinical data - is reviewed for its bearing on conceptions of the neural organization of consciousness. A novel principle relating target selection, action selection, and motivation to one another, as a means to optimize integration for action in real time, is introduced. With its help, the principal macrosystems of the vertebrate brain can be seen to form a centralized functional design in which an upper brain stem system organized for conscious function performs a penultimate step in action control. This upper brain stem system retained a key role throughout the evolutionary process by which an expanding forebrain - culminating in the cerebral cortex of mammals - came to serve as a medium for the elaboration of conscious contents. This highly conserved upper brainstem system, which extends from the roof of the midbrain to the basal diencephalon, integrates the massively parallel and distributed information capacity of the cerebral hemispheres into the limited-capacity, sequential mode of operation required for coherent behavior. It maintains special connective relations with cortical territories implicated in attentional and conscious functions, but is not rendered nonfunctional in the absence of cortical input. This helps explain the purposive, goal-directed behavior exhibited by mammals after experimental decortication, as well as the evidence that children born without a cortex are conscious. Taken together these circumstances suggest that brainstem mechanisms are integral to the constitution of the conscious state, and that an adequate account of neural mechanisms of conscious function cannot be confined to the thalamocortical complex alone.},
    address = {Gamla Kyrkvagen 44, SE-14171 Segeltorp, Sweden. gyr694c@tninet.se},
    author = {Merker, Björn},
    doi = {10.1017/s0140525x07000891},
    issn = {0140-525X},
    journal = {The Behavioral and Brain Sciences},
    keywords = {consciousness, cortex, sc},
    month = feb,
    number = {1},
    pages = {63--81},
    pmid = {17475053},
    posted-at = {2013-12-04 15:56:06},
    priority = {2},
    title = {Consciousness without a cerebral cortex: A challenge for neuroscience and medicine},
    url = {http://dx.doi.org/10.1017/s0140525x07000891},
    volume = {30},
    year = {2007}
}

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Removing large parts of cortex—even a full hemisphere—does not result in a loss of consciousness.

Absence epilepsy—sudden loss of consciousness with amnesia but not always with total loss of cognitive function—has been induced by electrostimulation of the upper brainstem, but not of cortical regions.

The brainstem may be involved in creating consciousness.

Cortical structures do not always control our overt behavior. Instead, sub-cortical areas sometimes override cortical tendencies.

SC receives input and represents all sensory modalities used in phasic orienting: vision, audition, somesthesis (haptic), nociceptic, infrared, electoceptive, magnetic, and ecolocation.

Cortex uses the actuators through the midbrain and basal diencephalon. Since the midbrain is much smaller than the neocortex in humans, it acts as a bottleneck which integrates, serializes, and coordinates overt behavior.

As integrated, serial, and coordinated behavior is a feature of consciousness, it makes sense that the midbrain may play an important part in making consciousness.