Demystifying Consciousness

Sudden, violent, irregular movement of limbs; a cold sensation of fear and a sense of confusion; brief loss of memory and consciousness — These are the severe symptoms of epileptic seizures, which affect nearly 50 million people worldwide. Epilepsy is a neurological disorder caused by abnormal or hypersynchronous electrical activity within the brain. For those who suffer from it, the disorder means coping with a condition that can be controlled, but not cured. For members of the Blumenfeld Lab at Yale Medical School, epilepsy may also mean unlocking the secrets of consciousness.

The consciousness system, which is a set of specialized cortical and subcortical brain structures, has been rigorously studied throughout the last century. Most of these brain structures have been identified with the use of modern techniques such as functional magnetic resonance imaging (fMRI). Additional advances in brain imaging, computer science, and genetic methods have yielded a wealth of information, including knowledge about genes, signaling pathways, and brain regions associated with consciousness.

fMRI images of a human brain from different viewpoints during an epileptic seizure. Yellow and orange regions are overactive compared to the normal state, while the blue and green regions are underactive. Such fMRI studies tell us what parts of the brain are needed for maintaining consciousness. Courtesy of YaleNews.

However, consciousness is much more than the sum of independent activities of individual brain regions. Uncovering consciousness also involves understanding how these regions interact. Dr. Hal Blumenfeld, Professor of Neurology, Neurobiology and Neurosurgery at Yale, explains, “My feeling is that consciousness, like life itself, can be defined by a group of characteristics … Conscious things could be defined as those that are awake, attentive, have emotions, can potentially form memories, etc.” According to Blumenfeld, the advantage of this definition is its identification of properties that can be tested experimentally. Transient impairments of consciousness during epileptic seizures allow the Blumenfeld Lab to study these neuronal interactions that are essential to consciousness.

Blumenfeld’s “network inhibition hypothesis” explains how consciousness, which is normally maintained by mutual interactions between cortical and subcortical parts of the consciousness system, is impaired by abnormal electrical activity in the temporal lobe. According to this hypothesis, cortical-subcortical interactions are necessary for maintaining consciousness. Many studies support this hypothesis, including one in which the Blumenfeld Lab monitored electrical activity of particular brain regions following in vivo stimulation. Results show that epileptic seizures are not only associated with abnormal activity in the temporal lobe, but also with abnormal activity in anatomically connected structures such as the upper brain stem reticular formation and midline subcortical structures.

Midline brain structures that make up the consciousness system, also known as the neuronal correlates of consciousness. The temporal lobe plays a particularly essential role in understanding impaired consciousness in epileptic seizures. Courtesy of Wikimedia Commons.

Despite the work of researchers such as Blumenfeld, science has a long path to tread before fully demystifying consciousness. Some believe advances in science will eventually yield a complete picture, while others argue for features of consciousness called “qualia” that are inaccessible to the third-person investigation. Blumenfeld holds the former, more optimistic outlook, suggesting research on art and expression as an inlet into the first-person aspects of individual consciousness. Regarding future research, he states, “I think the biggest challenge now is to figure out how to put all this information together, to get a big-picture view of how the system works as a whole to generate consciousness.”