Consciousness

Consciousness has two components: arousal and content. Impairment of arousal can vary from mild (drowsiness or somnolence), to obtundation, to stupor to coma.

Contemporary science is based on the claim that all reality is material or physical. There is no reality but material reality. Consciousness is a by-product of the physical activity of the brain. Matter is unconscious. Evolution is purposeless. This view is now undergoing a credibility crunch. The biggest problem of all for materialism is the existence of consciousness. Panpsychism provides a way forward. So does the recognition that minds are not confined to brains ¹⁾.

Prior to the mid-1990s, there was a lack of operational definitions available to clinicians and researchers to guide the differential diagnosis among disorders of consciousness. As a result, patients were lumped together into broad categories often based on the severity of the disability (e.g. moderate, severe, extremely severe). These diagnoses were performed without regard to salient differences in behavioral and pathological characteristics. In a three-year period spanning from 1994–1996, three position statements regarding the diagnostic criteria of disorder of consciousness were published.

The “Medical Aspects of the Persistent Vegetative State” was published by the American Academy of Neurology (AAN) in 1994. In 1995, “Recommendations for Use of Uniform Nomenclature Pertinent to Patients With Severe Alterations in Consciousness” was published by the American Congress of Rehabilitation Medicine (ACRM). In 1996 the “International Working Party on the Management of the Vegetative State: Summary Report” was published by a group of international delegates from neurology, rehabilitation, neurosurgery, and neuropsychology. However, because the diagnostic criteria were published independently from one another, the final recommendations differed greatly from one another. The Aspen Neurobehavioral Work-group was convened to explore the underlying causes of these disparities. In the end, the Aspen Work-group provided a consensus statement regarding definitions and diagnostic criteria disorder of consciousness which include the vegetative state (VS) and the minimally conscious state (MCS).

Perceptual consciousness.

Sleep

Consciousness disorders.

Spinal cord stimulation (SCS) has been suggested as a therapeutic technique for treating patients with disorder of consciousness (DOC). Although studies have reported its benefits for patients, the underlying pathophysiological mechanisms remain unclear.

In a pilot study, functional near-infrared spectroscopy was used to measure the hemodynamic responses of 10 disorder of consciousness (DOC) patients to different SCS frequencies (5 Hz, 10 Hz, 50 Hz, 70 Hz, and 100 Hz). In the prefrontal cortex, a key area in consciousness circuits, Si et al., found significantly increased hemodynamic responses at 70 Hz and 100 Hz, and significantly different hemodynamic responses between 50 Hz and 70 Hz/100 Hz. In addition, the functional connectivity between prefrontal and occipital areas was significantly improved with SCS at 70 Hz. These results demonstrated that SCS modulates the hemodynamic responses and long-range connectivity in a frequency-specific manner (with 70 Hz apparently better), perhaps by improving the cerebral blood volume and information transmission through the reticular formation-thalamus-cortex pathway ²⁾.

The aim of a study was to measure the effects of SCS on the EEG of patients in a minimally conscious state (MCS), which would allow them to explore the possible workings underpinning of the approach. Resting state EEG was recorded before and immediately after SCS, using various frequencies (5Hz, 20Hz, 50Hz, 70Hz and 100Hz), for 11 patients in MCS. Relative power, coherence, S-estimator and bicoherence were calculated to assess the EEG changes. Five frequency bands (delta, theta, alpha, beta and gamma) and three regions (frontal, central and posterior) were divided in the calculation. The main findings of this study were that: (1) significantly altered relative power and synchronisation was found in delta and gamma bands after one SCS stimulation using 5Hz, 70Hz or 100Hz; (2) bicoherence showed that coupling within delta was significantly decreased after stimulation using 70Hz, while reduction of coupling between delta and gamma was found when using 5Hz and 100Hz. However, SCS of 20Hz, 50Hz and sham stimulation did not induce changes in any frequency band at any region. This study showed EEG evidence that SCS can modulate the brain function of MCS patients, speculatively by activating the formation-thalamus-cortex network ³⁾.