Impaired consciousness caused by injury of the lower ascending reticular activating system: evaluation by diffusion tensor tractography

A 34-year-old male patient underwent conservative management for traumatic hemorrhage in the right frontal lobe（Figure 1A）.The patient lost consciousness for approximately 4 weeks and experienced post-traumatic amnesia continuously from the time of the accident.The patient’s Glasgow Coma Scale score（Teasdale et al.,1974）was 6

Recovery of multiply injured ascending reticular activating systems in a stroke patient

Consciousness is controlled by ular activating system （ARAS）. lower and upper parts between activation of the ascending retic- The ARAS consists mainly of the the thalamus and cerebral cortex （Edlow et al., 2012; Yeo et al., 2013; Jang et al., 2014）. Because the ARAS is composed of several neuronal circuits connecting the brainstem to the cortex. These neuronal connections begin from the reticular formation （RF） of the brainstem and the intralaminar nucleus of thalamus to the cerebral cortex （Gosseroes et al., 2011）. In addition, the ARAS system also includes several brainstem nuclei （such as dorsal raphe, locus coeruleus, pedun-culopontine nucleus, median raphe and parabrachial nucleus）, non-specific thalamic nuclei, hypothalamus, and basal forebrain （Fuller et al., 2011）.

Restoration of an injured lower dorsal ascending reticular activating system in a patient with intraventricular hemorrhage

The ascending reticular activating system（ARAS）plays a key role in the control of arousal and awareness for consciousness（Paus,2000;Zeman,2001;Van der Werf et al.,2002;Weiss et al.,2007;Siposan and Aliu,2014）.It is well known that the ARAS originates from the reticular formation（RF）of the brainstem,and connects to the cerebral cortex via intralaminar to the cerebral cortex （Paus, 2000; Zeman, 2001; Van der Werf et al., 2002; Yeo et al., 2013; Jang and Kwon, 2015）. The hypothalamus is involved in the regulation of sleep and awareness which is associated with the main timekeeper of consciousness （Lin, 2000; Lin et al., 2011）.

Ascending reticular activating system of the brain

There were two stages in the history of the studies on ascending reticular activating system of the brain(ARAS). The first stage began with the ARAS discovery by Magoun and Moruzzi and the following investigations using the methods of stimulation and lesion at that time mainly in acute cats. These studies led to the hypothesis of a "diffuse"and "unspecific" ARAS of the brain stem. The second stage was associated with using more precise neurophysiological and histochemical methods mainly in chronically operated free-moving cats and rats. By 2010, the idea of the ARAS as an organized hierarchy of the cerebral "waking centers" distributed along the entire cerebral axis and releasing all the known neuromediators of low molecular weight together with the most important neuropeptides was formulated. To date, the aforementioned hypothesis has been revised again. The glutamatergic activating system has been discovered and described in detail. Presumably, this system is responsible for the appearance of electroencephalogram(EEG) arousal reaction and maintenance of the neocortex in the state of tonic depolarization during wakefulness and rapid eye movement(REM)sleep. Its destruction results in a deep comatose-like state. At the same time, the activity of all other "waking centers" is probably the result of the cortical activation.