## 1 Introduction  
Recently, studies on the discovery and treatment of new diseases have been accelerated by the dramatic development of medical technologies. As our understanding of the human brain has widened, studies on the causes and treatments of diseases related to brain diseases have been intensively conducted [1; 2; 3]. Studies on the treatment and prevention of dementia, which is among the most threatening diseases to humans both socially and medically and seriously deteriorates patients' quality of life, have been intensively conducted, substantially advancing our mechanistic understanding of dementia and the development of diverse methods and drugs to treat dementia [3; 4; 5]. Specifically, many studies on cognitive function deterioration and preventive drugs have widely accepted the theory that a major cause of cognitive dysfunction is brain nerve cell death, due to persistent exogenous stress or accumulation of oxidants, which lead to cognitive function deterioration and consequent brain diseases, such as dementia [6; 7; 8]. Therefore, many studies on cognitive and memory impairments, such as dementia and Parkinson's disease, have concentrated on mechanisms that protect brain nerve cells by preventing the accumulation of metabolic oxidants through antioxidant activity or rapid decomposition of gene oxidants and the development of drugs for such mechanisms [9; 10; 11]. Therefore, drugs, such as donepezil, rivastigmine, and galantamine have been developed to control and/or enhance the neuronal signaling pathway linked to p-ERK/p-CREB/BDNF. However, after extended use, these synthetic drugs show adverse side effects, such as vomiting, hand tremors, and heart disease [12; 13; 14]. Accordingly, remarkable findings have been reported from studies on natural products that protect cranial nerves by exerting antioxidant activity, and these products have relatively fewer side effects [15; 16; 17]. Most of these studies have fundamentally focused on suppressing cognitive function and memory loss through antioxidant-mediated cranial nerve protection. However, rather than exhibiting intense antioxidative effects in the brain nerve cells and their activation sites, natural products suppress the deterioration of cognitive function resulting from overall antioxidative activity throughout the body, so the actual effects have been remarkably lower than expected in most cases [18; 19]. Among the recent studies on suppressing cognitive function and memory loss, those featuring natural products with functions beyond simple antioxidant activity to directly suppress memory deterioration by inhibiting inflammation in brain nerve cells have attracted substantial attention [20]. In particular, the brain damage-induced activation of pro-inflammatory cytokines, such as TNF-\(\alpha\) and IL-6, can evoke brain inflammation, which results in various neurodegenerative diseases like ischemia, trauma, infection, Alzheimer's disease and Parkinson's disease [20; 21; 22]. There is recent strong evidence that continuous stress and diverse inflammation in the brain could be a major and direct cause of dementia and memory impairment, due to the continuous accumulation of inflammatory cytokines in the brain. While many efforts have been made to reduce the production of these inflammatory cytokines to indirectly attenuate degenerative brain diseases, more detailed studies on the mechanism underlying delayed neurodegeneration should be carried out based on our understanding of the blood-brain barrier [23; 24]. Therefore, the development of functional natural materials that more efficiently prevent and treat dementia is possible if the materials can selectively inhibit brain nerve cell inflammation and exert antioxidative activity [25; 26]. To this end, a variety of natural resources have been developed recently, including _Spirulina_ which has attracted much attention.