Maxine H. Krengel,a,b Yelena Bogdanova,a,c Jeffrey A. Knight,a,c,d

Low-level laser (light) therapy (LLLT) has been suggested as an

effective treatment for a range of brain traumas and diseases [1-

5]. Though the exact mechanism is still being studied, research has

shown that red and near-infrared (NIR) light is able to penetrate

the skull [6, 7] and trigger reactions that elevate mitochondrial

adenosine triphosphate (ATP) production [8]. Transcranial LLLT

(tLLLT) increases local, regional cerebral blood flow in humans with

traumatic brain injury (TBI) [9], and in severe depression cases [10].

Increase in ATP and focal increase in regional cerebral blood flow

are important factors that could contribute to recovery in central

nervous system disorders [11]. In this chapter, we explore a variety

of uses of tLLLT, including improvement in cognition in chronic

TBI and improvement in sequelae of stroke, including improved

language behavior in chronic stroke when aphasia is present (loss

of language abilities, primarily associated with left hemisphere [LH]