PAGE 3 BRAINHEARING TECHNOLOGY RESEARCH We use explicit processing when conditions are suboptimal. The speech does not match our stored knowledge of language. This can happen due to interference in the speech signal before it reaches our ears or due to alterations from our auditory system. Explicit processing requires the use of working memory which serves as a mental “blackboard”. We temporarily work on what was heard and try to decipher it. If we can’t figure out what was said, we can keep holding the information we heard in working memory, erase our mental blackboard and try again. If it takes too long to decipher, we can miss the next thing that is said. Also, if we don’t have enough working memory to keep what was heard available until we solve the puzzle, understanding is lost. (Rönnberg et al 2011; Rudner et al 2011a; Rudner et al 2011b; Rönnberg et al 2008). Explicit processing requires effort and more cognitive resources (Pittman et al 2014; Ng et al 2013; Rudner et al 2012). It is like having to do mental gymnastics at the same time you are listening. McGarrigle and colleagues (2014) proposed a definition of listening effort as “the mental exertion required to attend to, and understand, an auditory message”. Listening effort has been evaluated using a variety of methods. The listener can rate or report how they feel, try to understand speech while completing one or more additional tasks, or measurements can be made of their body’s physiologic responses to listening. Functional Magnetic Resonance Imaging (fMRI) studies have found more of the brain must participate in the explicit processing effort (Davis et al 2014; Husain et al 2011). These studies showed that when listening effort is necessary to understand what is said, the brain recruits additional areas. With aging or hearing changes, an area of the brain called the anterior cingulate is activated and there is increased bilateral brain activation. The anterior cingulate is area of the brain believed to be associated with error detection and conflict monitoring. Activation of this area indicates the brain recognizes there is a mismatch of what is heard compared to what is stored in long term memory. This implies that listening effort is a physical phenomenon related to increased mental energy use. Increased listening effort is thought to cause fatigue, stress, and more stress-related absences from work (Natchtegaal et al 2012; Natchtegaal et al 2011; Kramer et al 2006; Hetú et al 1988). Increased listening effort also negatively impacts the person’s ability to multitask. (Sarampalis et al 2009). The BrainHearing™ approach to design of compression has been shown to reduce listening effort for both children and adults in the difficult listening situations of background noise, The BrainHearing™ approach to hearing technology design reduces listening effort for both children and adults. including when both speech and unwanted sound occur at the same time and in the same location (Pittman et al 2014). Very few hearing instruments actually employ the BrainHearing™ based technology of linking compression functions between the ears. Research has shown how linking compression binaurally improves the ability to hear in background noise. (Ibrahim et al 2013; Wiggins & Seeber 2012). People have difficulty understanding because we don’t live in an “optimal” world. Sub-optimal conditions cause the redundancy of details inherent in speech to be reduced or lost. When we are in sub-optimal conditions, our auditory system and cognitive functions lose effectiveness. We need to use every detail in speech redundancy at our disposal to figure out what is said. This is when having access to every little detail matters. When what is heard doesn’t match what we know, we have to quickly access our cognitive “blackboard” and expend mental effort to decipher what was said.
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