By: Dr. Matthew Seldine
Individuals who experience tinnitus may or may not have hearing loss. There are many cases where normal- or near-normal hearing individuals experience the perception known as tinnitus. For these individuals the perception of tinnitus commonly results in an increased subjective hearing impairment that cannot always be explained by the conventional audiometric evaluation.
What may help audiologists and researchers better understand this subjective hearing impairment is something called learning theory; specifically the concepts of working memory and cognitive load. Working memory is a brain function responsible for attention, problem-solving, and memory. Its capacity is very limited, able to encode, store, and retrieve only about 5 to 9 informational chunks of information at any one time. Cognitive load stands for the amount of mental effort required at any one time. The more complex the task, the more mental effort is required, the greater the cognitive load. The greater the cognitive load, a larger number of informational chunks must be processed.
Here is the problem that connects tinnitus, working memory, and cognitive load together.
As the number of complex tasks increases, working memory has to increase, and then cognitive load has to increase. But as cognitive load increases, working memory capacity starts to decrease (remember, 5 to 9 informational chunks).
The ability to retain, process, and respond to speech is directly related to working memory capacity. For those with impaired working memory, they have difficulty with multitasking, require more time to recall information, and are slower at taking in and making sense of information. The rapid nature of speech requires rapid auditory processing, which increases cognitive load and reduces working memory capacity. When you add in challenging environments (think those with background noise resulting in degraded speech signals) this puts an even greater burden on working memory, further increasing cognitive load, which can further “interfere with language processing and memory of what is being heard.”
Tinnitus has been shown to reduce working memory capacity. This additional component adds more stress to the already delicate balance between working memory and cognitive load. As a result, subjective hearing handicap is seen to increase among those normal- and near-normal hearing individuals who also report tinnitus, but not because of their inability to process auditory information. Rather, it is based on the explanation of reduced working memory and increased cognitive load.
Referenced from “Learning Theory and Subjective Hearing Problems in Tinnitus Patients,” by Steven L. Benton, AuD. The Hearing Journal, October 2020, pg. 42-43