Auditory Working Memory Uses Semantics

Scientists want to know what happens in the brain when a person experiences imagery or mental acts that they re-enact in their mind after the object is gone. Some think imagery and perception share definite neural structures. Studies completed on the activated brain regions during an imagination are associated with sensory processing and processing or retrieving information. Visual imagery is similar to auditory imagery when manipulated in the brain; people can hear sounds in their heads. The imagery task involved retrieval of musical semantic memory when a tune was demonstrated. The working memory is also being used to rehearse the initial pitch and retrieve the following pitch while also making comparisons (Halpern & Zatorre, 1999).

The first goal of the study was to confirm the activation of the auditory association areas in the superior temporal gyrus during silent auditory tasks. Second, the authors thought if they took out the lyrics from the music it would show an irregular activation in right temporal and frontal lobes. Third, if the working memory is associated to music does it activate the dorsolateral frontal lobe? Finally if a person had to imagine a tune recently played would there be any asymmetry in dorsolateral frontal cortex.

PET scans were used on subjects who had years of musical training to measure the brain activity in these four previous areas. The music used was tunes that were familiar to people such as classical tunes from Broadway productions, commercials, television shows, and popular songs. All the participants indicated they were able to hear the music in their heads.

The study confirmed that musical imagery was found in the right auditory association cortex along with the supplementary motor area. When the musical imagery involved retrieval from musical semantic memory the right inferior frontal region, the middle frontal areas, together with right auditory association areas in superior temporal gyrus were all activated. The left frontal area and the supplementary motor area are activated when the imagery does not involve semantic retrieval. This leads to the point that auditory association areas do process imagined music that is familiar to people. The activation in auditory cortex during the imagined tune is related to the auditory stimulation. Only associative cortical regions were activated in the imagery tasks, which agree with the first question in the study. The right auditory cortical activation in the right hemisphere processes tonal patterns, due to reactions from the perceptual and imagined musical tasks. The right hemisphere broadens the perceptual breakdown to include the complex tonal imagery processes. A person uses their semantic memory when retrieving and imagining a familiar tune.

Another region activated by the music retrieval was the right thalamus. The neural conductor during semantic memory retrieval could depend on what is being retrieved. Mostly, the right hemisphere is involved when retrieving familiar tunes. The right hemisphere has already been determined to process the perception and discrimination of musical information. The episodic memory could have been activated during the tasks, but it should have used mostly semantic memory because the music only played a few notes, the rest had to be retrieved from the long-term memory. When generating an auditory image the supplementary motor area is significant because it is correlated with auditory and motor memory systems.

Previously the authors thought the imagery tasks would require the auditory working memory in the left frontal area. Now this study has shown semantic musical memory is controlled by the right frontal lobe. The dorsolateral regions in the frontal lobe work with the working memory to process verbal and figural information. They normally find more activity in the right frontal areas, the areas activated in the left must be a result of the participants using their working memory.

Reference:

Halpern, AuthorA.R., & Zatorre, R.J. (1999). When that tune runs through your head: a pet investigation of auditory imagery for familiar melodies. Cerebral Cortex. 9 No. 7, 697-704.