Auditory imagery
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In psychology and neuropsychology, auditory imagery is the subjective experience of hearing in the absence of auditory stimulation. It occurs when one mentally rehearses telephone numbers, or has a song "on the brain": the phenomenon is usually defined to be spontaneous (that is, not under direct conscious control); it can be distressing. Auditory imagery is used by neuropsychologists for investigating aspects of human cognition.
Research into Auditory Imagery
The following entry is excerpted and adapted from Kosslyn, Ganis, and Thompson, "Neural Foundations of Imagery," Nature Reviews Neuroscience 2.9, 635-642 (2001) by permission from Nature Reviews Neuroscience , Copyright 2005 Macmillan Magazines Ltd.
Note: This entry is a discussion of research into auditory imagery. For a definition of mental imagery, please see the entry of that name, which serves as a parent entry to this one. Please also see other two entries that fall under this heading: visual mental imagery and motor imagery.
Do the first three notes of the children's song Three Blind Mice ascend or descend? Most people report that they 'hear' the song in the process of deciding. Remarkably little research has addressed auditory imagery per se. Zatorre and Halpern (1993) studied brain-damaged patients to discover whether specific brain areas are crucial for auditory imagery. They compared a group of patients who had had the left or right temporal lobe removed (for the treatment of otherwise intractable epilepsy),with otherwise similar control subjects. In one condition, the subjects heard a familiar song while also reading the lyrics, and judged which of two particular words had the higher pitch. In another condition, the subjects saw the lyrics and made the same judgments, but did not actually hear the song, and so had to rely on mental imagery. The patients with right temporal lesions were impaired in both conditions compared with both other groups. These findings show that at least some of the neural structures that are crucial for pitch discrimination during perception have a similar role during imagery.
Most neuroimaging research on auditory imagery has focused on imagery for music. Zatorre et al. (1996) asked whether auditory imagery draws on the same mechanisms used in auditory perception. Their subjects either listened to songs and judged the relative pitch of pairs of words, or imagined hearing songs and made the same judgments. No auditory stimulation was present during the baseline condition, which required the subjects to judge the relative length of visually presented words. PET revealed that many of the same areas were activated in common in these tasks, including bilateral associative auditory cortex, or Brodmann area (BA) 21/22 (in spite of the fact that the left temporal lobe has often been identified with the perception of language, and the right with music or environmental sounds), bilateral frontal cortex (BA 45/9 and 10/47), left parietal cortex (BA 40/7) and supplementary [[motor cortex]] (BA 6). The bilateral activation in associative auditory cortex observed in this study, in apparent contrast to the patient studies, might indicate that some of the activated areas were not essential to these tasks.
Indeed, in a subsequent study, Halpern and Zatorre (1999) asked musically trained subjects to listen to the opening notes of familiar (non-verbal) melodies and then to continue 'hearing the melody with the mind's ear'. Again using PET, they found activation in two regions of the right temporal lobe (the superior and inferior temporal cortex), which is consistent with their earlier study of brain-damaged patients; both of these areas are involved in storing and interpreting non-verbal sounds. Moreover, auditory imagery of a melody that required retrieval from memory also activated two right-hemisphere regions, in the frontal lobe and superior temporal gyrus (which is crucial for auditory perception). Finally, the supplementary motor area (SMA) was also activated by auditory imagery, regardless of whether the melody was retrieved or simply rehearsed online. This is interesting, because no overt behavior was required. Halpern and Zatorre believe that stored movements are used in this sort of imagery; this makes sense for melodies, in which case we can subvocalize the tune as part of the process of retrieving the information.
Finally, Griffiths (2000) reports a study of patients who became deaf and then hallucinated hearing music. These patients were neither psychotic nor beset with an obvious neurological problem, such as epilepsy. Griffiths was able to perform PET while the patients had such hallucinations, and found that the posterior temporal lobes, in the auditory cortex, were activated as well as the right basal ganglia, the cerebellum and the inferior frontal cortices.
In summary, auditory imagery appears to draw on most of the neural structures used in auditory perception. However, in contrast to visual imagery, in which the early visual cortex seems to be activated (see below), there is no evidence that the first auditory cortical area to receive input from the ears - area A1 - is activated during auditory imagery.
Mental Imagery References
For a complete list of refernces, please see the entry on mental imagery.
