Musical brains: a study of spontaneous and evoked musical sensations without external auditory stimuli

Our observations confirm that musical sensations with no external stimuli, either spontaneous or evoked, occur in normal individuals and that a biological substrate can be demonstrated by brain single photon emission computed tomography (SPECT).

There are individuals, usually musicians, who are seemingly able to evoke and/or have spontaneous musical sensations without external auditory stimuli. However, to date there is no available evidence to determine if it is feasible to have musical sensations without using external sensory receptors, or if there is a biological substrate for these sensations.

A group of 100 musicians and another of 150 otolaryngologists were asked if they had spontaneous musical auditory sensations and/or were capable of evoking them. SPECT evaluations with Tc(99m)-HMPAO were conducted in six female musicians while they were evoking these sensations or, in one case, while she was having them spontaneously. In three of them an additional SPECT was conducted in basal conditions (having been asked to avoid evoking music).

In all, 97 of 100 musicians had spontaneous musical sensations; all 100 could evoke and modify them. Of the 150 otolaryngologists, 18 (12%) were musicians. Of the 132 nonmusicians, spontaneous musical sensations occurred in 52 (39.4%), 72 (54.5%) could evoke and 23 (17.4%) were able to modify them, 58 (43.9%) did not have spontaneous musical sensations nor could they evoke them. The musical sensations of the 72 otolaryngologists that could evoke were less elaborated than those of musicians. NeuroSPECT during voluntary musical autoevocation demonstrated significant (>2 SD) increased activation of executive frontal cortex in Brodmann areas 9 and 10, secondary visual cortex (area 17), and paracingulate (areas 31 and 32). There was also activation in the para-executive frontal cortex (areas 45 and 46). In the basal ganglia there was activation in thalamus and lentiform nucleus. Deactivation below 2 SD was demonstrated by mean values in the cingulate gyrus, Brodmann areas 23 and 24, and subgenual area 25. Deactivation was also demonstrated when minimal values were analyzed in the same areas plus area 4 and areas 36 and 38, the latter in the pole of the temporal lobes. In three patients comparison of basal state with autoevocation demonstrated activation in executive frontal cortex (areas 8 and 9), para-executive cortex (area 45), primary auditory cortex (area 40), the right thalamus, and lentiform nucleus.