Читаем Hallucinations полностью

I do not simply “recall” these songs. The music playing in the house is as loud and clear as any CD or concert. The volume increases in a large space such as a supermarket. The music has no singers or words. I have never heard “voices” but once heard my name called urgently, while I was dozing.

There was a short time when I “heard” doorbells, phones, and alarm clocks ring although none were ringing. I no longer experience these. In addition to music, at times I hear katydids, sparrows, or the sound of a large truck idling at my right side.

During all these experiences, I am fully aware that they are not real. I continue to function, managing my accounts and finances, moving my residence, taking care of my household. I speak coherently while experiencing these aural and visual disturbances. My memory is quite accurate, except for the occasional misplaced paper.

I can “enter” a melody I think of or have one triggered by a phrase, but I cannot stop the aural hallucinations. So I cannot stop the “piano” in the coat closet, the “clarinet” in the living room ceiling, the endless “God Bless America”s, or waking up to “Good Night, Irene.” But I manage.

PET and fMRI scanning have shown that musical hallucination, like actual musical perception, is associated with the activation of an extensive network involving many areas of the brain—auditory areas, motor cortex, visual areas, basal ganglia, cerebellum, hippocampi, and amygdala. (Music calls upon many more areas of the brain than any other activity—one reason why music therapy is useful for such a wide variety of conditions.) This musical network can be stimulated directly, on occasion, as by a focal epilepsy, a fever, or delirium, but what seems to occur in most cases of musical hallucinations is a release of activity in the musical network when normally operative inhibitions or constraints are weakened. The commonest cause of such a release is auditory deprivation or deafness. In this way, the musical hallucinations of the elderly deaf are analogous to the visual hallucinations of Charles Bonnet syndrome.

But although the musical hallucinations of deafness and the visual hallucinations of CBS may be akin physiologically, they have great differences phenomenologically, and these reflect the very different nature of our visual worlds and our musical worlds—differences evident in the ways we perceive, recollect, or imagine them. We are not given an already made, preassembled visual world; we have to construct our own visual world as best we can. This construction entails analysis and synthesis at many functional levels in the brain, starting with perception of lines and angles and orientation in the occipital cortex. At higher levels, in the inferotemporal cortex, the “elements” of visual perception are of a more complex sort, appropriate for the analysis and recognition of natural scenes, objects, animal and plant forms, letters, and faces. Complex visual hallucinations entail the putting together of such elements, an act of assemblage, and these assemblages are continually permuted, disassembled, and reassembled.

Musical hallucinations are quite different. With music, although there are separate functional systems for perceiving pitch, timbre, rhythm, etc., the musical networks of the brain work together, and pieces cannot be significantly altered in melodic contour or tempo or rhythm without losing their musical identity. We apprehend a piece of music as a whole. Whatever the initial processes of musical perception and memory may be, once a piece of music is known, it is retained not as an assemblage of individual elements but as a completed procedure or performance; music is performed by the mind/brain whenever it is recollected; and this is also so when it erupts spontaneously, whether as an earworm or as a hallucination.

5

The Illusions of Parkinsonism

James Parkinson, in his famous 1817 Essay on the Shaking Palsy, portrayed the disease that now bears his name as one that affected movement and posture, while leaving the senses and the intellect unimpaired. And in the century and a half that followed, there was virtually no mention of perceptual disorders or hallucinations in patients with Parkinson’s disease. By the late 1980s, though, physicians had begun to realize (and only in response to careful inquiry, for patients are often reluctant to admit it) that perhaps a third or more of those being treated for Parkinson’s experienced hallucinations, as Gilles Fénelon and others reported. By this time, virtually everyone diagnosed with Parkinson’s was medicated with L-dopa or other drugs that enhance the neurotransmitter dopamine in the brain.