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HOME > PAST ISSUE > July-August 2010 > Article Detail

MACROSCOPE

The Widening Gyrus

Concert pianists could be model organisms for studying the physiological basis of intellectual greatness

Charles T. Ambrose

2010-07MacroAmbroseFA.jpgClick to Enlarge ImageAn old question: What accounts for highly intelligent and greatly gifted individuals? Three centuries ago, phrenologists thought that geniuses could be distinguished from criminals by the shapeliness and bumpiness of their skulls. When Charles Darwin’s head was considered by a German psychological society, one member declared that Darwin “had the bump of reverence developed enough for ten priests.” In 19th-century Europe and America, a number of distinguished academics bequeathed their brains for anatomical study—Gauss, Broca, Gall, Pavlov, Osler and others. Some probably sought to leave behind posthumous confirmation of their own genius. Originally, the anatomists compared gross weight and volume of brains and made what they could of the various lobes and surface convolutions. With the advent of microscopic anatomy, they were able to look for histological differences, yet by 1928 researchers were concluding that nothing in these early studies provided “a basis from which mental abilities [might] be inferred.” However, neurophysiologists of that era were beginning to identify specific areas of the brain responsible for general motor function and sensory activity. In recent decades, neurohistologists have developed cytoarchitectonics, enabling them to count neurons and support cells—oligodendrocytes, astrocytes and glial cells—in different areas of the brain. And during the past decade, brain imaging with positron emission tomography and functional magnetic resonance imaging (fMRI) has allowed noninvasive localization of various functions and responses. Even with these new tools the essential question—whence talent?—remains an enigma.

The most revered modern genius was Albert Einstein, who died at age 76 in 1955 at Princeton. His brain had a circuitous fate; for several years it rested in a jar of formaldehyde in a Kansas closet, was later carried to Berkeley and is now preserved in Hamilton, Ontario. At McMaster University, Einstein’s brain was compared with brains of an age-matched male group. It was within normal limits except for the parietal lobes, which were 1 centimeter (15 percent) wider than that of the control group. This region of the brain is responsible for visual-spatial cognition and mathematical thinking, and according to Sandra F. Witelson, presumably achieved its distinctive form early in Einstein’s life, based on the understanding at that time of cerebral development. Each of Einstein’s posterior parietal lobes consisted of one distinct compartment instead of the usual two separated by the Sylvian fissure. Earlier, at the University of California, Berkeley, Marian Diamond and coworkers had reported that the isocortex (the outer six layers of gray matter) of Einstein’s left parietal lobe (Brodmann area 9) contained 77 percent more glial cells per neuron than brains of 11 normal males aged 47 to 80. This ratio “suggests a response by glial cells to greater neuronal metabolic need … [and] might reflect the enhanced use of this tissue in the expression of his unusual conceptual powers.”

Ranking surely with mathematical geniuses in intellectual stature are people with acute musical ability, such as eminent composers, conductors and concert performers. For great pianists, several functions are involved: hearing/perception/appreciation, memory and performance. Hearing involves the primary auditory cortex, which is confined largely to the anteriomedial region of Heschl’s gyrus (anterior transverse gyrus of the temporal lobe). A study published in Nature Neuroscience in 2002 reported that this gyrus is 2.3 times as large and twice as active in the brains of professional musicians as in nonmusicians, suggesting plasticity in human brains expressed under conditions of intense musical training. The histologic nature of that increase has not yet been studied.

In the mid-19th century, Jean Pierre Flourens (1794–1867) maintained that cognitive functions are the integrated activity of the entire brain. And recently, Nobel laureate Eric Kandel and psychiatrist Larry Squire reiterated the point that “Memory is not a unitary faculty of the mind but is composed of multiple systems that have different logic and neuroanatomy.” For example, memory involves two systems: short- and long-term memory, which are located in different regions of the brain. Long-term memory consists of two types: explicit/declarative/conscious recall of facts and events, and implicit/nondeclarative/unconscious recall of motor skills, habits and so on. Both types have been localized by various authors in the isocortex of the “upstream” brain regions—specifically, in the frontal and parietal cortices and medial temporal lobes. Complicating the study of memory storage is the assumption that remembering “what” and “how to” are different matters that may be centered in different regions of the neocortex. At present it is unknown to what degree the association areas for specific memories are circumscribed. For example, we don’t know whether the remembered experience and knowledge of a Chopin étude resides in the same region of the cortex as a Bach prelude.

Concert pianists not only memorize massive amounts of music, they also engage complex motor skills, as both hands play different notes and chords, often at high speed and with different tempos and rhythms, while their feet work the piano’s pedals. It is reasonable to suppose that certain areas of the motor cortex of concert pianists are very highly developed.

2010-07MacroAmbroseFB.jpgClick to Enlarge ImageThe localization of motor function began when Flourens’s French countryman, Marc Dax (1771–1837), reported aphasia in right-handed patients suffering a stroke with right hemiplegia—that is, disability due to some left hemisphere injury. Several decades later this observation was corroborated by Paul Broca (1824–1880), and the motor speech area in the left cerebral hemisphere was eponymized as Broca’s area (left inferior frontal gyrus). The localization in the brain of sensory and motor functions engaged early neurophysiologists, but of late they have focused more on localization of memory. Compared with memory and hearing (meaning the entire complex response to auditory stimulation), motor functions may be more localized and possibly easier to investigate. They have been mapped out in discrete projection areas on the cerebral hemisphere’s surface, as depicted by the famous motor homunculus devised by the neurosurgeon Wilder Penfield (see figure at right).

The process by which fine motor skills are honed may have parallels with how memory storage is increased, hence the preceding digression. The mechanisms proposed for enhanced memory have centered on one of two alternative explanations: existing synapses may change as a result of changes in local gene expression, yielding new proteins and possibly increasing the number of vesicles near the presynaptic membrane, and/or new synapses may be generated (synaptogenesis). In memory studies little attention has thus far been given to a third possibility: neurogenesis. In key motor areas, increased synapses and increased synaptic efficiency may account in part for piano virtuosity, but I suggest that neurogenesis should also be considered.





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