Hartzell, J.
BCBL
Natural speech is only partially predictable--we never know exactly what we ourselves, or our interlocutors will say. Though our speech production must follow our language's rules of grammar and syntax, correct spelling and phonology, and correct pronunciation and intonation, the exact sequence of words is somewhat creative, and more often than not somewhat unpredictable. This is the nature of 'free speech.' Our models of language production in the human brain are largely based on studies involving free speech, so these models necessarily include brain regions and circuits that must be involved in this creative, always somewhat unpredictable aspect of free speech. To date, though, research has not clarified what brain circuitry underpins the ability to, online, creatively combine information from our verbal memory system and turn this into our unpredictable free speech.
One approach to this question is to use a contrast effect, examining the brain circuitry underpinning highly, or even completely predictable speech, and compare such circuitry with that of free speech. To do so, we studied the brain structure of verbal memory specialists in India who train intensively for nearly 10 years to exactly memorize and recite 40,000 word ancient Sanskrit texts. This traditional practice is centered on exacting memorization and precise, invariant verbal reproduction, resulting in what is effectively 100% predictable speech. We compared the grey and white matter of 21 professionally trained Vedic Sanskrit Pandits with that of controls matched for age, gender, ethnicity, handedness, eye-dominance, and approximate education level. The differences between the two groups were striking, suggesting that extensive neural regions and circuits are engaged for intensive, exacting verbal memory and its oral reproduction. The results also indicated that the bilateral Broca's areas may play key roles in the creative dimensions of free speech in a manner not previously appreciated (or predicted).