A hundred dhoti-clad young men sat cross-legged on the floor in facing rows, chatting amongst themselves. At a sign from their teacher the hall went quiet. Then they began the recitation. Without pause or error, entirely from memory, one side of the room intoned one line of the text, then the other side of the room answered with the next line. Bass and baritone voices filled the hall with sonorous prosody, every word distinctly heard, their right arms moving together to mark pitch and accent. The effect was hypnotic, ancient sound reverberating through the room, saturating brain and body. After 20 minutes they halted, in unison. It was just a demonstration. The full recitation of one of India´s most ancient Sanskrit texts, the Shukla Yajurveda, takes six hours.

I spent many years studying and translating Sanskrit, and became fascinated by its apparent impact on mind and memory. In India's ancient learning methods textual memorization is standard: traditional scholars, or pandits, master many different types of Sanskrit poetry and prose texts; and the tradition holds that exactly memorizing and reciting the ancient words and phrases, known as mantras, enhances both memory and thinking.

I had also noticed that the more Sanskrit I studied and translated, the better my verbal memory seemed to become. Fellow students and teachers often remarked on my ability to exactly repeat lecturers’ own sentences when asking them questions in class. Other translators of Sanskrit told me of similar cognitive shifts. So I was curious: was there actually a language-specific “Sanskrit effect” as claimed by the tradition?

When I entered the cognitive neuroscience doctoral program at the University of Trento (Italy) in 2011, I had the opportunity to start investigating this question. India's Vedic Sanskrit pandits train for years to orally memorize and exactly recite 3,000-year old oral texts ranging from 40,000 to over 100,000 words. We wanted to find out how such intense verbal memory training affects the physical structure of their brains. Through the India-Trento Partnership for Advanced Research (ITPAR), we recruited professional Vedic pandits from several government-sponsored schools in the Delhi region; then we used structural magnetic resonance imaging (MRI) at India’s National Brain Research Center to scan the brains of pandits and controls matched for age, gender, handedness, eye-dominance and multilingualism.

What we discovered from the structural MRI scanning was remarkable. Numerous regions in the brains of the pandits were dramatically larger than those of controls, with over 10 percent more grey matter across both cerebral hemispheres, and substantial increases in cortical thickness. Although the exact cellular underpinnings of gray matter and cortical thickness measures are still under investigation, increases in these metrics consistently correlate with enhanced cognitive function.

Most interestingly for verbal memory was that the pandits' right hippocampus—a region of the brain that plays a vital role in both short and long-term memory—had more gray matter than controls across nearly 75 percent of this subcortical structure. Our brains have two hippocampi, one on the left and one on the right, and without them we cannot record any new information. Many memory functions are shared by the two hippocampi. The right is, however, more specialized for patterns, whether sound, spatial or visual, so the large gray matter increases we found in the pandits’ right hippocampus made sense: accurate recitation requires highly precise sound pattern encoding and reproduction. The pandits also showed substantially thickening of right temporal cortex regions that are associated with speech prosody and voice identity.

Our study was a first foray into imaging the brains of professionally trained Sanskrit pandits in India. Although this initial research, focused on intergroup comparison of brain structure, could not directly address the Sanskrit effect question (that requires detailed functional studies with cross-language memorization comparisons, for which we are currently seeking funding), we found something specific about intensive verbal memory training. Does the pandits’ substantial increase in the gray matter of critical verbal memory organs mean they are less prone to devastating memory pathologies such as Alzheimer's? We don't know yet, though anecdotal reports from India's Ayurvedic doctors suggest this may be the case. If so, this raises the possibility that verbal memory “exercising‘ or training might help elderly people at risk of mild cognitive impairment retard or, even more radically, prevent its onset.

If so, the training might need to be exact. One day I was filming four senior pandit teachers demonstrating the different recitation speeds. Partway into one session all four suddenly stopped. “What’s wrong?‘ I asked. “One of us made a slight error," came the response. "I don’t mind," I said. "Yes, but we do," and they restarted the entire recitation from the beginning.

Author's note: Senior personnel responsible for this project were not involved in the conception or writing of the blog text; it was not presented to them for approval; any opinions or conclusions expressed in the blog are Dr. Hartzell's alone.

This post was written by a graduate of the online course Share Your Science: Blogging for Magazines, Newspapers and More, offered by Scientific American and the Alan Alda Center for Communicating Science at Stony Brook University, with sponsorship from the Kavli Foundation.