Brain Size: What Does it Mean?

05 Jun Brain Size: What Does it Mean?

The size of one’s brain, or certain brain areas, has been extensively studied and implicated in many things including intelligence. This is a highly controversial topic, and research results must be carefully interpreted to avoid conclusions of causation when it may just be a correlation. For example, comparisons have been previously made across different ethnicities in brain size variance. Wet brain weight at autopsy as well as three-dimensional imaging studies suggest that Asian populations averaged the largest brains amongst any social or geographical group. These studies take into consideration corrections for body size, age and sex. In comparison to a worldwide platform, Asian students score the highest in math, reading and science in the Program for International Student Assessment.  Among Asian-Americans, this minority has the highest rate of obtaining a bachelor’s degree, highest marriage rate, highest success in the labor force and highest wealth. If other admission variables were valued secondary to academic excellence, Harvard would only enroll Asians. Therefore, we have an example of a group with the largest brain size and this same group seems to excel the most in academics and life achievements.

Einstein’s Brain

In slight contrast, autopsy photographs of Albert Einstein’s brain may suggest subtly different findings. While the actual brain of Einstein is no longer intact and in fact, some of the pieces are lost and cannot be found, photographs from the 1950s suggest that his brain may be “average” size (weighting 1,230 grams), but certain areas of his brain are “larger.” To understand this, it’s important to know the cytoarchitecture of our brain. Intelligence and higher cognitive function are thought to be related to our brains most outer layer, called the cortex. Since the cortex is so important and needs to be large to enable complex human processes, the cortex is an extremely large sheet folded multiple times on itself to allow it to fit inside our skulls. These folds are called gyri. If you spread out the sheet of brain cells that make up your cortex, you would have a one-meter square sheet at about the thickness of a cracker.

In comparison to nonhumans, a mouse brain, for example, has few gyri which explains why a mouse has limited cognitive ability. Research suggests that Einstein may have had “extra gyri” and that certain focal areas of this cortex were unusual. This may explain the difficulty with which he acquired language, his preference for thinking in ways that included visual images rather than words and his early ability to excel on the violin. He had an enlarged prefrontal area, which is linked to his intense concentration and planning.

Similar differences in the cerebral cortex are proven in other species and human scenarios as well. Raccoons, who use their forepaws to explore their environments extensively, have greatly enlarged somatosensory forepaw representations in their brains. Blind humans who read Braille and upper limb amputees show long-term adaptations of hand areas in their cortex.

Brain Size and Structure

Again, the significance of brain size and structural differences are not yet fully understood, and the relationship of size to function/ intelligence is not completely clear in humans. However, a recent study in nonhumans appears to indisputably solve a century-old dispute. It finally appears conclusive that dogs are smarter than cats.  Studies measuring numbers of brain cells show that dogs have more brain cells (neurons) than cats. Cats have about 250 million cortical neurons, and dogs have about 530 million. Put that into the perspective of humans who have about 16 billion. In comparing different mammals, a trend of increased brain size, structure and number of neurons may be related to sociality. More socially interactive species have higher cognitive demands and larger brains than their solitary counterparts. This is why your cat commonly ignores you. It’s not that the cat is unimpressed, it may be that the cat lacks intellect.

Do you have questions about brain function? Contact us today at Rocky Mountain Brain & Spine Institute to get started. Remember to share your experience with us in a Google review. We appreciate patient feedback!