Brain asymmetry can refer to at least two quite distinct findings:

• Neuroanatomical differences between the left and right sides of the brain
• Lateralized functional differences: Lateralization of brain function
  Lateralization of brain function
  A longitudinal fissure separates the human brain into two distinct cerebral hemispheres, connected by the corpus callosum. The sides resemble each other and each hemisphere's structure is generally mirrored by the other side. Yet despite the strong anatomical similarities, the functions of each...
  
  

Neuroanatomical differences themselves exist on different scales, from neuronal densities, to the size of regions such as the planum temporale

Planum temporale

The planum temporale is an area of the human brain. It is the cortical area just posterior to the auditory cortex within the Sylvian fissure. It is a triangular region which forms the heart of Wernicke's area, one of the most important functional areas for language.The planum temporale shows a...

, to—at the largest scale—the torsion or "wind" in the human brain

Human brain

The human brain has the same general structure as the brains of other mammals, but is over three times larger than the brain of a typical mammal with an equivalent body size. Estimates for the number of neurons in the human brain range from 80 to 120 billion...

, reflected shape of the skull, which reflects a backward (posterior) protrusion of the left occipital bone

Occipital bone

The occipital bone, a saucer-shaped membrane bone situated at the back and lower part of the cranium, is trapezoidal in shape and curved on itself...

 and a forward (anterior) protrusion of the right frontal bone

Frontal bone

The frontal bone is a bone in the human skull that resembles a cockleshell in form, and consists of two portions:* a vertical portion, the squama frontalis, corresponding with the region of the forehead....

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