There are two cerebral hemispheres – right and left – divided down the centre by a deep fissure. The surface of the hemispheres is deeply fissured and grooved. The grooves are called sulci, and the ridges in between the grooves are called gyri.
The hemispheres are the place where our highest skills originate. Our ability to think, communicate, and perform highly coordinated tasks originate here.
There is a dominant and non-dominant hemisphere. The dominant hemisphere will control verbal functions such as speech, language, reading, writing and mathematical calculations. It also usually controls the dominant hand.
The non-dominant hemisphere is more involved with visual functions such as copying, drawing, visual memory and rhythm. Since the left side of the brain controls movement and interprets the sensation for the right side of the body, the left hemisphere is the dominant hemisphere for most people. Even in left handed people, the left hemisphere is still more likely to control speech and language function, even though the motor control of the left hand will be in the right hemisphere.
Each hemisphere is divided into four lobes: frontal, temporal, parietal and occipital. Each lobe has a different function:
- The Frontal Lobes assist in coordinated fine movement, the motor speech aspect, executive function, motivation, social skills, and certain parts of our personality
- The Temporal Lobes are important for memory, receptive language and our sense of rhythm and music
- The Parietal Lobes are important for the interpretation of sensory information (like reading and spatial relationships) and attention
- The Occipital Lobes are important for perceiving visual stimuli seen by the eyes
The areas at the base of the cerebral hemispheres are called basal ganglia. They communicate back and forth with the hemispheres, helping with habitual movements and posture, and with certain cognitive abilities.