The human brain is a complex organ that has many different functions. It controls the body and receives, analyzes, and stores information.
The brain can be divided down the middle lengthwise into a right and a left hemisphere. Most of the areas responsible for speech, language processing, and reading are in the left hemisphere, and for this reason we will focus all of our descriptions and figures on the left side of the brain.
- The frontal lobe is the largest and responsible for controlling speech, reasoning, planning, regulating emotions, and consciousness.In the 19th century, Paul Broca was exploring areas of the brain used for language and noticed a particular part of the brain that was impaired in a man whose speech became limited after a stroke. This area received more and more attention, and today we know that Broca’s area, located here in the frontal lobe, is important for the organization, production, and manipulation of language and speech (Joseph, Noble, & Eden, 2001). Areas of the frontal lobe are also important for silent reading proficiency (Shaywitz et al., 2002).
- The parietal lobe is located farther back in the brain and controls sensory perceptions as well as linking spoken and written language to memory to give it meaning so we can understand what we hear and read.
- The occipital lobe, found at the back of the head, is where the primary visual cortex is located. Among other types of visual perception, the visual cortex is important in the identification of letters.
- The temporal lobe is located in the lower part of the brain, parallel with the ears, and is involved in verbal memory.Wernicke’s area, long known to be important in understanding language (Joseph et al., 2001), is located here. This region, identified by Carl Wernicke at about the same time and using the same methods as Broca, is critical in language processing and reading.
In addition, converging evidence suggests that two other systems, which process language within and between lobes, are important for reading.
The first is the left parietotemporal system that appears to be involved in word analysis – the conscious, effortful decoding of words. This region is critical in the process of mapping letters and written words onto their sound correspondences – letter sounds and spoken words. This area is also important for comprehending written and spoken language.
The second system that is important for reading is the left occipitotemporal area. This system seems to be involved in automatic, rapid access to whole words and is a critical area for skilled, fluent reading.