The parietal lobes also are involved in the processing of spatial information. Damage to the parietal lobes can cause difficulty copying, or constructing, pictures of objects or designs (Berlucchi & Valar, 2018). Some deficits in attention also can result from damage to the parietal lobes. An unusual phenomenon called “neglect” can occur, usually following damage to the right parietal lobe (Vallar & Calzolari, 2018). Persons fail to attend to (i.e., they neglect) stimuli on the left side of their bodies, such as visual information, touch, and body position. For example, an individual may eat only food that is on the right side of a plate or move limbs only on the right side of the body. The neglect is not due to visual or motor impairments but, rather, to an attentional impairment. The frontal and temporal lobes are divided by the Sylvian fissure (Figure 2-1a). The temporal lobes house the primary auditory cortex, which processes sound information. The temporal lobes also are critically involved in learning and memory, as the What is a brain circuit? The brain operates in systems and circuits. As previously discussed, there is a division of labor in the brain, with some parts, for example, specialized for language, some for learning and memory, and some for the perception of visual information. But there is no one single part of the brain that produces language, understands speech, holds memories, or gives rise to emotions on its own. Each one of these psychological processes involves millions of neurons that are spread across different The language circuit A classic example will illustrate brain circuitry. The language system in the brain has been extensively mapped and the language centers in the brain are well known. The Wernicke- Geschwind Model of Aphasia (Geschwind, 1965) is the dominant classic model of speech production and comprehension. In this model, brain regions critical for the production of speech (i.e., Broca’s area in the frontal lobe) and parts that are critical for the comprehension or understanding of speech (i.e., Wernicke’s area in the temporal lobe) are central features (Figure 2-3). Other brain regions are important for reading and writing. All the language centers are connected into what is called a circuit , similar to an electrical circuit. In fact, brain cells use electricity, in part, to send messages within cells (recall that communication between cells is mostly accomplished with chemical messengers called neurotransmitters ), and thus the electrical circuit analogy is appropriate. The connections between different language centers in the brain allow the language centers to communicate with one another. For example, if a person is asked to repeat a word (Figure 2-3a), the path of information processing can be traced in the brain. First, the brain has to hear the spoken word, which occurs in the primary auditory cortex. Next, the spoken information is comprehended in Wernicke’s area. Speech is produced by Broca’s area and thus the brain now has to transfer information about the word from Wernicke’s area to Broca’s area. This connector part of the language circuitry is called the arcuate fasciculus . Once the information about the phrase reaches Broca’s area, the word is spoken aloud, which is facilitated by the primary motor cortex. The path of information for speaking a written word is illustrated in Figure 2-3b. This model has stood the test of time and is updated as more precise information about the neuroanatomy of language is learned (Tremblay & Dick, 2016).
hippocampi (see above) are located deep in the temporal lobes. Damage to the left temporal lobe can disrupt learning of new verbal information, and damage to the right temporal lobe can impair learning of information that is not easily verbalized. The temporal lobes are involved in several language functions, such as the comprehension of written text or spoken speech and the retrieval of the names of objects. The occipital lobes process visual information. When there is damage or disruption to certain parts of the occipital lobes, various disorders of visual perception can emerge, and some are quite dramatic and bizarre. For example, when there is damage to a region where the occipital and temporal lobes meet, a person can lose the ability to recognize familiar faces, a condition called prosopagnosia (Corrow et al., 2016). Damage to different parts of the occipital lobes can cause difficulty in perceiving objects in motion or in perceiving color.
BRAIN CIRCUITRY
parts of the brain and that work in concert with one another. When different, interconnected parts of the brain work together to produce behavior or to process information, they are said to form a brain circuit . Brain circuits simultaneously encompass ideas of localization of brain function and equipotentiality because there is division of labor in the brain but also distributed processing.
Figure 2-3a-b: Language Circuitry
Note: From Biological Psychology: An Introduction to Behavioral, Cognitive, and Clinical Neuroscience (7th Ed., p. 609, Figure 19.9), by S. M. Breedlove, M. R. Rosenzweig, and N. V. Watson, 2013, Sunderland, MA: Sinauer Associates, Inc. Copyright 2013 by Sinauer Associates. Reprinted with permission.
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