The Handy Psychology Answer Book. Lisa J. Cohen
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Название: The Handy Psychology Answer Book
Автор: Lisa J. Cohen
Издательство: Ingram
Жанр: Общая психология
Серия: The Handy Answer Book Series
isbn: 9781578595990
isbn:
What are the costs and benefits of brain complexity?
As brain structures have evolved toward greater complexity, we can ask what benefits complexity may offer. Are there any costs? In general, complexity allows for more flexibility. Complex systems have a broader repertoire of responses with which to adapt to complicated or changing circumstances. However, complexity is expensive. Complex systems take more energy and are more fragile than simpler systems. With more parts involved, it is easier for something to go wrong.
How costly is our brain?
Although our brain only weighs about three pounds (2 to 3 percent of the average person’s body weight), it uses up about 15 percent of the blood that our heart pumps out and about 20 percent of our body’s oxygen and glucose. In other words it uses up to ten times as much of the body’s resources as would be expected for its weight.
What terminology is important in brain anatomy?
Although we will try to stick to plain English in this book, it is useful to know the basic terminology used in the discussion of brain anatomy. As the brain is a three-dimensional structure, specific terms are used to distinguish up from down, back from front, and inside from outside. The terms anterior and posterior are used to refer to front and back, respectively, as are the Latin words rostral and caudal. Superior and inferior refer to top and bottom, respectively, as do the Latin words dorsal and ventral. Lateral refers to outside, while medial refers to the inside.
How do the Latin terms differ from the English ones?
The English terms are purely directional while the Latin ones are defined in reference to the body. Rostral and caudal are the Latin words for head and tail. Likewise, dorsal and ventral refer to the back and belly of a body (as in the dorsal fin of a shark). Medial means close to the body’s midline while lateral means away from it. Nonetheless, when we speak about the brain, rostral and caudal are generally understood to mean front and back, dorsal and ventral to mean top and bottom, and medial and lateral to mean inside and outside.
This illustration shows the lateral view of the brain.
What have we learned from animals?
Our understanding of the human brain is heavily indebted to the study of animal brains. Although the use of animals in biological research raises moral and ethical questions about animal rights, there is no question that much of our knowledge about the human brain derives from research on animal brains. Legally and ethically, we can perform much more invasive procedures on animal brains than we can on living human brains. Additionally, comparison of the brains of many different kinds of animals gives us critical insight into brain evolution.
What does the word phylogeny mean?
The word phylogeny means evolution. To say something is phylogenetically old means that it is old in evolutionary terms.
THE MAJOR STRUCTURES OF THE BRAIN
What are the major structures of the brain?
The brain is an intricate structure that looks like a boxing glove placed over a spiral of sea creatures. The outer layer of the brain is called the cortex, or the neocortex. It is a wrinkled surface that covers the top and sides of the brain. This is the part that looks like a boxing glove, albeit a wrinkled one. Underneath the cortex are the subcortical regions: the cerebellum and brain stem at the very base of the brain, the thalamus and related regions toward the middle of the brain, and the limbic system, which wraps around the thalamus. The basal ganglia are also in the middle of the brain, close to the thalamus.
THE CORTEX
Why is the cortex so wrinkled?
The surface of the cortex is covered with folds and looks somewhat like a walnut. These folds are referred to as convolutions. The rounded parts of the convolutions are called gyri, gyrus in the singular. The grooves between the gyri are called sulci (sulcus in the singular). These extra folds allow for much greater surface area, which in turn greatly increases the number of neurons that can fit into the relatively small space of the human skull. The more neurons we have, the more powerfully we can process information. To illustrate this efficient use of space, imagine an accordion or pleated paper fan, first folded up and then stretched out from end to end.
What are the four lobes of the cortex?
The cortex is divided into four lobes: the frontal, temporal, parietal, and occipital lobes. The frontal lobe comprises the front half of the cortex. It extends from the central sulcus forward. The thumb-like segments of the cortex are the temporal lobes. The parietal lobes cover much of the back surface of the cortex, extending from the central sulcus back to the border with the occipital lobe (the parietooccipital sulcus). Finally, the occipital lobes are at the lower back end of the cortex.
What is the difference between the cortex and the subcortical regions?
The distinction between the cortical and subcortical regions of the brain is an important one. The cortex is a relatively recent evolutionary achievement and the cortical structures are much more developed in humans than they are in more primitive animals. Most of the more complex psychological processes, the ones we think of as uniquely human, such as language, abstract thought, and reading, are controlled by the cortex. The subcortical regions process more fundamental psychological and even physiological functions. The lowest parts of the brain, closest to the spinal cord, are the oldest parts and regulate physiological processes we share with more primitive animals, such as breathing, heartbeat, and digestion.
What is the frontal lobe?
The frontal lobe is considered the seat of our intellect. It covers about half the human cortex and is the most recently evolved part of the brain. More specifically, it mediates our executive functions, a group of psychological functions that serve to control our behavior. These include planning, abstract thought, impulse control, and the control of behavioral sequences. As might be imagined, impairment in these areas can lead to significant problems functioning in the world. The frontal lobe has other functions besides executive functions, though. The most posterior region of the frontal lobe is called the motor strip and is involved with intentional movements. Additionally, Broca’s area, on the left posterior side of the frontal lobe, mediates speech production, or the translation of thought into spoken words.
What do the other cortical lobes do?
The three remaining cortical lobes are all involved with some aspect of sensation and perception. The occipital lobe is involved with vision. The parietal lobe processes both touch and taste (in the somatosensory strip) and the temporal lobes are involved with hearing. Additionally, the parietal lobes are involved with attention and visual-spatial information, while the temporal lobes mediate language, memory, and the recognition of familiar objects.
How do Brodmann areas map the cortex?
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