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?
In 1909, Korbinian Brodmann (1868–1918) tried to standardize the discussion of brain anatomy by creating a map of the cortex. He first divided the cortex into distinct regions based on the way neurons were organized (cytoarchitecture). He then numbered these regions from one to fifty-two. Only forty-five Brodmann areas are found in the human brain; the other seven are found in the monkey brain. Although brain structure may vary somewhat across individuals, this system has been extremely helpful for neuroscientists, giving them a common language with which to talk about brain anatomy. Nonetheless, there is still variation in the terms used, as many brain structures have several different names.
Do both sides of the brain do the same thing?
The two halves of the brain are almost, but not quite, identical. With regard to the cortex, there is considerable difference in the functions they perform. This difference between right and left sides of the brain is called lateralization. The left side of the cortex is involved with language comprehension and speech production. The right side of the brain is involved with spatial and emotional processing and facial recognition. Because of lateralization, the impact of brain damage (for example due to stroke) will differ depending on the side of the brain affected.
BENEATH THE CORTEX
What is the limbic system?
The limbic system is centrally involved in our emotions. The term was first introduced by American neuroanatomist James Papez (1883–1958) in 1937 and refers to a group of brain structures in the middle of the brain. The original Papez circuit included the hippocampus, the fornix, the mammillary bodies, the anterior nucleus of the thalamus, and the cingulate gyrus. Over time the boundaries of the limbic system were expanded, although the exact definition of the limbic system is still not universal. For our purposes, however, we can include the amygdala, hippocampus, septum, and cingulate gyrus. These regions are all involved with emotional and motivational processing. Although the hypothalamus is technically classified with a brain region called the diencephalon, we include it here because its functions are tightly connected to the other limbic structures.
What do the amygdala and the hypothalamus do?
The amygdala seems to be an early responder to emotionally significant signals from the environment. It is particularly reactive to fearful stimuli. The amygdala activates the hypothalamus, which in turn activates the autonomic nervous system, in part through control of important hormones. The autonomic nervous system regulates the physiological components of emotion. For example, imagine that a vicious dog has broken free of its leash and is now lunging toward you. Immediately, your amygdala responds to the perception of danger. It sends signals to the hypothalamus, which then activates the autonomic nervous system, resulting in the rapid heartbeat, sweaty palms, and heavy breathing associated with fear.
Where does the word amygdala come from?
The amygdala is a small, almond-shaped structure buried deep in the middle of the brain. Because of its oval shape, the amygdala was named after the Greek word for almond.
What does the hippocampus do?
The hippocampus is a caterpillar-like structure on the medial (inner) side of the temporal lobe and is heavily involved with memory. Early brain anatomists believed it looked more like a seahorse and named it after the Greek word for seahorse (hippo = horse). While the hippocampus does not process emotion, per se, it is located near the other limbic structures and carries memories of emotionally meaningful events. What we interpret as emotionally arousing, therefore, is heavily dependent on our memories of similar experiences.
What do the other limbic structures do?
The septum is a small area that is involved with the experience of pleasure among other functions. The cingulate gyrus is a long structure that wraps around numerous other subcortical regions and has attentional, emotional, and cognitive functions. More specifically, it is involved with decision-making.
What are the regions of the brain and their functions?
| Brain Area | Major Function |
| Cortex or NeocortexFrontal LobeParietal LobeTemporal LobeOccipital Lobe | Perception, Action, and CognitionIntentional Action and Executive FunctionsTouch, Taste, Spatial Processing, AttentionHearing, Language, Memory, Object RecognitionVisual Processing |
| Limbic SystemAmygdalaCingulate GyrusHippocampus | Emotion and MotivationEmotional Reactions, Fear MemoryEmotion, Attention
|