1.3 Organization of the Brain - A Brief History of Neuropsychology

MCAT Behavioral Sciences Review - Kaplan Test Prep 2021–2022

1.3 Organization of the Brain
A Brief History of Neuropsychology


After Chapter 1.3, you will be able to:

· Describe the major functions of the hindbrain, midbrain, and forebrain

· Recognize the most commonly used methods for mapping the brain

· Identify the structures protecting and surrounding the brain

Throughout this section, refer to Figure 1.4, which identifies various anatomical structures inside the human brain. As we discuss different parts of the brain, it’s important to remember the functions of these brain structures. Different parts of the brain perform remarkably different functions. For instance, one part of the brain processes sensory information while an entirely different part of the brain maintains activities of the internal organs. For complex functions such as playing a musical instrument, several brain regions work together. For the MCAT, you will need to know some of the basics about how the brain integrates input from different regions.

ImageFigure 1.4. Anatomical Structures Inside the Human Brain

The brain is covered with a thick, three-layered sheath of connective tissue collectively called the meninges. The outer layer of connective tissue is the dura mater, and is connected directly to the skull. The middle layer is a fibrous, weblike structure called arachnoid mater. And the inner layer, connected directly to the brain, is known as the pia mater. These three layers of connective tissue are shown in Figure 1.5. The meninges help protect the brain by keeping it anchored within the skull, and the meninges also resorb cerebrospinal fluid, which is the aqueous solution that nourishes the brain and spinal cord and provides a protective cushion. Cerebrospinal fluid is produced by specialized cells that line the ventricles (internal cavities) of the brain.

ImageFigure 1.5. Layers of the Meninges

The human brain can be divided into three basic parts: the hindbrain, the midbrain, and the forebrain. Notice that brain structures associated with basic survival are located at the base of the brain and brain structures with more complex functions are located higher up. The meaningful connection between brain location and functional complexity is no accident. In evolutionary terms, the hindbrain and midbrain were brain structures that developed earlier. Together they form the brainstem, which is the most primitive region of the brain. The forebrain developed later, including the limbic system, a group of neural structures primarily associated with emotion and memory. Aggression, fear, pleasure, and pain are all related to the limbic system. The most recent evolutionary development of the human brain is the cerebral cortex, which is the outer covering of the cerebral hemispheres. In humans, the cerebral cortex is associated with everything from language processing to problem solving, and from impulse control to long-term planning. Most of the key brain regions described in the following sections are summarized in Table 1.1.

Major Divisions and Principal Structures


· Forebrain

o Cerebral cortex

o Basal ganglia

o Limbic system

o Thalamus

o Hypothalamus


o Complex perceptual, cognitive, and behavioral processes

o Movement

o Emotion and memory

o Sensory relay station

o Hunger and thirst; emotion

· Midbrain

o Inferior and superior colliculi


o Sensorimotor reflexes

· Hindbrain

o Cerebellum

o Medulla oblongata

o Reticular formation

o Pons


o Refined motor movements

o Heart, vital reflexes (vomiting, coughing)

o Arousal and alertness

o Communication within the brain, breathing

Table 1.1. Anatomical Subdivisions of the Brain

In prenatal life, the brain develops from the neural tube. At first, the tube is composed of three swellings, which correspond to the hindbrain, midbrain, and forebrain. Both the hindbrain and forebrain later divide into two swellings, creating five total swellings in the mature neural tube. The embryonic brain is diagrammed in Figure 1.6, and its subdivisions are described further in the following sections. Understanding the relationship between the structures of the developing brain and the fully developed brain is important. So the following sections describe both the structures of the developing brain and what those structures develop into.

ImageFigure 1.6. Subdivisions of the Embryonic Brain


Located where the brain meets the spinal cord, the hindbrain (rhombencephalon) controls balance, motor coordination, breathing, digestion, and general arousal processes such as sleeping and waking. In short, the hindbrain manages vital functioning necessary for survival. During embryonic development, the rhombencephalon divides to form the myelencephalon (which becomes the medulla oblongata) and the metencephalon (which becomes the pons and cerebellum). In the developed brain, the medulla oblongata is a lower brain structure that is responsible for regulating vital functions such as breathing, heart rate, and digestion. The pons lies above the medulla and contains sensory and motor pathways between the cortex and the medulla. At the top of the hindbrain, mushrooming out of the back of the pons, is the cerebellum, a structure that helps maintain posture and balance and coordinates body movements. Damage to the cerebellum causes clumsiness, slurred speech, and loss of balance. Notably, alcohol impairs the functioning of the cerebellum, and consequently affects speech and balance.


Just above the hindbrain is the midbrain (mesencephalon), which receives sensory and motor information from the rest of the body. The midbrain is associated with involuntary reflex responses triggered by visual or auditory stimuli. There are several prominent nuclei in the midbrain, two of which are collectively called colliculi. The superior colliculus receives visual sensory input, and the inferior colliculus receives sensory information from the auditory system. The inferior colliculus has a role in reflexive reactions to sudden loud noises.


Above the midbrain is the forebrain (prosencephalon), which is associated with complex perceptual, cognitive, and behavioral processes. Among its other functions, the forebrain is associated with emotion and memory; it is the forebrain that has the greatest influence on human behavior. Its functions are not absolutely necessary for survival, but are associated instead with the intellectual and emotional capacities most characteristic of humans. During prenatal development, the prosencephalon divides to form the telencephalon (which forms the cerebral cortex, basal ganglia, and limbic system) and the diencephalon (which forms the thalamus, hypothalamus, posterior pituitary gland, and pineal gland).


Neuropsychology refers to the study of functions and behaviors associated with specific regions of the brain. It is most often applied in research settings, where researchers attempt to associate very specific areas in the brain to behavior. Neuropsychology is also applied in clinical settings with evaluations of patient cognitive and behavioral functioning, as well as the diagnosis and treatment of brain disorders. Neuropsychology has its own experimental methodology and technology.

Studying human patients with brain lesions is one way that researchers have determined the functions of the brain. In order to conclude that a specific structure of the brain is responsible for a specific function, researchers look for patients that exhibit damage to that structure coupled with a loss of the function. One problem in studying human brain lesions, however, is that such lesions are rarely isolated to specific brain structures. When several brain structures are damaged, the impairment could be attributed to any of the damaged structures, and pinpointing a specific link between brain structure and function becomes difficult.

One method for studying the relationship of brain regions and behaviors is to study brain lesions in lab animals. The advantage of this approach is that precisely defined brain lesions can be created in animals by extirpation. Researchers can also produce lesions by inserting tiny electrodes inside the brain and then selectively applying intense heat, cold, or electricity to specific brain regions. Such electrodes can be placed with great precision by using stereotactic instruments, which provide high-resolution, three-coordinate images of the brain. Ethical or cruelty concerns notwithstanding, such studies have greatly increased our understanding of comparable neural structures in humans.

Another neuropsychology method involves electrically stimulating the brain and recording consequent brain activity. While operating on the brain, a surgeon can stimulate a patient’s cortex with a small electrode. This stimulation causes groups of neurons to fire, thereby activating the behavioral or perceptual processes associated with those neurons. For instance, if the electrode stimulates neurons in the motor cortex, the stimulation can lead to specific muscle movements. If the electrode stimulates the visual cortex, the patient may “see” flashes of light that are not really there. By using electrical stimulation, neurosurgeons can thus create cortical maps. This method relies on the assistance of the patient, who is awake and alert. Because there are no pain receptors in the brain, only local anesthesia is required. Electrodes have also been used in lab animals to study deeper regions of the brain. Depending on where these electrodes are implanted, they can elicit sleep, sexual arousal, rage, or terror. Once the electrode is turned off, these behaviors cease.

Electrodes can also be used to record electrical activity produced by the brain itself. In some studies, individual neurons are recorded by inserting ultrasensitive microelectrodes into individual brain cells and recording their electrical activity. Electrical activity generated by larger groups of neurons can be studied using an electroencephalogram (EEG), which involves placing several electrodes on the scalp. Broad patterns of electrical activity can thus be detected and recorded. Because this procedure is noninvasive (it does not cause any damage), electroencephalograms are commonly used with human subjects. In fact, research on sleep, seizures, and brain lesions relies heavily on EEGs, like the one shown in Figure 1.7.

ImageFigure 1.7. Electroencephalogram (EEG) during REM Sleep

Another noninvasive mapping procedure is regional cerebral blood flow (rCBF), which detects broad patterns of neural activity based on increased blood flow to different parts of the brain. rCBF relies on the assumption that blood flow increases to regions of the brain that are engaged in cognitive function. For example, listening to music may increase blood flow to the right auditory cortex because music is processed in that region in most individuals’ brains. To measure blood flow, the patient inhales a harmless radioactive gas; a special device that can detect radioactivity in the bloodstream can then correlate radioactivity levels with regional cerebral blood flow. This research method uses noninvasive computerized scanning devices.

Some of the other common scanning devices and methods of visualization used for brain imaging include:

· CT (computed tomography), also known as CAT (computed axial tomography) scan, in which multiple X-rays are taken at different angles and processed by a computer to produce cross-sectional images of the tissue.

· PET (positron emission tomography) scan, in which a radioactive sugar is injected and absorbed into the body, and its dispersion and uptake throughout the target tissue is imaged.

· MRI (magnetic resonance imaging), in which a magnetic field that interacts with hydrogen atoms is used to map out hydrogen dense regions of the body.

· fMRI (functional magnetic resonance imaging), which uses the same base technique as MRI, but specifically measures changes associated with blood flow. fMRI is especially useful for monitoring neural activity, since increased blood flow to a region of the brain is typically coupled with its neuronal activation.


MRI techniques are dependent on the reaction of hydrogen to a magnetic field, and the scientific principles behind MRI scans are also applied in NMR techniques, which can be found in Chapter 11 of MCAT Organic Chemistry Review.

MCAT Concept Check 1.3:

Before you move on, assess your understanding of the material with these questions.

1. What are the main functions of the hindbrain? Midbrain? Forebrain?






2. What are some of the methods used for mapping the brain?

3. What structures surround and protect the brain?

Behavioral Sciences Guided Example With Expert Thinking


Expert Thinking

Multiple sclerosis is a demyelinating disease that results in a host of neurological and physiological symptoms including muscle weakness, numbness, spasms, visual problems, pain, unstable mood, and fatigue. This last symptom is interesting because it is effort-independent; patients express a subjective feeling of fatigue as a result of performing physical tasks that are not typically physically or mentally taxing. To investigate a mechanism for this phenomenon, researchers used the following fMRI mask to highlight regions of interest in measuring neural resource use with respect to subjective fatigue in MS patients:

MS symptoms. The author finds fatigue interesting because it is subjective. Used fMRI to investigate.

Independent Variable (IV): MS (probably versus control) Dependent Variable (DV): fMRI activity detection differences


Figure 1 fMRI mask

Mask shows regions of interest for the study

Region B is a structure called the putamen, a part of the basal ganglia. It is connected to and provides pathways of communication for many structures in the brain, and generally influences and regulates motor behaviors such as planning, learning, preparation, and execution of motor sequences.

Region B = putamen: communication and motor behaviors

Researchers found no difference in activity in region B between patients with relapsing-remitting MS and controls. However, it was found that region C showed increased activation over the course of a non-fatiguing tonic grip task in MS patients. This increased activation correlated positively with subjective fatigue, and was not present in healthy control subjects. Furthermore, control subjects showed increased activation in region A over the course of the task, and no such activation occurred in MS patients.

Results: region B not implicated in MS-related fatigue, but C shows more activity and A shows less.

Adapted from: Svolgaard O, Andersen KW, Bauer C, Madsen KH, Blinkenberg M, Selleberg F, et al. (2018) Cerebellar and premotor activity during a non-fatiguing grip task reflects motor fatigue in relapsing-remitting multiple sclerosis. PLoS ONE 13(10): e0201162. https://doi.org/10.1371/journal.pone.0201162

Based on the functions of the regions studied, what do these results suggest about the nature of subjective fatigue in MS patients compared to healthy participants?

Our first step in answering this question is to identify the regions presented in the study that are referenced in the question stem. For this particular question, we don't have to worry too much about the structure of the experiment, as most of the information we need is in the results and the description of the regions. The author gives us the name and function of region B: the putamen, described in paragraph 2. This information is helpful because the actual brain isn’t color coded and labeled, and due to the low structural resolution of the image, it’s tough to tell exactly what region B is from the shape of the mask. On Test Day, using the image alone, we might be able to infer that region B is part of the midbrain and therefore, like other structures of the midbrain, it is probably involved in some kind of relay system. But the additional information in the passage text gives us insight that the picture alone just cannot provide. The passage also says that activity in region B is the same in MS patients and controls, allowing us to infer that difficulties in relaying motor signals are probably not the cause of subjective fatigue.

Based on our outside content knowledge, region C is the cerebellum, which we know is responsible for coordinating movement and for maintaining posture and balance. A differential increase in activity here implies that patients with MS may need more resources to perform motor tasks the longer these tasks are maintained.

Region A is in the forebrain. If we’ve studied the regions of the cerebrum, we might recognize this region as the premotor cortex, which is responsible for higher-level motor control and motivation. However, even without the specifics, we can guess that this region of the forebrain has something to do with executive motor control because of its general location. From the noted activity pattern in the final paragraph, we can guess that increased activity in region A helps to prevent subjective fatigue; thus, for MS patients, a lack of activation in this region may contribute to their experience of increased subjective fatigue.

We now have enough information to form a general picture of events here. In MS patients, the cerebellum is more active, presumably consuming more resources during maintained motor movements than the cerebellum of their healthy counterparts. This increase in resource consumption could be the MS patient’s brain attempting to accommodate for functions from other regions that have been lost as a result of disease, or could indicate a greater overall demand on cognitive processes involving movement. This overtaxing of cerebellar resources is most likely related to the increase in subjective fatigue experienced by MS patients.