Chapter 1

Brain and Function in the Context of
Acquired Brain Injury

1.1 Case Study
1.2 The Brain is Who You Are
1.3 Brain Physiology and Behaviour
1.4 What is Acquired Brain Injury?
1.5 What Happens When the Brain is Damaged?
1.6 Who Does Acquired Brain Injury Affect?
1.7 Brain and Function

1.1 - Case Study

Adam was 5 years old when he fell down the basement stairs while hurrying to catch up with his 7- year-old brother. He was dazed and lay motionless for a few minutes at the bottom of the stairs, until Mom came to help. After a few tears, Adam seemed OK and eagerly followed Mom into the kitchen for a cookie. Later that day he began to vomit and his mother was concerned enough to take him to the hospital where he was initially diagnosed with concussion.

Over the next few weeks and months, Adam’s “personality” seemed to change. He was more obstinate and easier to anger; he was slower than usual, even lazy, when asked to do simple things like get ready for school. His kindergarten teacher noticed a change in his social behaviour with others. By the end of the year, the school’s recommendation was for Adam to retry kindergarten. His parents, at the suggestion of the school team, took Adam for a full physical exam which, after a referral to a neurologist, resulted in a CT scan. Adam was finally diagnosed with a mild brain injury.

1.2 - The Brain is Who You Are

Since the brain is responsible for the most complex of human functions such as thinking, problem solving, emotions, consciousness, and social behaviour, it, essentially, controls and defines your personality or who you are. It also controls basic bodily functions such as breathing, eating, sleeping, moving, and the five senses and is responsible for how we think, feel, perceive, and act in the world—it is the organization of who we are.

If an external force is strong enough to either fracture the cranial bones, or an internal rotational force occurs due to impact causing the brain to hit or scrape against the inside of the skull, the brain will tear and/or neurons will be damaged—and we will change.

1.3 - Brain Physiology and Behaviour

The brain is made up of cells called neurons, and, with the spinal cord, makes up the central nervous system (CNS).

At birth, we have essentially all the neurons we will ever have for the rest of our lives. Although most neural differentiation is accomplished by 6 months postnatally, development continues until we are 25 years old in terms of growth in size, dendritic connections, the process of parsing (natural progression of neurons dying), and myelination (formation of myelin on axons).

Structure and Function of the Brain

The brain is quite fragile and has a soft jelly-like consistency. In order to protect this fragile organ, the body has developed three lines of defense.

1st Line of Defense - Hair and Skull

• Hair prevents excessive heat loss
• The skull provides a bony case that encapsulates and protects the brain from external impact (note: the inner surface of the skull is not entirely smooth, but contains rougher areas and ridges along its ventral portion)

2nd Line of Defense - The Meninges

• Three thin membranes found between the skull and the brain which serve to protect the integrity of the brain’s physical structure and provide shock absorption
• Also known as the blood-brain barrier, the meninges surround the brain and spinal cord and form a barrier which selectively controls the transportation of all substances into and out of the brain.

3rd Line of Defense - Cerebrospinal Fluid

• Fluid found within the ventricles of the brain and in between the meninges which can serve as a cushion or shock-absorber and provide a fluid vehicle for transportation of material.

The Neuron

The most basic, functional unit of the nervous system is the nerve cell or neuron. Neurons carry information to and from the brain, integrate and interconnect the various regions of the brain and body, and store information. We are born with approximately 100 billion CNS (Central Nervous System) nerve cells and 10 trillion PNS (Peripheral Nervous System) nerve cells.

Unlike the other cells in our body, those of the nervous system cannot divide—in other words, at birth we have essentially all the neurons we will have for the rest of our lives.

Fortunately each neuron can make anywhere between one and 10,000 connections with other neurons, resulting in a massive number of inter-connected networks throughout the brain—sufficient for a lifetime. These connections are extremely fragile and even minor damage to any of these networks can cause disruptions and impairments in function and behaviour.

Brain Organization

A. The Brainstem - connects the base of the brain to the spinal cord at the level of the neck and upwards through the bottom (central) surface of the brain. It controls basic life functions such as breathing, heart rate, blood pressure, arousal (sleep/wakefulness), and aids in maintaining alertness. In addition, the brain stem acts as the relay station for motoric and sensorial input and output between the brain and the peripheral nervous system. Damage can result in coma, dysarthria (speech difficulties), choking, fatigue (cognitive and physical), and disorientation. (For more information see Section 1.7a)

B. The Cerebellum - is primarily involved in controlling balance and equilibrium, and coordination of fine and gross body movements. Damage to the cerebellum can result in tremors, loss of motor control, slurred speech, impairments in balance (i.e., dizziness, vertigo, difficulty in standing or walking), and difficulties in precise motor fluency (e.g., timing of an action adjustment of force). (For more information, see Section 1.7b)

C. Subcortical Structures

Basal Ganglia - These structures control gross motor function such as posture and balance as well as the initiation of and management of voluntary movement, e.g., walking, clutching, reaching. (For more information, see Section 1.7c)

Limbic System - This system consists of several different structures (hippocampus, mamillary bodies, amygdala, septum, fornix, etc.), which together permit the expression of emotions, the establishment of memories, and the coordination of these as a function of cortical awareness. (For more information, see Section 1.7d)

Thalamus - This is the central relay station for incoming sensory information which directs information towards the cortex for awareness and perception and towards other parts of the brain which are reliant on information from our external environment. (For more information, see Section 1.7e)

Hypothalamus - This structure is at the very base of the brain and controls the body through its direction of the pituitary gland and the autonomic nervous system. In doing so, it regulates and directs behaviours that are fundamental and necessary for our survival, namely: feeding, drinking, sleeping, reproduction, temperature control, and emotion (negative and positive). (For more information, see Section 1.7e)

D. The Cerebrum - is divided into right and left halves, referred to as “hemispheres.” The cerebral hemispheres are the most highly evolved and most complex part of the entire brain. Their outer layer, the cortex, is folded into numerous convolutions, called gyri, to provide more surface area within the limited space allowed by the skull. These gyri are so tightly packed that only about 30% of the cortex is actually visible from the outside surface. The cortex integrates information from lower systems and adjacent areas, allowing us to perceive, interpret, and react meaningfully to our environment.

The Cerebrum - Thought and Control of Behaviour

The cortex has two main functions:

1. Produce thoughts that monitor and analyze incoming information to the brain.
2. Control behaviours such as action, interpretation, initiation, planning, organization, and self-awareness.

The cortex allows us to perceive the outside world.

• Our thoughts are organized.
• Our experiences are individualized and stored in
  memory.
• Speech is understood and produced.
• Scenery is seen.
• Music is heard.

 

The Left and Right Cerebral Hemispheres: Language and Spatial Skills

Each hemisphere is responsible for the opposite side of the body. The right hemisphere controls movement and receives information from the left side of the body, and the left hemisphere does the same for the right side of the body.

In nearly all right-handed individuals and most lefthanded individuals:

• The left cerebral hemisphere is specialized for language skills such as speaking, listening, reading, and writing.
• The right hemisphere is specialized for spatial abilities such as knowing directions, solving puzzles, drawing pictures, and recognizing familiar objects or people.

Across individuals there is a wide range in the level and partitioning of dominance between the left and right hemispheres. Rather than being strictly hardwired, the brain’s plasticity allows for occasional compensation for a certain loss of function when the other hemisphere has been damaged. However, many factors impact this effect. (For more information, see Section 1.7f)

Lobe Function: Input vs. Output

The cerebral cortex is divided into 4 distinct lobes separated by grooves called sulci. The 3 major lobes located towards the back of the brain are known as the temporal, occipital, and parietal lobes. Each is specialized for receiving, perceiving, and interpreting a particular kind of sensory information: namely, hearing, vision, and touch, respectively. Since these lobes take in information (e.g. sensations) from the outside world, they are known as the input lobes.

The frontal lobe located towards the “front” of the brain is different from the other lobes because its primary role is integration and response to the environment, at output. The frontal lobe receives and integrates the information (e.g., sensations) from the other lobes, and then determines the best way to interact with the environment based on the sensory information.

Damage to Specific Regions of the Brain

Different regions of the brain specialize in different functions. Therefore, damage can lead to different types of deficits and difficulties, depending on the area of the brain that has been affected. A focal (localized) injury will usually result in very well-defined deficits. A diffuse (covering a wide area of the brain) injury may result in a broad spectrum of deficits that may vary in severity.

Frontal Lobes

• Disruptions in complex motor skills, including speech
• Difficulties planning, organizing, and sequencing events
• Loss of control over emotions and behaviour (i.e., personality changes), decreased self-awareness, poor judgment and reduced social skills
• Decreased attention and loss of memory

Parietal Lobes

• Reading, writing, and language disorders
• Difficulty recognizing visual and tactile information
• Difficulty with dressing, drawing, and hand-eye coordination
• Distortions in body image and spatial abilities (i.e., inattention to information received on one side of the visual field)

Temporal Lobes

• Specific memory impairments (i.e., prosopagnosia— inability to recognize faces)
• Difficulty understanding spoken language (i.e., aphasia)
• Impaired sense of smell

Occipital Lobes

• Impairments in visual awareness and recognition (For more information, see Section 1.7g-j)

1.4 - What is Acquired Brain Injury?

ABI, or acquired brain injury, is any type of sudden injury that causes temporary or permanent damage to the brain. Damage that is associated with some kind of trauma to the head such as a concussion, a fall, or a motor vehicle collision is known as a traumatic brain injury. Injuries can also occur as a result of other factors, such as: anoxia (e.g., near drowning), toxicity, infection, or cerebral vascular accident (CVA, e.g., stroke).

1.5 - What Happens When the Brain is Damaged?

The brain is made up of cells called neurons, which are unique to the central nervous system. At birth, we have essentially all the neurons we will ever have for the rest of our lives.

Once the nucleus (or cell body) of the neuron has been damaged, the neuron is unable to successfully reconnect or heal itself. Therefore, once a neuron is injured and dies, the damage to the brain as a whole is permanent.

Disconnection of the Neural Pathways

The brain is an interconnected network of neurons that communicate with each other. Through communicating with each other, neurons rely on one another to pass along vital information. If a group of neurons becomes damaged and dies, then the neurons with which they once communicated will no longer receive information. Once those neurons are no longer receiving information from the damaged neurons, they will become inactive and die as well. This is how one centre of injury can result in damage in distal (distant) and other areas.

Three Levels of Severity of Injury

When assigning a diagnosis, medical professionals will define the severity of a brain injury by using the terms mild, moderate, or severe. The size of the injury does not always predict the level of dysfunction. Other factors, such as age at injury, cause of injury, and, most of all, site of injury determine functional outcome and (dis)ability.

1.6 - Who Does Acquired Brain Injury Affect?

ABI does not respect a person’s age, or socioeconomic levels. It can and does strike young and old, rich and poor alike. Statistics show that male adolescents and adults under the age of 25 are the population at greatest risk. The greatest increase in ABI occurrences, not surprisingly, is in the fastest growing demographic group, namely seniors who are at increased risks for falls.

It is important to know that when an ABI occurs, the effects ripple out from the injured person to impact on family, friends, classmates, co-workers, and the community in general. Schools become a major player in reintegrating and accommodating students who experience ABI; but the school should seek to ally itself with the family and other significant parts of the community. In this way the school can benefit from strategies proven in other venues, and be a part of a coordinated program to achieve optimum functioning for the student.

The remainder of this resource binder will focus on the impact of ABI on students, both inside and outside of the classroom and how educators and others in the educational system can help to meet the needs of these students so that they can experience success.

As educators, it’s important to become more informed about ABI so that you can help provide a safe and structured learning environment. Many simple procedures included in this guide can be put in place and will dramatically improve both the functioning of the classroom and the student’s future.

1.7 - Brain and Function

Tables a-j provide information on areas of the brain and the result of injury to those specific regions.

Table (a) Brainstem

Where is it?	What does it do?	What happens when it is injured?
The brainstem is located at the base of the brain and extends down to become the spinal cord. Three main parts make up the brainstem, including the medulla, the pons, and the midbrain.	The medulla controls basic involuntary life functions such as respiration, blood pressure, heart rate, and body temperature control. In the pons and extending up through the midbrain is a structure called the reticular activating system. This system affects sleep onset and a person's level of alertness.	- A disturbance in breathing, heart rate, or other vital bodily functions. - Decreased levels of alertness and arousal. - Dysphagia - difficulty swallowing food and water. - Sleeping difficulties (e.g., insomnia, sleep apnea). - Disturbance in sleep/wake cycles.

Table (b) Cerebellum

Where is it?	What does it do?	What happens when it is injured?
The cerebellum is located underneath the lower back part of the cerebral hemispheres.	- Controls balance, timing and equilibrium. - Coordination of both fine and gross body movement such walking, sitting down, and manipulating objects with the hands.	- Ataxia - failure in muscle coordination (e.g., a limb may appear to shake, making it difficult to use the limb). - Balance problems, making it difficult to stand or walk independently. - Difficulty reaching out and grabbing objects. - Persistent dizziness or vertigo. - Slurred speech.

Table (c) Basal Ganglia

Where is it?	What does it do?	What happens when it is injured?
The basal ganglia are a small collection of neurons located deep inside the cerebral hemispheres on either side of the thalamus.	- Control of involuntary movement such as that seen in resting-type postural movement and body position when there is no voluntary movement. - Initiating voluntary movement such as walking or talking.	- Movement disorders such as an inability to initiate voluntary movements (e.g., person needs to be cued to take a step before beginning to walk). - Lack of postural control or control over body position (e.g., person will slouch to one side when sitting at rest).

Table (d) Limbic System

Where is it?	What does it do?	What happens when it is injured?
The limbic system is a ring-like collection of structures deep within the cerebral hemispheres adjacent to the basal ganglia.	- Areas of the limbic system like the hippocampus are responsible for storing and recalling explicit memories. - Others, like the amygdala are involved in the production of feelings or emotions.	Numerous problems of internal body regulation and higher behaviours can result, such as: - Memory and learning difficulties. - Inability to explicitly recall information. - Extreme inappropriate emotional states.

Table (e) Thalamus

Where is it?	What does it do?	What happens when it is injured?
The thalamus sits at the top of either side the brain stem in the centre of the brain.	- Central relay station for incoming sensory information. The thalamus decides where the information must go within the cortex and sends it there to be perceived and analyzed.	This is dependent on which sensory receiving area is damaged (e.g., if it is the visual receiving area, information will not be properly sent to visual areas in the cortex and visual deficits will result).
The Hypothalamus is directly below (hypo) the thalamus at the base of the brain.	- The hypothalamus controls the behaviours that require us to interact with our environment in order to survive such as the regulation of feeding, drinking, sexual behaviour, sleeping, temperature control, and emotional expression.	Hypothalamic damage can result in deficits such as: - How to recognize when the stomach is full or empty. - How to recognize when the body needs fluids. - How to recognize when the body needs rest. - Regulation of sexual urges/signals. - Emotional Lability - Bouts of uncontrollable crying or laughing.

Table (f) Left and Right Hemispheres of the Brain

	Left Hemisphere	Right Hemisphere
Processing & Analysis of Information	- Logical. - Sequential. - Analytical. - Concentrates on details. - Deductive reasoning.	- Holistic. - Global. - Parallel processing. - Comprehension. - Inductive in reasoning.
Specialized Skill	- Verbal. - Lexical aspects of relative spatial abilities. - Relationships between self and environment. - Analytical space-time concepts (e.g. numerical operations). - Language (speaking, listening, reading, writing).	- Spatial abilities (knowing directions), especially in 3 dimensions without reference. - Solving puzzles. - Drawing pictures. - Recognizing objects and people. - Nonverbal language (timing, intention, pragmatics). - Space-time complex concepts (e.g., physics).
Sensory Perception & Motor Function	- Responsible for the right side of the body's skeletal muscles and somatosensation. - Interprets the left visual field. - Bilateral audition.	Responsible for the left side of the body's skeletal and muscles and somatosensation. - Interprets the right visual bilateral field. - Audition.

Table (g) Frontal Lobe

Where is it?	What does it do?	What happens when it is injured?
The frontal lobe is located at the front of the brain just behind the forehead.	- Provides executive control over much of the brain's higher functions. - Consciousness. - Self-awareness. - Judgment. - Initiation/Motivation. - Control over emotional responses. - Planning / Sequencing. - Word formation. - Prospective memory - remembering to do something.	- Inability to synthesize signals from the environment. - Inability to assign priorities. - Inability to make decisions. - Inability to initiate actions. - Inability to control emotions. - Inability to behave and interact socially and make plans. - Changes in personality. - Inflexible, simplistic, and/or concrete thinking. - Poor judgment. - Inability to plan a sequence of complex movements needed to complete multi-stepped tasks. - Inability to behave appropriately in social situations.

Table (h) Parietal Lobes

Where is it?	What does it do?	What happens when it is injured?
The parietal lobe is located on both sides of the head near the top and to the back.	- Responsible for perceiving, analyzing, and assembling touch information from the body. - Integrates visual, auditory, and touch information in order to formulate complete impression of the world. Left parietal lobe Area where letters come together to form words and where words are put together in thoughts. Right parietal lobe Responsible for understanding the spatial aspects of the world including recognizing shapes, being aware of one's body in space and deficits.	- Difficulties with hand and eye coordination. Left parietal lobe - Inability to recognize or locate touch sensations from the right side of the body. - Inability to know the meaning of words. - Anomia - inability to name objects. - Dyscalculia - inability to do mathematic calculations. - Agraphia - Inability to locate the words for writing. Right parietal lobe - Inability to recognize or locate touch sensations from the left side of the body. - Perceptual Agnosia - "not knowing" (e.g., not able to recognize familiar objects touched by the hands). - Difficulty with drawing objects. - Lack of awareness of certain body parts and/or surrounding space.

Table (i) Temporal Lobes

Where is it?	What does it do?	What happens when it is injured?
The temporal lobe is a large thumb-shaped extension of the cerebral hemispheres located near the temples on either side of the head.	A small section at the top of each temporal lobe, known as the auditory cortex, is responsible for hearing. The temporal lobes are also involved in memory acquisition, perception, and categorization of objects. - Involved in processing auditory information (e.g., sound discrimination, comprehension of language, listening, reading; music). - Important for memory acquisition, storage. - Important for sense of smell. - Involved in complex visual analysis. Left temporal lobe - Specialized for the comprehension of language such as listening and reading. Right temporal lobe - Specialized for the comprehension of music.	- Disturbances with selective attention to what is seen and heard. - Memory problems. - Categorization problems. Left temporal lobe - Wernicke's Aphasia - An inability to read and comprehend what someone is saying (e.g. , can form word associations but they are not language based). - Persistent talking. Right temporal lobe - Inability to recognize and appreciate music. - Prosopagnosia - difficulty in recognizing faces. - Difficulty understanding spoken language (i.e., some types of aphasia). - Specific memory impairments (e.g., Prosopagnosia/inability to recognize faces). - Impaired detection of smell.

Table (j) Occipital Lobe

Where is it?	What does it do?	What happens when it is injured?
The occipital lobe is located in the extreme rear of the cerebral hemisphere at the back of the brain.	This lobe is dedicated entirely to vision in terms of detection, identification, and interpretation of objects.	- Visual agnosia - not consciously knowing that one has seen an object. - Difficulty locating objects in the environment. - Colour Agnosia - difficulty with identifying colours. - Word Blindness - difficulty in recognizing words. - Inability to track the movement of objects.

Chapter 2