Dementia and the Different Parts of the Brain Affected

UNDERSTANDING HOW KEY FUNCTIONS OF THE BRAIN ARE AFFECTED BY DEMENTIA

You do not have to become an expert on the brain to be a good dementia health care worker. However, having a basic awareness of the brain’s functioning may help you to understand some of the difficulties a person with dementia is experiencing. It can also help to explain some of the behaviours you may find challenging and difficult to comprehend.

The level of damage taking place in the brain (‘neurological impairment’) will vary from one person to another depending on the type of dementia they have and the areas of the brain affected. A part of the brain severely damaged in one person may be left completely intact in another person, even though they both have dementia. This helps to explain why people with dementia vary so much in the ways they behave and in what they can and cannot do.

For example, a person may be able to play the piano well, long after forgetting the names of the pieces of music. This is because the memory needed to recall a sequence of physical movements is stored in a different area to that responsible for remembering facts such as names. Similarly, although a person may have difficulties with speaking, they may be able to sing or hum a favourite tune quite fluently. Again, this is because there are different parts of our brain responsible for speaking and for singing.

Below is an illustration of the side view of the outer layer of the brain (The cerebrum):

Cortex (Cerebrum)
The cortex, or cerebrum, is made up of two hemispheres (or sides) connected by a band of tissue called the corpus callosum. These hemispheres control speech, intelligence, and memory. There are specific centres for specific functions; for example, the speech centre governs the ability to form sounds into meaningful words, phrases, etc.
Left Hemisphere
The Left hemisphere controls the right side of the body. It controls speech, comprehension, arithmetic, and writing.
Right Hemisphere
The right hemisphere controls the left side of the body. It is responsible for more abstract skills, such as creativity, spatial ability, and artistic and musical skills.

Each cerebral hemisphere is divided into lobes. (In this illustration, the Frontal Lobe, the Temporal Lobe, the Parietal Lobe and Occipital Lobe are all the different parts that make up the Cortex).

Frontal Lobe
The frontal lobe is located in front of the cerebrum behind the forehead. It is the centre for judgment, reasoning, behaviour, movement, personality, motivation, interpretation and inhibition of impulses. It also plays a role in controlling emotions, social skills, and expressive language.

Parietal Lobe
The parietal lobe sits just behind the frontal lobe. It is responsible for receiving and processing the sensations of touch (for example, pain, heat, cold, pressure, size, shape, and texture). It covers language, spatial awareness and recognition. It analyzes the combined information coming in from all five senses. It is also closely linked to writing and speech fluency.

Temporal Lobe
The temporal lobe is located alongside the frontal and parietal lobes, just above the ear. It is the centre for the senses of hearing, taste, and smell. It is also involved in receiving auditory information and in memory and speech.

Occipital Lobe
The occipital lobe rests in back of the cortex behind the parietal and temporal lobes. Damage to this area may affect sight, such as perceiving or understanding visual information.

Cerebellum
The cerebellum is located beneath the cerebral cortex in the back of the skull. It is smaller than the cortex. Its job is to transmit and coordinate the signals from the cortex. It also controls the movement of voluntary muscles, balance, posture, and in coordinating movements.

Brain stem
The brain stem is in front of the cerebellum and beneath the cerebral cortex. It connects the spinal cord to the cortex. Its role includes passing messages back and forth between various parts of the body and the cerebral cortex.

The brain stem coordinates the body's functions such as breathing, blood pressure and pulse. It also contains the reticular formation which is responsible for consciousness, drowsiness, and attention. Originating in the brain stem are 12 cranial nerves.

These nerves control smell, hearing, vision, eye movement, facial sensations, taste, and swallowing. They also control muscle movements in the face, neck, shoulders, and tongue.

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The Limbic System (The Emotional Brain)
Deep within the brain is the limbic system, sometimes called the emotional brain. It links your brain stem and automatic body functions with the more highly evolved intellectual areas of the cerebral cortex.

The limbic system consists of several structures:

Hypothalamus
The hypothalamus is in charge of homeostasis, or maintaining the body's status quo. It regulates body temperature, hunger, and thirst, and is involved in emotion and your sleep cycle.

Hippocampus
The hippocampus is vital to learning and memory, particularly converting your short-term memory into long-term. This part of the brain also helps you comprehend spatial relationships and navigate the world around you. The hippocampus is one of the first parts of the brain that suffers damage from plaques and tangles in the course of Alzheimer's disease.

Thalamus
The thalamus serves as a relay station for nearly all sensory information that travels to and from the cerebrum and the rest of the body.

Amygdala
The amygdala controls memory, emotion, and fear. It triggers the so-called fight-or-flight response.