Persons diagnosed with Alzheimer’s disease have four distinct physiological changes occurring in their brains. These are the classic features happening as the brain becomes more and more damaged during the disease process. Knowing and understanding these disease features are responsible for the changes in your loved one’s health and mental abilities, can make your family’s journey easier. We all respond better to a crisis when we are prepared and understand the reasons behind new and disturbing changes.
These changes are also seen in other forms of dementia. Remember it is possible for a person to have more than one type of dementia at a time. The following is a description of the four changes and a breakdown of the areas of the brain and their functions.
Shrinkage – Sulci (grooves and furrows in outer brain) and the Gyri (well developed folds of outer brain) shrivel and pull apart. The weight and size of the brain withers from three pounds to one pound.
Cerebral Spinal Fluid – Temporal and Frontal Lobes fill with fluid and the four ventricles become grossly enlarged.
Neurofibillary Tangles – Tau proteins are insoluble twisted fibers found inside nerve cells. They form part of a structure is called a microtubule. These microtubules carry nutrients to and from the nerve cells. The Tau proteins become abnormal and collapse the microtubule, starving the cells.
Plaque – Housekeeping cells cease to remove fragmented pieces of dead Amyloid from between nerve cells (neurons). Over time, these fragments accumulate on the nerve endings forming bone-like plaques.
Cerebrum, Cerebellum and the Limbic System
The Cerebrum: The largest part of the brain contains the four lobes, Temporal, Frontal, Parietal and Occipital.
Temporal Lobe: Language, Hearing and Smell – Generally the start of the disease process and the beginning stages of amnesia and aphasia. The left lobe contains Broca’s Area (ability to talk) and Wernicke’s area (comprehension of spoken and written words), the right lobe contains singing and swearing.
Frontal Lobe: Memory, Speech, Rational Thought, Judgment, Personality, Attention, Problem Solving, Planning and Imagination – Once the disease enters here, familiar persons begin to notice changes in behavior or cognitive abilities, and amnesia, aphasia and agnosia are cited.
Parietal Lobe: Sensory Perception (pain, touch, taste, temperature and pressure) – Alzheimer’s patients have difficulty determining their environment. For example, they may not know they’re cold, or be able to relay accurate information about pain. Amnesia and aphasia are tied to this lobe’s responses to stimuli.
Occipital Lobe: Visual Association (depth & distance perception) – An Alzheimer’s patient loses the inability to interpret what the eye is seeing. For example, three dimensional vision is lost, shiny floors appear like water, dark flooring looks like a hole.
Cortex: Skilled Movement – Everything associated with movement, from an overall lack of coordination, to reaching for an item and missing, to changes in gait, to pilling (rolling fingers) behaviors can be observed. Apraxia is beginning and agnosia is evident.
Cerebellum: Latin for “little brain” Equilibrium, Posture, Movement and Muscle Coordination –increased gait imbalance, increased loss of coordinated movement, decreased ability to chew and swallow – advanced apraxia
Medulla Oblongata: Breathing, Heart Rate and Blood Pressure – drop in stability and stabilization of the body’s systems
Limbic System: A group of interconnected structures that mediate emotions, learning and memory.
Thalamus: Sensory integration and motor integration. The thalamus receives information and relays it to the cerebral cortex and vice versa.
Hypothalamus: Pea-sized portion of the brain, it controls body temperature, emotions, hunger, thirst, appetite, digestion and sleep.
Amygdala: These two almond-shaped structures control emotion.
Hippocampus: This crescent-shaped structure forms and stores memory
and is involved in learning.
Mid-brain: Located behind the frontal lobes, it controls breathing, reflexes and swallowing reflexes.