Our brain is a multilayered organ that contains billions of nerve cells and neurones that have been laid and organised into bundles, circuits and interconnecting pathways. Billions of connections, neurotransmitters and synapses that are dependent upon chemical reactions between each neurone to enable the electrical impulse to travel the nerves to the desired muscle group to effect action. More subtle brain activity is affected by chemicals called neuropeptides. Neuropeptides do not carry messages directly, but their purpose is to regulate the activity of other neurones. By doing, so they affect memory, pain, emotion, pleasure, moods, hunger, sexual behaviour and other basic processes. The networks in your brain are constantly changing in response to experience. New synapses and connections are formed and existing connections may grow stronger. Other synaptic connections may grow weaker and may even cease to exist if not used or stimulated.
Our brain function can be divided into two systems.
- The Central Nervous System: Our brain and Spinal Column
- The Peripheral Nervous System: All parts of the nervous system outside the brain and spinal column: including the Somatic Nervous System: which carries the message to and from the organs and skeletal muscles and the Autonomic Nervous System: that serves the internal organs and glands: it is self governing and controls the heart rate, digestion, perspiration. These two systems operate together to coordinate the body`s internal reactions to events in the outside world.
The Spinal Cord connects the brain to other parts of the body. It carries bundles of nerves that lead to the 31 spinal nerves of the peripheral nervous system. Further up, 12 pairs of cranial nerves leave the brain directly. Together, these nerves keep the entire body in communication with the brain.
Cerebral Hemispheres
The top section of the brain or the Cortex, is divided into the left and right cerebral hemispheres. They are joined by the Corpus Callosum which is a thick fibrous band of connective neural tissue, allowing one side of the brain to communicate with the other.
The Left Hemisphere is responsible for language, speaking, writing and understanding. It is superior to the right hemisphere in performing the processes of mathematics, judging time and coordinating the complex movements for speech.
The Right Hemisphere is responsible for perceptual skills, such as recognising patterns, faces and melodies, putting together puzzles, or drawing a picture. It also helps you express emotion. Although the right hemisphere is restricted in most language function, it is active in the evaluation and appreciation of humour, irony and sarcasm. It helps us with the subtleties of pragmatic language function.
The Frontal Lobes: Are associated with higher mental abilities and plays a role in self control, emotion and personality.
It contains the motor cortex that directs the body`s muscles and a specific area called Brocha`s area that controls, language on the left side. The Premotor Cortex is responsible the sequential integration of movement patterns of speech.
The Parietal Lobes are located at the top of the cortex and are responsible for touch, temperature and pressure.
The Temporal Lobes are located on each sides of the brain. They are responsible for the reception and processing of incoming auditory information. An associated area of the temporal lobe is Wernickes Area. This important area lies within the left side temporal lobe. If damaged, the individual may hear the word but may lose its meaning. Subsequently their expressive speech may be jargon in nature, as they are not monitoring what they are saying.
The Occipital Lobes are located at the back of the brain and are primarily concerned with vision, visual perception and visual memory. A tumour or haemorrhage in this region may cause a visual agnosia. Agnosia is an inability to recognise common objects, and faces. The patient may describe the parts of the object or picture but is unable to integrate the parts into a whole.
Subcortex
These areas are within and underneath the brain. These essential areas are vital for life. They include the areas that flower upwards from the spinal cord:
- Medulla: Reflex control, heart rate, breathing and swallowing
- Pons: Acts as a bridge between the medulla and other brain areas. Influences sleep and levels of arousal
- Cerebellum: Regulates posture, muscle tone and the coordination of all muscle movements. The cerebellum also stores memories related to habits and skills
- Reticular Formation: Lies inside the medulla and brain stem. As messages surge into the brain, the R.F. gives priority to some and disregards others. It doing so it influences attention. It also modifies outgoing messages to the body that effects muscle tone, posture and movements of the eyes, face, head, body and limbs. It also controls reflexes involved in breathing, sneezing, coughing and vomiting.
- Thalamus: Acts as the final switching station of sensory information on its way to the cortex. Vision, hearing, taste and touch all pass through this area. The thalamus is a control centre for emotions and basic motives. Damage to this area can cause loss of any of our senses except smell.
- Hypothalamus: Laying just under the Thalamus, exerts powerful control over eating, drinking, sleep cycles, body temperature and other basic motives and behaviours. It influences the pituitary gland (the master of all the endocrine glands). It is a crossroads that connects many other areas of the brain. It is the final command post where many behaviours are organised, decided upon and verified before messages leave the brain causing the body to react.
- Limbic System: Consists of the hypothalamus, parts of the thalamus, the amygdala and the hippocampus. It has a major role in producing emotion and emotive behaviour. Laughter has its origins in the Limbic system.
- Amygdala: The amygdala has control of fear and anger. The amygdala provides a primitive quick pathway to the cortex, necessary for survival, i.e.: fight or flight response in both humans and animals.
- Hippocampus: is important in the formation and management of memories. It lies inside the Temporal lobes and helps us navigate through space, especially on the right side.
Our brain is a vast information processing system, capable of growth and change when damage occurs. My years of experience in assessing, diagnosing and treating adult acute brain injury and streaming into adult rehabilitation, was both challenging and rewarding. In this environment, communication and swallowing disorders have as their basis a cognitive/ neurological origin. Understanding and appreciating how the brain is constantly revising its circuits and pathways to changing experiences and damage, gives hope to not only the patients, but the clinicians who are stimulating and encouraging the return of function.
Mr Craig Gorman
Speech Pathologist
Melbourne Speech Clinics
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