The Effects of Brain and Spinal Cord Injuries on Behaviour
Research shows that the brain and spinal cord form the Central Nervous System (CNS) which controls all physical, cognitive and emotional behavior. The CNS also houses the Autonomic Nervous System (ANS). The ANS maintains life-supporting functions like heartbeat, blood pressure, respiration and digestion autonomically (automatically). The peripheral nervous system (PNS) is the network of nerve fibres and neurons that transmit motor control messages from the brain via the spinal cord to muscles allowing physical movement. Research further shows that injury to the brain or spinal cord will be reflected in a range of behavioural changes that range from minor interference in movement to total loss of all movement and possibly retardation plus extreme dependence on mechanical life support devices and human carers.
The brain is protected by the skull and is divided into two hemispheres. The hemispheres are connected by the corpus callosum, a thick bundle of nerve fibres that facilitate communication between the hemispheres. Each hemisphere exercises control over the opposite of the body, called contralateral control. The hemispheres also contain individual brain organs. The brain can also be divided into four sections, called lobes. Each lobe contains organs that deal with similar behaviours. The four lobes are the frontal, parietal, occipital and temporal lobe. Diagram 1 shows the division of lobes plus the cerebellum and brain stem which are also vital to sustaining life playing a role in the CNS, ANS and PNS. Following is a brief description of the behaviours dealt with by each lobe and how behaviours change if brain damage occurs including to the brain stem and cerebellum.
Diagram 1: (http://www.yourbrainattack.com/brain-functions.htm by Dr William Winslade)
The frontal lobe is responsible for: how we interact with our surroundings and react to our environment; the way we make judgments on our daily routines; emotional responses; the words we chose and how we assign meaning to those words; expressing language; the way we associate words to objects; and memory for habits and motor activities.
Damage to any part of the frontal lobe can result in: paralysis of various body parts; problems remembering the order of steps in sequential movement eg brushing teeth could result in rinsing mouth then putting paste on brush and putting brush away; difficulty interacting with others, mood changes, personality changes; loss of flexible thinking; stuck on one thought; unable to focus on a single task; loss of problem solving ability; and loss of ability to express language (Broca’s aphasia).
The temporal lobe is responsible for hearing, memory, visual perceptions and categorising of objects.
Damage to the temporal lobe can result in: problems recognising faces, called prosopagnosia; comprehension of spoken words called Wernicke’s aphasia; can’t focus selective attention to what we are doing (never complete the stroop test again); unable to talk about an object or identify it, or even say what sort of category it might belong to; short-term memory will no longer function properly, if at all; increase/decrease in sexual behaviour; may suffer persistent talking; and possibly an increase in aggressive behaviour.
The occipital lobe specialises in vision.
Damage to the occipital lobe can result in: sight may be patchy, problems with visual field cuts, or finding items located in the environment; inability to identify colour; may experience hallucinations, or visual illusions; have word blindness; inability to recognise drawn objects, or the movement of an object; and problems with reading and writing in general.
The parietal lobe deals with ability to locate something in the environment for visual attention; location for touch perception; voluntary goal directed movements; manipulating objects with our hands and fingers; also the centre in the brain where different senses all combine to allow for understanding a single concept.
Damage to the parietal lobe can result in: inability to focus visual attention; unable to attend to one object at a time; loss of ability to be shown an object and name it; can’t produce words from memory for writing; problems trying to read because inability to recognise the word; can’t draw objects; difficulty in distinguishing left from right, loss of awareness of certain body parts and the area surrounding them causing problems with self care; loss of ability to maths; inability to focus visual attention and problems with hand and eye coordination.
The brain stem is responsible for the autonomic nervous system (ANS). It provides control and monitoring of life sustaining processes such as breathing, respiration rate, swallowing, reflex action to things seen and heard; controls sweating, blood pressure, digestion, temperature; influences level of alertness; sleeping; and our sense of balance as we transfer weight walking, standing etc. The ANS maintains these functions without our conscious awareness.
Damage to the brainstem will result in: difficulty to breathe and control respiration rate without mechanical assistance, in fact life may be dependent on mechanical assistance; inability to swallow food/liquids; problems with perception of the surrounding environment, everything may seemed warped; no longer able to balance and move normally; dizziness and nausea; and sleeping difficulties.
The cerebellum controls coordinated and voluntary movement; balance and equilibrium; some memory for reflex physical movement.
Damage to the cerebellum will result in an inability to coordinate fine movements like playing the piano; no more walking; unable to extend arm and grasp objects, no rapid movements; constant tremors; dizziness; and slurred speech.
Disease can also occur and damage the brain. For example, Huntington’s disease is a degenerative disease of the entire brain. It starts with tremors of the arms called chorea and small facial ticks and slowly progresses over 15-20 years resulting in almost loss of movement as well as uncoordinated movement due to each part of the brain decaying including sequential movement. Cognitive functions and uncontrollable emotions such as increased aggression also occur and when the ANS becomes affected it can interfere with breathing and heartbeat resulting in fatality.
If the blood supply is interrupted to the brain either by rupture, or by blockage called a stroke this can result in death or leave a person with no movement on one side of the body. If the nerve damage is enough the person may suffer deformities in the face and twisted limbs. These are devastating behavioural changes and people who survive must endure long and hard rehabilitation in an effort to re-educate the brain trying to get the blood to flow through to other neurons that may bridge small gaps to improve their quality of life.
The spinal cord’s purpose is to extend the brain’s ability to send and receive messages and control to muscles and limbs. The spinal cord is a thick bunch of nerve fibres that run down the center of our back and is protected by the backbone. Two types of neurons line each side of the cord. Afferent neurons carry sensory information to the brain eg temperature, pain. Efferent neurons carry messages from the brain via the spinal cord to skeletal muscles allowing voluntary movement. If the spinal cord is damaged behavioural changes in physical movement will be impaired resulting from the brain’s inability to send and receive message from the damaged segment, or from the cord below the damage.
The backbone is made up of segments called vertebrae and they cover and protect the spinal cord. They can be divided into four sections of 7 cervical, 12 thoracic, 5 lumbar and 5 sacral-lumbar (5 fused vertebrae from the coccyx) shown at diagram 2. The first letter of each section and the number vertebrae form a reference system. A complete cut anywhere stops the brain from sending and receiving messages from the damaged segment and from that below. It is not surgically repairable. Rehabilitation can improve coping ability depending on the severity of spinal cord injury (SCI). Partial cuts to the cord will also result in behavioural changes. Injuries to the spinal cord do not affect thinking ability, or prevent someone from experience emotions such as the tragedy of losing all movement, or even partial movement.
Diagram 2 (http://www.sci-recovery.org/sci.htm)
Cervical spinal cord injuries (SPI):
SCI at C1–3 results in total loss of arm and leg movement. They can speak, swallow, and control head movement. They cannot cough or breathe without mechanical assistance. They have extreme dependency on life-support systems and human carers. Internal organ function will also be affected as physical movement aids the body’s ability to operate its digestive, waste systems and muscle tone.
People with complete C4 SCI: No arm or leg movement and situation is similar to that of C1-3 except problems with coughing and breathing may not be as severe. They may also still have neck and should movement and can operate an electric wheelchair by a chin driven device.
C5 SCI cannot move their trunk or legs. Limited movement of their arms, shoulders and elbows is possible but no finger or wrist movement. Due to loss of trunk muscles they will tire very quickly low endurance and not be able to take deep breaths. Assistance to cough is required and must wear a body brace in wheelchair. They will also experience problems with internal organ control and bowel and bladder control.
C6 SCI is similar to C5 SCI except they may be able to move
shoulders, bend elbows, and extend their wrists. They will tire quickly and have
difficulty taking deep breaths, may need help to cough. No finger control but can close hand.
C7–8 SCI does has lost movement of legs and trunk. They should be able to move their shoulders and bend and straighten their elbows and wrists, but have limited use of their fingers. Endurance is affected due to loss of their trunk muscles. Weakness in breathing and coughing. Can flex fingers and partially extend fingers. May have thumb movement.
Thoracic spine injuries usually result in lower limb paralysis.
T1–9 SCI: cannot move their legs; have varying degrees of trunk movement; weakness in breathing and coughing with higher thoracic levels of injury.
Thoraco-lumbar injuries usually result in lower-limb paralysis called paraplegia. SCI at T10–L1 SCI results in no leg movement, but will have good trunk movement. Sometimes walking is possible depending on severity of injury although body braces and assisting devices will need to be used. Wheelchair is still used frequently (electric) for this level of injury as arms may not be strong enough for manual.
Lumbar-sacral injuries usually result in partial lower extremity paralysis. SCI at L2–S5 SCI may have partial to full control of lower extremities involving
varying degrees of weakness of the hip, knee, ankle, and foot. Walking is possible although muscles may be weak, sometimes a walking frame may be used.
June 2009 Karen Williams - Neuropsychology student, ACS.