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THE HUMAN BRAIN
The human brain sits at the top of our living caduceus, controlling bodily functions in near perfect homeostasis. As the body's command centre, it is jealously guarded, 'floating' in a nourishing and protective sea of Cerebro Spinal Fluid (CSF), bounded by the meninges - the dura mater (which means literally - 'Strong Mother'), the sub-arachnoid space and the pia mater, and of course the hard casing of the human skull.
Nevertheless, even a slight blow to the head from any angle can potentially cause substantial damage to the delicate nerve fibres and neural networks that form our functional and thinking patterns.
Obtaining a general
understanding of the brain and its functions is important to understanding the
rehabilitation process in any presenting difficulty. It is very important,
however, to understand that rehabilitation concerns the whole person not
just the 'affected part'. The identification of an individual problem simply
gives the therapist areas in which to focus treatment plans designed to work
toward the rehabilitation/rebalancing of the whole person. Each problem
area affects other areas. Resolving one problem often has a major impact on
other problems. For example, reestablishing postural balance and eliminating
dizziness greatly enhances concentration and attention, which allows for
improved cognition and problem solving.
The Basic Divisions of the Human Brain.
Diagrammatic Sagittal Detail.
Dysfunction or injury to the
brain may occur in a specific location, or may be diffuse (many different
locations). Difficulties resulting from brain dysfunction include:
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Visual illusions - inaccurately seeing
objects.
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Word blindness - inability to recognize words.
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Difficulty in recognizing drawn objects.
- Inability to recognize the movement of an
object (Movement Agnosia).
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Difficulties with reading and writing.
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Short term memory difficulties
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Personality changes and/or emotional lability
FRONTAL LOBES (or Prefrontal cortex): Located at forehead above eyes.
The frontal lobes receive input from various neocortical regions including the dorsomedial thalamic nucleus, and the parietal association
cortex. The prefrontal orbital cortex, however, receives fibres
from the pars magnocellularis of the mediodorsal thalamic nucleus, and from the mesencephallic recticular
formation as well as from limbic structures. In this way the prefrontal cortex
appears to receive information about all sensory modalities and also about
motivational and emotional states of the individual. There are strong efferent
connections to the motor and pre motor cortex, the basal ganglia and the
caudate nucleus. Orbital-prefrontal regions send fibres
into the hypothalamus, subthalamus, septum, mesencephalon and the pons.[11.]
Functions associated with the
frontal lobes:
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Conscious thought
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Concentration
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Perseverance
- Judgement
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Attention span
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Impulse control - self monitoring and
supervision
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Problem solving
- Organisation
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Critical thinking
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Forward thinking
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Ability to feel and express emotions
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Empathy
Decreased activity in the
prefrontal cortex is a finding often cited in people who have cognitive
difficulty, such as in schizophrenia or major depression. Abnormal frontal
activity is a major factor in ADD & ADHD. The prefrontal cortex is involved in mediating
concentration, impulse control and critical thinking.
The Cingulate System:
At the top of the brain, in
the middle of the frontal lobes is an area of the brain termed the "cingulate gyrus". It is the part of the brain which allows you to shift your
attention from thing to thing, to move from idea to idea, to
see the options in life. Feelings of safety and security have also been
attributed to this part of the brain. The term that possibly best relates to
this part of the brain is 'cognitive flexibility'.
Functions of the Cingulate System:
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Allows shifting of attention
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Helps the mind move from idea to idea
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Allows the mind to see options
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Cognitive flexibility (helps you go with the
flow)
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Adaptability
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Ability to cooperate
Increased activity in the top,
middle portions of the frontal lobes is frequently cited as a finding in
obsessive-compulsive disorder, a condition where people become
"stuck" on certain thoughts or behaviors. Aggressive people often
become "stuck" on real or imagined injustices and think about them
over and over. Oppositional, and addictive behaviours are also evident. Chronic pain, eating disorders
and road rage appear to accompany cingulate
dysfunction.
TEMPORAL LOBES:
Located at sides of head above ears, the temporal lobes form the wings of the
soul of our living caduceus.
Functions:
The dominant side is usually
the left hand side and governs-
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Hearing ability
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Understanding and processing language
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Memory aquisition -
particularly long term memory
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Some visual perceptions
- Categorisation of objects.
The nondominant
side or right side governs-
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Recognition of facial expressions
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Decoding vocal intonation
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Rhythm
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Music
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Visual learning
Observed Problems:
- Difficulty in recognizing faces (Prosopagnosia).
- Difficulty in understanding spoken words (Wernicke's Aphasia).
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Disturbance with selective attention to what
we see and hear.
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Difficulty with identification of, and
verbalization about objects.
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Short-term memory loss.
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Interference with long-term memory and amnesia
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Increased or decreased interest in sexual
behavior.
- Inability to categorise
objects (Categorisation).
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Right lobe damage can cause persistent
talking.
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Increased aggressive behavior.
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Dark or violent thoughts
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Religious or moral preoccupation
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Social skill troubles
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Emotional instability
- Hypergraphia (excessive writing)
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Periods of spaciness
or confusion
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Seizures
BRAIN STEM:
Located deep in the brain, leads to spinal cord. Often referred to as The
'Reptilian' or 'Primitive' Brain. The majority of the cranial nerves exit from
the brain stem at the pons.
Functions:
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Breathing
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Heart Rate
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Swallowing
- Reflexes to seeing and hearing (Startle
Response).
- Controls sweating, blood pressure, digestion,
temperature (Autonomic Nervous System).
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Affects level of alertness.
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Ability to sleep.
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Sense of balance (Vestibular Function).
Observed Problems:
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Decreased vital capacity in breathing,
important for speech.
- Swallowing food and water (Dysphagia).
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Difficulty with organisation/perception
of the environment.
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Problems with balance and movement.
- Dizziness and nausea (Vertigo).
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Sleeping difficulties (Insomnia, sleep apnea).
CEREBELLUM:
Located
at the base of the skull, and attached to the rear of the brain stem. It is
sometimes referred to as The Little Brain.
Functions:
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Coordination of voluntary movement
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Balance and equilibrium
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Some memory for reflex motor acts.
Observed Problems:
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Loss of ability to coordinate fine movements.
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Loss of ability to walk.
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Inability to reach out and grab objects.
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Tremors.
- Dizziness (Vertigo).
- Slurred Speech (Scanning Speech).
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Inability to make rapid movements.
LIMBIC SYSTEM:
Is
a group of cellular structures
located between the brainstem and the cortex. It is often
referred to as the mammalian brain.
Functions:
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Maintaining homeostasis - body temperature,
blood pressure, heart rate, blood sugar levels.
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Controls appetite and sleep cycles
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Strongly linked to emotional reactions that
have to do with survival.
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Sets the emotional tone of the mind
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Filters external events to internal states
(creates emotional colouring)
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Ear marks events as internally important
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Stores highly charged emotional memories
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Modulates motivation
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Promotes bonding
- Directly processes the sense of smell (which
is another reason why aromatherapy can be so effective)
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Modulates libido
The limbic
system has two key components -
the hypothalamus
(below the thalamus) and
the pituitary gland.
The hypothalamus regulates
eating, drinking, sleeping, waking, body temperature, balance and many other
functions. Through a combination of electrical and chemical messages, it
directs the pituitary gland - the master gland of the body.
Problems with the limbic
system include:
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Moodiness, irritability and clinical
depression
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Increased negative thinking
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Negative perceptions of events
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Decreased motivation
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Appetite and sleep problems
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Increased or decreased sexual responsiveness
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Social isolation
The human brain has evolved
over time, and from the archeological records, it has demonstrated spectacular
growth in the past few million years.
This growth, presumably in consciousness as well as size and capacity for creativity, allowed us to change the environment in which we live and our ability to make those changes is increasing. The problem lies in the fact that our ability to create always leaps ahead of our ability to adapt. Thus we are locked in a cycle of adapting to unprecedented situations.
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