www.alzheimers.org.uk
The brain and behaviour
Alzheimer's disease is a degenerative condition associated with a progressive loss of nerve
cells or neurons. The disease gradually pervades most areas of the brain. However, the
evolving pattern of damage can vary greatly between different individuals. As a result, each
person with the disease may have a complex set of difficulties and experiences which are
peculiar to them. This information sheet explains which areas of the brain are largely
responsible for which skills and abilities, and how the changes in behaviour, memory and
thought we see in people with Alzheimer's may be a direct result of the way the disease has
affected the brain.
The brain consists of three main sections: the hindbrain, the midbrain and the forebrain (see
figure 1). The hindbrain and midbrain are mainly concerned with basic life support functions
such as blood pressure and respiration. In contrast, the forebrain is responsible for the majority
of higher brain functions such as memory and language.
The cerebral cortex
The most important part of the forebrain is the cerebral cortex, a thin shell covering the surface
of the forebrain. This thin layer is tightly crumpled and folded to increase its surface area. As a
result the cortex alone contains an astonishing ten thousand million brain cells (the 'grey
matter'). Beneath this densely packed cortex lie bundles of fibres (the 'white matter') which
transport information around the cortex and to other brain regions (see figure 3).
The lobes
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, www.alzheimers.org.uk
To help us describe the different parts of the brain, the forebrain has been divided up into four
sections or 'lobes' which are shown in figure 2. The occipital lobe is located at the back of the
brain and deals primarily with visual information from the eyes. The parietal lobe lies in the
upper rear portion of the brain and is concerned with information about spatial relationships
and structure. The temporal lobe lies beneath the parietal lobe and is involved in memory.
Finally, the frontal lobe can be thought of as our executive and management centre. We shall
discuss the functions of each lobe in more detail later.
The hemispheres
The brain is also physically divided into two halves or hemispheres, left and right. The
hemispheres are not entirely separate - they are connected by a large bundle of fibres which
allows them to talk to one another. While these hemispheres look almost identical from the
outside, one hemisphere is usually dominant over the other. In all right handed people and the
majority of left handed people, it is the left hemisphere which is dominant.
Organising principles
There are certain principles which appear to govern the organisation of the brain. The division
between the hemispheres signals one of these principles - lateralisation. Lateralisation literally
means that some functions are best performed by the left side of the brain, while others are
mainly supported by the right side. In the human nervous system, the left hemisphere controls
the right side of the body and the right hemipshere controls the left side of the body. Not all
functions are so equally shared though. For example, language tends to be a function of the
dominant hemisphere of the brain (usually the left side).
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The brain and behaviour
Alzheimer's disease is a degenerative condition associated with a progressive loss of nerve
cells or neurons. The disease gradually pervades most areas of the brain. However, the
evolving pattern of damage can vary greatly between different individuals. As a result, each
person with the disease may have a complex set of difficulties and experiences which are
peculiar to them. This information sheet explains which areas of the brain are largely
responsible for which skills and abilities, and how the changes in behaviour, memory and
thought we see in people with Alzheimer's may be a direct result of the way the disease has
affected the brain.
The brain consists of three main sections: the hindbrain, the midbrain and the forebrain (see
figure 1). The hindbrain and midbrain are mainly concerned with basic life support functions
such as blood pressure and respiration. In contrast, the forebrain is responsible for the majority
of higher brain functions such as memory and language.
The cerebral cortex
The most important part of the forebrain is the cerebral cortex, a thin shell covering the surface
of the forebrain. This thin layer is tightly crumpled and folded to increase its surface area. As a
result the cortex alone contains an astonishing ten thousand million brain cells (the 'grey
matter'). Beneath this densely packed cortex lie bundles of fibres (the 'white matter') which
transport information around the cortex and to other brain regions (see figure 3).
The lobes
Page 1
, www.alzheimers.org.uk
To help us describe the different parts of the brain, the forebrain has been divided up into four
sections or 'lobes' which are shown in figure 2. The occipital lobe is located at the back of the
brain and deals primarily with visual information from the eyes. The parietal lobe lies in the
upper rear portion of the brain and is concerned with information about spatial relationships
and structure. The temporal lobe lies beneath the parietal lobe and is involved in memory.
Finally, the frontal lobe can be thought of as our executive and management centre. We shall
discuss the functions of each lobe in more detail later.
The hemispheres
The brain is also physically divided into two halves or hemispheres, left and right. The
hemispheres are not entirely separate - they are connected by a large bundle of fibres which
allows them to talk to one another. While these hemispheres look almost identical from the
outside, one hemisphere is usually dominant over the other. In all right handed people and the
majority of left handed people, it is the left hemisphere which is dominant.
Organising principles
There are certain principles which appear to govern the organisation of the brain. The division
between the hemispheres signals one of these principles - lateralisation. Lateralisation literally
means that some functions are best performed by the left side of the brain, while others are
mainly supported by the right side. In the human nervous system, the left hemisphere controls
the right side of the body and the right hemipshere controls the left side of the body. Not all
functions are so equally shared though. For example, language tends to be a function of the
dominant hemisphere of the brain (usually the left side).
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