Chapter 2- The Brain: An overview of structure and function

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9 Feb 2011

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PSYB57- Chapter 2- The Brain: An overview of structure and function
Increasing number of cognitive psychologists have become interested in the
functioning of the brain as the foundation for cognitive activity
One of the ongoing challenges for c.p. is developing and applying methods of inquiry
that can conclusively link cognitive processes to underlying neural activity
Goal of cognitive neuroscience is to determine how cognitive functions are affected by
damage to certain brain structures and whether its possible to recover cognitive
functions following brain injury due to strokes, disease and accidents
The brain grows from 0 to 350g during the prenatal period; the max. weight of the
brain is 1350g, which is achieved when the individual is about 20 years old
Structure of the brain
Phylogenetic division: hindbrain, midbrain, and forebrain
Hindbrain- develops originally as one of the 3 bulges in the embryos neural tube.
Structures within the hindbrain are most primitive. The brain stem (a structure
consisting of the medulla and pons in the hindbrain, as well as the midbrain and
certain structures of the forebrain) comprises about 4.4% of the entire weight of the
brain; the cerebellum comprises an additional 10.5%
The hindbrain consists of 3 major structures: the medulla oblongata- transmits
information from the spinal cord to the brain and regulates life supporting functions
such as breathing, heart rate, blood pressure, coughing, sneezing and vomiting. The
pons also acts as a neural relay centre, facilitating the crossover of information
between the left side of the body and right side of the brain and vice versa. It is also
involved in balance and in the processing of both visual and auditory information
The cerebellum contains neurons that coordinate muscle activity. It is one of the
primitive brain structures. It also governs balance and is involved in general motor
behavior and coordination
Brain lesions in the cerebellum can cause irregular and jerky motions, tremors and
impairment of balance and of gait. It has also been implicated in peoples ability to
shift attention between visual and auditory stimuli and in dealing with temporal
stimuli such as rhythm
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Midbrain- is located in the middle of the brain. Structures of the midbrain, such as
inferior and superior colliculus are involved in relaying information between other
brain regions, such as the cerebellum and forebrain
Another midbrain structure, the reticular formation, helps keep us awake and alert
and is involved in the sudden arousal we may need to respond to a threatening or
attention grabbing stimulus
Forebrain- the part of the brain containing the thalamus, hypothalamus,
hippocampus, amygdale and the cerebral cortex
Thalamus- switching station for sensory information; also involved in memory
Hypothalamus-controls the pituitary gland by releasing hormones; also controls
homeostatic behaviours such as eating, drinking, temperature control, sleeping,
sexual behaviours and emotional reactions
Hippocampus- involved in formation of long term memories
Amygdala- modulates the strength of emotional memories and is involved in
emotional learning
Cerebral cortex- consists of 6 layers of neurons with white matter beneath, which
carries information between the cortex and the thalamus or between different parts
of the cortex
The cortex is divided into 4 lobes: the frontal, parietal, temporal and occipital.
The left and right hemispheres are connected by the corpus callosum (In the case of
the frontal, parietal and occipital lobes) and the anterior commisure (in the case of
the temporal lobe)
Central sulcus divides the frontal and parietal lobes and the lateral sulcus divides
the frontal and temporal lobes
Parietal lobe contain the somatosensory cortex which is located in the postcentral
gyrus; involved in processing of the sensory information from the body (touch, pain,
pressure or temperature)
Occipital lobe processes visual information; temporal lobe processes auditory
information as well as ability to recognize certain stimuli such as faces
Damage to temporal lobes can result in memory disruption because the lobes are
right above structures such as the amgdala and the hippocampus
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The frontal lobes have 3 separate regions: motor cortex (in the precentral gyrus)
directs fine motor movement; the premotor cortex seems to be involved in
planning such movements. The prefrontal cortex is involved with executive
functioning (planning, making decisions, implementing strategies, inhibiting
inappropriate behaviours and using working memory to process information)
Damage to certain parts of the prefrontal cortex can also result in changes in
personality, mood, affect and the ability to control inappropriate behavior
The prefrontal cortex shows the longest period of maturation; it is one of the last
structures to mature and is the first to go in aging effects seen toward the end of
It is hypothesized that brain regions that show the most plasticity over the longest
periods may be the most sensitive to environmental toxins or stressors
Localization of function
Mapping of the brain; what brain region does what
Original idea of localization traces back to Gall, who believed in faculty
psychology- the theory that different mental abilities, such as reading or
computation, were independent and autonomous functions carried out in different
parts of the brain
Gall believed that different locations in the brain were associated with different
Galls student developed the study of phrenology- the idea that psychological
strengths and weaknesses could be correlated to the relative sizes of different brain
Major problems with 2 assumptions made about phrenology: 1) that the size of a
portion of the brain corresponded to its relative power and 2) that different faculties
were absolutely independent
We now know that different mental activities, such as attention and perception are
not wholly distinct and independent, but rather interact in many different ways
We also know that the overall size of the brain or a brain area is not indicative of the
functioning of that area
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