PSYC 211 Chapter Notes - Chapter 1-2: Motor Neuron, Unipolar Neuron, Cerebral Hemisphere

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24 Mar 2015
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Chapter 1 Introduction
Understanding Human Consciousness: A Physiological Approach
Animism: ancient belief that all moving objects have animating spirits that causes them to move
As people learned more about nature, they abandoned this approach in favour of physical explanations for
inanimate moving objects but still believed that something controlled human behaviour – a mind, soul, or
spirit.
Mind-body question: What role does the mind play?
-Dualism: belief that the mind and body are separate, where the body is physical and made up of
matter but the mind is not
-Monism: belief that everything consists of matter and energy, the mind is a phenomenon
produced by the workings of the nervous system
Consciousness: refers to how humans are aware of and can tell others about their thoughts, perceptions,
memories, and feelings
- Can be altered by changes in the structure or chemistry of the brain
- Communication may have given rise to the phenomenon of consciousness, our ability to send and
receive messages with others enable us to do the same within our own heads, to think and be
aware of our own existence
Blindsight: shows that behaviour can be guided by sensory information of which we are unaware of,
perceptions do not have to enter our consciousness to affect our behaviour
The brain has several mechanisms involved in vision:
1. Primitive: resembles that of fish and frogs, evolved first, responsible for controlling eye and hand
movements and drawing attention to sudden movements occurring off to the side of the vision
field,
2. Mammalian: more complex, evolved later, responsible for speech and thinking (in words) and the
ability to perceive surroundings
In some people, if the mammalian visual system is damaged, they cannot see objects in his/her blind view
but can still accurately reach for them by using their primitive system
- Suggests that consciousness is not a general property of all parts of the brain: since the primitive
visual system evolved before the development of brain mechanisms linked to consciousness, it
does not have these connections and thus, we are not conscious of the visual information that it
detects
- Only the mammalian system has direct connections with parts of the brain responsible for
consciousness
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Split Brain: studies show that people who have undergone surgical procedures disconnecting parts of the
brain linked to perception with parts linked to verbal behaviour also disconnects them from consciousness
- Suggests that parts of the brain involved in verbal behaviour may be responsible for
consciousness
This procedure is used for people with severe epilepsy that cannot be controlled by drugs. In these
individuals nerve cells in one part of the brain become uncontrollably overactive and the over-activity is
transmitted to the other side of the brain. Both sides then stimulate each other resulting in an epileptic
seizure
-Corpus callosum: a large bundle of nerve fibres that connect corresponding parts of one side of
the brain with those of the other
-Split-brain operation: brain surgery that is used to treat epilepsy in which the corpus callosum is
cut, disconnecting the two hemispheres of the brain
Sperry and Gazzaniga 1966: studied patients with disconnected hemispheres
Cerebral hemispheres: two symmetrical halves of the brain which constitute the major part of the brain
- Receive sensory information and control movements of the opposite side of the body
- When disconnected: sensory mechanisms, memories, and motor systems no longer exchange
information
Because the left hemisphere is the only one that controls speech, people can only converse with that one
side. The operations of the right hemisphere are difficult to detect, those who have undergone the surgery
often feel as if their left hand (controlled by the right side of the brain) has a mind of its own
- i.e. when reading a book held in the left hand, a patient may put it down even if it is of interest
because the right hemisphere cannot read, patients may even make obscene gestures without
meaning to
The olfactory system: exception to the general rule in which sensory information crosses from one side of
the body to the opposite side of the brain
- If an odor is sensed through only the left nostril, the patient is able say what the smell is because
the information is received by the side controlling speech
- If an odor is sensed through only the right nostril, the right hemisphere can perceive and identify
the odor but the patient will say that he/she smells nothing because the left hemisphere which
controls speech has not sensed the odor
- This reinforces the conclusion that we become conscious of something only if information about
it is able to reach the parts of the brain (left hemisphere) responsible for verbal communication
Unilateral Neglect: a syndrome in which people ignore objects located toward their left and the left sides
of objects located anywhere, most often caused by damage to the right parietal lobe
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Parietal lobe:
- Concerned with the body and its position: receives information from the skin, muscles, joints,
internal organs, and parts of the inner ear (balance)
- Receives auditory and visual information
- Responsible for information about the movement and location of body parts with the location of
objects in space around us
This syndrome is not simply just blindness in the left side of the visual field, in fact individuals can see
things located to their left and can tell when a something touches their left side but ignore such stimuli
and act as if the left side of the world and of their bodies do not exist (are not conscious of them).
Volpe, LeDoux, and Gazzaniga 1979: presented patients with pairs of visual stimuli (one on the left side
and one on the right side), the patients report only seeing the right side stimulus but when asked whether
the two stimuli were identical, they answered correctly even though they were unaware of the left side
stimulus
- People with unilateral neglect must then be able to perceive more than just the right visual field:
to notice only the left side of objects, they must be able to perceive the entire object in order to
distinguish between the two sides
Bisiach and Luzzatti 1978: suggested that unilateral neglect extended to a person’s imagination
- Patients were told to describe the Piazza del Duomo (landmark in Milan) from both the north and
south end, patients could only describe the right side each time: showed that they could perceive
the entire piazza but could only visualize them when they were in the right side of their imaginary
visual field
Although most people with unilateral neglect show both types of symptoms (ignoring left side of
themselves and of objects), research shows that they are produced by damage to different regions of the
brain.
Perception of Self
Ehrssin, Spence, and Passingham 2004 studied the importance of the parietal lobe in feelings of body
ownership with the rubber hand illusion. Subjects had their right hand in view and left hand hidden which
was replaced with a fake one. Researchers found that if both the real and fake left hand were stroked
synchronously and in the same direction, the subjects began the experience the fake as their own. If the
hands were stroked at different times and directions, the subjects would not experience the fake as their
own.
- MRI scans during the experiment showed increased activity in the parietal lobe and then in the
premotor cortex: involved in planning movements, when subjects began to experience the fake
hand as real (activity not present if the stroking was uncoordinated)
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