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Lecture 6

PHIL 101 Lecture Notes - Lecture 6: Visual Cortex, Absence Seizure, Blindsight


Department
Philosophy
Course Code
PHIL 101
Professor
Mc Lear
Lecture
6

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Distinguish three questions:
1. Why is consciousness (what is its nature)?
2. Why is there consciousness (what is its function)?
3. How could there be beings with consciousness (given assumptions about what
kinds of things there could be)?
The "Target Reasoning" Functions of Consciousness
Consciousness has a function
We can find out what the function of consciousness is by studying the cognitive
psychology of patients with specific cognitive impairments or abnormalities
Two Kinds of Abnormal Psychology
1. Blindsight
2. Epileptic Seizure
'petit mal' or 'absence' seizure
Blindsight Abnormal Psychology
Blindsight is a syndrome involving patients who have brain damage in the first stage of
visual processing, the primary visual cortex. These patients seem to have "holes" in their
visual fields. If the experimenter flashes stimuli in these holes and ask the patient what
was flashed, the patient claims to see nothing but can often guess at high levels of
accuracy, choosing between two locations or directions or whether what was flashed was
an X or an O (Block, 278).
Blindsighted patients lack consciousness (in some sense) of regions of their visual field but
have a better than chance ability to discriminate objects in those "blind" parts of the visual field
Absence Seizures
In such cases (of epileptic seizures), electrical disorder leads to a loss of function in the
higher brain stem… As a result the patient suffers a loss of conscious experience in the
phenomenal sense although he can continue to react selectivity to environmental stimuli
1. Abnormal psychological conditions, such as blindsight and "absent" seizures,
may indicate the function of consciousness
2. When consciousness is missing under such conditions, subjects cannot A) report
or reason about the relevant nonconscious representations, nor use them in guiding action
B) exhibit flexibility and creativity in their thought and action
3. Therefore, consciousness enables information represented in the brain to be
used in reasoning, reporting, and rationally guiding action
4. Therefore, consciousness promotes flexibility and creativity in thought and action
Confusion about Consciousness
A "Mongrel" Concept
The concept <consciousness> is a 'mongrel" in the sense that it is ambiguous between a
number of different and independent notions of being 'conscious'
1. Sentience- able to discriminate, categorize and react to stimuli
2. Wakefulness- awake and capable of attending to something
3. Autonomy- deliberate control of behavior
4. Introspection- internal accessibility of mental state
5. Communicability- reportability of mental state
6. Phenomenal Consciousness- 1st person experience- what its like to be
something
Two Kinds of Consciousness
Phenomenal Consciousness: A mental state with "experimental properties" that constitute
"what it is like" to experience something
A state is P-conscious if it has experimental properties
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