This is a very detailed summary on Chapter 9 - Agency & Free Will of the Consciousness book (S.Blackmore) Third Edition
If you read the summary you do not need to read the book
Basic question of free will: whether or not we are free to choose our actions and make decisions
- Whether consciousness has any role to play in our acting freely or feeling that we do
Religion:
- Threats and promises are meme-tricks which benefit religious memes by keeping people
hopeful or afraid
Main problems: (for free will and for its absence)
1) Determinism: i f the universe by deterministic laws - then everything is inevitable, no room
for free will, no point of doing anything
Modern Philosophers: non-compatibilists: argue that if the universe is deterministic, then free will
must be an illusion
Compatibilists: many and varied ways in which determinism is true and free will remain free
Widespread rejection of free will as a magical or supernatural force
2) Moral Responsibility: If I am not truly free to choose my actions, then how can I be held
morally or legally responsible for them ?
THE NEUROANATOMY OF VOLITION
While consciousness may feel as cause of voluntary action, when we look inside the brain we see a
lot of areas involved in carrying out the different phases of a voluntary action
Network of brain regions in the medial and lateral frontal cortex, & the parietal cortex => thought
to be related to ‘internally guided’ behaviour
Multiple areas of neural activity converge on primary motor cortex, which carries out motor
commands by sending signals through the spinal cord to your muscles
Externally triggered actions: activation in Cerebellum and Premotor cortex
Intentional actions: activity in Prefrontal regions:
- Supplementary motor area (SMA): sequence and program motor acts to fit motor plan
- PreSMA: m ay be source of early part of readiness potential (activity leading to muscle
movement) & anterior cingulate: emotions, pain & attention to, selection of, info needed
for action
- Broca’s Area: p roduces motor output for speech
Damage:
Dorsolateral prefrontal cortex: lack of spontaneous activity, and repetitive, stereotypic actions
Lesions in preSMA: prone to automatic actions in response to environmental triggers, as though
unable to stop themselves eating an apple they see in front of them, or putting on a garment
because it’s there.
Lesions of the prefrontal region and corpus callosum: can cause complaint of ‘alien hand’, in
which patients say that their hand has a will of its own
Corpus Callosum: produce anarchic hand syndrome: patient’s two hands fight to produce
opposite effects
Unconscious motivations measured:
Effects in basal forebrain - unnoticed stimuli around you affect your motivations
Long-term decision:
fMRI - ventromedial prefrontal cortex: involved in encoding goal values and activity in DLPFC:
modulated value signals when participants exercised self-control
, Volition modelled as a set of
decision processes that each
specify details of an action. The
decision whether to perform an
action has both early and motivated
component and a final predictive
check
Parts of the fronto-parietal network might be involved in this strategic aspect of the tasks, by
helping track the sequence of responses across trials in working memory
Attending to the intention led to stronger activation of the preSMA, supporting the ‘shared circuit
view’ that the same areas are involved in objective control and the subjec- tive experience of
control (but contrasting experiment no overlap)
THE HALF-SECOND DELAY IN CONSCIOUSNESS
Libet's - Half Second delay: half a second of continuous neuronal activity is required for
consciousness
Early experiments: sensory cortex of conscious, awake participants was stimulated with
electrodes, small part of skull cut so exposed somatosensory cortex and electrodes applied
- Result: patients reported definition conscious sensation of being touched on skin of hand
Using this - Libet found a minimum intensity below which no sensation is elicited no matter how
long the stimulation is
- This liminal intensity no experience was reported unless the stimulation continued for at
least an average of 0.5 sec. → shorter duration: intensity required to produce a reported
experience rose steeply
Sensory stimuli: normally produce an ‘evoked potential) in relevant areas of cortex by 10-20ms
after presentation
BUT libet found: single pulse applied to the thalamus or medial lemniscus (parts leading to
somatosensory cortex) can induce an evoked potential that appeared the same as the induced by
sensory stimulus
- BUT - single pulse never produced conscious sensation (regardless of its intensity and size
of the evoked potential)
Conclusion; Neuronal adequacy for conscious sensation is only achieved after half a second of
continuous stimulation in somatosensory cortex
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