Transcript No Slide Title

NEUROSCIENCE OF
DECIDING, CHOOSING & ACTING
For Psychology 216, Fall 2009
Freedom is not some extra feature or characteristic (see Smullyan, Is God
a Taoist).
Freedom from determinism is not necessary for social and legal responsibility. Although, some
are arguing that neuroscience should change the legal system.
“Cognitive neuroscience, by identifying the specific mechanisms responsible for behaviour,
will vividly illustrate what until now could only be appreciated through esoteric
theorizing: that there is something fishy about our ordinary conceptions of human action
and responsibility, and that, as a result, the legal principles we have devised to reflect
these conceptions may be flawed.”
– Greene & Cohen (2004) For the law, neuroscience changes nothing and everything. Philos
Trans R Soc Lond B Biol Sci. 359:1775-1785.
“Brains do not commit crimes; people commit crimes. This conclusion should be selfevident, but, infected and inflamed by stunning advances in our understanding of the brain,
advocates all too often make moral and legal claims that the new neuroscience does not
entail and cannot sustain.”
– Morse (2006) Brain Overclaim Syndrome and Criminal Responsibility: A Diagnostic Note. Ohio
State Journal of Criminal Law 3:397-412
Goal of this presentation is to consider whether a sufficiently enriched compatibilism
can be achieved from the marriage of law, philosophy, psychology and neuroscience
to provide useful leverage on questions of criminal responsibility.
But this requires agreeing on what we mean by “decision”, “choice”, “intention” and
“action”.
Definitions
• Choice – action in the context of alternatives to satisfy a goal, desire
or preference
CoffeeCoffee!
or tea?
• coffee or tea?
• choices take time
• Action – anything we do
• Actions have reasons - “I did”
• Events just have causes - “It happened”
• Reasons for actions are explanations in terms of purposes, i.e., intentions
• A particular movement may be intentional under one description but not
under another
• e.g., a wink or a blink
• Decision – deliberation when alternatives vague, payoffs unclear or
habits reversed
• New Guinea Peaberry or Bella Vista F.W. Tres Rios Costa Rica?
Characteristics of decision
Unlike choices, decisions cannot be predicted. The source of
decisions is inaccessible to introspection.
"I feel that way right now. Ask me in two or three months
and I may change. I don't think I will. I'm pretty sure
that's my decision."
— Michael Jordan on his retirement from professional
basketball. Associated Press, 17 July 1998
“I look forward to playing and hopefully I can get to that
point where I can make that decision.”
— Michael Jordan on his anticipated return to
professional basketball. Associated Press, 19 July 2001
Refining definition of decision
Distinguish two meanings
(1) As quantitative rules describing behavior (Game theory, Economics)
• But average measures of outcome do not specify mechanism
(2) As process producing behavior
• Mechanism with a particular architecture
• Plausible mechanisms can be modeled mathematically, e.g.,
biased choice theory, signal detection theory
diffusion, random walk
EBRW, ITAM, TVA
Decision as process has two distinct meanings
(1) Decide to
• Alternative actions
• Can be identified with choosing
• Good/bad but not true/false
(2) Decide that
• Alternative categories
• True/false
Now that we have the philosophical issues sorted out, how
does the brain work?
In particular, what is the link between neural causes and intentional reasons?
For “lower” animals and reflexes the mapping of brain state to behavior is
one-to-one
For higher mammals the mapping of brain states to
behavior (and mental states?) is many-to-one.
This is how neural causes can coexist with
intentional reasons.
What are “brain states”?
Systems
Circuits
Cells
Channels
The goal of cognitive neuroscience is to understand how
mental processes (like deciding what to do) come from
events in the brain.
Channels in the membrane don’t decide.
No single neuron decides.
10 neurons don’t.
Do 100?
1,000?
1,000,000?
1012 must because that is how many neurons are in your brain!
An experimental system
How does the brain
choose where to look?
How does the brain
control when to move?
How does the brain
correct errors?
V er
10°
H or
2 sec
Are intentions “real”?
“The state of a man’s mind is as much a fact as the state of his digestion” (Lord Justice Bowen in Edginton v.
Fitzmaurice, 1885)
To be real (physical), intentions must be supervenient on the brain. Specifying this relationship constitutes a
linking proposition which entails the following:
• bridge locus
• levels & signals – spikes, LFP, ERP, fMRI, etc.
• what is a brain state?
• Channels, neurons (glia), local circuits, modules, areas, global circuits?
• necessity of mathematical or computational model to translate between neurons and function
• e.g., interactive race model of countermanding performance (impulse control)
• many : 1 and 1 : many mapping of brain & behavior
• provides room for intentional reasons to coexist with neural causes
• “…every action begins with intention in the sense that intentions must be the immediate cause of those
bodily movements through which persons act for those movements to be actions at all” (p 2, M. Moore
2008). How does intention gain causal efficacy? Must trace path back from muscles to intention.
• “how” entails when + where
• when? >100 ms & <1,000-2,000 ms before movement
• where? anatomically before but connected with motor/premotor circuits, capable of
accomplishing what intentions must do (not motor, not sensory, memory + planning +
representing entails PFC)
• how? (a) When must explanation translate from neural to cognitive terms? (b) Scientific
explanation must account for Prob(move) & response time (both correct & error)
Teller DY. 1984. Vision Research 24:1233-1246
Schall JD. 2004. Ann Rev Psychol 55:23-50
How the brain chooses where to look
Response time
Neural activity
Choices are made when neurons resolve alternatives
0.0
0.1
Time from array presentation (sec)
0.2
Thompson, K.G., D.P. Hanes, N.P. Bichot and J.D. Schall (1996) Perceptual and motor processing stages identified in
the activity of macaque frontal eye field neurons during visual search. Journal of Neurophysiology 76:4040-4055
What if the alternatives are hard to distinguish?
Or the consequences are uncertain?
Look at the brighter of the two visual stimuli.
Correct earns $1,000.
Incorrect costs $1,000.
Earn
$1,000
Pay
$1,000
A procedure to probe the timecourse of decision process
Response time
Correct
Error
150
100
50
0
-100
chfefss1_4
Spikes/sec
Choosing target versus
choosing eye movement
0
100
200
300
400
Time from search array (ms)
Time from search array (ms)
Time from search array (ms)
Murthy A, Thompson KG, Schall JD. (2001)
Dynamic dissociation of visual selection from
saccade program-ming in frontal eye field. J
Neurophysiol. 86:2634
150
100
50
0
-100
chfefss1_4
• Different movements can
occur based on a single
representation of the world
Spikes/sec
One-to-many mapping
0
100
200
300
400
Time from search array (ms)
• If the brain
“knew” where the
target was, why
did it make an
error?
Time from search array (ms)
• Why do you say
things you don’t
mean? The mouth
moves faster than
the mind…
Time from search array (ms)
Neural Activity
Another network of neurons controls when gaze shifts
0.0
0.1
Time from stimulus (sec)
0.2
Hanes, D.P. and J.D. Schall (1996) Neural control of voluntary movement initiation. Science 274:427-430.
Many-to-one mapping
• The same eye movement can originate from different brain states
• An eye movement of a given direction can be evoked by activation of a
particular site in the superior colliculus or frontal eye field
• or by simultaneous stimulation of two different sites
+ 90 °
+ 60 °
0°
0°
-3 0 °
10 °
0°
A zim uth
2°
-6 0 °
5°
A zim u th
1 0°
20°
-9 0 °
E le va tion
E le vatio n
0°
+ 30 °
But what about errors?
The medial frontal lobe monitors consequences and conflict.
Error-related neuron activity
Error-related negativity
A ctivatio n (sp ike s/sec)
sto p s igna l
60
N o n -c an c ele d
e rro r
40
N o s to p s ig n a l
20
0
-2 00
0
200
40 0
Tim e F ro m sacc ad e (m sec)
Stuphorn V, Taylor TL, Schall JD (2000) Performance monitoring by
supplementary eye field. Nature 408:857-860.
100 200
300 400 500
Time from EMG onset (msec)
from Gehring and Fencsik, Journal of Neuroscience
21(23):9430-9437
Reconciling intentional reasons with neural causes
• If a given body movement can arise from different brain states, then the
dependence of behavior on intention can be explained in terms of the
representational content of the intention (reasons) and not its neural realization
as such (causes)
• A movement can be called an intentional action if and only if it originates from a
cognitive state with meaningful content which is the reason for the action
• The representation of a single focus of activation in the brain leading to an
eye movement of a particular direction can be distinguished from the
representation of two foci of activation leading to the same saccade through
averaging.
• But, the two mappings of neural representations onto saccades do not have
equal status.
• “Averaging” eye movements are maladaptive because they direct gaze to neither
stimulus; they are unintentional errors that must be corrected to achieve the goal of
vision.
• In contrast, an accurate saccade to one of the two stimuli would achieve the goal
of vision and more likely would be owned as intentional.
• Self-monitoring distinguishes “I did” from “it happened”
Where do we go from here?