Lecture 23: Decision Making Flashcards
Theories of decision making
1) Theories of logic: cost-benefit analysis – feelings don’t matter (decision-making was only rational, did not depend on emotions)
➢Decision-making theorists assumed that risky decision making was
essentially a cognitive activity entirely lacking an emotional component. Ex: when you decide between studying doing an all nighter or getting some rest –> you will base your decision on your previous learning. When you are struggling on an exam, you will have an emoional feeling that will influence your future decisions, it will impact connectivity.
2) Other theorists highlighted the role of the affect experienced during the time of deliberation prior to making decisions, especially in situations where logic cannot be applied. This means that even before making your decision, emotion will play an important role in making that decision, in your deliberation.
➢Antonio Damasio formed the somatic-marker hypothesis in the 90s (revolutionary)
What part of the brain is associated with the somatic marker hypothesis (Bishara showed this)?
The ventromedial prefrontal cortex is associated with the somatic marker hypothesis that can explain decision making.
What is the hypothesis for the role of the VMPFC in decision making (the somatic marker hypothesis)?
- Emotional dysfunction and decision making problems of VMPFC patients led Antonio Damasio and colleagues to proposes that a defect in emotion and feeling plays an important role in impaired decision making.
- VMPFC patients do not seem to be able to link knowledge about a situation/specific outcome with emotional experience from the past.
We understand that is is maybe not about the emotional component per se, but it is maybe about the prediction. It is maybe about making the link between what we experience and the potential outcome of a decision.
What was Damasios argument to the role of the VMPFC in decisio making?
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Damasio argued that the decision-making deficits following VMPFC damage were due to
an inability to use emotion-based biasing signals generated from the body (or ‘somatic markers’) when appraising different response options (Damasio, 1996, 2004).- when our body experiences something that is positive or negative it will generate what we call a somatic marker.
- When making decisions, a crude biasing signal (a somatic marker) arising from the periphery (i.e. the body – soma) or the central representation of the periphery (i.e. the brain) indicates our emotional reaction to a response option. If you associate a specific stimulus with an emotion first, it comes from he body (we feel it) but with learning, when we see this stimulus we can predict that it will generate a reaction from our body so it can be generated in the brain.
➢For example, a knot in your stomach and sweating when you place a large bet at thecasino.
➢Butterflies in your stomach and increase in heart rate when you decide to ask your
crush out on a date - These signals can function at an overt level or at a covert level. You can be aware of them or unaware.
How can we explain the somatic marker hypothesis using neuroanatomy/neurophysiological processes?
Researchers think that the amygdala connects to the ventromedial prefrontal cortex and to the insula. And these regions will also connect to the brain stem and other sensory nuclei.
Important to remember that the amygdal, vmPFC and insula connect. And these 3 regions connect with the brainstem and body. This is what we call the body loop.
This schematic representation of emotional somatic signal is associated with when the somatic marker is driven by the body. When we learn, we do not need the body anymore, the “as if loop”. Here, the somatic marker is in the brain because it is driven by previous experiences which reward or punish. With learning, decision making will chance and will depend on usig this hypothesis on the somatic marker.
“An emotional/somatic signal derived from previous experiences with reward or punishment facilitates the
implementation of an advantageous choice under
conditions of uncertainty” (Bechara et al. 1996).
The ‘body loop’ vs the ‘as if’ loop
- Somatic markers can reflect actions of the body proper (the ‘body’ loop) or the brain’s representation of the action expected to take place in the body
(the ‘as-if’ loop). In other words, the brain can construct a forward model of changes it expects in the body, allowing the organism to respond more rapidly to external stimuli without waiting for that activity to actually emerge in the periphery. - These signals can function at an overt level (where the individual is consciously aware of the emotions and bodily changes associated with a particular response option) or at a covert level (where the individual is
unaware of his/her emotions and bodily activity).
the role of the VMPFC in decision making - patients with lesions to this part.
- According to Damasio, Bechara and colleagues, the VMPFC is central to the generation of these somatic markers.
- VMPFC patients have ‘myopia for the future’, where the individual is unable to predict long-term punishments and rewards based on previous emotional experience (Bechara et al., 1994). They are not able to predict their own reaction to their decision - cannot predict long-term punishement or reward based on previous emotional experience.
- How examined this experimentally? With the Iowa Gambling Task!
Somatic Markers Examples
I.e. somatic markers are changes in the body and mind:
* E.g. feeling positive/negative –> having butterflies in your stomach, feeling anxious
* feeling like you are about to “lose it”/”break down and cry” –> feeling elated and conquer the world, feeling angry
* + feeling your muscles (e.g. shoulders/neck/jaw/stomach) tense up/relax
* + representation of these states in different structures of the brain
Function of Somatic Markers
*Help our cognitive processes make decisions
*Help distinguish good (advantageous) choices from bad
(disadvantageous) choices
*Acquired from our previous experiences with rewarding (pleasant) and punishing (unpleasant) stimuli/events
Somatic Marker Hypothesis:
* Emotional (somatic) mechanism may indicate the potential consequences of an action
* and so help make an advantageous decision when selecting among different responses
Iowa Gambling Task (Methods)
The essential feature of this task is that it mimics real-life situations in the way it factors uncertainty, reward and
punishment (and have to forgo short term benefit for long-term profit)
➢Start with a 2000$ loan of fake money
➢Four decks of cards
➢Select any card in any deck
➢Every card brings reward (different $)
➢Some cards bring both reward AND penalty
➢Goal = maximize profit
In the course of the game, subjects learn:
* Deck A or B -> 100$ and high penalty
* Deck C or D -> 50$ and low penalty
*In the long term, decks A and B are disadvantageous
because they cost more, a loss of $250 in every 10
cards.
* Decks C and D are advantageous because they
result in an overall gain in the end, a gain of $250
in every 10 cards.
Iowa Gambling Task (results)
As the task progresses from the first to the 100th trial (i.e. 100 cards selected in total):
➢ Healthy controls gradually make more selections of
cards from the good decks (C and D) and fewer
selections from the bad decks (A and B). After a few trials (like 20) they will learn that it is best to pick C and D.
➢ Patients with lesions in other parts of the prefrontal
cortex, or in areas outside the prefrontal cortex, perform in a manner similar to that of normal subjects.
➢ In sharp contrast, patients with bilateral lesions of the VMPFC do not increase the number of their selection of cards from the good decks (C and D); they persist in selecting more cards from the bad decks (A and B). They do not learn. They will not understand tthat the highest punishment is associated with the worst decision.
Interpretation of Iowa Gambling Task results
What drives this behaviour?
* These results demonstrate that the VMPFC patients’ performance profile is comparable to their real-life inability to learn from their previous mistakes…
* What may be the underlying cause?
Skin conductance response
Skin conductance response: measuring the response of the skin during the task. Essentially, they were testing the somatic marker hypothesis.
* Three types of responses recorded:
(i) The reward SCRs, those occurring after turning cards with reward only.
(ii) The punishment SCRs, those occurring after turning cards with reward and punishment.
(iii) The anticipatory SCRs, those occurring before turning a card from a deck, during the time the subject ponders which deck to choose.
* When you make a decision, usually it is made based on evidence. This sensory information will guide you in your decision, as well as other factors (including the skin conductance response prior to decision making)
* Healthy controls and VMPFC patients generate SCRs as a reaction to reward or punishment.
* VMPFC patients have a specific impairment in their ability to generate anticipatory SCRs that signal negative consequences.
* Affects their decision making.
Skin conductance response
Do these anticipatory responses develop after
the healthy subjects knows which decks are
good or bad, or precede such explicit knowledge??
Are we conscious of what decks are good or bad? Yes, at one point we learned concsioulsy that I will chose the decks C and D (do we see these SCR before the moment we realize what deck we should chose, does the brain know things we are not aware of?)
- In another version of the experiment, every time a subject (healthy or patient) had picked ten cards, the game was stopped briefly and the subject was asked to
describe whatever they knew was going on in the game - The analysis of the healthy subjects’ answers suggested that they went through four distinct
periods across the task. - The VMPFC patients differed.
What are the 4 distinct periods during the Iowa gambling task
The four distinct periods:
1) A pre-punishment period, when subjects sampled the decks, before they encountered any punishment (measure your baseline)
2) A pre-hunch period, when subjects began to encounter punishment, but had no clue about what was going on in the game. The Skin conductance response has increased significantly. During the pre-hunch phase, the normal controls will choose the advantageous deck, even though they are nit aare of which deck is better. This can be explained by the SCR which is driven by the brain.
3) A hunch period, when subjects began to express a hunch about the decks that were riskier, even if they were not sure about their guess.
4) A conceptual period, when subjects knew very well which decks were the good ones, which decks were the bad ones and why.
→ Measured SCR during these phases, in relation to performance
The two different group of lesioned people in these experiments.
In these studies, they had two types of patients: patients that had more extensive lesions (Group A) and patients that have less extensive lesions (Group B).
Group A: we can see that even the regions in the forebrain are impacted. All the medial prefrontal cortex is lesioned compared to Group B.
Results from the emotional mechanism that improves memory.
- Repetition improved recall in both groups.
- Both groups demonstrated improved recall for emotionally charged images.
- In other words, VMPFC patients are able to use emotional content in order to enhance their memory,
suggesting that the mechanism through which emotion modulates decision making is different from that through which emotion modulates memory. - Conclusion is that patients with VMPFC damage can perform the task, they have this advantage for emotional pictures. So wehen you have an additional lesion to the basal forebrain, you are not able to perform correctly on memory tasks. So there is a dissociation between emotion and decision making.
- Emotional mechanism can bias decision making, but they are distinct from emotional mechanisms thatt improves memory
Brodmann areas to know
Decision Making and Working Memory are Distinct
Operations of the Prefrontal Cortex –> Delay Response Task
There is one memory card task where therre is four cards. Some of them are faced up, some of them are hidden and then. Afterwards, you have to identify which one were hidden and which one were faced up. There is a delay because you are using your working memory.
Results from delayed response task and decision making task (gambling task)
- Only those VMPFC patients (4) who had damage
that extended posteriorly to the basal forebrain
showed working memory impairment. - VMPFC patients with more anterior damage had
normal WM scores. - Only the patients with right hemisphere DLPFC
lesions were impaired on the working memory
tasks. All patients with left DLPFC frontal lesions
had normal working memory → nonverbal task
Basal forebrain
- The basal forebrain structures are located in the forebrain to the front of and below the striatum. They include the ventral basal ganglia (including nucleus
accumbens and ventral pallidum), nucleus basalis, diagonal band of Broca, substantia innominata, and the medial septal nucleus. - Involved in cortical arousal and attention – receives both cortical and amygdala inputs and projects to prefrontal cortex.
- so decision making and working memory are DISTINCT operations of the prefronntal cortex and we can see this in patients with VMPFC lesions.
