Download
1 / 40
400 likes | 561 Vues
[week 1 Introduction] How we understand ‘human mind’ from the brain?. Jaeseung Jeong, Ph.D Department of Bio and Brain Engineering, KAIST. What is going to happen next?. The marshmallow experiment on deferred gratification.
E N D
[week1 Introduction]How we understand ‘human mind’ from the brain? Jaeseung Jeong, Ph.D Department of Bio and Brain Engineering, KAIST
The marshmallow experimenton deferred gratification • This study was conducted in 1972 by psychologist Walter Mischel of Stanford University. • A marshmallow was offered to each child. If the child could resist eating the marshmallow for 15 mins, he was promised two instead of one. • The scientists analyzed how long each child resisted the temptation of eating the marshmallow, and whether or not doing so was correlated with future success.
Follow-up studies of Marshmallow test • Mischel discovered there existed an unexpected correlation between the results of the marshmallow test, and the success of the children many years later. • The first follow-up study, in 1988, showed that "preschool children who delayed gratification longer in the self-imposed delay paradigm, were described more than 10 years later by their parents as adolescents who were significantly more competent". • A second follow-up study, in 1990, showed that the ability to delay gratification also correlated with higher SAT scores.
Failed children: low academic performance. SAT scores are 210 lower than students of success. Big difference in annual income in 30 years
How do we explain Marshmallow test results based on brain functions • A 2011 study indicates that the characteristic in Marshmallow test remains with the person for life. • Additionally, brain imaging showed key differences between the two groups in two areas: the prefrontal cortex (more active in high delayers) and the ventral striatum in Basal Ganglia (an area linked to addictions). [BJ Casey et al., (August 29, 2011). "From the Cover: Behavioral and neural correlates of delay of gratification 40 years later". Proceedings of the National Academy of Sciences 108 (36): 14998–15003.]
What are the differences in behaviors during the experiment between two groups of children?
Ability of self-control • Teaching children to pretend that a marshmallow was only a picture helped them resist the treat for much longer. • “If they imagine a picture, they can wait as if it were a picture.” • ‘Perception’ is really important for self-control.
SHOP experiment by Brian Knutson et al. • Knutson and his team have been putting subjects inside a magnetic resonance imaging scanner. • This technique is called functional MRI, and it's about watching the brain in action. In an important paper published last year in Neuron, Knutson's team identified by fMRI what he called a “hedonic competition between the immediate pleasure of acquisition and an equally immediate pain of paying.”
Where are more oxygen deliveredin the brain, activated regionsor non-activated regions?
The scanner works by measuring the blood oxygen level dependent (or BOLD) signal. When we think, ponder, evaluate, giddily anticipate or even fret, oxygen-carrying blood flows to particular brain regions doing the work.
The experiment of SHOP • Subjects were rolled inside the scanner, where they could see a small video screen that displayed products available for purchase—DVDs, books, games, small electronic devices. • After a short interval, the price of the product was displayed, and subjects could choose whether to make a purchase. • The scanner was activated during three distinct times: product presentation, price display and decision.
Outcomes of SHOP experiment • When the subjects thought about whether they wanted the product, the scanner showed that blood flow was increased to an area called the nucleus accumbens (NAcc), an area of the brain particularly receptive to dopamine, a chemical that promotes desire. • When the subject was evaluating the price, the medial prefrontal cortex (MPFC) became active; that's where humans tend to process value judgments, goals and other “executive function” information. • In addition, greater activity in an area called the insula, a region associated with unpleasant emotions and the anticipation of loss, was seen in the brains of subjects who decided not to make a purchase.
j Spike reception: EPSP, summation of EPSPs Spike reception: EPSP threshold -> Spike i Threshold Spike emission (Action potential) Brain is an information processor
Neuronal Oscillations • infra-slow: 0.02-0.1 Hz, • slow: 0.1-15 Hz (during slow-wave sleep or anesthesia) • Slow oscillation (0.2-1 Hz), • Delta (1-4 Hz), • Spindle (7-15Hz), • Theta (generated in the limbic system) • fast: 20-60 Hz, • ultra-fast: 100-600 Hz.
Important issues in this lecture • What is the marshmallow test? What are the difference between the children of success and failure for their attitudes and behaviors? What is the interpretation (and implications) of the results in terms of neurobiology? • What is the SHOP experiment of Knutson group? What are the implications of the results in this study? • What are the principles of fMRI and EEG: how to measure brain activations using these techniques. What are the advantages of the EEG over other neuroimaging methods?
