大脑的复杂性研究

王大辉

2011.07.22

2011 年北京师范大学系统科学暑期学校

Out line

Brain is the adaptive response to environment Building blocks of the brain Different philosophy about how the brain

works Time compensation as an example of the holism.

The computational research on decision making and working memory

Working memory Decision making

The primary response to and adaptation to the environment: the genetic DNA varies with the changes of environment.

Very slow (years, hundred years), many generations

Example: the origin of new species

Response to the invasion of bacteria, toxin and other organism in environment: the immune system.

Slow (hours, days, even months), in one generations

Example: cold

黄色中性粒细胞吞噬棕色炭疽热细胞人体淋巴细胞

Detection and response to the fast variation of the environment: the neural system.

Fast (milliseconds, second), in one generations

The neural system makes the animal detect and respond to the environment almost simultaneously. The occurs of the neural system is a tremendous progress of the evolution.

The evolution of the neural system

对称放射形神经系统 ( 水母 ) ，受到刺激后向任意方向运动。

线状的神经系统 ( 头尾结构 ) ，具有精确的头部和尾部可以限制选择同时也减少混淆外界信息。

在头部形成膨大的脑，对信息的快速收集和处理具有帮助

人脑适应性调整的三个阶段 基因，形成大脑和神经系统的蓝图，是

生物对生存环境的响应以及将来环境的预测。

生物诞生后，遗传物质根据经验作精细的调整，学会对付威胁和利用机会生存的技能

对某些瞬间的过程的适应，对瞬间发生的状况作出最佳的响应。

Building blocks of the brain

Macaque unfolded visual cortex

Wiring Diagram of the Visual System(Van Essen and Felleman)

Topographic Maps,:sensory system +somatarysome +motor system +basal ganglia

~80% of neurons in the cortex are excitatory “pyramidal cells”~20% of neurons in the cortex are inhibitory “interneurons”

Different philosophy about how brain works Reductionism: brain can be explained by breaking it down into smaller component parts

Behaviorism assumes that all behavior can be reduced to simple building blocks of S-R (stimulus- response) and that complex behavior is a series of S-R chains

Biopsychology - Explanations for the cause of mental illnesses are often reductionist. Genetics, and neurochemical imbalances are frequently highlighted, as being the main cause of these disorders. In the case of schizophrenia for example excess production of the neurotransmitter dopamine is seen as a possible cause. This view clearly has implications for treatment. Gender can also be reduced to biological factors (e.g. hormones). Also, language can be reduced to structures in the brain, e.g. Broca’s area, Wernicke’s area (but holism could state: influence of family, education, social class on language). Another example of biological reductionism is aggression – e.g. testosterone levels.

Structuralism – One of the first approaches in psychology. Wundt tried to break conscious experiences down into its constituent (i.e. basic) parts: images, sensations and feelings

Holism: approaches that emphasizes the whole rather than their constituent parts, the whole is greater than the sum of its parts

Social Psychology looks at the behavior of individuals in a social context Perception – This is were the brain understands and interprets sensory informatio

n. Visual illusions show that humans perceive more than the sum of the sensations on the retina.

Time compensation- how can players hit the fast moving tennis.

Speed of tennis: 200~225Km/h=56~63m/s Tennis court size: length~23.77m,width~8.23m

Signal from retina to cortex ~50-100ms Signal from cortex to foot ~20 ms the computation of cortex: longer time ~500ms

The intensive training, habitual learning (basal ganglia) shortens the reaction time to 200 ms

It is necessary that brain anticipates the future.

Working memory

PATRICIA S. GOLDMAN-RAKIC 1996 PNAS

PATRICIA S. GOLDMAN-RAKIC 1995 Neuron

Weiwei Zhang, Steven J. Luck 2008 Nature

Paul M. Bays, Masud Husain 2008 Science

A unifying account for the discrete-slot and shared-resource

models of WM capacity

A continuous network maintains multiple objects of an

analog feature as slots in WM

Two (fade-out and merging) dynamical phenomena underlie

limited WM capacity

Recurrent excitation and normalization explain dynamically

allocated shared-resource

Decision making

Roitman and Shadlen (2002),Gold and Shadlen (2007)

The simulation model

Xiaojing Wang(2002)

Mean field analysis

Kong-Fatt Wong and Xiao-Jing Wang(2006), Xiao-Jing Wang(2008)

The multiple choices decision making

Churchland, A.K., Kiani, R., and Shadlen, M.N. (2008).Moran Furman, Xiao-Jing Wang(2008)

Materials and Methods

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Unbiased decision making

Biased decision making

The noise plays an important role in the decision making

Behavior

Neural substrate

Neuronal behaviorNeuron interaction

Emergency

Theoretical approach

fMRI, fNIR

ElectrophysiologyElectrode recording

What

Why and How

Thanks for your attention !

The researches are supported by NSFC and Open Fund of NKCNL