Early Ideas about Brain and Behavior

1. Early Ideas about Brain and Behavior

2. Mind, Brain and Behavior • Neuroscientists want to unify the science of the mind with the science of the brain. • Actions of the brain underlie all behavior. • What we call mind is a range of functions carried out by the brain. • Neural science explains behavior in terms of brain activities. • Where does psychology fit?

3. Where Does Mind Reside? • Which part of the body is the seat of the soul, the repository of memory? • Aristotle (384-322 B.C.) said the heart. • Hippocrates (460-379 B.C.) said the brain. • Galen (130-200 A.D.) agreed with Hippocrates: • Cerebrum vs cerebellum • Ventricles do the work

5. 19th Century Views • By the 1800’s, the nervous system had been completely dissected and gross anatomy described. • Injury to the brain disrupts functioning. • Brain communicates with the body via nerves. • The brain has parts that probably perform different functions. • The brain follows laws of nature and operates like a machine.

6. Understanding by Analogy • Metaphors have always been drawn from discoveries in the physical world: fluid mechanics, windmills, man as machine. • Modern analogies: • Mind as switchboard • Mind as computer

7. Discarded Theories • Fluid in ventricles, flow of humors • Galen • Body as machine explained by mechanics • Nerves as hollow tubes full of gas or fluid • Descartes • Nerves as “wires” • Galvani, du Bois-Reymond, Muller, Helmholtz

9. The Discovery of the Neuron • Golgi developed a silver staining method that revealed the cell body and projections of the neuron. • Ramon y Cajal used the technique to show that neurons do not quite touch. • Neurons are a network of separate (discrete) cells that communicate. • Galvani showed that the signaling is electric.

10. Nissl Stain Golgi Stain

11. Localization vs Distribution • Are specific functions carried out in specific regions of the brain? • Are functions an emergent property of brain activity as a whole? • Today’s neuroscience still debates this. • The answers appear somewhere between the two extremes.

12. Two Alternative Views • Cellular connectionism: • Individual neurons are the signaling elements of the nervous system, arranged in functional groups • Supported by empirical observations of Ramon y Cajal, Wernicke, Jackson, Sherrington. • The aggregate field view: • All regions of the brain participate in all mental functions. • Mind is NOT completely biological

13. The Localization Debate • Gall – the brain consists of 35+ organs corresponding to mental faculties. • Observable through bumps on the head. • Phrenology – anatomical basis for personology • Flourens – “…all perceptions, all volitions occupy the same seat…” • Aggregate field view • A reaction against strict materialism (mind not completely biological).

15. The Discovery of Localization • Imaging techniques that show the brain in action confirm that certain functions are carried out in specific areas of the brain. • This was difficult to see early on because of parallel processing • Each function is subserved by more than one neural pathway. • When one pathway is damaged, others may compensate, making localization harder to see.

17. Support for the Field View • Lashley found that the greater the lesions, the greater the impairment in functioning. • No matter where lesions were made, learning was impaired. • Mass action -- brain mass, not specific regions was most important to functioning. • Maze learning involves multiple functions, so it is unsuitable for studying localization.

18. The Current View • Functions consist of multiple processes that occur in specific areas of the brain. • Imaging studies reveal the different processes, called elementary operations. • Processing is both serial and parallel. • Even the simplest mental activity requires coordination of processes in multiple areas of the brain. • Such processing appears introspectively seamless.