Brain and Behavior Chapter 1
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?
Understanding by Analogy Metaphors have always been drawn from discoveries in the physical world: fluid mechanics, windmills, man as machine. Discarded theories: Fluid in ventricles, flow of humors (Galen) Body as machine explained by mechanics Nerves as hollow tubes full of gas or fluid Vibrating “aetherial Medium”
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.
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.
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.
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).
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.
Organizational Principles Two hemispheres – left, right Each with four distinct lobes: Frontal – thinking, planning, control of movement Parietal – tactile sensation, body image, space Occipital – vision Temporal – hearing, learning and memory, emotion Each lobe has folds: Gyri (gyrus) – crests (flat areas) Sulci (sulcus) – grooves (areas folded in)
Organization (Cont.) Contralateral control: The left hemisphere controls the right side of the body. The right hemisphere controls the left side of the body. Sensory information from one side of the body is interpreted by the opposite brain hemisphere. Some brain functions are localized to a hemisphere.
Localization of Language Aphasia – a difficulty of language caused by brain injury (such as with stroke). Broca – described patients who can understand language but not speak. Results from damage to Broca’s area. Wernicke – described patients who can speak but not understand language. Results from damage to Wernicke’s area.
A Language Circuit Wernicke’s areas and Broca’s areas are part of a connected circuit for receiving and producing language. Wernicke predicted conduction aphasia – a disorder produced by breaking the connection between the two regions. Results in paraphasia – omitting and substituting parts of speech. Also, inability to repeat phrases.
Brodmann Areas Different areas of the brain with different functions have different kinds of neurons. Brodmann mapped the areas based on the kinds of cells found: Cytoarchitectonic method 52 functionally distinct areas identified by number.
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.
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.