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CHAPTER 19

Psychobiology - attempts to explain psychological phenomena in terms of their biological foundations. *Our small sample of psychobiological research includes the pioneering work of Karl Lashley and two illustrious psychobiologists he influenced—Donald Hebb and Roger Sperry. Karl Spencer Lashley (1890-1958)      

Born on June 7, in Davis, West Virginia. Only child His father was a businessman and politician, his mother was a school teacher University of West Virginia – undergraduate education University of Pittsburgh – graduate education Johns Hopkins University – received PhD in 1914, he also came under the influence of his professor, John Watsons in this University  1916 – he was interested in seeking the neurophysiological bases of conditioned reflexes. Ended collaboration with Watson but remained close friends  Brain activity is more like the Gestaltists’ description than the behaviorists’  Mass action - the cortex works as a unified whole - learning is distributed across all parts of the brain rather than stored in a single regions, with the degree of impairment proportional to the amount of brain that was damaged.  Equipotentiality - any part of a functional area of the brain could perform the function associated with that area. The brain acts as an integrated whole not as a mechanistic switchboard. Donald Olding Hebb (1904-1985)    

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Born on July 22 in Chester, Nova Scotia. Both of his parents are medical doctors Dalhousie University – received his BA with the lowest grade average a person could have and still graduate McGill University – graduate student in psychology in spite of his poor undergraduate performance (presumably because the chair of the psychology department at McGill was a friend of Hebb’s mother). He studied Pavlovian psychology at McGill and was convinced of its value. He received his Master’s degree in 1932. University of Chicago – he worked with Lashley. His initial concurrence with Pavlovian psychology was converted into outright opposition

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Harvard – obtained PhD(1936) after Lashley invited him. He remained there for an additional year as a teacher and research assistant. Montreal Neurological Institute(1937) – work with the illustrious brain surgeon Wilder Panfield. “Experience in childhood normally develops concepts, modes of thought, and ways perceiving that constitute intelligence. Injury to the infant brain interferes with that process, but the same injury at maturity does not reverse it.” Cell Assembly – every environmental object we experience fires a complex package of neurons. The neural interconnections in a newborn’s brain are essentially random. It is experience that causes this network of neurons to become organized and provide a means of effectively interacting with the environment. When a cell assembly fires, we experience the thought of the environmental object or event to which the assembly corresponds. Environmental objects do not need to be present for us to think about them. Reverberating neural activity – allows neurons that were temporarily separated to become associated. Phase sequences – temporally integrated series of assembly activities; it amounts to one current in the stream of thought. Just as the various neurons stimulated by an object become neurologically interrelated to form a cell assembly, so do cell assemblies become neurologically interrelated to form phase sequences. Phase sequence can be fired by internal or external stimulation or by a combination of the two; when one or more assemblies in a phase sequence fire, the entire phase sequence tends to fire. When the entire phase sequence fires, a stream of thought—a series of ideas arranged in some logical order—is experienced. Childhood learning involves the slow buildup of cell assemblies and phase sequences, and this kind of learning can be explained using associationistic terminology. Adult learning, however, is characterized by insight and creativity and involves the rearrangement of already existing cell assemblies and phase sequences. Childhood learning can be explained in terms of associationistic principles, adult learning is better explained in terms of Gestalt principles. Hebb’s idea was instrumental in the development of the newest and most influential form of artificial intelligence(AI). Arousal theory – relationship between level of activity in the small brain structure, called the reticular activating system (RAS), and cognitive and behavioral performance

Roger w. Sperry (1913 -1994)  

born on August 20 in Hartford, Connecticut. Orbelin College – received his BA in English(1935)

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University of Chicago – PhD in zoology (1941) After receiving his doctorate, Sperry studied with Lashley at the Yerkes Laboratories in Orange Park, Florida (1942–1946) The split-brain preparation – sperry pursued his interest in the routes by which information is transferred from one side of the cerebral cortex to the other. Sperry and his colleagues discovered two possible routes for such interhemispheric transfer—the corpus callosum (a large mass of fibers that connects the two halves of the cortex) and the optic chiasm. A brain that has had its corpus callosum and its optic chiasm ablated is referred to as a split-brain preparation. with split-brain preparation, a seizure begun in one hemisphere would not have a mechanism available to spread its influence to the other hemisphere and thus increase its intensity. They found that each hemisphere had its own characteristic range of cognition, memory, emotion, and consciousness Under Sperry’s leadership, research on the “left brain” and the “right brain” became very popular Jerre Levy, his one-time colleague oppose his idea. Levy emphasizes the point that in people with normal brains, the contributions of the two hemispheres to thought and behavior are inseparable. Levy concludes, “The popular myths are misinterpretations and wishes, not the observations of scientists. Normal people have not half a brain nor two brains but one gloriously differentiated brain, with each hemisphere contributing its specialized abilities. . . . We have a single brain that generates a single mental life”

New connectionism  

form of artificial intelligence (AI) Thorndike’s connectionism and new connectionism have in common the postulating of neural connections between stimuli (input) and responses (output).

Antecedents 

Hebb’s rule - If neurons are successively or simultaneously active, the strength of the connections among them increases. Hebb rule, continues to be applied even in the most recent systems.

Neural networks  

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New connectionism utilizes as its model a complex system of artificial neurons A system of input, hidden, and output units that is capable of learning if the mathematical weights among the units are systematically modified either according to Hebb’s rule or by back-propagation. 3 kinds of neurons in a neural network: input, hidden, output synaptical changes are simulated by modifiable mathematical weights, or loadings, among the units in the network

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GOFAI (Good old-fashioned AI / Parallel distributed processing - processes one sequence of information at a time in an if-then fashion; neural networks process several sequences simultaneously. processes symbolic information according to rules; neural networks process only patterns of excitation and inhibition expressed as mathematical weights within the system. This also known as “symbolicism”, for its attempt to describe intelligence in symbolic terms. Its basis is what has been termed the “symbol system hypothesis”, which states that it is possible to construct a universal symbol system, this is he claim that computers are the right kind of machines to think. A shortcoming of GOFAI, and its sequential processing of information, is that any disruption in the flow of information causes the entire system to fail.

Black-propagation systems   

Require a “teacher” to provide feedback concerning the program’s performance. Ex. NETtalk Words are fed into the system and their influence travels through the hidden units until they are coded into phonemes.

Behavioral Genetics 

branch of psychobiology that studies the genetic influence on cognition and behavior.

Ethology   

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branch of zoology ethos = habit, custom, character Ethologists typically study a specific category of behavior (such as aggression, migration, communication, territoriality) in an animal’s natural environment and attempt to explain that behavior in terms of evolutionary theory. Species-specific behavior - how members of various species typically behave under certain environmental conditions.

Sociobiology  

According to David Barash (1979, p. 10), humans possess a biogrammar that structures our social behavior, just as the innate rules of grammar structure our verbal behavior....