116 Lecture 12.S10

116 Lecture 12.S10 - CBNS 116 Lecture 12 - The Limbic...

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CBNS 116 Lecture 12 - The Limbic System Lecture notes by Todd Fiacco ASSIGNMENT: In Nolte read Chapter 23, “The limbic system”, pp. 594-605. FOR NEXT LECTURE: In Nolte read Chapter 24, “Formation, modification, and repair of neuronal connections”, pp. 616-626. TODAY'S LECTURE: The big picture: The limbic system is a collection of cortical and subcortical structures that is interposed between the hypothalamus and neocortex (especially multimodal prefrontal association cortex of the frontal lobe). This location is well suited to its function in serving as a “bridge” between autonomic impulses coordinated by the hypothalamus and voluntary “conscious” actions to respond to these homeostatic signals. Many include the hypothalamus as part of the limbic system; this is because the functions of the limbic system are heavily tied to hypothalamic functions due to the direct connections between these two structures. However, the limbic system is uniquely involved in two major functions to which it is primarily associated: learning and memory in the brain, and outward manifestations of emotions, especially fear, and emotional aspects of memory. The amygdala and hippocampus are the central components of the two major limbic subsystems that underlie these functions . The amygdala is one of the most heavily connected structures in the brain, having perhaps more direct connections to cortical and subcortical areas than any other single brain structure. This might explain the prominent role that emotions play in all aspects of our thought processes, both conscious and subconscious, affecting anything from everyday decision making, what we may or may not commit to memory, our reproductive drives, and even sculpting each of our unique personalities. The hippocampus may very well be the most heavily studied region in all of the brain, and is the centerstone of the most famous human lesion study of all time: the case of famous patient H.M., who had both hippocampi surgically removed in an effort to ameliorate epileptic seizures. While the severity of H.M.’s seizures subsided, he was no longer able to produce any new memories. This was the first scientific evidence demonstrating the importance of the hippocampus in learning and memory. Due to the important role that the hippocampus plays in neuroscience research, a separate lecture will be devoted to understanding its circuitry and physiology. The focus of this lecture will be on the amygdala.
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I. What structures make up the “limbic system”? [Lecture images part 3, slides 3-6]. A. The limbic lobe . The limbic system is characterized by a “border” (limbus) of cortex ( the limbic lobe ) surrounding the junction between the diencephalon and each cerebral hemisphere, first described by Paul Broca in 1878. Limbic cortex is an evolutionarily ancient type of cortex, also called paleocortex or archicortex consisting of only a few layers of cells. It actually occupies most of the surface of each cerebral hemisphere in
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116 Lecture 12.S10 - CBNS 116 Lecture 12 - The Limbic...

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