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Chapter 2

Cognition chapter 2.docx

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University of Guelph
PSYC 2650
Dan Meegan

Chapter 2: The Neural Basis for Cognition (Page29-52, 64-72) Capgras Syndrome: An initial Example  Capgras Syndrome: Fully able to recognize the people in their world but is utterly convinced that these people are not who they appear to be. Most common in elderly. (People they love have been replaced by imposters) o What’s going on here?  According to some researchers, facial recognition involves two separate systems in the brain, one of which leads to a cognitive appraisal (“I know what my father looks like, and I can perceive that you closely resemble them”), and the other to a more global, emotional appraisal (“You look familiar to me and also trigger a warm response in me”).  The concordance of these two appraisals then leads to the certainty of recognition (You are my father).  In Capgras syndrome, the latter (emotional) processing is disrupted, leading to the intellectual indentification without the familiarity response. The Neural Basis for Capgras Syndrome  Neuroimaging techniques: Developed in the last few decades, that allow researchers to take high-quality, three-dimensional “pictures” of living brains, without any way disturbing the brain’s owners.  Some types of neuroimaging data provide portraits of the physical makeup of the brain (Through MRI scans)  These scans suggest a link between Capgras syndrome and abnormalities in several brain areas, indicating that our account of the syndrome will need several elements  One site of damage in Capgras patients is in the temporal lobe. This damage probably disrupts circuits involving the amygdala (serves as the emotional evaluator), helping an organism to detect stimuli associated with threat or danger.  With damaged amygdala, people wont experience the warm sense of feeling good when looking at a loved ones familiar face.  People with Capgras Syndrome also have brain abnormalities in the frontal lobe, specifically in the prefrontal cortex which is extremely active when a person is engaged in tasks that require planning.  fMRI: allows us to track moment by moment activity levels in different sites in a living brain.  With damage in the frontal lobe, Capgras patients may be less able to keep track of what is real and what is not, what is sensible and what is not. What do we learn from Capgras Syndrome?  Recognition of all stimuli involves 2 separate mechanisms: One that hinges on factual knowledge, and one that’s more emotional and ties to the warm sense of familiarity  The damage to the amygdala is probably the reason Capgras patients experience no sense of familiarity when the look at faces they know well.  The damage to the prefrontal cortex helps us understand why Capgras patients offer such crazy hypotheses about their skewed perception. The Study of the Brain  The human brain weights between 3 and 4 pounds; roughly the size of a small melon.  Contains a trillion nerve cells. Each of which is connected to 10,000 or so others—for the total of roughly 10 million billion connections.  Also contains a huge number of glial cells Hindbrain, Midbrain, Forebrain  Hindbrain: sits directly atop the spinal cord and plays an essential role in maintaining the body’s overall tone; specifically, the hindbrain helps maintain the body’s posture and balance, and it helps control the brains level of alertness. o The largest area of the hindbrain is the cerebellum. Damage to this organ can cause problems in spatial reasoning, in discriminating sounds, and in integrating the input received from various sensory systems.  Midbrain: Plays an important part in coordinating your movements. There are also circuits that relay auditory information from the ears to the areas in the forebrain where this information is processed and interpreted.  Forebrain: (Surrounds the entire midbrain and most of the hindbrain)  Cortex (Latin word for “tree bark”) refers to an organs outer surface, and many organs each have their own cortex. o Thin covering ob the outer surface of the forebrain. The cortex constitutes 80% of the human brain. It consists of a very large sheet of tissue (if stretched out, it would cover more than 2 sq ft). It is crumpled up and jammed into the limited space inside the skull. o Its this crumpling that produces the brains most obvious visual feature—the wrinkles, or convolutions, that cover the brains outer surface o Some of the “valleys” between the wrinkles are actually deep groves that divide the brain into different sections. The deepest groove is the longitundinal fissure, running from the front of the brain to the back, which seperates the left cerebral hemisphere from the right.  The frontal lobes form the front of the brain—right behind the forehead.  The central fissure divides the frontal lobes on each side of the brain from the parietal lobes, the brains topmost part.  The bottom edge of the frontal lobes Is marked by the lateral fissure, and below it are the temporal loves.  At the very back of the brain, connected to the parietal and temporal lobes, are the occipital lobes. Subcortical Structures  Underneath the cortex, are the subcortical parts of the forebrain. One of these parts, the thalamus, acts as a relay station for nearly all the sensory information going to the cortex.  Directly underneath the thalamus is the hypothalamus, a structure that plays a crucial role in controlling motivated behaviours such as eating, drinking and sexual activity.  Surrounding the hypothalamus and thalamus is the limbic system. Included here is the amygdala, and close by is the hippocampus, both located underneath the cortex in the temporal lobe. These structures are essential are essential for learning and memory Lateralization  All parts of the brain come in pairs  There are differences in function between the left side and the right ride structures.  Commissures: thick bundles of fibers that carry information back and forth between the 2 hemispheres.  The largest commissure is the corpus callosum  “Split brain patient” still having both brain halves, but with communication between the halves severely limited. Data from Neuropsychology  neuropsychology: the study of the brains structures and how they relate to brain function.  Clinical psychology: understands the functioning of intact, undamaged brains by careful scrutiny of cases involving brain damage.  A Lesion(specific area of damage) in the hippocampus produces memory problems but not language disorders; a lesion in the occipital cortex produces problems in vision but spares the other sensory modalities.  Damage to the left side of the frontal lobe is likely to produce a disruption of language use; damage to the riht side of the frontal lobe doesn’t have this effect Data from Neuroimaging  Computerized axial tomography (CT scans): study the brains structure. Rely on X-rays  Positron emission tomography (PET scans): study the brains activity. Start by introducing a tracer substance such a glucose into the body; the molecules o this tracer have been tagged with a low dose of radioactivity and the scan keeps track of this radioactivity, allowing us to tell which tissues are using more of the glucose and which are using less.  The computer reconstructs a 3 dimensional map of the brain. For CT scans, the map tells us the shape, size, and position of structures. For PET scans, the maps tells us what regions are active at any point in time  Magnetic resonance imaging(MRI): relies on the magnetic properties of the atoms that make up the brain tissue, and it yields fabulously detailed pictures of the brain.  Functional magnetic resonance imaging(fMRI): meausres the oxygen content in the blood flowing through each region of the brain. Picture of brains moment by moment activities. Data from Electrical Recording  Neurons do the brains main work  Neurtransmitters: Once a neuron is activated it releases the transmitter, and this chemical can then activate (or de-activate) other, immediately- adjacent neurons. This neuron receives this chemical signal and then send the signal onward to still other neurons  Process requires two types of communication: “between neurons” which involves what we just desciribes; and”within neuron: which is demanded by the fact that neurons generally have an input end and an output end. The input end is the portion of the nueiron that’s most sensitive to neurotransmitter. The output end is the portion of the neuron that releases the neurotransmitter, sending the signal on to other neurons.  How do neurons get the signal from one end of the cell to the other? o Electrical pulse, made possible by a flow of charged atoms in and out of the neuron.  This is the basis for electroencephalography-- a recording of voltage changes occurring at the
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