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Chapter 2

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University of Guelph
PSYC 2650

Cognition – Chapter 2 Capgras Syndrome - Fully able to recognize people in their world, but utterly convinced that these people are not who they appear to be. They believe that their real son or real husband has been kidnapped (or worse). This person often insists that there are slight differenes between the “imposter” & the person they have replaced – changes in personality or appearance.  Facial recognition involves 2 separate systems in the brain; one leads to cognitive appraisal (“I know what my father looks like, & I can percieve that you closely resemble him”) & the other leads to a more emotional appraisal (“You look familiar to me & also trigger a warm response”). In Capgras syndrome the emotional processing is disrupted, leading to identification without the familiarity response. - Neuroimaging techniques allow researchers to take high-quality, 3D pictures of living brains. They can tell us about the physical makeup/structure of the brain.  In older studies PET scans were used for this reason, currently MRI scans are often used. - One damaged site in CS brains is in the temporal lobe on the right, which probably disrupts circuits involving the amygdala (serves as an “emotional evaluator” – helping detect threatening/dangerous stimuli as well as indicators of safety or rewards). - CS brains also have abnormalities in the frontal lobe, to the right of the prefrontal cortex. (The frontal lobe has been found to be active in planning & analyis, and much less active when dreaming or hallucinating)  With damage to this area, CS patients may be less able to keep track of what is real/sensible & what is not. - Also evidence that recognition of all stimuli involves 2 separate mechanisms – one hinging on factual knowledge & one that is more emotional. - Note that our understanding of Capgras syndrome depends on a mix of cognitive psych & cognitive neurosci, in which we test & confirm the hypothesis with. - CS can illuminate broader issues about the nature of the brain & mind (amygdala plays a part in helping people remember emotional life events or making decisions that rest on emotional evaluation).  Therefore this can give us clues about the processes underlying memory/decision-making. - CS also teaches us about how parts of the brain must work together for even the simplest achievement. The Study of the Brain - CS also illustrates that we need some technical foundations before we can develop theories about it. - The human brain is divided into the hindbrain, the midbrain & the forebrain.  The hindbrain sits atop the spinal cord & includes several crucial controlling functions (e.g. ensures rhythmic breathing & heartbeat). It also helps maintain posture, balance & the brain’s level of alertness. - The largest area of the hindbrain is the cerebellum: body movements, balance, spatial reasoning, sound discrimination, & integrating input from sensory systems.  The midbrain coordinates movements (precise eye movements), regulate the experience of pain, & contains circuits that relay auditory information from ears to processing/interpretation areas in the forebrain.  The forebrain is the largest & most interesting region. The cerebral cortex is a thin outer surface that constitutes 80% of the human brain because it is crumped into convolutions that allow it to cover less space. - Some of the grooves between wrinkles actually divide the brain into different sections. The deepest (the longitudinal fissure) runs from the front to the back of the brain & separates the 2 hemispheres. Other fissures divide the cortex in each hemisphere into 4 lobes. - The frontal lobes form the front brain (right behind the forebrain). The central fissure divides the frontal lobes on each side of the brain from the parietal lobes (the top). The bottom of the frontal lobes is marked by the lateral fissure, & below it are the temporal lobes. At the very back of the brain, connected to parietal & temporal lobes, are the occipital lobes. - Subcortical structures of the forebrain: - Thalamus: relay station for all sensory information going to the cortex. - Hypothalamus: directly beneath the thalamus, crucial role in controlling motivated behaviours such as eating, drinking, & sex. - Limbic system: surrounding both ^  made up of amygdala & hippocampus located beneath the cortex in the temporal lobe. They are essential for learning & memory. - The left & right structures in each pair have roughly the same shape & pattern of connections to the other brain areas. - The 2 hemispheres work together; this integration is made possible by commissures (think bundles of fibers that carry information back & forth between the 2 hemispheres). The largest of these is the corpus callosum.  A severed corpus callosum = split-brain. - Left brain: language, right brain: spatial judgement. - The hemispheres pool their specialized capacities to produce a seamlessly integrated single mental self (it is wrong to think that more “right-brain thinking” = more creativity). - Neuropsychology: the study of the brain’s structures & how they relate to brain function. - Clinical neuropsychology: understand the functioning of intact, undamaged brains by careful scrutiny of cases involving brain damage. - Lesion: specific area of damage. - CT scans (x-rays = 3D picture) - PET scans (tracer substance) - MRI (very detailed pictures including oxygen & blood flow to each region) – tell us where the event took place - Neurons get their electric pulse from their input end to their output end by en electrical pulse. The current of neurons is great enough to be detected by electrodes on the surface of the scalp (EEG) – tell us when the event to place  These all have their weaknesses, so they are often combined.  Another limitation is that many of these techniques only provide corelational data; therefore the supplementary data needed often comes from the study of brain lesions. - Transcranial magnetic stimulation (TMS) is useful because strong magnetic pulses cause a temporary disruption in the brain region & allows us to see what functions are compromised when a part of the brain tissue is non-functional. - Localization of function: aimed toward figuring out what’s happening where in the brain. The Cerebral Cortex - Enormous amount of information processing – greatest interest for cognitive psychologists. - Many regions divided into 3 categories: motor areas (brain tissue crucial for organizing & controlling bodily movements), sensory areas (tissue essential for organizing & analyzing the information we receive from the senses), & association areas (support many regions, specifically the act of “thinking”). MOTOR AREAS - Areas of the cortex serve as “departure points” for signals leaving the cortex & controlling muscle movement; other areas are the “arrival points” for information coming from the eyes, ears, & other sense organs. These are called primary motor projection areas (primary motor projection areas & primary sensory projection areas). - The motor projection area is tested by applying a mild electrical current to this area in animals, which causes specific movements depending on the site. These movements show a pattern of contralateral control – stimulation to the left hemisphere causes movement on the right side. - Projection areas form a sort of map – particular positions correspond with particular body parts. The motor projection area “map” is located on a strip of tissue toward the rear of the frontal lobe. SENSORY AREAS - Somatosensory area: located in parietal lobe, just behind motor projection area – information from your skin senses.  Patient reports tingling in a specific area if this region is stimulated. - Auditory area: in temporal lobes – primary projection area for hearing. If directly stimulated, the patient will head clicks, buzzes & hums.  An area in the occipital lobes is the primary projection area for vision; stimulation here produces the experience of seeing flashes of light/visual patterns. - The sensory projection areas differ from each other but they also have features in common which parallel the attributes of the motor projection area. In somatosensory, each area of the cortex is represented by a body part. Body parts near each other are typically nearby in the brain. In visual, each region of visual space has its own cortical representation & adjacent areas are the same in the brain. In the auditory area, different sound frequencies have their own cortical sites. - In each sensory map, assignment of cortical space is governed by function, not by anatomical proportions. - In sensory areas there are also contralateral connections – but not contralateral to body parts, it is contralateral with regard to physical space (like the visions or sounds coming from the left side are percieved by both eyes/ears, but processed by the right hemisphere). ASSOCATION AREAS - The remaining 75% of the cerebral cortex is referred to as the association cortex – these areas associate simple ideas & sensations to form more complex thoughts & behaviours. - Lesions in the frontal lobe cause apraxias, distrubances in the initiation or organization of voluntary action. Other lesions (occipital cortex or back of parietal lobe) lead to agnosias, difficulty identifying familiar objects. Visual agnosia – recognize something by touching it but not looking at it; auditory agnosia – recognize a face but not a voice. - Other lesions (usually parietal lobe) produce neglect syndrome – individual ignores half the visual world (only shave half of face, on eat half his plate, etc.) - Aphasia when lesions in areas near lateral fissure. - Damage to prefrontal area causes many problems, mainly with planning & implementing strategies, or difficulty inhibiting their behaviour or confusions.  * These clinical patterns make it clear that the so-called association cortex contains many subregions, with all working together in virtually all aspects of our daily lives. Brain Cells - A trillion neurons & many more glia (help guide development of nervous system in infants/fetus, support repairs if nervous system is damaged, maintain/control the flow of nutrients to the neurons & more). Specialized glial cells provide electrical insulation surrounding neurons – increases signal speed. May also constitute their own signaling system within the brain. - Cell body: contains nucleus & elements needed for metabolic processes. - Dendrites: “input” side, receive signals from other neurons - Axon: “output” side, sends neural impulses to other neurons. - When a neuron has been sufficiently stimulated, it releases a minute qua
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