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Lecture

Memory and Cognition- ch2.docx

12 Pages
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Department
Psychology
Course Code
PSY100H1
Professor
Pare, Dwayne

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Memory and Cognition Chapter 2 – The Neural Basis of Cognition Capgras Syndrome: An Initial Example - Damaging virtually anywhere in the brain will produce specific – and sometimes disruptive- symptoms - Capgras syndrome – this disorder is rare on its own, but accompanied with Alzheimer’s syndrome – result from various injuries to the brain - Are able to recognize the people in her world but if convinced that they are not who they appear to be o the real person has been kidnapped and the person on the scene is a well trained imposter - insist that there are slight differences between the real person and the imposter such as tiny changes in appearance - can lead them to desperate steps - have murdered the imposter in an attempt to end the charade and reloacate the real character - facial recognition requires two separate systems in the brain, one of them leads to cognitive appraisal (you closely resemble my father) and an emotional appraisal (you trigger a warm response in me) - in capgras the latter emotional processing is disrupted leading to the intellectual identification without the familiar response o you resemble my father but trigger no sense of familiarity, so you must be someone else The Neural Basis for Capgras Syndrome - neuroimaging techniques – allow researchers to take high quality, three dimensional pictures of living brains - these scans suggest a link between Capgras syndrome and abnormalities in several brain areas - one site of damage is the temperol lobe particularly on the right side of the head - disrupts circuits involving the amygdala, serves to be the emotional evaluator – detect stimuli associated with threat and danger - also important for detecting positive stimuli – indicators of safety and rewards - therefore people with capgras don’t feel the warm sense of feeling when looking at a loved ones face - also have brain abnormalities in the frontal lobe, specifically in the prefrontal cortex - Fmri – allows us to track moment to moment activity levels in different sites of the brain - The prefrontal cortex is active when a person is engaged in tasks that require planning or careful analysis o Is less active when someone is dreaming- this is why dreams are not logical and bizarre - With damage to 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 o Weird beliefs can emerge unchecked, including delusions What do we Learn from Capgras syndrome? - Some evidence comes from psychology labs and confirms the suggestions that recognition of all stimuli does involve two separate mechanisms - The damage to the amygdala Is probably the reason Capgras patients experience no sense of familiarity when they look at faces they know o In turn helps us understand the crazy hypothesis about their skewed perceptions - Our understanding of Capgras comes from both the cognitive psychology and the cognitive neuroscience – use both to test the hypotheses – can illuminate broader issues about the nature of the brain and the mind - The amygdala plays a role in decision making, especially decisions that rest on emotional evaluations of ones options – tells us that our theorizing needs to incluse a broadly useful “emotional evaluator” o Capgras tells us that this emotional evaluator works in a fashion separate from the evalution of factual information, providing us a way to think about the occasions in which someone’s evaluation of the facts point toward a conclusion, while the emotional evalution points toward a different conclusion - Capgras also tells us that the parts of the brain have to work together for the simplest achievement o To recognize your father:  Store memory on what he looks like  Another part responsible for the visual input you receive when looking at his face  Emotional evaluation of the input  Another site assembles all the data from the other sites, registers the fact that the face being suspected does match thte factual recollection of your fathers face and produces a sense of familiarity The Study of the Brain - Human brain weighs between 3-4 pounds, the size of a melon - Trillion nerve cells – roughly 10 million billion connections - Different parts of the brain perform different jobs – know this because the symptoms produced by brain damage depend heavily on the location of the damage ex. Phineus Gage Hindbrain, Midbrain, Forebrain - The hindbrain sits directly atop spinal cord and includes several structures crucial for life functioning - The hindbrain also plays an essential role in maintaining the bodys overall tone, the posture and balance, and it helps control the brains level of alertness - The largest area of the hindbrain is the cerebellum – damage to it can cause problems in spatial reasoning, in discriminating sounds and integrating the input from various sensory systems - The midbrain o Coordinates movement, precise movement of your eyes as you explore the visual world o Relays auditory information from the ears to the ares in the forebrain o Helps to regulate pain - Forebrain o Surrounds the midbrain and hindbrain o The cortex is the outer surface – consists of 80% of the human brain  Very large sheet of tissue, if stretched out would be 2 feet  The crumpling that produces the brains most obvious visual feature – the wrinkles, or convolutions that cover the brains outer surface  The valleys between the wrinkles are called grooves  The deepest groove is the longitudinal fissure running from the front of the brain to the back  Seperates the left cerebral hemisphere from the right  Other fissures divide the brain into four lobes  The frontal lobe – forms the front of the brain, right behind the forehead  The central fissure divides the frontal lobes on each side from the parietal lobes, the brains topmost part  The lateral fissure is the bottom edge of the frontal and below it are the temporal lobes  At the back of the brain connected to the parietal and the temporal is the occipital lobes Subcortical Structures - Found underneath the cortex - The thalamus acts as a relay station for nearly every sensory information going to the cortex - Underneath the thalamus is the hypothalamus – controls motivating behaviors such as eating, drinking, and sexual activity - Surrounding the thalamus and the hypothalamus – together form the limbic system o The amygdala, the hippocampus – underneath the cortex in the temporal lobe o Are essentially for learning and memory - People show more complex, longer lasting memories for emotional events, compared to similarily emotionally flat events – this is lost when the amygdala is damaged Lateralization - All parts of the brain come in pairs – there are differences in function between the leftside and the rightside structures with the left hemisphere structure playing a somewhat different role from the right hemisphere - The two halves of the brain work together, the functioning of one side is closely integrated with that of the other side – done by commissures – thick bundles of fibers that carry information back and forth between the two hemispheres o The largest one is the corpus callosum - When you break the corpus callosum – the two brain halves lose communication and you find that the right hemisphere is responsible for tasks such as spatial judgement and left for language capacities - The two hemispheres work together, with each providing its own skills which contribute to overall performance o Are NOT competitiors – but pool their specialized capacities Data from Neuropsychology - The study of individuals who have suffered brain damage whether through accident, disease or birth defect is called neuropsychology: the study of brain structures and how they relate to brain function - Clinical neuropsychology seeks to understand the functioning intact, undamaged brains by careful scrutiny of cases involving brain damage - A lesion in the hippocampus produces memory problems but not language disorders, a lesion in the occipital cortext produces problems in vision but spares the other sensory modalities - The consequence of a lesion depends on which hemisphere is damaged o Left side of the frontal lobe – disruption of language use o Right side of the frontal lobe – does not have the same effect Data from Neuroimaging - Use CT scans to study the brains structure and PET scans to study the brains activity o CT relys on X-rays and PET relys on tracer substance such as glucose - For both the primary data are collected by a bank of detectors surrounding the head; a computer then compares the signals received by each of the detectors and use this information to pinpoint the source of each signal - For CT tells us the shape, size, and postion of the structures within the bain - For PET show us what regiosn active at a particular time - MRI relies on magnetic properties of atoms that make up the brains tissue - Fmri – measures the oxygen content of blood flowing in the brain – accurate reading of neural activity in any region of the brain - CT and MRI are stable, FMRI and PET are highly variable, depend on what task the person is performing Data from Electrical Recording - The brain contains a trillion nerve cells – neurons- and the neurons do the brains main work - They communicate with each other via neurotransmitters - Two types of communication o One type: between neurons – a neuron releases the transmitter substance and this activates or de-activates another neuron o Second type: within neuron – neurons have an input end and and output end o The input end is the portion of the neurons that’s most sensitive to NT – where the signal from the neurons is received o The output is the portion of the neuron that releases the NT, sends it on to the other neurons o - How do they get the signal from one end to the other end o Made possible by the flow of charged atoms in and out of the neurons o The current generated by all of the together is great enough to be detected by sensitive electrodes placed on the surface of the scalp o Electroencephalography – a recording of voltage channels occurring at the scalp that reflect activity in the brain underneath o Electroencephalogram – EEG  Sometimes we want to measure the changes in EEG in the brief period just before, during and after the event – these are referred to as event-related potential The Power of Combining Techniques - Each of these research tools have there own strengths and weaknesses - Researchers deal with these limitations by means of strategy commonly used in science – seek data from multiple sources so that we can use the strength of one to make up for the shortcomings of the other o Ex. EEG tells us when the certain event took place and the Fmri tells us where the activity took place - These also only provide correlational data - Ex. Brain area called the fusiform face area seems to be active whenever a face is perceived o A different possibility may be just that the activation is a by-product of face perception and does not play a crucial role o Ex. Car speedometer becomes more activated when the car goes faster but this doesn’t mean that it caused the speed or is necessary for the speed o Its correlated with the car’s speed by in no sense causes the speed - We need other data to ask whether the brain site plays a role in causing that function … comes from studies in brain lesions … if it disrupts a function its an indication that it does play some role in its function - Transcranial magnetic stimulation - creates a series of strong magnetic pulses at a specific location on the scalp causing temp. disruption of brain region Localizaiton of a Function - Localization of function – the function of specific brain structures - Ex. Capgras – people with this had a damaged amygdala o Need to know the function of the amygdala – rely on data telling us that the amygdala is involved in many tasks involving emotional appraisal - “mental pictures” – how much do they have in common with ordinary seeing? o Localization data allows us to reveal overlap between the brain structures needed for the two activities – tells us that they have a great deal in command The Cerebral Cortex - Region where enormous amounts of information processing take place - Divided into the motor areas, sensory areas and association areas Motor Areas - Specific areas of the cerebral cortex – signals leave the cortex and control muscle movement - Other areas are arrival points coming from the eyes, ears, and other sense organs - Both together called the primary projection areas, departure points called the primary motor projection area and the arrival points the primary sensory projection area - Evidence for motor o Put mild electric current to this area in animals – caused specific movements o Show a pattern of contralateral control – stimulation of the left hemisphere produced movements in the right - Known as “projection areas” because they form maps of the external world o Particular postions of the cortex correspond to particular parts of the bosy or locations in space o Areas of the body that we can move with great precision such as the fingers or the lips have a lot more cortical area devoted to them Sensory Areas - Info form the skin sense is projected to a region in the parietal lobe, just behind the motor projection area; known as the somatosensory area - If stimulated report a tingling sensation in a specific part of the body - Ex. The “auditory area” – will hear clicks, buzz or hums - Each of these sensory areas provide a map of the sensory environment – each of the body’s surface is represented by cortical region on the cortex o Areas that are near to each other are similarly nearby in the brain o Ex. In the auditory projection are, different frequencies of sounds have their own cortical sites and adjacent brain sites are responsive to adjacent frequencies - The assignment of space is governed by function not anatomical proportions o Ex. Part of the body that are not discriminating with regard to touch get little area o Sensitive areas like that lips, tongue, fingers get more space o In occipital – more area given to the fovea – part of the eye that is sensitive to detail - Contralateral connections o The sensory areas in the left hemisphere receive main input from the right side of the body vice versa o Visual projection  Not contralateral with regard to body parts, contralateral with regard to physical space  The visual projection area in the right receives info from both the left and right eye but the info it receives corresponds to the left half of visual space – the same holds true for the left Association Areas - The motor and sensory make up only small part of the cerebral cortex – about 25% o The remaining area is referred to as the association cortex – associate simple ideas and sensations in order to form more complex thoughts and behaviors - The large volume of brain tissue can be subdivided into both functional and anatomical grounds - Some lesions in th
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