04 Lecture 4 PSYB55 Cognitive Neuroscience PDF

lOMoARcPSD|10910327 04 Lecture 4 PSYB55 Introduction to Cognitive Neuroscience (University of Toronto) Studocu is not sponsored or endorsed by any college or university Downloaded by Armin Mollahajlou ([email protected]) lOMoARcPSD|10910327 Lecture 4 Perception Perception Being able to mak...

lOMoARcPSD|10910327 04 Lecture 4 PSYB55 Introduction to Cognitive Neuroscience (University of Toronto) Studocu is not sponsored or endorsed by any college or university Downloaded by Armin Mollahajlou ([email protected]) lOMoARcPSD|10910327 Lecture 4 Perception Perception Being able to make sense of sensory inputs. The job of the brain is to make sense of the neural signals to understand he world around  Vision/ olfactory/ audition/ touch From sensation to Perception Sensation The process of sensation is the ability of sensory receptors to detect and capture physical energy/input from the environment in an effort to better understand it.  Capture the information/signals (light sound, etc.)  Sensation: raw data is processed by sensory receptors – eyes, nose. Ears, skin, tongue, etc. Transduction The process of transduction is the ability to take physical energy from the environment, converting them into neuronal signals (ability to convert the physical energy/input into neural signals)  Converting the information into neural signal Perception The process of perception is sending those neural signals to the brain and decoding them to understand what you are sensing.  Decoding the information/signals (understanding what the sets of action potential are reflecting)  Sensations are processed in the brain Transduction The process of transduction is the ability to take physical energy from the environment, converting them into neuronal signals (ability to convert the physical energy/input into neural signals)  A variety of appropriate neuronal signals are being captured  Signals then be replied to he brain so they can be analyzed  The decoding of the signals – perception Each sense has an elaborate set of neural machinery designed to capture information with the greatest fidelity/quality possible Downloaded by Armin Mollahajlou ([email protected]) lOMoARcPSD|10910327 Gross anatomy of the eye For the perception of vision, it starts with the eye  Light information enters the eye and is refracted by the lenses of the eye, then sent to the back of the eye where the specialized photo receptors exist (retina)  The part of the retina that focuses on high acuity vision is known as the fovea.  The fovea is a highly specialized region of the retina. It is the spot of highest visual acuity in the eye and produces the sharpest vision and greatest color discrimination. The resolution or sharpness in vision is because of the high concentration of cone cells in the fovea.  Photoreceptions in the retina are being activated o Cones  Decodes for colors, and high quality (photoreceptors that are concerned with color and high visual quality processing)  Photopsin  Three types of cones, defined by their sensitivity to different regions of the visible spectrum  430 (blue), 530 (green), 560 (red)  Densely packed near the center of the retina, called fovea o Rods  Decodes for motion, and the peripheral vision and low light/dim lighting conditions processing (photoreceptors that care more about motion and processing the periphery)  Rhodopsin, pigments quickly become depleted hence cease to function, little user of the day  There are far more rods than cones, while they are distributed throughout the area Light passes from top to bottom. The light must pass through a variety of consolidation cell know as bipolar and ganglion cells (seen in blue and yellow in the above image) to reach the phot receptors. How is that possible? Wouldn’t that create some sort of shadowing, or problem in that location particularly since light has to travel through these consolidation cells? Well, these cells are translucent, meaning that the light can pass through them. The light can be capture appropriately by the consolidation cells so that we can appropriately construct an accurate image of what we are seeing. The consolidation cells consolidate the information from each eye and all the nerve fibers will ultimately leave the eye at the optic nerve. The light information is being consolidated through a series of neurons  Information leaves the eye through the optic nerve, the bundle of nerves o When the photoreceptors are activated the information, they receive is consolidated and take away from the eye, the Optic Nerve is a bundle of nerves that carry this information while leaving the eye. o There are no photoreceptors where the optic nerve exists (blind spot)  There’s a point in the back of the eye that doesn’t capture visual information called the Blind spot o Blind spot, the spot where the optic nerve leaves the eye o Present no photoreceptors o Blind spots are being filled in by brain through the binocular vision, because the other eye gets the information the blind spot missed (we don’t see a blind spot because or brain fills the gap i.e what is missed by the right eye is picked up by the left and vice versa which allows our brain to shows us a whole picture as if nothing is missing) Vision deficit Downloaded by Armin Mollahajlou ([email protected]) lOMoARcPSD|10910327 There are a lot of things that can go wrong with the eye, but have nothing to do with brain  Cataract - lens get blurry  Stigmatism - the lens of the eye is not perfectly symmetrical that affects the refraction of the eye  Macular degeneration - a deficit that is becoming more common o Macular is on the center of your retina, aids in providing a sharp, central vision that is needed for reading o When the macular degenerates, the central vision becomes destroyed (neurons that help you see someone can no longer do that job) o Left with the periphery vision Retinal implant device Invented in an effort to restoring vision loss. The chip device can be implanted behind the retina and simulates what the retina does. It can also be wired up in such a way that it can communicate with the rest of the brain to help an individual know what they are seeing (artificial retina).  Designed to capture light information and send it down to the optic nerve  Your brain would be able to see, yet only a crude image because there are only 1500 light-sensitive microphotodiodes o Allowing the blind to navigate and make simple discriminations Incredibly complex but something like this would not be possible without a detailed understanding of how the eye process vision in the brain Primary projection pathway of the visual system The visual field is being separated into two, while both eyes would capture part of both visual filed  Each eye captures a little bit of each visual field  The light information leaves the eye via the optic nerve o If each eye captures information from each side of space, how is the brain going to piece all of the information of one side of the visual field together? o Processing challenge can be overcome by passing some information from each eye to the other side of brain There is a left visual field and right visual field, each eye can capture input from each visual field (right or left). The input from both fields is taken away from each eye by the optic nerve, but if each eye get info from each field how does the brain put it together? -> The optic chiasm is a crossing that ensure the entire right visual field ends up on the left side of the brain and vice versa. We don’t know why this reverse thing happens. So, some info crosses at the optic chiasm.  The crossing of the optic nerves at the optic chiasm o Ensuring the entire side of one of the visual filed ends up on the contralateral side of the brain (after the cross at the optic chiasm, one side of visual space is then processed by the opposite side of the brain)  Left visual field  right side of the brain  Right visual field  left side of the brain o The information from the periphery (information from the far right and far left) is what crosses at the chiasm, therefore any damage to the structure would cause tunnel vision  We’ve been able to get powerful validation of the phenomena though neuropsychology  We can study this by observing a patient with cancer on the pituitary gland that sits on top of the optic chiasm which when becomes cancerous can press on the optic chiasm and block that info from being crossed. The result of this is tunnel vision (can see central vision well but difficulty seeing the periphery vision). This tells us that if the periphery is lost in tunnel vision, the optic chiasm must be crossing info from the far left and far right. Downloaded by Armin Mollahajlou ([email protected]) lOMoARcPSD|10910327 The left visual field info goes to the right hemisphere of the brain and vice versa, both the signals then make a stop at the thalamus (sensory relay station) and then goes to the occipital lobe in primary visual cortex  Most of the information takes a stop at the thalamus o There are different parts of thalamus that the visual information goes to, but the predominant area that it goes to is called the lateral geniculate nucleus (higher-order, mammalian processing pathway) o The left thalamus processes information from the right visual field and vice-versa. o Information then radiate the primary visual cortex (first point in the human cerebral cortex where visual processing is analyzed)  Information continues its way to the occipital lobe V1 o The first part of the brain that processes visual information 90% of the visual fibers in the brain follows this path; the other 10% goes another way to the brainstem Hemianopias Anywhere along this pathway can be damaged (stroke, trauma, MS)  Depending on the location of damage, the visual impairment varies  Given the acknowledgment of this primary visual pathway, by knowing the place of destroy can make predictions with high certainty of the visual impairment o This demands a perfect understanding of the system Retinotopic map The map of the retina is being impressed on the brain; the light information is being delivered in an orderly manner. The full retinotopic map (on each side of the cortex) contains a representation of the entire contralateral hemisphere.  Keep in mind the map is upside down, and backwards o This map is being articulated so well, and fairly consistent across people that it gives the ability to predict the visual impairment with high certainty  Damage/injury to the map would lead to the development of blind spots, scotoma o Total loss of the right occipital lobe - left side blindness o This is called cortical blindness because the blindness is caused by brain injury, not an impairment in the eyes  Sensation is attached because the eyes are doing their work  Perception is eliminated because the brain lost the ability to decode the information The entire retina is mapped on to the cortex. The map is upside down and reversed (for example, the upper left quadrant of the visual field is processed by the bottom right occipital lobe). If you damage this map, you develop blind spots, called Scotoma. For ex: if you have a lesion in upper right occipital lobe than you will have blind spots in the bottom left quadrant of your visual field in each eye. If you damage the left occipital lobe you lose vision in the right field. We call these loss of visions cortico-blindness to clarify that they are caused by damaged brain and not damaged eyes. In this dysfunction, the eyes work fine, they capture info and send it to the brain, but the perception process is lost by the brain. As mentioned before 10% of the neural fibers that go to the brainstem in some cases give people with corticoblindness a sense of perception (their will see everything as dark, but they can still navigate when they move). Downloaded by Armin Mollahajlou ([email protected]) lOMoARcPSD|10910327 Fascinating aside The occipital lobe is entirely dedicated for vision. There is impressive evidence about congenital blindness (eye disfunction)  Someone born without the ability to see, perhaps due to an abnormality/dysfunction at the level of the eye  With congenital blindness, the whole occipital lobe dedicated only for function has been shown to undergo a brain reorganization (therefore it is still useful). The occipital lobe can be reprogrammed under very particular circumstances to process other type of sensory information  Through neural plasticity, the occipital lobe, normally dedicated to vision, gets remapped to help with touch o Research shows the occipital lobes are being activated when the blinds are reading braille o Parts of the hand can indeed be mapped onto the occipital lobe when people are reading braille o This is limited to congenital blindness. If someone has been exposed to light previously (loss their vision after being born with normal vision, the occipital lobe does not show the same remapping)  This might be due to the fact that the occipital lobe was already specialized for visual processing, so much as that it could not be remap to the full extend after losing vision  While there are visual experiences, the occipital lobe can still engage in visual imagination, this is probably a factor that renders the plasticity  When someone loses a sense, the other sense becomes more sensitive because of the neural plasticity o More of the brain area is dedicated to the other sense  Ex: loses vision but increase the sensitivity of hearing V4 Color processing center HOW WE DISCOVERED THE COLOR AREA OF THE BRAIN? We discovered this by showing subjects two identical images one color and one greyscale (subtraction method). The images itself didn’t have objects but just shapes. This is how we discovered V4, an area critical for interpreting color info that comes from the cones in the retina.  Any area in the occipital lobe is incredibly sensitive for color processing, it is critical for color analyses of information specifically from the cones.  It is critical not only for visual processing of the external world, but also visual imagination when eyes closed (a strawberry is red)  One of the first things studied with fMRI There are lot of ways to study this,  It first had the experiment set up to have the person open their eyes to look at something visually, then close their eyes o This method is not the best method because the control is not a fair test o The back of the brain is activated for color processing; however, the other activated area might also be due to visual complexity.  One way is to ask the person to look at an image with colors, then the exact same image in monochrome o The picture shown is purely blocks of color o Because there is no object recognition involved, just color o Subtraction method allows to give a more specific areas underlying the color processing process (we are left with the area of the brain that cares about processing colors) o Any brain activity that is the result of the subtraction should then be attributable to the processing of color. o This is how we discovered V4, an area found on both hemispheres critical for interpreting color information that comes from the cones in the retina.  This area is engaged to far lesser degree when only grey scale information is being processed Color constancy Downloaded by Armin Mollahajlou ([email protected]) lOMoARcPSD|10910327 Under different light conditions the color of things change by shade but the actual color doesn’t change, it is important that our visual system recognizes this constancy. We can study this under different lighting conditions and what we observe is that V4 hold steady across both conditions. So, one of the functions of V4 is to hold down the color perception when it changes with lighting. It is important for the visual system to recognize the colors of the object did not change, but rather it is the lighting  There has to be a mechanism that stabilize the color  Across different lighting condition, V4 hold steady, thus the ability to recognize the color remains constant is a function of V4 o Therefore the visual experience would not change dramatically as the lighting change When you show someone a blue strawberry and red strawberry, in both cases their V4 region lights up because you are processing color but in the red strawberry case more areas of the brain aside from V4 light up, this is due to you thinking about the last time you ate a strawberry or your feelings towards how strawberries taste etc. These extra areas don’t light up with the blue strawberry because that color doesn’t make sense and you have never processed it before. V4 operates in opposite ways like most of the brain, colour on the left side of space is processed by the right side V4 and vice versa. Stimuli coloration When you show someone a blue strawberry and red strawberry, in both cases their V4 region lights up because you are processing color but in the red strawberry case more areas of the brain aside from V4 light up, this is due to you thinking about the last time you ate a strawberry or your feelings towards how strawberries taste etc. These extra areas don’t light up with the blue strawberry because that color doesn’t make sense and you have never processed it before. By showing something with a mismatch of colors (e.g.: blue strawberry), V4 is being activated because it is processing color o Seeing something that is true to form in terms of color, V4 and several other areas are being activated too  The brain is engaging with past memories and/or emotions or knowledge associated with the object o Yet, when seeing something with a mismatch of colors, the V4 is only processing the colors, but probably not linking to areas involving memories and emotions Selective attention to a quadrant V4 is indeed also contralaterally linked, this can be examined by showing blocks on color on the quadrant and mapped on Downloaded by Armin Mollahajlou ([email protected]) lOMoARcPSD|10910327 We have provided a variety of pieces evidence that demonstrate the Visual Area 4 (V4) seems to play an important role in the processing of color. Neuroimaging techniques like PET scans or fMRI scans have all helped reveal this (that V4 is activated when an individual is seeing colors. However, neuroimaging research is correlational. There is a correlation between an individual perceiving colors in the world and the activation of the Visual Area 4. This does not prove that V4 is the brain area that processes color, it only strongly suggests it. The way to provide even more compelling evidence that V4 processes color is to understand what they effects would be if the area was damaged. What happens when you damage V4?  What color blindness refers to in general is when a cone or set of cones in the eyes work differently, the most common type of color blindness is telling the difference between red and green. This, however, is referring to visual impairment in color recognition due to damage to the eye. This is much more likely to happen in men than women  When you have impairment in color recognition due to damage in the brain in the V4 area is called Cerebral Achromatopsia.  This inability to see colors happens even when you imagine it in your mind. This tells us that the color mechanism that is used to see the external world is also used to imagine colors in our head. Cerebral achromatopia (without color due to brain injury) The inability to see/perceive colors (any color) because of brain injury, in comparison to typical colorblindness  A rare disorder of color perception because it involves damage only to V4 and maybe surrounding areas Dichromats, typical colorblindness (inability to distinguish some colors. This is caused by deficits in the cone photoreceptors and not by damage in the brain) Achromatopia  Cerebral - the brain, not the eye  A - failure of doing something (in neurology)  Chrome - color Because there is a V4 on both side of the brain   Chromatic (both fields of achromatopsia when both V4 are being damaged) and monochromatic if only one side is damaged o There are two complaints most reported by patients regarding psychosocial effects  Food looks disgusting  Flesh looks disgusting when they are grey in color, thus often not interested in sex o Patients often report that the colors have become a bland palette of “dirty shades of gray”.  Shades reflect variation in lighting, rather than hue (a gradation or variety of a color, tint) However, this condition is often rare because brain damages are often widespread (mentions in the brain injury studies). Thus, the chance of only having V4 damage is exceptionally uncommon o Although uncommon, it is possible Downloaded by Armin Mollahajlou ([email protected]) lOMoARcPSD|10910327 We must recognize that other visual processing areas around V4 that are incredibly important. One of them, found in the temporal lobe is the Fusiform face area which is specialized for facial recognition. Not being able to see faces properly is called Prosopagnosia. However, in this disorder individuals can see color. We can do the lesion overlap method to identify the brain region that is important for this. They did it for Achromatopsia and Prosopagnosia and found V4 was common in both cases. Lesion overlap The technique is commonly used in patients with different visual impairment, as it allows us to understand which specific brain area is underlying the processes  The cooler the color, the more commonly the brain area is damaged in the patients with the same disease A. Achromatosia  V4 - People with the inability to see color have damage to V4 B. Prosopagnosia  The inability to see faces properly, different area other than V4 are damaged  Ability of seeing colors is fine because the V4 is intact Downloaded by Armin Mollahajlou ([email protected]) lOMoARcPSD|10910327 V5 Motion processing center (area MT)    An area that is strongly concerned with the processing of motion and direction V5 also exists on both sides of the brain The inability to process motion would lead to distorted visual processing (i.e. failure to recognize something in motion is a coherent object)  lies in the middle temporal lobe region of the macaque monkey, although the same area is found in the occipital lobe in humans MT The first tempt in studying V5 was also done by using subtraction method We showed subjects pixel images that were static and flickering while scanning their brain. The used the subtraction method to understand which area were common for motion processing and we found V5. When we perceive something as moving even though it isn’t, like kinetic images, the V5 area is active.      An image in monochrome without objects, it consists of a complex black-and-white collage of squares (pixels) The same image with black dots popping up and down in the white spots Trying to simulate motion in the simplest way The image isn’t even an object so we do not have to worry about other mental abilities like object recognition kicking in Subtraction method: movement – movement = area of the brain interested in movement Processing illusory motion When someone see a static object and thinks it is moving, V5 is active  V5 being activated seems to be part of the reason we see movement when movement isn’t actually there  It fires up as much as if the object was actually moving (visual illusion) Cerebral Akinetopsia Difference between V4 and V5:  V4 is hard to stimulate with TMS because it is not easy to access from the skull (V4 is located at the inferior of the occipital lobe, more medial), but V5 does not have this problem (V5 is located at the most anterior portion of the occipital lobe, lateral part of the cerebral cortex).  Because V5 is on the lateral part of the cortex, it offers the possibility that you could use brain stimulation to simulate and see what would happen if you disrupted the function of V5  By stimulating V5, and asked to make a movement judgement would lead to the inability of processing motion  Using TMS to temporarily disable the V5 region impair our ability to perceive things that move. This is done by disrupting visual judgement while something is moving. This induces an artificial inability to process motion called Cerebral Akinetopsia. The inability to process visual motion because of brain injury (selectively caused by dysfunction to V5)  Cerebral - brain, not eyes  A - failure to, inability of  Kine – motion, movement Patient with Akinetopsia described their visual experience as capturing a motion with a camera (there are only snapshots)  Rather than seeing objects moving continuously, they would appear in one position, and then another  Thus, they are not able to cross a street safely, or driving because these requires judgement of visual motion  The ability to judge the direction, and the speed of the motion are being impaired Downloaded by Armin Mollahajlou ([email protected]) lOMoARcPSD|10910327 Specificity of V5 neurons Neurons in V5 cares about the direction of movement, and velocity, instead of only translating movement.  There are individual neurons measured by neurophysiology that care about certain direction of movement o The neurons fire the most when the object is moving in the desired direction  The firing rate of the neurons was also being measured when the object was being moved in the optimal direction with different velocity Neurons in V5 care not only about movement but also about direction. Individual neurons measured by neurophysiology show us that some neurons not only care about angle or orientation they care about velocity (direction and speed) too. Damage of V5 Damage to one side of the brain in V5 would not impair visual motion in the corresponding visual field  It does not work the same way as V4.  It is unknown why this is the case, but patients with cerebral Akinetopsia have damage bilaterally  If you damage V5 on the right, you can still perceive motion in the left and vice versa (doesn’t work the same way as color). Cerebral Akinotopsia almost always occurs only when there’s impairment to both V5 regions (bilateral hemisphere damage of V5).  This suggests that both side work together while damage to one side might lead to compensation by the other side of the brain  If the V5 area is damage in both hemispheres, as it might be with severe Cerebral Akinetopsia, the ability to judge movement can be incredibly impaired. Interestingly, this seems to co-occur naturally when individuals have damage to both parts of the temporal lobes (bi-temporal lobes lesions) Visual cortex The further along a processing pathway you go the more complex the decoding of the signals become, for ex: in primary visual cortex it cares about line and borders, it doesn’t go into much detail, it just deals with segmentation issues of shapes. As you continue down the pathway to V4 and V5 it gets more detailed. The point is that early on the pathway you start set up images and they get more and more detailed as they progress down the path.  The occipital cortex is the first lobe of the brain where visual information is processed/analyzed  As a mental process advance from the occipital lobe (coded yellow in the diagram) towards the temporal cortex (coded red in the diagram), a visual stimulus gets more and more complex as you continue down the processing pathway.  Therefore, the further along the information travels, the more complex the presentations are  Over 30 distinct cortical visual areas have been identified in the monkey, while evidence suggested there are more in the humans. V1 - information about lines, boarders - very simple things, trying to present segmentation o The early stations of the visual cortex are setting the stage for the build of complex visual messages V4, MT, PO - start to care about patterns TE, 7a - eventually the recognition of faces and objects    Why would it be useful for primate brain to have evolved so many visual areas?  Visual processing is hierarchical - each area, representing the stimulus in a unique way, successively elaborates on the representation derived by processing in earlier area Downloaded by Armin Mollahajlou ([email protected]) lOMoARcPSD|10910327 Synesthesia A neurodevelopmental disorder that individuals seems to be born with where one sensory automatically crossed with another. This disorder is not due to neurological damage and is permanent. This occurs more in females and left- handed people. One sensory experience automatically crosses with another sensory experience in a consistent, systematic way that would not normally happen  Thus, patients see the world differently  There is an idiosyncratic union between sensory modalities    It is developmental, patients are not born this way Not a disease, nor neurological problem, but an interesting wrinkles that occur in a small number of people during development The prevalence of this situation varied across studies, some say 1%, while some suggested 10% o Females are more likely to be synesthetic o Lefties are far more likely to be synesthetic Types of Synesthesia Grapheme-color (letter to color)  Viewing specific alphabets only in specific font color all the time raw degree of consistency over time for a specific individual) o There is a systematic color associated to each letter  Each letter would be shown by itself to describe the color  The patient would come back to the lab a year later and being asked the exact same thing o Raw degree of consistency overtime for a specific individual  Not consistent across patients, but consistent over time for an individual o Synesthesia is a personal experience; therefore, it requires clever methods to verify and explore this unique phenomenon  Modified versions of Stroop Task  The stimuli are letters, while the key manipulation is whether the colors of the letters are congruent or incongruent to the subject’s synesthetic palate  Synesthetes are faster to name the colors of the letter when the physical color matches the concurrent colors of a particular letter B. Chromesthesia (sound to color)  You hear a sound and see color in front of you o Hearing a sound would see color in front of you o This could happen with music Spatial sequence synesthesia (see numbers in space)  Spatial sequence synesthesia consists of visualizing certain spaces in physical space  A form of spatial synesthesia connected to ordinal lists. In this kind of synesthesia, individuals visualize a spatial sequence when thinking about a list or data set. Auditory-tactile  Hearing something and feeling a touch (You hear a sound and you feel a touch feeling) Mirror-touch synesthesia  You see someone touching their arm, you feel your arm being touched. Downloaded by Armin Mollahajlou ([email protected]) lOMoARcPSD|10910327 Linking fMRI and DTI in grapheme-color synesthesia The connection between the letter areas and the color areas are significantly stronger in the synesthesia  The area of the brain that process colors and letters are more strongly connected to each in individual with Grapheme-Color synesthesia than individual who do not present the condition Why? - not known fMRI  Synesthetes showed increased activation in V4 and STS o Colored-hearing synesthesia - when listening to words, the individuals reported seeing specific colors o When listening to tones, they see no colors DTI  greater anisotropic diffusion o Grapheme-color synesthesia o Larger white matter tracts in the right inferior temporal cortex, and left parietal cortex, and bilaterally in the frontal cortex o In or Grapheme-color synesthetes, we examine whether the white matter connections between the visual word forming area and color area is stronger than normal. It turns out that’s how it actually works. The connection between the orthography areas and V4 left side color area are significantly stronger. (Left side is language based). One question you can ask whether two graphene color synesthetes view alphabets in the same colors? Answer: They are similar but not identical Therefore, synesthesia is associated with both abnormal activation patterns in functional imaging studies and abnormal patterns of connectivity in structural imaging studies Multisensory areas of the cortical areas Multisensory integration Integration of the multimodal information to increase the sensitivity and accuracy of perception. It takes place at many different regions in the brain, both subcortically and cortically. 1. Subcortically, the superior colliculus Contains orderly topographic maps of the environment in visual, auditory, and somatosensory domains. The response of the cell is stronger when there are inputs from multiple senses compared to input from a single modality. 2. Cortically, superior temporal sulcus (STS) There are connections coming from and going to the various sensory cortices. There are association areas in the brain where multiple sensory are being integrated (this occurs in the majority of the brain)  People with synesthesia might have stronger connections in some particular association areas of the brain McGurk Effect The perception of speech, what you believe that you hear, is influenced by the lip movements that your eyes see. When multiple different sense come together, and a conflict between them arises, the brain always believes vision (not all senses are equal)  Vision wins by changing what you hear, the sounds we hear can be influenced by visual cues.  By closing your eyes, you are able to remove the visual contamination and hear the correct sounds This is because the brain judge’s visual information in most circumstances to be the most reliable, and therefore, it gives the most weight. Something similar is the rubber hand illustration. Downloaded by Armin Mollahajlou ([email protected]) lOMoARcPSD|10910327 Downloaded by Armin Mollahajlou ([email protected]) lOMoARcPSD|10910327 Downloaded by Armin Mollahajlou ([email protected])