Hemispheric Lateralisation & Split-Brain Research | Biopsychology | AQA Psychology

have you ever heard people say that they are more of a right brained or left brained person perhaps you've even taken an online test yourself to discover if you're right brained or left brained but what if what's more important is a part of your brain that connects the left and the right together hey everyone welcome back to Bear it in mind in this video we're going to explore hemispheric lateralization and split brain research at the end of the video there'll be some practice questions so that you can check your understanding and link below is a free worksheet that goes with this video so say hello again to your brain did you know that your brain has two sides to it or what's called two hemispheres a left and a right so hemispheric lateralization is the idea that certain functions are controlled by one side of the brain and not the other in the previous video we talked about localization of function and we need to now distinguish between that and lateralization a mental process can be localized in the brain I.E its function tends to be in a specific location in the brain but it does not necessarily have to be in only one side of the brain which would be lateralized in other words it's not just the lobes of your brain that are specialized for function the two halves of our brain have specific processes and behaviors they control too amazingly it's thought that your left hemisphere controls the right side of your body and the right hemisphere controls the left side of your body the idea that the hemispheres control opposite sides of the body is called Contra lateral organization the word Contra means opposite just like when we use the word contradict if you've ever known someone who's had a stroke you can tell which side of the brain the stroke took place on by which side of the body has been impacted if they are struggling to move on the right side it's because the left hemisphere has been damaged there's also another a Telltale sign that the stroke happened in the left hemisphere but I'll let you try and spot that as we go through this video so now let's look again at the language centers in the brain to help us understand hemispheric lateralization in the previous video we talked about Brooker and vernica area including broas and vernica Aphasia Aphasia is the term given to someone who has lost the ability to understand or produce speech Paul brocker studied a patient known as tan because regardless of the question he was asked he always responded tan tan he clearly had a problem with speech production when brocker carried out a postmart examination on his brain they found lesions in his left frontal lobe leading to the suggestion that the ability to produce speech is located in this area this is localization of function additionally broa went on to study eight other patients who had similar language problems all of these patients had lesions in their left front Hemisphere and then there's vernica Aphasia Cal Vera patients all had lesions in the brain in the left tempal lobe and they have problems not with producing speech but with comprehending speech notice from these cases that language appears to be lateralized the ability to produce and understand speech appears to be in the left [Music] hemisphere now we can develop our understanding of hemispheric lateralization further by exploring split brain research in your brain you have a bundle of nerve fibers called a Corpus colossum this connects the two sides of your brain the two hemispheres split brain patients are people who've had their Corpus colossum cut so that communication between the two hemispheres is removed this was done as a last resort to try to treat the severe epilepsy they were suffering for neuros psychologists Roger sper and Michael gazer split brain patient provide you the opportunity to explore how lateralized the brain actually is to understand what they discovered we need to talk about left and right visual Fields this is crucial for understanding how their patients behaved you have a left and a right visual field information from your left visual field goes to your right Hemisphere and information from the right visual field goes to the left hemisphere sper presented the visual information to only one visual field at a time time how did he do this well he had the participants stare at a cross on the screen and then they would flash the visual information to one side of the cross for only one tenth of a second too quick for them to have time to move their eye across the image now remember when information is presented to only one of the hemispheres in a split brain patient this information is not shared with the other hemisphere because the part of the brain that transfers this information the Corpus colossum has been cut only one side of the brain has the information sper and Gaza conducted many different experiments including describe what you see tasks tactile tasks and drawing tasks as we consider each one pause the video to see if you can work out what the results might be in the describe what you see task a picture was presented to either the left or right visual field and the participant had to Simply describe what they saw if the image of an apple was presented to the left visual field which would go to the right Hemisphere or to the right visual field which would go to the left hemisphere what do you think the split brain patient would say after each one if the image of an apple was flashed to the right visual field the patient would say they saw an apple this is because the information from the right visual field is processed by the left hemisphere which as we've seen is's thought to be for speech and language and so the split brain patient can can respond verbally and say they saw an apple however if the image of an apple was flashed to the left visual field the patient would say that they saw nothing this is because the information from the left visual field is processed by the right hemisphere which can see the picture but as it has no speech and language abilities whilst it knows it's an apple it cannot share this information with the left hemisphere where the ability to speak is located and so says nothing in the tactile test tactile meaning touch an object was placed in the patient's left hand which would be processed by the right hemisphere or the right hand which would be processed by the left hemisphere and they had to either describe what they felt or select a similar object from a series of alternate objects what do you predict would happen if they held it in their right hand which would go to their left hemisphere they could describe the object they felt if they held it in the their left hand which would go to their right hemisphere they couldn't describe what they felt finally in the drawing task participants were presented with a picture in either their left or right visual field and they had to simply draw what they saw what do you predict would happen if presented to the left visual field which would go to the right hemisphere they could clearly draw the picture with their left hand if presented to the right visual field which will go to the left hemisphere the image they drew with their right hand was never as clear in fact consider this situation if you presented the word face to the right visual field which would go to the left hemisphere they would say they saw the word face however if you presented the word face to the left visual field their right hemisphere they would say they saw nothing as we have just seen But if you then ask them to draw it they could they could draw a face and only when they had seen on the page that they drawn a face would they say it was a face so from sper and gaza's Research into split brain patients what did they conclude about how the brain is lateralized while it became evident that the left hemisphere is specialized for language whereas the right hemisphere is specialized for visual motor [Music] skills now let's evaluate all this Research into hemispheric lateralization one of the main strengths of the split brain research is how scientific it is this is because their experiments had a remark able level of control over the procedures this can be seen in how highly specialized and standardized those procedures were for example sper presented the information at one tenth of a second so that the split brain patient would not have time to move their eye across the image and so spread the information across both sides of their visual field thus ensuring the information went to only one of the hemispheres this level of control and standardization allowed them to replicate the research many times as well as carry out different variations to learn more about hemispheric lateralization however the split brain research has been criticized because there are a number of extraneous variables firstly the amount of disconnection between the hemispheres varied between patients the extent to which the Corpus colossum had been cut was greater in some patients than others secondly there was a lack of a valid control group this is because all the split brain patients had suffered from epileptic seizures whereas the control group had no history of epileptic seizures they were not a direct comparison and thirdly some of the split brain patients had experienced drug therapy to help with their epilepsy for much longer than others and as such this may be an extraneous variable that affects the brain's ability all of these extraneous variables undermines how much we can learn about hemispheric lateralization from this split brain research another issue with the research relates to the sample sizes this is because the split brain research often involves very few participants all of whom are rather unusual in that they have suffered severely from epilepsy their epilepsy may have caused unique changes in their brain which may affect what they find from their research it could be argued therefore that they are not representative of the wider population meaning the research is limited in its extent to which it can tell us about hemispheric lateralization because the research lacks population validity another interesting issue with what split brain research tells us about hemispheric lateralization is that there are some contradictory findings for example Gaza himself wrote an article in 1998 titled the split brain revisit it in which he reported on a patient referred to as JW split brain research had suggested that the right hemisphere was unable to handle even the most basic language however his patient JW had now developed the capacity to speak out of the right hemisphere with the result that he could now speak about information presented to the left or to the right brain all as a result of the brain's ability to change and adapt called brain plasticity now it's time to check your understanding of what we've covered I'll present one question at a time and you can pause the video to answer it yourself first and then press play again to reveal the answer [Music] next we're going to explore brain plasticity and how your brain can potentially recover from trauma to watch that click the video on the screen now or link below I hope you found this video helpful and we'll see you in the next one

Channel: Bear it in MIND

Views: 3,453

Keywords: psychology facts, human psychology, biopsychology, hemispheric lateralisation a level psychology, split brain experiment, split brain patient, split brain drawing, gazzaniga split brain, roger sperry split brain experiment, corpus callosum split brain, biopsychology revision a level, biopsychology aqa a level psychology, Paul Broca, Karl Wernicke, Broca's area, Wernicke's area, bear it in mind, psychboost, tutor2u

Id: NB8gP3mWOuY

Length: 12min 59sec (779 seconds)

Published: Wed Jan 03 2024