 speech is a complicated process which is brought about by interaction of different areas in the brain. So how do we actually communicate? We can communicate by expressing our thoughts in terms of language that is by speaking and we can also express by writing and also by sign language so using the hand gestures also. So there are various ways of communication and for actually expressing we should understand what the other person is also telling. So we need to hear what the other person is speaking and in case of writing we need to read and interpret the meaning of the words and we need to understand what is the meaning of the sign language which the person is using or any hand gestures what the person is using. So for that we need to basically interpret what is coming from outside or maybe what is coming from inside that is from our internal thoughts that also we express isn't it. So that need to be understood interpreted and then we have to express ourselves. So for this there are various areas. Let us see what is these areas how they interact and if there is damage to these areas what will be the problem. So first important area is Wernicke's area. This area is important for comprehension that is understanding the speech. This area is located in the superior temporal gyrus just posterior to the auditory area. So that is Wernicke's area and if we see the Broadman's area what is it? It is area number 22. Then there is another one that is Broca's area and Broca's area is located in the inferior frontal gyrus. This is Broca's area and in Broadman's area term it is area number 44. Now when we are talking about these areas we mean that these areas are located in dominant hemisphere. So they are not located in both the hemispheres of the brain. They are located in dominant hemisphere and nowadays this concept of dominant and non-dominant hemisphere has been replaced by another concept that is categorical and representational hemisphere. So this dominant hemisphere is categorical hemisphere which is basically left hemisphere in 96% of right-handed people, right-handed people and 70% of left-handed people. So mostly it is left hemisphere. By the way this Broca's area is for sentence formation okay sentence formation and word pronunciation. So after understanding we need to devise a plan what we are going to speak isn't it? So that plan of sentence formation and word pronunciation is done by Broca's area. So let us go into details of these with the help of a flow chart. So this Wernicke's area as I told you that it is important for comprehension of the speech. So for comprehending something first you need to perceive what you are about to comprehend. So Wernicke's area receives the information from lot of other areas and these include auditory cortex. I told you it is located just behind the auditory cortex and as children we start hearing first the speech of others isn't it? So its location just behind the auditory cortex helps a lot right? Then there is information from visual cortex also not directly. The information from visual cortex passes to angular gyrus and this is very important because angular gyrus is important for making meaning of the red words. So it makes you understand what is the meaning of the words you are reading the printed words that is angular gyrus. So that information is also going to the Wernicke's area. Then we also sometimes interpret by hand language sign language as I told you some gestures isn't it? So that information from visual cortex is also going to Wernicke's area plus you know that blind people can read by moving their fingers over the printed letters. So that means tactile information also from sensory association area that I have not shown here that also goes to the Wernicke's area. Then for expressing to the person who is in front of you you need to know where the person is standing isn't it? So that information also goes to the Wernicke's area that is the spatial coordinate of the person. So you see basically the association areas of all three lobes the parietal lobe occipital lobe and temporal lobe from that information is going to Wernicke's area. Then you need to understand what is the emotion of the speech what is the tone of the speech just if somebody says something without any tone color it may be very difficult to understand what the person is actually meaning isn't it? For example somebody can say aha so that means there is some happiness in that somebody can say aha so there is some disappointment in that right so we need to understand the emotions attached and that also goes to Wernicke's area. Then as I told you that maybe we want to express ourselves without even the listening to others that is we have our own internal thoughts also then if we want to change the speech somebody something talking something else but we want to express something else so all our elaborated thoughts whatever if you want to communicate the thought process should reach to that particular area so that you are able to understand those thought processes also. So you see Wernicke's area is receiving information from lot of areas isn't it? So it interprets this okay and comprehends all the incoming information and then via our create fasciculus it is a fasciculus which is the connection between the Wernicke's area and Broca's area so via our create fasciculus Wernicke's area sends the information to Broca's area which as I told you is important for sentence formation right and word pronunciation word pronunciation and after that this Broca's area sends the plan to the motor cortex because we have to express ourselves and for that entire motor machinery has to be recruited so that is motor cortex basal ganglia cerebellum and that is important for articulation that is movement of the mouth, lips, tongues, jaws for proper expression or maybe the hand gestures so we need proper coordination for this proper initiation and stoppage of movement which will be brought about by the basal ganglia right then there is another area that is the ex-ner's area located in premotor cortex ex-ner's area that is important for expression of the written words for writing our speech that is the ex-ner's area and then obviously the information is going to the motor cortex for expression so these are the various areas involved in the speech now to understand little bit more let us try to see what will happen if these areas are damaged so coming back to our original flowchart suppose this Wernicke's area is damaged Wernicke's area is damaged then what is going to happen the person will not be able to comprehend anything which is by means of reading or whatever he is hearing he will not be able to comprehend so it causes aphasia okay which is basically a speech disorder speech disorders which have caused you know damage to these speech areas though and those are known as aphasias in that articulation is normal in aphasia okay so damage to Wernicke's area Broca's area arqueate fasciculus ex-ner's area or the angular virus all will lead to aphasias so damage to Wernicke's area leads to what is known as sensory aphasia sensory aphasia or fluent aphasia fluent aphasia why fluent see the person is able to do the sentence formation and word pronunciation which is happening in the Broca's area so the speech will be fluent but will it have any meaning no it won't have any meaning because the person is not able to understand what is going on so anything he will speak which will not have any meaning rather sometimes he creates his own new words right so this kind of aphasia sensory aphasia is full of jargon so jargon is basically it is an understandable speech and there is new logisms new logisms means a formation of new words which don't have any meaning so for testing for Wernicke's aphasia we have to ask a question to the patient regarding comprehension and in that basically a yes no question is asked for example we can simply ask can a dog fly can a pigeon fly like that is if he understands he will answer in yes or no so that is sensory aphasia now if there is a damage in Broca's area what will be the trouble the person will be able to understand everything they will clearly answer the yes no question but they will not be able to form the sentence properly and they will have a broken speech basically they will want to convey everything in one or two words only and that to those word pronunciation will not be normal so this damage to Broca's area causes something known as motor aphasia or Broca's aphasia or non-fluent aphasia non-fluent aphasia the person is understanding but his speech is non-fluent okay then what will happen if there is damage to angular gyrus see I told you angular gyrus is important for making meaning of red words printed words so in this case the person will be able to understand and communicate in the speech which is being heard okay that will all be normal he will be able to communicate its thoughts also but when given something to read then they will not be able to interpret that so inability to understand the printed words that is angular gyrus aphasia or what is dyslexia so that is causing dyslexia right next if there is damage to ex-ner's area which I told you is for expressing the written speech then what will happen again the person will be able to express himself verbally but will not be able to express himself by writing so that is when damage to ex-ner's area occurs okay now what will happen if there is damage to our quate fasciculus what will happen that is known as conduction aphasia conduction aphasia so the person will be able to understand what the person is hearing or the word what the person is reading but the information will not go to Broca's area okay so it is like Broca's area will make sentence formation will do word pronunciation but there is no connection with one case area so that speech will also be meaningless okay so it is a kind of fluent aphasia only because the person is speaking normally Broca's area intact means it will be fluent aphasia but there is one difference from what we saw in CERN 3 aphasia or one case aphasia in the sense the person here understands also now what will happen the person will speak and he will speak something nonsense full of jargon now he will understand his own words and he will understand that okay he is speaking something which is totally nonsense so he will try to correct himself again and again so that is conduction aphasia which is basically a kind of fluent aphasia another type of aphasia is global aphasia what is global aphasia global aphasia is where both varnike's area and Broca's area will be damaged so the patient will not be able to answer a yes no question also and his speech will be non-fluent as well no sentence formation will occur so this was in very brief concept of physiology of speech thanks for watching the video if you liked it do press the like button share the video with others and don't forget to subscribe to the channel physiology open thank you