Presentation on theme: "Major Sections of the Brain"— Presentation transcript:
1Major Sections of the Brain In talking about where things are located in the brain, the brain is divided into three main regions, forebrain, midbrain, hindbrain
2The Brain Three important parts Brain Stem (including the cerebellum and thalamus)Limbic SystemCerebral CortexThe brain has three main parts to it – the brain stem, limbic system, and cerebral cortex. The brain stem is responsible for automatic survival functions.The limbic system is associated with emotions like fear and aggression and drives like for food and sex. The cerebral cortex is the ultimate information-processing center (it’s the computer that organizes and runs the show).
3Older Brain Structures/Lower Level Functions BrainstemMedullaPonsReticular formationThalamusCerebellumLimbic systemAmygdalaHypothalamusHippocampusThe brain has three main parts to it – the brain stem, limbic system, and cerebral cortex. The brain stem is responsible for automatic survival functions (this stops working and you are screwed). The limbic system is associated with emotions like fear and aggression and drives like for food and sex. The cerebral cortex is the ultimate information-processing center (it’s the computer that organizes and runs the show).
4Brainstem Survival and maintenance functions Crossover point where most nerves to and from each side of the brain connect with body’s opposite sideThe brain stem is composed of the medulla, cerebellum, pons, reticular formation, and thalamus. It’s located at the back of the neck, where the spinal cord enters the skull and swells (you can feel it).
5BrainstemMedulla - heart rate, breathing, blood pressure and has pathway for motor movementPons – Helps coordinate movementReticular Formation –Sleep and arousalThe medullar is basically an extension of the spinal cord. It regulates breathing, heart rate, blood pressure, and has pathways for motor movement. Damage to the medulla almost undoubtedly leads to death because it controls such basic survival mechanisms.The Pons contains fibers that connect the two hemispheres of the cerebellum. It also contains fibers that transmit information from body to brain and to body.The Reticular Formation is a diffuse group of cells whose axons and dendrites course in many directions. The descending pathways modulate movement. The ascending pathways deal with sleep and attention. It also filters some of the sensory input from spinal cord and relays it to other areas of the brainIn the sixties, a series of studies by Moruzzi and Magoun demonstrated the importance of the reticular formation to the functioning of sleep. When the researchers stimulated the reticular formation, cats who had previously been asleep, awoke suddenly and cats that had previously been awake showed rapid arousal. When the reticular formation was damaged, the cats engaged in persistent sleep, from which they did not wake (though if you’re familiar with cats, I wonder how they noticed). They concluded that waking results from activity in the reticular formation, while sleeping results from decreased activity of reticular formation.The reticular formation is also vital in the functioning of attention. Electrical stimulation of the reticular formation leads to an increase in brain activity and damage to it leads to decreased brain activity (similar to that seen in comatose patients). It is highly susceptible to drugs and damage from drug abuse.
6Brainstem Thalamus Sits at the top of the brainstem Relays sensory info (except smell), spatial sense, and motor signals to sensory areas of cerebral cortex and transmits replies to cerebellum and medullaHelps regulate consciousness, sleep, and alertnessOne consequence of damage = fatal insomniaThe thalamus is shaped like two footballs, side by side, one in each half of the brain. The relay center is really a super-complex relay station. It takes in information from your senses and sends it on to the appropriate parts of the brain. There is very minimal processing done at this step – it’s really not ‘understanding’ the information but simply sending it on.The brain stem also includes the cerebellum, which is found in nearly all vertebrates (size in different species is a function of the range and complexity of their movements). The cerebellum controls learned/skilled motor movements, it provides the “programs” for the control of skilled movements. This is particularly true for those that are repeated and become automatic (walking, typing, talking).
7Cerebellum – “Little Brain” Nonverbal learning and memory,Coordinates voluntary movement and balanceControls Learned/skilled movements that are automatic (i.e., walking)
8Cerebellum DamageAffects fine movement, gait, equilibrium, posture, and voluntary movement causingErrors in force, direction, speed and amplitude of movements.
9Other Cerebellum Damage Dysarthria – speech articulationDysmetria – judging distances and range of movementsDysdiadokinesia – inability to perform rapid alternating movementsOther Ataxia
11Limbic System Hypothalamus Hippocampus Amygdala Hunger, thirst, body temp., reproductive behaviorControls pituitary glandEmotion and “Reward Center” (Olds & Milner (1954))HippocampusForms new memories (episodic)Spatial orientationAmygdalaAggression, fear, and perception of themProcessing/encoding emotional memoriesRegulating feedingThe limbic system is a donut-shaped area in the center of the brain. This region is responsible for much of the influence on the body’s hormonal system (which in turn, controls much of our emotions such as fear and anger, as well as our basic motives for things like food and sex). There are four main parts to the limbic system – the hypothalamus (which controls the pituitary gland), the hippocampus, and the amygdala).Similarly, the hypothalamus also influences reproductive behavior (destroying the hypothalamus ceases copulatory behavior in rats and dogs; stimulation of it will lead to increases in copulatory behavior).The hippocampus is the part of the brain that processes memory. If damage is done to this area, people are unable to create new memories. There is a very famous case that demonstrates this difficulty. A man by the initials of H. M. suffered from epilepsy as a child. In an attempt to control his epileptic seizures, doctors did surgery on his brain and removed a portion, part of which was the hippocampus. He no longer suffered from epilepsy, but without his hippocampi, everything in his memory vanished after a few minutes. He could not form long-term memories and his short-term memory only lasted about five minutes. When his family moved across town, he kept returning to old house because he didn’t have the memory that they had moved.The amygdala also has three main functions – regulating feeding, memory, and emotion. Lesions to the amygdala can lead to extreme weight loss, or weight gain (destroy all leads to weight loss; destroy some, leads to weight gain). The amygdala also assists in the perception and encoding of emotion and emotional memories, specifically those associated with fear and aggression. Stimulating part of the amygdala can lead to an aggressive response in animals, while stimulating another portion can lead to a fearful response. However, there are a number of factors that influence fear and aggression, so this isn’t the only place of the brain that influences those behaviors.In general, there isn’t ONE part of the brain for any type of behavior/mental process. There are typically several areas that have different influences on such complex things as our behavior and thoughts.
12Limbic System Damage Hypothalamus – Death Amygdala – Loss of fear, impaired emotion recognition in faces, impaired recognition of social emotions, impaired memory for emotional materialHippocampus – Amnesia (anterograde), failure to remember spatial layouts/landmarksH.M.shows damage in Alzheimer’s
13Question?The limbic system is involved in controlling basic drives important for our survival as a species, feeding and reproducing. But it is also instrumental to the experience of fear and aggression.What do you make of the fact that these two particular emotions (unlike say, happiness or melancholy) are controlled by the same system that helps ensure our survival?What does Memory have to do with this?
14Cerebral CortexFabric of interconnected neural cells that covers the cerebral hemispheresCortex=barkUltimate control and information processing structureHigher Functions/Newer neural networks85% of brain weightAxons project down into brain, connecting it with other brain structures
15Cerebral Cortex Two halves, four lobes, separated by Fissures Frontal lobeJudgement, planning, Decision-making, inhibition, personalityMotor cortexParietal lobeSensory cortex (touch)Math, spatial reasoningTemporal lobeAuditory cortex, visual memory languageOccipital lobe – all visionVisual cortexAssociation areas throughoutAnd just in case you were wondering – humans don’t have the largest brains. Porpoises, whales, and elephants all have larger brains that humans do.The cerebral cortex is the interconnected neural cells that cover the cerebral hemispheres – this is the body’s ultimate control and information-processing center. The cortex is broken up into four parts, which are found on both of the hemispheres.The frontal lobe is behind the forehead and accounts for half of the volume of the cerebral cortex and is considered the ‘seat’ of intelligence and abstract thinking and making judgments. The frontal lobe also houses the motor cortex. The motor cortex controls voluntary movements (like walking, talking, and chewing). There is an interesting story about the first documented case of injury to the frontal lobe (this doesn’t mean it was the first time that this area of the brain was damaged in a person but that this was the first time that doctors could identify which part of the brain was injured).Phineas Gage was the foreman of a railway construction gang working near Cavendish, Vermont. On 13th. September 1848, an accidental explosion of a charge he had set blew his tamping iron through his head.The tamping iron was 3 feet 7 inches long and weighed 13 1/2 pounds. It was 1 1/4 inches in diameter at one end and tapered over a distance of about 1-foot to a diameter of 1/4 inch at the other. The tamping iron went in point first under his left cheek bone and completely out through the top of his head, landing about 25 to 30 yards behind him. Phineas was knocked over but may not have lost consciousness even though most of the front part of the left side of his brain was destroyed. Dr. John Martyn Harlow, the young physician of Cavendish, treated him with such success that he returned home to Lebanon, New Hampshire 10 weeks later.Some months after the accident, probably in about the middle of 1849, Phineas felt strong enough to resume work. But because his personality had changed so much, the contractors who had employed him would not give him his place again. Before the accident he had been their most capable and efficient foreman, one with a well-balanced mind, and who was looked on as a shrewd smart business man. He was now fitful, irreverent, and grossly profane, showing little deference for his fellows. He was also impatient and obstinate, yet capricious and vacillating, unable to settle on any of the plans he devised for future action. His friends said he was “No longer Gage.”As far as we know Phineas never worked at the level of a foreman again. According to Dr. Harlow, Phineas appeared at Barnum’s Museum in New York, worked in the livery stable of the Dartmouth Inn (Hanover, NH), and drove coaches and cared for horses in Chile. In about 1859, after his health began to fail he went to San Francisco to live with his mother. After he regained his health he worked on a farm south of San Francisco. In February 1860, he began to have epileptic seizures and, as we know from the Funeral Director’s and cemetery interment records, he died on 21st. May 1860.No studies of Phineas Gage’s brain were made post mortem. Late in 1867 his body was exhumed, and his skull and the tamping iron sent to Dr. Harlow, then in Woburn (MA). Harlow reported his findings, including his estimate of the brain damage, in 1868. He then gave the skull and tamping iron to what became the Warren Museum of the Medical School of Harvard University where they were much studied. They are now on display at Harvard’s Countway Library of Medicine.Typically, damage to the frontal lobe leads to shallow emotional displays, no decrease in IQ, but an increase in forgetfulness (especially with those tasks that need sustained attention), and impairment in goal-directed behavior.The parietal lobe contains the sensory cortex. This is where all information coming in from your sensory organs is processed, and dealt with as needed. One example of the effect of damage to this area of the brain is that people can no longer recognize an object by touch alone. Another example is the disorder known as prosopagnosia. Sometimes when damage is done to the parietal lobe, people lose the ability to recognize faces. They can look in the mirror and not recognize themselves or look at their family and friends and have no idea who these people are. Now, the ability to recognize objects is unimpaired, as is the ability to recognize people by their voice (so as soon as their wife or husband started talking, the person may recognize who they are). Another example of damage to the parietal lobe is that of unilateral neglect. Damage done to the right parietal cortex results in neglect of the left-hand side of the body (though it doesn’t work the other way around). The person may ‘disclaim’ such that they neglect the left side of the body (though they typically deny that they are doing this). They may only dress the right side of the body and may only shave the right side of the face.The temporal lobe includes the auditory areas, which receive auditory information (from the opposite ear). The temporal lobe also handles the storing of visual memories and language comprehension. Dichotic listening techniques (where you present different sounds to each ear) shows that right handed people recall more information that was presented to the right ear.And the occipital lobe is the portion of the cerebral cortex that includes visual areas, which receive visual information from the opposite visual field.
16Two Cerebral Hemispheres Contralateral arrangement – the left hemisphere receives inputs from and controls the right side of the body and vice versaWork together on many functions but can also simultaneously carry out different functions with minimal duplication of effortCorpus callosumThick band of nerve fibers connects the two hemispheres
22Functions of the Cortex Primary Motor CortexOrigin of most of the corticospinal tract meaning, projects to the spine so it can send motor signals down to various body parts and tell them to move.Specific movements tend to be represented rather than specific muscles.Also projects to thalamus and basal ganglionAssociation Areas = Premotor CortexIn front of the motor stripReceives many of the same connections as the motor cortex but most of its outputs go to the motor cortexResponsible for more complex movementsDiscovery of the motor cortex– 1870 Gustav Fritsch and Eduard Hitzig, mild electrical stimulation to the motor cortex of a dogMapping the motor cortex – Otfrid Foerster and Wilder Penfield in awake surgical patients
23Association Areas of the Cortex The ¾ of the cortex, across all four lobes not devoted to sensory or muscle activity.Interpret, integrate information processed by the sensory areas, link sensory inputs with stored memoriesIn the frontal lobesenable judgment,planning, processing memories,inhibitions, and personalityIn parietal lobesenable mathematicaland spatial reasoningIn right temporal enable facialRecognition.Although Einstein’s brain was normal weight, his parietal lobes were large and unusually shaped
24Association AreasMore intelligent animals have increased “uncommitted” or association areas of the cortex.The association areas, unlike the motor and sensory areas, can’t be mapped in the same way but damage to different association areas has revealed the importance of these areas in planning, judgment, personality, and morality.The frontal lobes do not finish maturing and developing until a person is in their 20’s
27Language cortical Areas Left Hemisphere Broca’s AreaPierre Paul BrocaLanguage productionBroca’s aphasia:- Language Comprehension unaffectedbut language production is impaired or lost speech non-fluent, labored, aware when they say something wrongDamage to homologous area (in Right hemisphere)difficulty generating inflections of voice
28Language Cortical Areas Wernicke’s Area- Carl Wernicke- Understanding of written and spoken languageRight Homologous area plays a role in processing subordinate meanings of ambiguous words (“river” when given “bank”) while Wernicke’s processes dominant word meanings (“teller” when given “bank”) and in understanding inflections of speech.Wernicke’s Aphasia- Language comprehension is affected- Speech retains normal rhythm and syntax but is largely meaningless
29Specialization and Integration Complex human behaviors involve multiple specialized areas and association areas working together.
34Hemispheric Specialization Left brainGood with literal interpretations of languageMore active when a person is deliberatingMore “rational”Right BrainMaking inferences about words and modulating speech to convey meaningOrchestrates sense of selfBetter with quick, intuitive responsesPerceives objects betterMore involved in emotion, spatial reasoningPeople with intact brains also show left‐right hemispheric differences in mental abilities.A number of brain scan studies show normal individuals engage their right brain when completing a perceptual task and their left brain when carrying out a linguistic task. Although both hemispheres are involved in language, the right brain is the verbal one, capable of producing speech, as evident from split brain studies.
35Divided Consciousness The Right hemisphere is nonverbal but it can still make itself understood
36Split Brain Patients http://www.youtube.com/watch?v=aCv4K5aStdU With the corpus callosum severed, objects (apple) presented in the right visual field can be named. Objects (pencil) in the left visual field cannot.
37Left hemisphere – language, logic, laughter Logical, verbal, sequentialPositive emotionsRight hemisphere –Spatial, emotional intuition, music, “big picture”(People with damage to the left hemisphere may lose their ability to speak but not sing (a right hemisphere task). They can redevelop language by learning to sing everything they want to say!)
38DWhat is the large composite letter?H (right brain active, “big picture”)2. What is the small component letter?D (left brain active)
42When asked to SAY what they saw, they answer __________________ FORK SPOONWhen asked to SAY what they saw, they answer __________________(spoon)When asked to pick up what they saw with their left hand, they will pick up a ______.(fork)
43A split brain patient has a picture of a knife flashed to her left hemisphere and that of a fork to her right hemisphere. She will be able toA. identify the fork using her left hand.B. identify the knife using her left hand.C. identify the knife using either hand.D. identify the fork using either hand.Answer: A
45Dr. J briefly flashed a picture of a key in the right visual field of a split-brain patient. The patient could probablyA. verbally report that a key was seenB. write the word “key” using her left handC. draw a picture of a key using the left handD. none of the above
46What will happen as a neurosurgeon sedates the entire right cerebral hemisphere of a patient who is asked to count aloud with both arms extended upward?A. her left arm will fall and she will become speechlessB. her right arm will fall and she will become speechlessC. her left arm will fall and she will continue countingD. her right arm will fall and she will continue counting
47People should typically recognize familiar words more rapidly when spoken into their __________ ear. Answer: rightPeople should typically recognize familiar melodies more rapidly when played into their ________ ear.Answer: leftNote: Not all people have such simple separations between hemispheres. Women (more than men) tend to use both sides of their brain when interpreting language.
48Unilateral NeglectAfter damage to the right hemisphere, some patients exhibit indifference to the left side of their world – “hemi-neglect”The neglect can be multimodal, affecting auditory, visual, somatosensoryRelated to the right side’s involvement in spatial reasoning and sense of self. Damage to the left side does not have this effect.Classically associated with damage to right posterior parietal cortex. What does this area do?Drawing is of a clock and was done by a person with left side neglect.Patients showing hemispheric neglect for a limb may walk with a limp, accidently close their arm in doors or hold strong, persistent belief that the neglected limb does not belong to them but to someone else (“alien hand syndrome”). They might only dress the right side of their body and shave or put make-up on the right half of their face only. If the neglect is visual, they might only eat food on the right side of their plate, or write only on the right side of a page.Neglect may be multimodal and may even effect memories of scenes –representational neglectStudies have found that even though a person with visual neglect may not report seeing things on the left side, they do see it and register it at least on a subconscious level. This has been shown using semantic priming - In one experiment, stimuli to the left which were unreported (neglected) by the patient, nevertheless speeded subsequent responses to a word if it was semantically related to the neglected item (e.g., tree and apple) compared to if it was unrelated (e.g., bed and apple). Another study showed a patient pictures of an undamaged house and one burning with the flames on the left side of the house (Marshall & Halligan, 1988). When asked which house they would prefer to live in, a patient with left-sided neglect, who did not report seeing the flames of the burning house, nevertheless chose the undamaged house significantly more often.
49Theories of lateralization – Why? May increase neural capacityDominance by one side prevents the simultaneous initiation of incompatible responses/actionsMay increase capacity for parallel processing in the two hemispheresBut then why do we display a consistent preference at the population level? Shouldn’t there be an equal ratio of left to right side preference?Specializing one hemisphere for a particular function leaves the other hemisphere free to perform other functions, avoiding useless duplication and making a more efficient use of neural tissue (Denenberg, 1981).
50Theories of Lateralization – How? Lateral birth position and neonatal head orientation preference are both predictors of handednessLateral asymmetry in the uterine environment and maternal anatomy my lead to the left side of the uterus being more “favorable” for fetal positioning.But then why would we have any lefties at all?With head positioned in the left side of the uterus, the right ear faces outward. This leads to the right ear having a slight aural sensitivity advantage over the left, which may contribute to the left-hemispheric advantage in speech perception and language functions.Speech perception is established by birth and even newborn infants can distinguish their mother’s voice from voices of other women.
51HandednessLefties are more likely than righties to process language with either the right hemisphere or with both hemisphere. 96% of righties process language primarily with left hemisphere.Left-handedness is more common among musicians, mathematicians, pro baseball players, architects and artists.Do you think there is a connection?
52HandednessIn the past, left-handedness was stigmatized in our society and as children, lefties were “trained” to use their right hands.Because most thingsare made for righties,lefties are moresusceptible toaccidental injury.On average, leftieslive 9 years thanpeople who are right-handed
53HandednessGiven these facts about left-handedness as well as what you have learned about research methods, what do you make of this graph?
54The Brain’s Plasticity Plasticity occurs during normal brain development but it is also the brain’s ability to modify itself after injury or loss of functionPhantom limbEnhanced peripheral vision in deaf peopleThe brain is sculpted by our genes and by a person’s environment and experiencesNeural tissue reorganizes and in some cases regenerates (neurogenesis)Constraint induced therapyV.S. RamachandranWhen an area of the brain is damaged, brain cells surrounding the damaged area may change structure and function allowing them to take on the functions of the damaged cells.When an area of the brain stops receiving inputs, for example, if a limb is lost or a person loses their eyesight, the area of the brain that used to receive information from that part of the body can be appropriated to serve other functions, usually by whatever areas are closest to that brain area.
55Plasticity – the brain’s capacity to reorganize Blind person’s sensory cortex for their fingers may expand.In blind people, the visual cortex is activated when they read Braille.In deaf people, some visual information is process in the temporal lobe.Hemispherectomy – removal of an entire hemisphere of cerebral cortex; if surgery performed when young, other hemisphere takes over
56PlasticitySlow destruction of Broca’s area by tumors leaves speech relatively intact. Its function shifts to nearby areas.
57domestic cats have…- thicker skulls and smaller brains- less cone photoreceptors in their retina than wild catswild cats tend to have….- a greater total density of ganglion cells in their retinasThe total neuron number and volume of the lateral geniculate nucleus (LGN) is larger in wild cats than in the domestic catThe actual cell size of the neurons in the LGN is the same in both wild and domestic cats