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Chapter 4

Chapter 4. Part 1 – The Brain. The cerebral cortex Cerebral Hemispheres Corpus Callosum Four lobes of the cerebral cortex The Frontal Lobe Parietal Lobe Temporal Lobe Occipital Lobe Hemispheric Specialisation Left hemisphere specialisations Right hemisphere specialisations

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Chapter 4

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  1. Chapter 4 Part 1 – The Brain Grivas, J., Letch, N., Down, R. & Carter, L. (2010). Psychology VCE Units 3&4 (4th ed.) Melbourne: MacMillan

  2. The cerebral cortex Cerebral Hemispheres Corpus Callosum • Four lobes of the cerebral cortex The Frontal Lobe Parietal Lobe Temporal Lobe Occipital Lobe • Hemispheric Specialisation Left hemisphere specialisations Right hemisphere specialisations • The reticular activating system • The thalamus Grivas, J., Letch, N., Down, R. & Carter, L. (2010). Psychology VCE Units 3&4 (4th ed.) Melbourne: MacMillan

  3. Nervous System • Our nervous system can be organised into different divisions. • There are 2 major divisions – the central nervous system (CNS) and the peripheral nervous system (PNS). • CNS consists of brain and spinal cord. PNS consists of all other parts of the nervous system. • Brain is the CBD. PNS is all the roads that carry the messages both incoming and outgoing. Spinal cord connects the two. Grivas, J., Letch, N., Down, R. & Carter, L. (2010). Psychology VCE Units 3&4 (4th ed.) Melbourne: MacMillan

  4. Grivas, J., Letch, N., Down, R. & Carter, L. (2010). Psychology VCE Units 3&4 (4th ed.) Melbourne: MacMillan

  5. The brain • Known as the ‘master organ’. Controls everything. • Encased in skull – weighs 1.5kg • Consistency offirm jelly. • Gap between brain and skull which is filled with fluid for protection. • Complex structure of billions of neurons and trillions of connections. These connections form pathways which enable transmission of information – neurotransmission. • Neurons are organised into identifiable structures within the brain. • These are all connected and work together however for the purpose of study we focus on these regions separately. Grivas, J., Letch, N., Down, R. & Carter, L. (2010). Psychology VCE Units 3&4 (4th ed.) Melbourne: MacMillan

  6. The cerebral cortex • Convoluted (folded) outer layer or covering of the two cerebral hemispheres (halves). • Surface area of 0.25m² (4 pages of text book) and is about 2-4mm thick, therefore, to fit inside skull it is all screwed up like a piece of paper. 1/3 is visible when looking at the brain – rest is hidden in ‘folds’. • Contains about ¾ of brain’s neurons. • Involved in information processing = perception, language, learning, memory, thinking and problem-solving, as well as the planning and control of voluntary bodily movements. Grivas, J., Letch, N., Down, R. & Carter, L. (2010). Psychology VCE Units 3&4 (4th ed.) Melbourne: MacMillan

  7. The cerebral cortex • Some areas are dedicated to specific functions… • Primary visual cortex – receiving and processing visual information from the eyes • Sensory cortex areas – processes information from our different senses • Motor cortex areas – processes and sends information about voluntary bodily movements • Association cortex areas – integrates sensory, motor and other information and involved in more complex mental abilities such as perceiving, thinking and problem solving. • It’s believed that the size of a species cerebral cortex is linked to intellectual ability. • What functions is known but how these are performed not a lot if known. Grivas, J., Letch, N., Down, R. & Carter, L. (2010). Psychology VCE Units 3&4 (4th ed.) Melbourne: MacMillan

  8. Cerebral Hemispheres • Cerebral cortex is divided into two halves – hemispheres, known as left and right hemisphere. • These are almost symmetrical that appear to be separated by a deep groove running from front to back. However, these are not separated; they are connected at several points by tissue. The largest and most important of these strands is a bundle of nerve fibres called the Corpus Callosum. • Each hemisphere appear to be alike in overall size, shape and structure, also particular parts of the hemisphere responsible for different functions are located in the similar place. • Each hemisphere has sensory and motor areas that perform the same sensory and motor functions for a different side of the body. Grivas, J., Letch, N., Down, R. & Carter, L. (2010). Psychology VCE Units 3&4 (4th ed.) Melbourne: MacMillan

  9. Cerebral Hemispheres • Left hemisphere receives sensory information for the right side of the body and controls movement for the right side. • Right hemisphere receives sensory information for the left side of the body and controls movement for the left side. • Each hemisphere also has specialised functions. Left = Language…Right = not dependent on language – spatial, visual, recognition, tunes… Grivas, J., Letch, N., Down, R. & Carter, L. (2010). Psychology VCE Units 3&4 (4th ed.) Melbourne: MacMillan

  10. Corpus Callosum • Band of nerve tissue connecting the left and right hemisphere and serves as the main communication pathway between them. • It is a ‘bridge’ for neural messages to pass between hemispheres. • Evidence supports that one hemisphere is more dominant than the other, but they do not function independently. Both hemispheres involved in virtually everything that we do. They interact via this corpus callosum. • Not the only connection. There is many more. This is the most important though. Grivas, J., Letch, N., Down, R. & Carter, L. (2010). Psychology VCE Units 3&4 (4th ed.) Melbourne: MacMillan

  11. Four lobes of the cerebral cortex • Each hemisphere can be divided into four anatomical regions = Cotrical Lobes. Each area is associated with different structures and functions. • The lobes contain areas of cortex that have specialised sensory and motor functions, as well as areas of cortex referred to as association cortex. Grivas, J., Letch, N., Down, R. & Carter, L. (2010). Psychology VCE Units 3&4 (4th ed.) Melbourne: MacMillan

  12. Cerebral Cortex • Association Cortex – are different areas commonly called association areas. Each has one or more functions that integrate information from sensory, motor and other brain areas that enable us to think, feel and behave as we do. • Sensory areas – receive and process information from sensory receptors in the body. Sensory receptors convert information into neural (‘nerve’) impulses and transmit to the sensory areas in the brain. Different sensory areas are located in different lobes of the brain. • Visual information – Primary Visual Cortex – Occipital Lobe • Auditory information – Primary Auditory Cortex – Temporal Lobe • Skin and skeletal muscles – Primary Somatosensory Cortex – Parietal Lobe. • Motor areas – receive and process information about voluntary bodily movements – intentional movements. Only one area – Primary Motor Cortex – Frontal Lobe. Sends neural messages to various parts of the body. • Association areas – located in all four lobes of each hemisphere. Receive and process information from sensory and/or motor areas, as well as other structures or association areas within the brain. Grivas, J., Letch, N., Down, R. & Carter, L. (2010). Psychology VCE Units 3&4 (4th ed.) Melbourne: MacMillan

  13. Grivas, J., Letch, N., Down, R. & Carter, L. (2010). Psychology VCE Units 3&4 (4th ed.) Melbourne: MacMillan

  14. The Frontal Lobe • Largest of four lobes. Upper forward half of each cerebral hemisphere. Grivas, J., Letch, N., Down, R. & Carter, L. (2010). Psychology VCE Units 3&4 (4th ed.) Melbourne: MacMillan

  15. The Frontal Lobe • Located at the rear of each frontal lobe running roughly across the top of your head is a strip of neural tissue = Primary Motor Cortex – involved in controlling voluntary bodily movements through its control of skeletal muscles. • Primary motor cortex in the left frontal lobe controls body movement on the right side of the body. • Primary motor cortex in the right frontal lobe controls body movement on the left side of the body. Grivas, J., Letch, N., Down, R. & Carter, L. (2010). Psychology VCE Units 3&4 (4th ed.) Melbourne: MacMillan

  16. The Frontal Lobe • Forward section of each frontal lobe are association areas that receives information from other lobes to enable us to perform complex mental functions (planning, estimating, decisions). • Also involved in attention, personality, control of emotions and expression of emotional behaviour. ~Phineas Gage P186~ • “executive role” in thinking, feeling and behaving because it is the end point for sensory information received and processed in other lobes and coordinates functions of other lobes and determines many behavioural responses. Grivas, J., Letch, N., Down, R. & Carter, L. (2010). Psychology VCE Units 3&4 (4th ed.) Melbourne: MacMillan

  17. The Frontal Lobe • Specific areas along the cortex are involved in different movements of body parts. Parts that are able to move with precision take up more space than those that we have less control over. Grivas, J., Letch, N., Down, R. & Carter, L. (2010). Psychology VCE Units 3&4 (4th ed.) Melbourne: MacMillan

  18. Broca’s area • Left frontal lobe next to motor cortex areas that control face, tongue, jaw and throat. Slightly above left ear. • Production of articulate speech (clear and fluent). Coordinating movement of muscles required for speech. • Also linked to and interacts with areas of cerebral cortex that are involved with meaning of words and structure of sentences (grammar). • Apparent with speech impairments that result when Broca’s area is damaged. Grivas, J., Letch, N., Down, R. & Carter, L. (2010). Psychology VCE Units 3&4 (4th ed.) Melbourne: MacMillan

  19. Parietal Lobe • Located behind frontal lobe – upper back half of brain but not rearmost. • Receives and processes sensory information from the body and skin senses (somatosensory) and other sensory areas in the brain. Grivas, J., Letch, N., Down, R. & Carter, L. (2010). Psychology VCE Units 3&4 (4th ed.) Melbourne: MacMillan

  20. Parietal Lobe • Somatosensory cortex – Located at the front of each partietal lobe, just behind the primary motor cortex (separated by a groove). Enables us to perceive bodily sensations. • Somatosensory cortex in the left parietal lobe receives and processes information from the right side of the body. Somatosensory cortex in the right parietal lobe receives and processes information from the left side of the body. • Parietal lobe also has association areas that receives and integrates other information from within lobe or other parts of brain. Eg: body in space – sound and vision. • Attention and spatial reasoning – temporal lobe of right hemisphere but evidence supports parietal lobe through ‘spatial neglect’ (look at later). Grivas, J., Letch, N., Down, R. & Carter, L. (2010). Psychology VCE Units 3&4 (4th ed.) Melbourne: MacMillan

  21. Parietal Lobe • Involved in sensations of touch received from specific body parts. Amount of cortex allocated to particular body part corresponds with sensitivity and use of. Grivas, J., Letch, N., Down, R. & Carter, L. (2010). Psychology VCE Units 3&4 (4th ed.) Melbourne: MacMillan

  22. Temporal Lobe • Lower central area of the brain, above each ear. • Primarily involved in auditory perception but also plays an important role in memory (each lobe contains hippocampus), in aspects of visual perception such as our ability to identify objects and recognise faces and in our emotional responses to sensory information and memories. Grivas, J., Letch, N., Down, R. & Carter, L. (2010). Psychology VCE Units 3&4 (4th ed.) Melbourne: MacMillan

  23. Temporal Lobe • Primary Auditory Cortex – receives and processes sounds from both ears. Each primary auditory cortex has specialised areas that receive and process different features of sound. Frequency (pitch) and Amplitude/Intensity (loudness) processed in different areas of cortex. • Verbal sounds (words) = left primary auditory cortex. Non-verbal (music) = right primary auditory cortex. However there is some overlap. • Also has association areas, involved with memory (linking emotion to memories), object identification and face recognition. • People with amnesia (partial or complete memory loss) often have damage to either or both temporal lobes which is responsible for receiving, processing and storing memory facts, how to do things and personal experiences (b’days). Grivas, J., Letch, N., Down, R. & Carter, L. (2010). Psychology VCE Units 3&4 (4th ed.) Melbourne: MacMillan

  24. Wernicke’s area • Cortical area towards rear of temporal lobe, next to primary auditory cortex and connected to Broca’s area by bundle of nerve. • Left hemisphere ONLY. • Speech production and comprehension of speech (interpreting sounds of human speech). • When a word is heard, processed in primary auditory cortex of left temporal lobe, but the word cannot be understood until it has been processed by Wernicke’s area. • Not vital for understanding but more to locate appropriate words from memory to express meanings. • Damage causes impairment in understanding speech and to speaking. Grivas, J., Letch, N., Down, R. & Carter, L. (2010). Psychology VCE Units 3&4 (4th ed.) Melbourne: MacMillan

  25. Occipital Lobe • Rearmost area of each cerebral hemisphere (back of your head). • Sense of vision. • Damage = blindness. • Some areas in the other lobes play role in visual functions. • Primary visual cortex – base of each occipital lobe. Comes there from visual sensory receptors (photoreceptors) located on the retina. Grivas, J., Letch, N., Down, R. & Carter, L. (2010). Psychology VCE Units 3&4 (4th ed.) Melbourne: MacMillan

  26. Occipital Lobe • Each hemisphere receives and processes half of the visual information. Box 4.12 p 224. • The left half or each eye (which receives visual sensory information from the right half of visual field) send information only to the visual cortex in the left occipital lobe. • The right half or each eye (which receives visual sensory information from the left half of visual field) sends information only to the visual cortex in the right occipital lobe. • Neurons in the primary visual cortex and surrounding ‘secondary’ visual areas ate specialised to respond to different features of visual information Eg: direction of lines, edges, shapes, motion, colour etc. • Association areas interact with primary visual cortex to select, organise and integrate visual information. Also interact with the other lobes and memory, language and sounds. This enables meaningful interpretation. Grivas, J., Letch, N., Down, R. & Carter, L. (2010). Psychology VCE Units 3&4 (4th ed.) Melbourne: MacMillan

  27. Grivas, J., Letch, N., Down, R. & Carter, L. (2010). Psychology VCE Units 3&4 (4th ed.) Melbourne: MacMillan

  28. Dorsal stream – locating objects or spatial perception (determining where an object is and relating it to other objects in a scene). “Where” pathway – active when performing tasks that require decisions about spatial relationships between objects. • Ventral stream – object perception and recognition. “What” pathway – active when performing tasks of identifying objects. • Case study on D.F. page 197 of text. Grivas, J., Letch, N., Down, R. & Carter, L. (2010). Psychology VCE Units 3&4 (4th ed.) Melbourne: MacMillan

  29. Hemispheric Specialisation • Although each have specialised functions, both hemispheres are involved in nearly all functions usually together and in a coordinated manner. • Damage to left – difficulties with language-related activities (understanding speech, talking fluently, reading and writing). • Damage to right – difficulties with visual and spatial tasks (reading a map, geometric shapes). Mentally picture. Grivas, J., Letch, N., Down, R. & Carter, L. (2010). Psychology VCE Units 3&4 (4th ed.) Melbourne: MacMillan

  30. Grivas, J., Letch, N., Down, R. & Carter, L. (2010). Psychology VCE Units 3&4 (4th ed.) Melbourne: MacMillan

  31. Brain stem • Difficult to determine where your spinal cord ends and brain begins. This is due to spinal cord is a continuation of the brain stem (hindbrain). Looks like a stem the brain sits on. • 3 anatomical structures • Medulla • Cerebellum • Pons • Running through the centre of the brain and upward through the midbrain to the forebrain (the area under the cerebral cortex) is the reticular formation. • Microscope – looks like a white netting or lace – ‘reticular = network’ • Controls sleeping and waking. Grivas, J., Letch, N., Down, R. & Carter, L. (2010). Psychology VCE Units 3&4 (4th ed.) Melbourne: MacMillan

  32. The reticular activating system (RAS) • Network of neurons that extends in many directions from the reticular formation to different parts of the brain and spinal cord. • Ascending tracts (upward nerve pathways) extend to the cerebral cortex.Descending tracts (downward nerve pathways) extend to the spinal cord. Grivas, J., Letch, N., Down, R. & Carter, L. (2010). Psychology VCE Units 3&4 (4th ed.) Melbourne: MacMillan

  33. The reticular activating system (RAS) • Regulates arousal (‘alertness’). When RAS is less active we are likely to go to sleep. Anaesthetics work by reducing activity of RAS. Damage to RAS disrupts sleep-wake cycle. • RAS influences attention. Sends out a steady stream of neurons to keep us alert. Highlights potentially important information. • Bombards cortex with stimulations when greater attention is needed. Can filter out weak incoming sensory information allowing brain to concentrate. • Can call attention to two or more sources of sensory information to focus on relevant information. • One way of routing sensory information to cerebral cortex. Grivas, J., Letch, N., Down, R. & Carter, L. (2010). Psychology VCE Units 3&4 (4th ed.) Melbourne: MacMillan

  34. The thalamus • Another way of routing sensory information to cerebral cortex. Filters information from the senses and transmits (‘relays’) to cerebral cortex. • Ascending RAS tracts connect to central areas in thalamus and appears to influence arousal and attention. • Located in middle of the brain – ‘gateway’ to lower part of the brain. • Receives information form all major senses apart form smell, that bypasses the thalamus straight to the cortex. Channelled through the thalamus, therefore crucial role in influencing arousal. • Damage – because major sensory relay might also cause cortex to misinterpret or not receive vital sensory information. • Also plays a role in attention – similar to RAS. • Closes the pathways while we sleep so that our brain can rest. • Study of that bloke with fatal familial insomnia Grivas, J., Letch, N., Down, R. & Carter, L. (2010). Psychology VCE Units 3&4 (4th ed.) Melbourne: MacMillan

  35. Grivas, J., Letch, N., Down, R. & Carter, L. (2010). Psychology VCE Units 3&4 (4th ed.) Melbourne: MacMillan

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