Cognition & The Brain - KMF 1023 PDF

Today’s topic Understand human cognition by looking at Cognition & the Brain physiological factors – The Mind’s Computer KMF 1023...

Today’s topic Understand human cognition by looking at Cognition & the Brain physiological factors – The Mind’s Computer KMF 1023 Basic background on neurophysiology & neuroscience COGNITIVE PSYCHOLOGY – Electricity in the Nervous System Lecturer: Norehan Zulkiply – Neural Communication FSKPM Universiti Malaysia Sarawak – Neural Information Processing Examples of methods used to study physiological cognition The Mind’s Computer Neuroscience Field of knowledge which was started more than 100 years ago Purpose: to study the biochemistry of the human body Earliest ideas regarding the brain – Leornardo da Vinci- hydraulic system in the brain – Descartes – ‘animal spirits’ in the brain controls the movements of the body Studies of the human brain The Brain’s Structure 2 hemispheres (symmetrical) Cognitive Neuroscience (a branch of Brain + spinal cord = “central nervous system” Neuroscience) attempts to study the human brain Major parts : cerebrum, cerebellum, medulla The most complex object in the universe- weighs Cerebellum : In charge of balance and approximately 1400gms, length = 15 cm 12 coordinating all of the muscles. Contains trillions of cells - 10 which are made up of networks of neurons to produce Medulla: Keeps your heartbeat and your intelligence, creativity, emotions, breathing regular. consciousness,memory etc.. Cerebrum: Controls thinking, moving and sensing. 1  The Brain’s Structure: CEREBRUM Cerebral Cortex Cerebral cortex (outside) Cerebral cortex (outside) – wrinkled surface; – 3mm thick, responsible for higher mental functions original Latin word = bark of – Frontal lobe a tree (kulit kayu) - Parietal lobe – Occipital lobe – Temporal lobe Subcortex (inside) Two Hemispheres – connected by Corpus callosum The four lobes Receive signals from the The Brain’s Structure: touch system, important for vision and attention Subcortex Subcortex (Inside) – Thalamus – Amygdala Limbic Higher – Hippocampus system functions- First place language, in cortex thought, where memory, visual Thalamus - processing information motor information from senses of vision, hearing & touch functions is processed Amygdala – emotions and emotional memories Hippocampus – formation of memories Language, memory, hearing, vision Neurons: The building blocks of Components of the Neuron our nervous system Main parts of a neuron: cell body, dendrites, axon Neurons- cells specialized to receive and transmit information in the nervous system Dendrites: Bring information to the cell body >>100 billion neurons (receive signals) – Comes in all shapes and sizes – Communicate with each other Axon : Takes information away from the cell Neurons run throughout our body in the nervous Body (send signals away) system Cell Body : The main part of the neuron – Provide the mechanism behind the functioning contains nucleus that keeps the cell alive of our senses Receptors = neurons specialized to receive information from the environment The connections among the neurons in all the different brain parts is what makes your brain work. 2  Components of the Neuron Neurons Synapse : a tiny space between the dendrite of one cell and the axon of another cell (contact point for 2 neurons) Axon hillock - where the axon meets the cell body Neurons communicate through the stimulation of electric impulses/ signals = “action potential” Electricity in the nervous system Receptors and Transduction Receptors transform environmental energy into electrical energy So, how do receptors change  Receptors = neurons specialized to receive information from the environment (visual, touch/pain, information from the hearing, smell, taste) environment into a form useful Transduction to neurons and the brain? – Changing one form of energy into another – Environmental energy is transformed into electrical energy – Leads to the generation of electrical signals, called action potentials, which have been linked to cognition E.g. Transduction Process Measuring Action Potentials Action potentials recorded using microelectrodes – Placed in / near an axon – Picks up electric signals that travel down the axon Oscilloscope- displays axon’s electric signals (it generates an instantaneous trace on the screen when correspond to the existence of voltage) Figure: The eye, showing the location of the retina lining the back of the eye, and how light energy enters the front of the eye through the pupil, and electricity leaves the back, in the optic nerve. 3 Figure (p. 31) (b) An action potential recorded by a microelectrode looks like this. The inside of Figure (p. 32) the axon becomes more positive, then goes back to the original level, all within 1 Records showing action potentials in a neuron that responds to light entering the millisecond (1/1,000 second). eye. (a) Presenting light causes an increase in firing; (b) increasing the light (c) A number of action potentials displayed on a compressed time scale, so a intensity increases the rate of firing further; and (c) even more light results in a single action potential appears as a “spike.” high rate of firing. How a neuron works How neurons communicate Neurons communicate through releasing neurotransmitters at Dendrites stimulated by other the synapse neurons The neurotransmitters that travel to the postsynaptic neuron cause a change in the membrane of the postsynaptic neuron, leading either an increase or decrease in the neuron’s rate of Stimulation travels from dendrites firing End of Cause synaptic Release of molecules to axon hillock Action Presynaptic vesicles to = neurotransmitters Axon Hillock Potential neuron open With enough stimulation, neuron fires electricity down axon. Action potential finally reached the end of an axon. How neurons process Neurotransmitters information Neurotransmitters are the Neurons process information messengers that travel by interacting with each between one brain cell and other. another. Interactions take place at the They are chemical signals synapses where one neuron (which include dopamine, releases its neurotransmitter acetylcholine and serotonin), onto other neuron (neural that neurons use to talk to processing/communication each other, which is what between neurons occurs ) makes your brain work. They help determine how Neural processing – you feel, think and act. accomplished by neural circuits ( groups of interconnected neurons) 4  Evidence for Modules & How Neurons are Organized Specialized Functions By Function Inferotemporal cortex Neurons in different areas respond best to – Function: perception – Damage to area: have difficulty different kinds of stimuli. to recognize objects. Specific areas of the brain serve different – E.g prosopagnosia (cannot functions recognize familiar faces) The property of different functions being found in Medial temporal (MT) area different brain areas  Localisation of Function – Function: perception of visual Modules= brain areas that specialize for specific movement – Damage to area: affects motion functions perception – E.g motion agnosia (moving objects appeared to be frozen) Evidence for Modules & Specialised Functions Broca’s Aphasia Wernicke’s area -For analysing spoken language Broca’s Aphasia (Speech affected) - Damage results in – Patient understands but cannot answer Wernicke’s aphasia appropriately spoken or written speech (Comprehension Broca’s area affected) – Inability to process language. Speech is not -for producing fluent coherent speech - Damage results in Eg. : – Why, yes…Thursday, er, er, er, no, er, Broca’s aphasia (speech Firday…Bar-bara…wife…and, oh, affected) car…drive…purnpike…you know…rest and…teevee (Gardner, 1975) Aphasia- difficulty in using language/symbols of communication Wernicke’s Aphasia Wernicke’s Aphasia (Comprehension/Understanding affected) Examples of Methods to study – Patient cannot understand spoken or written speech – Patient unable to understand any commands / physiological cognition questions – Speech is fluent but disorganized – Eg. : Boy, I’m sweating, I’m awful nervous, you know, once in a while I get caught up, I can’t mention the tarripoi, a month ago, quite a little, I’ve done a lot well. I impose a lot, while, on the other hand, you know what I mean, I have to run around, look it over, trebbin and all that sort of stuff (Gardner, 1975) 5  Techniques for studying the Single unit recording physiology of the brain Single unit recording Helps to understand what’s going on in a Event-related potentials single neuron Brain imaging Typically done with non-humans – PET – fMRI Brain lesion Neuropsychology Event-related potentials (ERP) Figure (p. 46) How attention affects the firing of single neurons Record response - An evidence from Single-Unit Recording Technique of many thousand neurons to (a) When a monkey is looking at the X and is not paying attention to the stimulus / event flashing light that is off to the side, a neuron in the cortex fires slowly; Recorded with electrodes placed (b) when the monkey pays attention to the light (while still looking at the on scalp X) firing of the neuron increases. Can tell us when and where activity is occurring Semantics vs. Syntax Brain Imaging – PET Physiological distinction in ERP (Osterhut et al., 1997): Takes advantage of the Positron emission tomography (PET) fact that blood flow increases in areas of the brain that are activated by Inject patient’s blood stream with cognitive task radioactive tracers – Sent to brain through blood flow Able to detect blood flow by tracing the radioactivity to specific modules of the brain Measures blood flow to Modules (Specific brain area): Modules: > blood = > activation – Eg. Reading – activates the visual (a)The N400 wave of the ERP is affected cortex by semantics. It becomes larger (dark line) (b) The P600 wave of the ERP is affected by syntax. It becomes larger PET scans tells us where and when when the meaning of a word does not fit the rest of the sentence. (dark line) when syntax is incorrect. brain activity happens (and check brain’s functions and disorder) 6  Brain Imaging – fMRI fMRI (functional Magnetic Resonance Imaging) Also based on blood flow No radioactive elements Hemoglobin, which carries Oxygen in the blood contains a ferrous molecules (magnetic properties) Presenting magnetic fields to the brain causes the hemoglobin molecules to line up like tiny magnets Principle - oxygen-rich blood is an index of brain activity Measure the activity in the part of the brain that is active Brain Lesioning Neuropsychology Brain Lesioning – removal of a portion of the Study of behavioral effects of brain brain damaged humans Case of patient HM Brain damaged (e.g caused by accidents/ – Severe epileptic seizures(penyakit sawan) stroke etc) caused the disruption in blood – Surgically removed hippocampus &“surrounding areas” in attempt to stop his severe epileptic. supply to an area of the brain – Operation did reduce HM’s seizures, but HM lost E.g double dissociations – situations in ability to form new memories. which one function is absent while another – Role of hippocampus in formation of new memories is present in one person and that opposite – Operation never repeated can also occur in other person Tables (p. 51) Table 2.2a: Double Dissociation: Two Broken TVs Table 2.2b: Double Dissociation: Two People with Brain Damage 7