Cognitive Neuroscience Methods Lecture 1 PDF

Lecture 1: Methods in Cognitive Neuroscience PSYC21022: Cognitive Neuroscience Dr. Wai Yeung [email protected] Lecture overview Introduction and what to expect Research methods in cognitive neuroscience  Cognitive Neuroscience approach...

Lecture 1: Methods in Cognitive Neuroscience PSYC21022: Cognitive Neuroscience Dr. Wai Yeung [email protected] Lecture overview Introduction and what to expect Research methods in cognitive neuroscience  Cognitive Neuroscience approach fastee timeswere. reactionecondsame word to Cognitive neuroscience provides a brain- ↑ based account of cognitive processes (thinking, perceiving, remembering etc.) Made possible by technological advances in studying the brain that are safer and less crude than Penfield’s method # sameword hassent Cognitive psychology provided word experimental paradigms and theoretical framework. - poste fasters Cognitive neuroscience tests psychological theories but local blood oxygen and RTs are just data, they do not tell us HOW things happen abc ↳ samecase& differen faster. (Dehaene et al., 2004) Methods for looking at the brain Single unit recording Electroencephalography (EEG) Magnetoencephalography (MEG) Positron Emission Tomography (PET) Magnetic Resonance Imaging (MRI) Functional MRI – fMRI Diffusion Tensor Imaging – DTI Functional Near-Infrared Spectroscopy – fNIRS Intracranial electroencephalography (iEEG) - ECoG Transcranial magnetic stimulation - TMS Transcranial electrical stimulation - tES (tDCS & tACS) Methods of Behavioural Neuroscience  Methods of Cognitive Neuroscience Spatial resolution Temporal resolution Ideally, we would like to record from single neurons….  a or -meas Electrophysiological techniques- - single cell recording animals/mammals Very small electrode implanted into axon (intracellular) or outside axon membrane (extracellular)↳ more popular mammals are small). in cneurons Records neural activity from population of neurons Single unit recording Electrodes, consisting of thin wires, are implanted into specific areas of the brain. Recordings of brain cell activities are made by measuring the electrical potential of nearby neurons that are in close proximity to the electrode.  see. th to is electea ke witintregion close me ↑ the T of electron frina less potential Y ↳ different W. W. Norton region. in What neuroimaging techniques can we use in humans?  Electroencephalography (EEG) The measurement of the electrical activity of the brain by recording from electrodes placed on the scalp. The resulting traces are known as an electroencephalogram (EEG) and represent an electrical signal from a large number of neurons The 10–20 system of electrodes used in an EEG/ERP experiment.  Electroencephalography (EEG) EEG signals represent the change in the potential difference between two electrodes placed on the scalp in time The EEG obtained on several trials can be averaged together time locked to the stimulus to form an event-related potential (ERP) ERPs can be recorded from the human scalp and ERPs are voltage fluctuations that are extracted from the ongoing electroencephalogram associated in time with particular event EEG by means of filtering and signal averaging. (visual, auditory, olfactory stimuli) https://www.youtube.com/watch?v=iXXxL0EOJqs The EEG signal needs to be averaged over many trials to generate an ERP because it has a ratio. low signal-to-noise  Using ERP to Study Face Recognition Different ERP peaks associated with different aspects of face processing The N170 is relatively specialized for faces, recorded from right PSTS (posterior superior temporal sulcus) The P300 – famous and familiar faces that a recognise min a i > - S face else ↳ you decideperson on't Youhow the ↳ name or not name person. 700-800ms to recognise is · Usually takes up to person or. not know the you Rousselet et al. (2004).  [ a The peakislesspronounce atients. an for p controlled A comparison between the ERPs from patients with Alzheimer’s disease and those from control subjects. A markedly reduced P300 is seen for the demented patients at each electrode site P300 = a positive peak at around 300msec.  MEG Magnetoencephalography (MEG) is an imaging technique used to measure the magnetic fields produced by electrical activity in the brain via - extremely sensitive devices known as SQUIDs. These measurements are commonly used in both research and clinical settings. Excellent temporal and spatial resolution ↳norpecita fur find a machine to be used. · MEG is very expensive , so you'll rarely & EEG has electric fields in the brain. has magnetic fields brain are MEG is similar to EEG except it a cold setting Our magnetic fields in the machines & are usually conducted · , in than MRI · uses a lot more energy that magnetic field. MEG is used to pick up usually weak so  Interim Summary – Recording Techniques Neuronal activity generates electrical and magnetic fields that can be measured invasively (single cell recordings) or non-invasively (EEG, MEG) Single cells studies tell us how neurons code information, by measuring their response to external stimuli When populations of neurons are active in synchrony, they produce an electric field that can be detected at the scalp (EEG). When many waves are averaged and linked to the onset of the stimulus, then an ERP is obtained An ERP is an electrical signature of all different cognitive components that contribute to processing of that stimulus. Systematically varying aspects of a stimulus (e.g. any face vs. famous face) may lead to variations in aspects of ERP waveform. This can tell us about the timing and independence of cognitive processes  Magnetic Resonance Imaging (MRI) Uses differential magnetic properties of types of tissue and of blood to produce images of the brain  Structural vs. Functional imaging Structural: different types of tissue (skull, gray matter, white matter, CSF fluid) have different physical properties – used to create STATIC maps (CT and structural MRI) Functional: temporary changes in brain physiology associated with cognitive processing (PET & fMRI)  #MRI to use it it we are interested in heurochemical changes. PET is not as precise as , tend PET – Positron Emission Tomography Measures local blood flow (rCBF) Radioactive tracer injected into blood stream Tracer takes up to 30 seconds to peak When the material undergoes radioactive decay, a positron is emitted, which can be picked up by the detector Areas of high radioactivity are associated with brain activity, based on blood volume  Carries to the brain & the oxygen has been used/completed it becomes deoxygenised. The deoxyhemo- Oxynemoglobin once · Oxygen globin properties that is picked up by the scanner magnetic. has know activities take place precisely but does rely · FMRI has good spatial resolution so we can where certain of blood. on the flow fMRI Directly measures the concentration of deoxyhemoglobin in the blood This is called the BOLD response (Blood Oxygen Level Dependent contrast) The change in BOLD response over time is called the hemodynamic response function The Hemodynamic Response Function peaks in 6–8 seconds. This limits the temporal - It compared to EEG its a lot slower resolution of fMRI - When. , takes about 5-8 seconds for blood to of the brain , reach certain areas  activation red. With fMRI we study correlation between brain activity more significanactivationla and stimulus timings fMRI can be used to produce activation maps showing which ↑ parts of the brain are involved in a particular mental process. Measure activity in voxels — or volume pixels the smallest distinguishable box-shaped part in 3D image  What Does it Mean to Say a Brain Region is "Active"? The brain has a constant supply of blood and oxygen; if it didn’t, it would die, this means we cannot literally stick someone in a scanner and read their thoughts (because the whole brain would look active) To infer functional specialization, one needs to compare RELATIVE differences in brain activity between two or more conditions This involves selecting a baseline or comparison condition  A region is "active" if it shows a greater response in one condition relative to another. If the experimenter chooses inappropriate conditions the regions of activity will be meaningless O O ! Y greaterresponse high difference.  Designing an fMRI study What are the brain regions involved in: 1. Recognizing written words 2. Saying the words 3. Retrieving the meaning of the words Peterson et al., 1988 Cognitive subtractions Cognitive subtraction – activity in a control task is subtracted from the activity in an experimental task Problems: difficulty of the baseline task Disagreements Between Imaging and Lesion Studies Evidence from Semantic Processing imaginadatais non to innnat the tim e. This region is critical  fMRI OF THE TEMPORAL LOBES Comparing two imaging methods in a semantic task TABLE 1 for participants to m Sample Stimuli Used in the Two Categorization Tasks lasted 3750 ms. Subj faster to respond to Cue 1 Cue 2 Cue 3 Target Response (RT) " 712 the ms) tha fourth or 736 ms) and same whether very the fe Semantic categorization of trial (9 e y had and 8% er bookcase cabinet bench COUCH “same” lobster mussel shrimp CLAM “same” As mentioned prev squirrel wolf fox LIME “different” tation durations an knife spoon fork MARBLES “different” image preprocessing they study ! was Letter categorization fMRI experiments. controlled fur it nether letters. aaaaaa aaaaa aaaa AAAAAA “same” E tween the two expe eifferent sssss lllll ssss llllll sssssss lll SSS YYYYY “same” “different” J for had result of optimizing ddd ddddddd dddddd RRRR “different” modality with the of the two experime parable. nant) hand and both reaction times and accuracy were Devlin et al., 2000 recorded. 1 EXPERIMENT 1 The letter categorization task shared the same stim- ulus and response characteristics, but had no lexical or The purpose of thi  obe ine I s imp activation in Neuroimaging whea fMRI Results Here > IFG (BA 44/45) IFG R.cerebellum BA 8 rIFG Areas of activation in the Semantic minus Letter categorization comparison Devlin et al., 2000  a MeDescalati , zuaction To owever a Gath Music for X Brea PET Results IFG (BA44/45) R. cerebellum Inferior temporal Anterior temporal pole (BA 38) gyrus (BA 20) this be Areas of activation in the Semantic minus Letter categorization comparison why might happening ? activations very close to nasal cauties and in these cavities , you may lose a bit of signal with mri so you may not pick up near temporal · Temporal lobes are lobes. the temporal lobes see it methods to image. we can · only when we develop  DTI – Diffusion Tensor Imaging An imaging method that uses a modified MRI scanner to reveal bundles of axons in the living brain Measures white matter organization based on limited diffusion of water molecules in axons We can visualize connections in the brain  Functional Near-Infrared Spectroscopy (fNIRS) Measures the same BOLD response as fMRI but in a completely different way ‘Light’ in infrared range passes through skull and scalp but is scattered differently by oxy- v. deoxyhemoglobin Portable and more tolerant of head movement but can’t image deep structures  Intracranial electroencephalography (iEEG) or ECoG The only method that gives us the high resolution in both place and time is intracranial recording, when we record directly from inside the human brain, when people are undergoing neurosurgery They are placed to locate the seizure and map function (for neurosurgery purposes) Recording straight from the cortical surface, approximately from tens of thousands of neurons  Intracranial recordings - in Humans (ECoG) Recorded extracellular activity from 1177 cells in human medial frontal and temporal cortices while patients executed or observed hand grasping actions and facial emotional expressions (control condition). Neurons in supplementary motor area SMA, and hippocampus responded to both observation and execution of actions observation execution observation execution Video Mukamel et al., 2010  Summary Methods for looking at the brain Electroencephalography (EEG) Magnetoencephalography (MEG) Positron Emission Tomography (PET) Magnetic Resonance Imaging (MRI) Functional MRI – fMRI Diffusion Tensor Imaging – DTI Functional Near-Infrared Spectroscopy – fNIRS Intracranial electroencephalography (iEEG) - ECoG