Q551 Brain and CognitionPowerPoint PresentationSlide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Anatomy-Exterior ViewAnatomy-Major StructuresAnatomy-Interior ViewAnatomy-Four LobesAnatomy-Major AreasAnatomy-Association CortiMajor Areas- Speech PathwaysSlide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Slide 37Slide 38Slide 39Slide 40Slide 41Slide 42Slide 43Slide 44Slide 45Slide 46Slide 47Slide 48Slide 49Slide 50Slide 51Slide 52Slide 53Sensing Techniques-Cat ScansSlide 55Slide 56Slide 57Sensing Techniques-PETSlide 59PET ScansSlide 61Slide 62Slide 63Slide 64Slide 65Slide 66Slide 67Slide 68Slide 69Slide 70Slide 71Slide 72Sensing Techniques-fMRIfMRI MethodMRI ScansSlide 76Slide 77Slide 78Slide 79Slide 80Slide 81Slide 82Slide 83Summary1Q551 Brain and CognitionCognitive Neuroscience“If the brain were simple enough to understand, we would be too stupid to understand it”2Brain and Cognition Week 3Gross Brain Anatomy and PhysiologySynaptic transmissionEEG/MEG/PET/fMRI3The Chemical Synapse4Chemical Neurotransmission“At rest”, the synapse (presynaptic side) contains numerous synaptic vesicles filled with neurotransmitter, intracellular calcium levels are very low (1).Arrival of an action potential: voltage-gated calcium channels open, calcium enters the synapse (2).Calcium triggers exocytosis and release of neurotransmitter (3).Vesicle is recycled by endocytosis (4).5Chemical NeurotransmissionOnce released, the neurotransmitter molecules diffuse across the synaptic cleft (about 20-50 nm wide).When they “arrive” at the postsynaptic membrane, they bind to neurotransmitter receptors (“lock-and-key” mechanism).Two main classes of receptors:Transmitter-gated ion channelsG-protein-coupled receptorsTransmitter-gated ion channels: transmitter molecules bind on the outside, cause the channel to open and become permeable to either Na+ (depolarizing, excitatory effect) or Cl– (hyperpolarizing, inhibitory effect).G-protein-coupled receptors have slower, longer-lasting and diverse postsynaptic effects. They can have effects that change an entire cell’s metabolism.6Excitatory Effects of NeurotransmittersEPSP = ExcitatoryPost-SynapticPotential7Inhibitory Effects of NeurotransmittersIPSP = InhibitoryPost-SynapticPotential8Integration of Synaptic InputsIn the CNS, many EPSP’s are needed to generate an AP in a single neuron.A single EPSP has, in general, very little effect on the state of a neuron (this makes computational sense).On average, the dendrite of a cortical pyramidal cell receives ~10000 synaptic contacts, of which several hundred to a thousand are active at any given time. The adding together of many EPSP’s in both space and time is called synaptic integration.9Synaptic Integration(a)Single input → single EPSP.(b)Three APs arriving simultaneously at different parts of the dendrite add together to produce a larger response (spatial summation).(c) Three APs arriving in quick succession in the same fiber can also result in a larger response (temporal summation).10Integration of Synaptic InputsDistal and proximal synaptic inputs:11Learning and PlasticityWe will return to these topics in a future week121314Anatomy-Exterior View15Anatomy-Major Structures16Anatomy-Interior View17Anatomy-Four Lobes18Anatomy-Major AreasFour Lobes:•Frontal Lobe•Parietal Lobe•Temporal Lobe•Occipital Lobe•Thalamus•Cerebellum19Anatomy-Association Corti20Major Areas- Speech Pathways21Cortical AnatomyRepresentation of Imaging Data Sets:- 3-D based- Surface basedBroca’s AreaMotor CortexVisual CortexAuditory Cortexgyrussulcus22Cortical AnatomyThe macaque monkey cortex - unfolded.Felleman and Van Essen, 1991.23Cortical Anatomy24“Brain Flattening”25Source: Marty Sereno, UCSD26Source: Marty Sereno, UCSD27“Brain Averaging”28Standardized Brain Atlas29Methods of Cognitive NeuroscienceNeurobiology:NeuroanatomyNeurophysiologyNeuroimaging TechniquesPETMRI/fMRIEEGMEGEvidence from DysfunctionLesionsDiseases of the CNSCognitive PsychologyComputational Approaches30Methods of Cognitive Neuroscience31NeurobiologyNeuroanatomy and neurophysiologyare often conducted in animalsystems (monkey, cat, etc.).Neuroanatomy:- Large-scale anatomy of the brain- Subdivisions of the cortex- Neuronal subtypes, layers- Morphology of single neurons32NeurobiologyNeurophysiology:- Recording of neural activity, often in the context of a stimulus or task (single-cell recording, local field potential recording, multi-electroderecording).- Electrical stimulation of neurons to study their role in perception or movement (micro-stimulation, surface stimulation)33Methods ComparisonMethod Space Time Neural Correlate-------------------------------------------------------------PET coarse coarse “brain activation”, metabolic(5 mm) (sec.) rate of tissue, incorporation of glucose, oxygen utiliz., receptor distribution, 2D-3D capable.fMRI coarse coarse “blood oxygenation state”,(2 mm) (1 sec.) “regional blood flow”,oxygenated/deoxygenated hemoglobin, 2D-3D, in register with struct. Scan.EEG coarse fine “electrical (field) potentials”,(?) (msec) surface electrodes arranged on skull, limited depth, inverseproblem, unknown source locations, allows correlationmeasures.MEG coarse fine “magnetic (field) potentials”,(?) (msec) SQUIDs arranged around head,sensitive to noise, similar advantages and drawbacks as EEG.34A New Method…Transcranial Magnetic Stimulation (TMS)35EEGThe electroencephalogram (EEG) measures the activity of large numbers (populations) of neurons.First recorded by Hans Berger in 1929.EEG recordings are noninvasive, painless, do not interfere much with a human subject’s ability to move or perceive stimuli, are relatively low-cost.Electrodes measure voltage-differences at the scalp in the microvolt (μV) range.Voltage-traces are recorded with millisecond resolution – great advantage over brain imaging (fMRI or PET).36EEGStandard placements of electrodes on the human scalp: A, auricle; C, central; F, frontal; Fp, frontal pole; O, occipital; P, parietal; T, temporal.37EEG38EEG39EEGMany neurons need to sum their activity in order to be detected by EEG electrodes. The timing of their activity is crucial. Synchronized neural activity produces larger signals.40The ElectroencephalogramA simple circuit to generate rhythmic activity41The ElectroencephalogramTwo ways of generating