Cognitive Neuroscience - Department Of Computer Science

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Cognitive NeurosciencePhilipp Koehn11 February 2020Philipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Cognitive Neuroscience1 Looking ”under the hood” What is the hardware thatthe mind runs on? Much progress in recent years– understanding electrochemical processes inneurons– probing neurons withelectrodes– MRI scans of brain activity But: still far away from a bio-chemical model of ”thinking”Philipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Information Processingin the Brain2 Consider the chain of events– you are asleep– the alarm clock rings– you press the snooze button What happens inside the brain?–––––sound wave hit your earyour ear converts it to sensory inputsignals reach the auditory areasignals are sent to the motor areayour arm actsPhilipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

3neuronsPhilipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Philipp KoehnNeuron4Artificial Intelligence: Cognitive Neuroscience11 February 2020

Philipp KoehnReceptor Neuron5Artificial Intelligence: Cognitive Neuroscience11 February 2020

Philipp KoehnTransmission of Signals6Artificial Intelligence: Cognitive Neuroscience11 February 2020

Philipp KoehnRecording Neural Activity7Artificial Intelligence: Cognitive Neuroscience11 February 2020

Philipp KoehnSequence of Action Potentials8Artificial Intelligence: Cognitive Neuroscience11 February 2020

Strength of Signal9 Strength of the signal is encoded in frequency of action potentials Each action potential has some magnitudePhilipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

10neural representationPhilipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Neural Representation11 Receptors identify very basic information– color at specific point in retina– pressure at specific point in skin– pain in part of an organ This information has to processed to higher level informationPhilipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Brain Tissue12 Neurons in the brain are connected in complex ways Signals are processed from receptor neurons to other neurons over several stages But: it is wrong to view this as a strictly layered processPhilipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Probing One Neuron13 We can use electrons to probe any neuron in the brain We present a cat with different stimula Example shapes Neuron is active when shape presented part of processing pipeline for shapePhilipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Hand Recognition Neuron14 Example: neuron in a monkey brain Shapes and strengths of neural activity shown Neuron most active when hand symbols are shownPhilipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Face Recognition NeuronPhilipp KoehnArtificial Intelligence: Cognitive Neuroscience1511 February 2020

Sensory Coding16 Specific neurons may be involved in––––detecting basic featuresrecognizing complex shapesidentifying class of objectsidentifying known object / person Sensory coding: encode various characteristics of the environment Our examples so far suggest specificity codingPhilipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

17Philipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

18Philipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

19Philipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Organization of the Brain20 Different areas of the brain deal with different brain functions Learning from brain injuries: double dissociation––– person A has brain injury and cannot do X, but still do Yperson B has brain injury and cannot do Y, but still do Xe.g., X recognize faces, Y recognize objectsX and Y operate independently from each other Learning from brain imagingPhilipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

MRI Scans of Brain Activity21 Measure brain activity in a specific voxel during specific cognitive task Contrast with baseline activity Quality (some numbers from the web)– as of 2011, best spatial resolution 0.3mm3, about 270-2700 neurons per voxel– functional MRI: 0.5*0.5*1.0mm, about 2500-25000 neurons per voxelPhilipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

22Functional magnetic resonance imaging (fMRI) Brain activity (neurons firing) increased blood flow Hemoglobin in blood contains ferrous (iron) molecule with magnetic properties Brain activity hemoglobin loses some oxygen, becomes more magnetic fMRI detects changes in magnetic fields Similar to MRI but uses the change in magnetization as basic measurePhilipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Regions in the BrainPhilipp KoehnArtificial Intelligence: Cognitive Neuroscience2311 February 2020

But it’s Complicated24 Observing a rolling ball Many different cognitive processes many brain regions involved All this seems very effortless to usPhilipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Summary25 We can easily study one individual neuron We can easily study regions of the brain But: tracking down exact processing pipelines is hard Human brain has about 100 billion neurons it would be hard even if we could record each individual neuronPhilipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

26visual perceptionPhilipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Receptors27 Photo-receptors in the eye detect intensity of light (red/green/blue)Philipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Primal Visual Cortex28 Detecting lines, especially horizontal and vertical linesPhilipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Secondary Visual Cortex29 Encodes combinationsof edge detectors– intersections and junctions– 3D depth selectivity– basic textures Simple visual characteristics–––––orientationspatial frequencysizecolorshape Start of invariant object recognition:recognize an object regardless of where it appears in the visual fieldPhilipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Visual PathwaysPhilipp KoehnArtificial Intelligence: Cognitive Neuroscience3011 February 2020

Deeper Processing: Places31 Parahippocampal place area (PPA)activated by places (top) but not other stimuli (bottom).Philipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Deeper Processing: Bodies32 Extrastriate body area (EBA)activated by bodies (top) but not other stimuli (bottom).Philipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Viewpoint Invariance33 We have to recognize an object when seen from different angles Interesting finding: time to match 3d objects related to relative angle( we mentally turn the object)Philipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Top-Down Processing34 What is in the red circle?Philipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Top-Down Processing35 What is in the red circle?Philipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Top-Down Processing36 What is in the red circles?Philipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Top-Down Processing37 Same blob in all the pictures:Philipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Principles of Object Perception:Good Continuation38 We assume that the rope continues when hidden Perception as a single strandPhilipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Principles of Object Perception:Prägnanz39 Prägnanz Conciseness, perception of image using simple shapes Figure seen as 5 circlesPhilipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Principles of Object Perception:Prägnanz40 Alternative interpretation: possible, but too complexPhilipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Principles of Object Perception:Similarity41 Similarity grouping similar items together (a) is perceived as rows or columns (b) is viewed as columnsPhilipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Principles of Object Perception:Similarity42 Similarity of colors initially grouped together More cogntive processing woman in front of beachmore plausible interpretationPhilipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Bayesian Inference43 In early processing stages, various possible interpretations considered Parallel processing of features, interpretations of elements of a scene Only distinct interpretations reach the consciousness (more on that later) Classic example: switch between two interpretations (intentionally or not)Philipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

44learningPhilipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Consolidation45 Remembering takes time Experiment (Müller and Pilzecker, 1900)––––step 1: a list of items to memorizecondition A: no pausecondition B: 6 minute pausestep 2: second list Condition B: Much better recollection (46% vs. 28%) Consolidation: process to transform new memoriesfrom a fragile state into permanent statePhilipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Synaptic Consolidation46 Recall– signals are transmitted at synapse– strength of synapse importance of input Repetition of stimulus strengthening of connection (”long term potentiation”)Philipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Systems Consolidation47 Initial experience activates neurons in the hippocampus (sensory memory) Reactivation– hippocampus replays neural activity– connections in cortex are formed– connections to original memory in hippocampus are lostPhilipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Reconsolidation48 When a memory is recalled, it becomes fragile more likely to be changed Experiment (Hupach et al., 2007)––––day 1: learn a list of wordsday 2, condition A: asked to remember training sesssion, learn new listday 2, condition B: just asked to learn new list of wordsday 3: asked to recall the list from day 1 Condition A: Worse recollection, mistakenly recalled words from data 2Philipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Artificial Neural Networks49 Neuroscience inspired research in artificial neural networks Latest trend: deep neural networks (many layers) Example: image classification More on that in future lectures.Philipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

50research of consciousnessPhilipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Consciousness51 Multiple meanings of ”consciousness”– vigilance state of wakefulness– attention focusing mental resources to task– conscious access information enters awareness and becomes reportable Currently increased research into ”conscious access” Conscious access can be detected in patterns of brain activityPhilipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Single Interpretations52 Each eye is shown different image Conscious perception is either the left-eye image, or right-eye image Not a merged image!Philipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Attentional Blink53 Perception experiment– showing sequence letters (100ms each)– ask subject to remember letters x and o– if two target letters follow too closely,only first one is remembered Conscious processing is busy with first letter Brain imagining shows that second letteris processed deep into visual systemPhilipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Masking Image54 Showing a target image for short duration Immediately followed by a masking image If target image is shown 50ms, it is not consciously perceived Note: In isolation much shorter exposure is sufficient It takes time for the consciousness to process informationprocessing can be overwritten by new informationPhilipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Subliminal Messages55 Image masking can be used to show informationthat does not reach consciousness But:Many experiments have shown that these images can effect decision makingPhilipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

56[video]Philipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Unconscious Processing57 Tremendous amount of unconscious processing In the image above image ”A” and ”B” have the same greyscalePhilipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

What is the Consciousness For?58 A Bayesian view– unconsciousness computes probability distribution– consciousness samples from it — picks one item Example––––what percentage of world’s airports are in the US?give second guesscompute averagecorrect answer is 34% Lasting thoughts, working memory Conscious cognitive processes: 12x13? Conscious thoughts can be communicated to othersPhilipp KoehnArtificial Intelligence: Cognitive Neuroscience11 February 2020

Cognitive Neuroscience Philipp Koehn 11 February 2020 Philipp Koehn Artificial Intelligence: Cognitive Neuroscience 11 February 2020. Cognitive Neuroscience 1 Looking ”under the hood” What is the hardware that the mind runs on? Much progress in recent years

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