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Cognitive psychologyLecture 1: Introduction to Cognitive PsychologyWhat is cognitive psychology?  Massive field of study, relevant to most areas of psychology  Do the fucking reading smh  Information-processing approach o Metaphor of human mind to computerKey concepts  Knowledge that we have inf...

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Cognitive psychology Lecture 1: Introduction to Cognitive Psychology What is cognitive psychology?  Massive field of study, relevant to most areas of psychology  Do the fucking reading smh  Information-processing approach o Metaphor of human mind to computer Key concepts  Knowledge that we have influences processing  Parallel processing: different streams at the same time

Lecture 1: introduction to sensation and perception Learning outcomes 1. Define sensation and perception 2. Identify important questions about human sensation and perception a. Research questions that psychologists would be interested in 3. Explain the concepts of bottom-up and top-down processing, as basic theories of perception 4. Outline the range of methods used to investigate sensation and perception a. Advantages and disadvantages b. What they can tell us

Definitions: sensation and perception 

Sensation: registering stimulation of the senses o The senses are stimulated by the environment o Change of air pressure stimulates hair cells → generates action potential, the brain knows it as sound

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o Perception: processing and interpreting sensory information o E.g. what the picture is, how loud that sound is Cognition: using perceived information to learn, classify, and comprehend o Learn, classify, and comprehend what is happening in the world o E.g. that sound is a seagull cry, you should protect your sandwich o Comprehend the world and make a decision about what to do next

Why is studying sensation and perception important? 

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When you do a sprint, there’s a pressure plate that registers anything before 100ms after the sound has gone off as a false start, because it takes at least that long for the brain to process the sound When an athlete is shooting a clay pigeon, they wear colour-filtered glasses to increase the contrast between the environment and the pigeon If a sensation is lost, atypical perception, sensation is reduced → we can help these people more if we understand sensation and perception more Knowledge can be used for evil  high frequency noise played so that younger people/teenagers go away so that shops get their target audience Can tell us not just about sensation and perception parts of the brain but about the brain in general

Fundamental concepts of sensation and perception    

Stimulus = changes in the world Light is a type of electromagnetic energy Different types of changes in the world are detected by different receptors and then processed by different parts of the brain The senses have discrete parts of the brain that do their processing

We must have:  A presented simulant

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A sensory organ to detect the stimulus Receptors within the sensory organ to pick up and send out electrical signals A place in the brain for this information to be processed, so the stimulus can be acknowledged

Sense

Stimulus

Receptor

Vision

Photoreceptors Chemoreceptors

Mouth

Chemoreceptors

Nose

Hearing

Electromagnetic energy Chemical composition Chemical composition Air pressure waves

Sensory structure Eye

Mechanoreceptors

Ear

Touch

Tissue distortion

Balance

Gravity, acceleration

Mechanoreceptors, thermoreceptors Mechanoreceptors

Skin, muscle, etc. Vestibular organs

Taste Smell

Cortex Primary visual cortex Primary taste, gustatory cortex Primary taste, olfactory cortex Auditory cortex Somatosensory cortex Temporal cortex

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General flow of information Sensation is about changes in the world Electromagnetic energy  light is a type of this

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Transduction: conversion of environmental energy to nerve signals (NOT via thalamus for smell) Feedback goes back to the thalamus, perhaps to the retina

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o What’s happening in the higher cortex can affect the lower levels

Processing 

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Bottom-up processing o Sensation and perception start from feature detection of stimulus e.g. physical characteristics and basic sensory processes o Complex thought/greater thinking not necessary to construct our world (outside of stimulus features) o Gibson (1950): information itself coming from sensory receptors allows for perception  Direct perception  Cognitive and perceptual scientist  Can we understand the world with only bottom-up processing? o Environment contains enough cues to provide context to aid perception e.g. texture can indicate depth of an object o Don’t need any categorisation, just need the features o Null hypothesis: the brain is doing bottom-up processing Top-down processing o Perceiver constructs their understanding of external stimuli based on past experiences and knowledge o Gregory (1966): “perception is not determined simply by stimulus patterns; rather it is a dynamic searching for the best interpretation of the available data” o Brain is constructing it’s understanding of the environment o Brain needs to structure the information and interpret information that could be ambiguous o Data: what we get from the world o Dynamic searching for the best interpretation: what the brain has to do  The information we get is quite partial and ambiguous, so the brain needs to do top-down processing in order to understand it

Investigation of sensation and perception (how do we investigate sensation and perception?) Staining  Staining: applying dye to brain tissue to show structure  Dead brain tissue → stain binds to particular receptors, highlights a particular type of neuron  Reveals the structure of the brain  Visual cortex is aka striate cortex (layers), different types of neuron in each of the layers  Know the structure, now what’s the function?

Single-cell recordings  Single-cell recordings (electrophysiology): remove a section of someone’s skull (only if they’re already having a medical operation) and stick a microelectrode into their brain v close to the neuron so that you can record the action potential  Electrode to brain cell/neuron to record electrical activity/action potential

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In the cat cortex, there are cells that are responsive to particular orientations Helps to identify selective cells If a bar rotates there’s a cell that fires, if it rotates the other way a different cell fires Selective neurons in the medial temporal lobe Measure from a really fine electrode the signals that are coming from a single neuron or nearby Use a microelectrode Measure the APs from neurons Epilepsy patients may have part of their skulls removed → researchers can go in during operation and measure

Advantages  This method identifies selective cells, cells that you’re specifically interested in particular things Case study  E.g. Quian Quiroga, Kraskov, Koch, & Fried (2009): found that single neurons can encode multimodal representations of people, representing individuals in multiple sensory modalities o Epilepsy patients implanted with depth electrodes to record from single cells o Presented with photos, text name, and spoken name of different people o Found selective neurons responded to information on individual people o Therefore, these neurons code for the concept of people themselves, not just their appearance/sound of their name o Selective cells have very narrow selective tuning, allows us to hold multimodal representations of different people (name, face, etc.) o Single neurons can code the representation of a person (complex ideas) o Certain neurons respond fondly to certain people o Measuring from the medial temporal lobe

fMRI (functional magnetic resonance imaging) scanning  Functional magnetic resonance imaging ( fMRI scanning): blood oxygen levels in the brain, visual/auditory tasks, record which parts of the brain are active Lesion studies  Lesion studies  Conducted on animals by knife (destroying axons) or by neurotoxins (destroys only the nerve cell) o Ethical issues o The brain changes in response to damage o Strong individual differences in humans  Conducted on humans with existing damage to the brain due to strokes, trauma, etc. o Neuropsychology o Involves studying a faulty brain system, may not function in the same way as someone without brain lesions o Might not know which exact part of the brain led to which exact function that was lost o Damage not located to a small area, lots of different packets of damage o More than one person having the same brain injury is incredibly unlikely  Phineas Gage o Experienced personality changes Virtual lesions – Transcranial Magnetic Stimulation (TMS)  Virtual lesions – Transcranial Magnetic Stimulation (TMS)  Not in lecture  Pulses of magnetic energy disrupt activity in a small part of the brain for a short period of time → can be used to investigate sensation and perception  When TMS applied to STS of the brain, able to identify if biological motion is impaired  Uses biological motion: points of light to show a person moving  Investigates how the brain reacts to loss of certain stimuli, how disruption of certain brain areas affects how we respond to biological motion tasks  Magnetic coil  magnetic energy  disrupt etc  Over the motor context  involuntary Optical imaging/Near infra-red spectroscopy (NIRS)  Optical imaging/Near infra-red spectroscopy (NIRS)  High powered cameras look at the structures of neurons e.g. cones in the retina  Nearly infra-red light shone towards the skull, penetrates the skull, bounces off the brain  Signal returned shows how much blood oxygen is going to reach each area at any given time  See how infra-red light at the skull is reflected  Can penetrate the skull, bounce on the brain, and then penetrate the skull back to the detectors again  Can subtract the blood flow and veins out because they are static

Event-related potential (ERP)  Event-related potential (ERP)  EEG system, electrodes all over the scalp to measure electrical activity over the scalp  Show subject a visual stimulus and see what the brain does to process it  Measuring electrical activity across the scalp as an event occurs  Net of electrodes on your head that receive and measure current  Electricity that’s going on in the brain  Detecting changes in current and electricity  Good for knowing the time course of processing, sensitive in its temporal resolution so you can see when a brain starts to respond to a particular stimulus Psychophysics  Psychophysics  Quantifying the relationship between physical stimuli and sensation and perception  Threshold: change from one perceptual experience to another  Absolute threshold: smallest intensity of stimulus required for detection  Differential threshold: smallest difference between two stimuli that can be detected (“just-noticeable difference”, JND) o Change the intensity of a stimulus until it can no longer be detected  Forced-choice procedures to detect which side has the stimulus in it  E.g. Blake, Turner, Smoski, Pozdol, & Stone (2003) found disrupted biological motion in children with autism, poorer performance than control children in biological motion tasks but not in global form tasks o Autism children had poorer than average performance at identifying biological motion, but not for a linear form task o Implies abnormal dorsal stream  Key concept is threshold: change stimuli in a physical way and see if the human eye detects  Two colours could be different scientifically and the human eye could not see it in that way  Jnd = just-noticable difference, units  Measuring thresholds o Method of adjustment, participant adjusts stimulus until it matches something else eg.g. w colour o Forced choice procedure  which side has the stimulus?  can draw psychometric function  Contrast increases  detection accuracy increases  Powerful in understanding perception  Measuring the psychological response to physical stimuli Illusions and introspection  Illusions and introspection: introspection is a valid way to ask questions about sensation and perception, but it is important to also study is systematically by using one of the other methods o Introspection: consider why you’re experiencing what you’re experiencing

Computation modelling  Computation modelling: using computer programs to model theoretical brain structures  Trying to get same outcome from computer program as in humans in order to test hypotheses

Lecture 1 reading: Mather 

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Occipital lobe o Visual cortex o Largest sensory area in the brain o Photoreceptors transduce light energy into action potentials to be carried to the primary visual cortex Variability in perceptual decisions When stimuli are very close together, perceptual responses are probabilistic Environmental energy Receptor cells Electrical nerve impulses →

Transduction: process by which sensory receptor cells convert environmental energy into electrical neural signals Cerebral cortex: outer layer of the human brain, contains millions of neurons that underlie conscious perception

Methods used to study perception Clinical studies  Tatsuji Inouye 1900s: Japanese war, figured out which brain areas damaged caused what Single unit recordings  Electrical Field Theory of perception → visual patterns were thought to set up corresponding fields of electrical activity across the surface of the cortex  Microelectrode recording → Stephen Kuffler, 1950s o Electrical activity is recorded from single cells in a live animal using fine insulated wires o Some retinal cells prefer small, bright spots of light, whereas others prefer large, dark spots o Individual cells are highly selective for specific line orientation, colour, size, etc. in the cortex Brain imaging  CT = computerised tomography o X-rays passed through the body at different angles  Reveals areas of brain damage  MRI and fMRI  MRI = short bursts of powerful radiowaves  fMRI = detects magnetic changes induced by variation in blood oxygen concentration o informs us about brain function

Psychophysics  The scientific study of relationships between physical stimuli and perceptual phenomena  Experiment is carefully controlled stimuli (usually by a computer) and you get highly constrained responses Artificial intelligence  Computation: the manipulation of quantities or symbols according to a set of formal rules  Alan Turing  Visual images converted into matrix → computer finds edges of object General principles of sensation and perception Physiological principles Neural impulses and transduction  Transduction: the process by which sensory receptor cells convert environmental energy (e.g. light, sound) into electrical neural signals o E.g. molecular changes in photoreceptors triggered by light absorption o E.g. mechanical deflection of tiny hairs by fluid currents in the inner ear  Information in the nervous system is carried by electrical impulses  Dendrites → axon → terminal buttons → neurotransmitter release → information carried by synapse → dendrites of next cell  Neural impulse: a brief, discrete electrical signal (action potential) that travels rapidly along a cell’s axon  Terminal button: a bud at the branched end of an axon, which makes contact with the dendrites of another neuron  Neurotransmitter: a chemical secreted across a synapse to pass on electrical signals from one cell to another o Can be excitatory or inhibitory  Photoreceptor: a specialised nerve cell that produces electrical signals when struck by light  Mechanoreceptor: a specialised nerve cell that produces electrical signals when subjected to mechanical deformation Hierarchical processing  Neural signals transmitted to several different structures in the brain  Between the neural signal transduction and arrival at the receiving area of the cortex, signals pass through synapses with successively higher levels of neural processing  Vision has 3 synapses between photoreceptors and the brain, hearing has 5  One synapse for each sense except olfaction is in the thalamus → sensory signals go to receiving area in the cortex → other cortical areas (association areas)  Signal flow is unidirectional up to the thalamus and bidirectional after  Inputs modified by interactions between cells  Resulting input differs from the input signal, signal has undergone a transformation

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Often, useful information is selected for, so less useful information is lost

Thalamus: dual-lobed mass of neurons in the middle of the brain, at the top of the brainstem and below the cerebral cortex, relays information to the cortex from other brain regions Cortical receiving area: area of the cortex where afferent (incoming) fibres from a sense organ terminate, aka primary sensory cortex Cortical association area: area of the cortex that receives info from neurons in a cortical receiving area, aka secondary sensory cortex

Selectivity  Each sensory system only responds to a particular range of stimuli  Sensory space: the range of effective stimuli for a particular system  Stimuli can vary along many different dimensions in a sensory space  This principle was founded by single-unit recording data o E.g. for certain cells in the retina, action potentials are only generated when a particular orientation of a line is shown. These photoreceptors only respond to a few inputs o Receptive field: limited spatial area of a cell’s response Organisation

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Each neuron has specific stimulus preferences Cells that prefer similar stimuli tend to be located close together in the brain

Specific nerve energy  The destination of the action potential in the brain determines different experiences Plasticity  Sensory systems adapt to the specific sensory environment the individual is in  E.g. initial itchiness of a shirt will subside in the afternoon as receptors in the skin adapt to their new environment Noise  A neuron’s level of activity can be measured in terms of frequency in generated electrical impulses  Varies from 0 to around 800 impulses per second  Typical rate for very active cell is 100-200 impulses per second General notes to sort through  Qualia: primitive mental states, such as sensory impressions induced by simulation of a sense organ (e.g. loudness, brightness, heat)  Prosopagnosia: a clinical condition resulting from brain damage, in which a patient is unable to recognise familiar faces, sometimes including their own (in the mirror or otherwise)  Adaptations of a sensory stimulus o Sensitivity changes so that a more intense stimulus is required to induce a perceptual response after adaptation o The apparent intensity of a stimulus diminishes o The rate at which sensory magnitude increase with stimulus level steepens. The response capacity of each sensory stimulus is limited where it can only respond to a certain range of stimulus levels at a time. Adaptation ensures that this restricted response is well matched to the stimulation  Psychometric function: a graph relating stimulus value (e.g. intensity) to the response rate of an available experimental subject (e.g. a proportion of “yes” responses)  Mechanoreceptors in the inner ear contain cilia (hair-like outgrowths)  Topographic map: a spatial arrangement of neurons in a neural structure (e.g. the cortex) in which nearby cells respond to nearby locations in the visual field of view  Cerebral cortex: outer layer of the human brain, contains millions of neurons that underlie conscious perception  Perceptual judgements usually involve a decision  Internal neural signals mediating perception are subject to fluctuation, so the computations performed during sensory processing must accommodate this variability  The mechanoreceptors in the inner ear contain cilia  Perceptual systems can be considered as representational systems. Internal brain states represent the state of the outside world