Cognative Flashcards
know everything
Cognition definition
Set of all mental processes that allow us to aquire knowledge/understanding through though, experience and the senses
Criticisms of the view that humans are stimulus response machines
Does not allow for parallel processing
Ignores top down processing
Top down processing
Stimulated by the individuals prior knowledge etc
Bottom up processing
Stimulated by external stimuli
Evidence that neurons represent specific information
Found a certain set of neurons fire when Luke Skywalker is mentioned (similar ones firing when other star wars things mentioned)
Rate coding
A greater rate of neuronal response is used to represent information
Temporal coding
A greater synchrony of neuronal responses is used to represent information
Possible types of coding (2) and which is more likely
Rate and temporal coding, temporal being more likely based of evidence
Different approaches to studying cognition (3)
Experimental Cognitive Psychology
Cognitive neuropsychology
Cognitive neuroscience
What is experimental cognitive psychology
Studying behaviour in lab setting (with manipulations), traditionally focusing on behavioural measures
Limitations of experimental cognitive psychology
Ecological validity (real-world translation)
Only indirectly measures cognition
Relies heavily on theory
What is Cognitive neuropsychology
Studying cognition in brain damaged patients to find specific brain areas role in cognitive functions
Limitations of cognitive neuropsychology (4)
Rare to get pre-damage measures for patients on performance
Often has complex damage in several regions
All brain damage is unique
the brain is unlikely to be modular
What is cognitive neuroscience
Relates brain structures and function to cognitive processes, usually by recording brain activity while tasks are completed
Tools in cognitive neuroscience (4) and their use
EEG for electrophysiology imaging
MRI for structural imaging
fMRI for functional imaging
TMS and TCS for brain stimulation
Single cell recordings
Very small electrode recordings from within an axon, or outside an axon membrane
When are single cell recordings used
Usually just on animals but known to be used on epileptics
EEG
Via electrodes in the scalp, it records the electrical activity of a large number of neurons firing together
Event related potential (ERP)
Average waveform from a task recorded multiple times, used to compare between conditions
Advantages (3) and disadvantages (2) of EEG
Adv: good temporal resolution, portable, cheap
Disadv: Spatial resolution, only measures brain’s surface
How MRI machines work
Very strong magnetic field (0.5-0.7 Tesla’s) on scanned area with single protons aligning to it. Alignment disturbed by short radio frequency pulse and the change is measured - different tissues realign at different times, giving brain map
Diffusion Tensor Imaging (DTI)
For structural imaging, it measures white matter (axons) by measuring the direction of water diffusion
How fMRI works
Doesn’t measure neural activity, it measures BOLD signals - oxygenated blood has higher signal than deoxygenated as it has less magnetic field disturbance
What does BOLD stand for
Blood Oxygenation Level Dependent signals
Hemo-dynamic Response Function (HRF)
The way blood changes to a stimulus
??
Advantage and disadvantages (2) of fMRI
Adv: spatial resolution
Disadv: temporal resolution, doesn’t directly measure neurons (inference required)
How TMS works and what it stands for
Uses short magnetic pulses that transiently affect electrical activity in a localised patch of tissue under the coil
Transcranial Magnetic Stimulation
How tDCS works and what it stands for
Uses small current flowing constantly from one electrode to another. Area under cathode is inhibited and under anode is excited
??
transcranial direct current stimulation
How tACS works and what it stands for
Uses small current alternating in flow from one electrode to another, inducing oscillations at different frequencies
??
transcranial alternating current stimulation
Advantages (2) and disadvantages (2) of tDCS / tACS
Adv: provides causal evidence, is mostly non-invasive
Disadv: stimulation is weak making weak effects, risky for epileptics
Summary of process of vision from eye to cortex (3)
Reception - absorbed by photons
Transduction - converted into electrochemical pattern in neurons
Coding - represented in the brain
Two types of retina and their function
Cones - process colour and sharpness of vision
Rods - process movement and dim light
How many 1) cones and 2) retina are there in the eye and where are each located
1) 6 million, mostly in the fovea
2) 125 million, in the outer regions of the retina (peripheral vision)
Trichromatic theory for eyes
As all colours mix into three primary colours, it was proposed the eye has three colour receptors responding at different wavelengths (found to be true)
Three colour receptors / cones in eye
Short wave length detects blue
Medium detects green (and yellow)
Long detects red
Problem with Trichromatic theory
Doesn’t account for the negative after image - e.g. staring at green square for a while makes a red afterimage for a second (opponent process) on white background after it disappears
Opponent process theory for eyes
Colour perception has 3 opponent processes: red/green, blue/yellow, light/dark. Combined in an opponent way
Duel process theory for eyes
Links opponent processes to the combinations of inputs from 3 cone types (trichromatic theory)
Support for opponent process theory for eyes
Opponent cells found in monkeys geniculate nucleus
Colour constancy
Tendency for a surface to appear the same colour despite a dramatic change in light source (brain makes sense of it - in concert with coloured lights, everyone still same colour) - proves perception is constructive
Parvocellular pathway
Sensitive to colour and fine detail, input comes mostly from cones
Magnocellular pathway
Mostly motion sensitive, inputs come from rods
Visual perception pathway summary from eye to brain
Retina to optic nerve to optic chiasm to Lateral Geniculate Nucleus to cortical area
Why your right visual field is processed by the left side and vice-versa
Signals cross from right visual field to the left side of the retinas, and come through in straight lines to left side of brain
Receptive fields
The region of sensory space in which light will cause neurons to fire
Retinotopy
Things spatially near to each other are processed by cells near to each other
Lateral inhibition
A reduction in activity of a neuron caused by a neighbouring neuron
Lateral Geniculate Nucleus (LGN)
Part of the thalamus, it is a subcortical relay for most sensory inputs and motor outputs, correlates incoming signals from the retina in space and time
Primary visual cortex (V1)
Extracts basic information (edges, orientations etc) from the visual scene and then some more complex information (colours, movement, shape etc)
Blindsight
Caused by damage to V1, patient cannot consciously report objects in space but can make some automatic visual discriminations through other visual pathways
Visual pathway to V1 (primary visual cortex) is called…
Genial ostriate route (thought to be fore conscious vision)
Central cullcus
Visual motor system (automatic)
‘Where’ pathway
After V1, goes through pariental processing pathway concerned with movement processing (‘vision for action’)
‘What’ pathway
After V1, goes through temporal processing pathway concerned with colour and form processing (vision for perception) - goes through lateral occipital and temporal lobe
Patient with lateral occipital cortex damage would lose function in….
Their ‘what’ pathway, difficulty locating and identifying objects (but can automatically interact with them)
Functional specialisation theory for vision
Different parts of visual cortex specialised for different visual functions
Function of V1 to V5 according to functional specialisation theory for vision
V1 - lines V2 - similar to 1 V3 - responds to form V4 - for colour V5 - for movement
Cortical achromatopsia
Damage to V4, a patient cannot see colours (often V2 and V3 damage also) but has fully functioning retina. However implicit colour perception intact as can still see through expectations from experience before damage
Akinetopsia
Damage to V5, deficit in movement visual processing with everything else intact
Challenge for functional specialisation theory for vision
How are V1 to V5 bound together to make sense, colour and shape are not seen separately
Visual perception synchronisation hypothesis
A potential solution to the challenge for functional specialisation, the functions (V1-V5) are synchronised (temporally coded) to bind together - likely attention dependent
Model for object recognition in steps
Early visual processing (colour, motion, edges etc)
Perception segregation (grouping visual elements)
Map this onto representation (expectations) in brain
Attach meaning to object (‘what’ stream)
Perceptual segregation
Separate visual inputs into individual objects
Gestalt Psychology
studying perceptual segregation
Law of Pragnanz
Of several possible geometric organisations, the one with the simplest, stablest shape will occur (assuming segregation early in processing)
Gestalts laws of perceptual organisation (4), how inputs are organised
Law of proximity (how close they are)
Law of similarity
Law of continuation (whether it carries on)
Law of closure (whether it is half blocked from sight)
Criticisms of Gestalts laws of perceptual organisation (3)
Mostly descriptive findings
Evidence relies heavily on introspection and 2D image examples
Does not include top-down processing’s effect on segmentation
Where V1 to V5 are located
The occipital lobe
Agnosia
Impairment of object recognition with no primary visual deficits
Types of agnosia (2)
Apperceptive and Associative
Apperceptive agnosia
Impaired process of constructing a perceptual representation (can see the parts, not the whole), associated with damage to lateral occipital lobes
Associative agnosia
Impaired process of understanding the function of objects (can see the whole but not the parts, impaired mapping of perception onto stored knowledge), associated with damage to left occpito-temporal lobe
Damage to bilateral ventral-medial occipital lobe causes…
Apperceptive agnosia, patient will perceive objects by parts (see a handle and brush, not a paintbrush).
Prosopagnosia
Patient that’s unable to recognise faces, caused by damage to Fusiform Face area (FFA) - part of the ventral stream
Debate of function of Fusiform Face Area (FFA)
Many believe its specialised to recognise faces, but some think its for expert processing of things constantly seen. However patients with prosopagnosia still have expert processing of other things
Uniqueness of faces for visual processing
Configurally / holistically processed (making prosopagnosia an apperceptive agnosia)
Horizontal information very important for recognition, also cannot be recognised up-side-down
Attention
The taking possession of something in vivid form by the mind
Why is attention necessary
It makes sense of the world, 108 bits per second travel through the optic nerve (much more than the brain can process), so attention needed to focus on necessary things to process
Experiments demonstrating attentions limits
Change blindness (Skoda advert) Attention blink Inattentional blindness (gorilla study)
Summary of inattentional blindness study
Told to watch video of two teams bouncing and passing a ball between themselves and count the passes. Because their attention was drawn, a large proportion did not notice a dancing gorilla coming on screen
(the more difficult the task set, the less they saw the gorilla)
Cocktail Party problem
How do humans focus in on one conversation/noise so well in a loud area with lots of other noises, yet also process other noises at a lower level and can attend to them if relevant to (e.g. hearing your name)
Very difficult to program computers to do this
When a voice is easier to attend to in a loud, cocktail party problem room (2)
Familiar voices (top down processing) Depends on features (high pitch easier than low)
Broadbent’s theory of sensory processing
Parallel inputs go to sensory register where they are filtered based on salience of physical characteristics. Inputs that pass the sensory register (bottleneck) go onto later, more complex processing
Problems with Broadbent’s theory of sensory processing (2)
Does not account for top-down processing’s influence on the sensory register
As seen in blindsight patients, stimuli that aren’t consciously registers still alter behaviour so must be processed further than Broadbent was proposing
Deutsch and Deutsch’s late selection theory of sensory processing
All stimuli is fully unconsciously analysed, with the most relevant passing the sensory register and coming to consciousness, effecting response more
Problem with Deutsch and Deutsch’s late selection theory of sensory processing
Imaging shows ERP’s to be smaller if it remains unconscious later on, indicating an earlier sensory register than they proposed
Treisman’s leaky filter, flexible theory of sensory processing
Unattended information is filtered after the sensory register, going through a hierarchy which takes physical characteristics and personal meaning into account. When limited capacity reached, hierarchy tests are precluded for all but the attended stimulus
Cognitive load
Phenomena that some simple tasks are completed simultaneously much worse than some complex ones - indicates processing semantic information is prioritised over physical characteristics
Endogenous attention
Internal choices that makes one react faster to stimuli in a peripheral part of space
Exogenous attention
External queues that make one react faster to stimuli in a peripheral part of space, only when the stimuli comes quickly after the queue
Posner’s attention systems (2)
Endogenous system (top-down) - controlled by intentions, expectations etc (depends on person!) Exogenous system (bottom-up) - automatically shifting attention from uninformative peripheral queues
Evidence for object based attention (not space)
Participants shown translucent, hybrid images of house and face and sometimes one moved. Brain area for each object was activated more when attending to that one, and even more so when object moved
Central capacity theory
A central executive function is flexibly used to direct attention (has limited resources)
What are dual task costs and why do they appear
Appear due to limited resources of attention, they are when two or more tasks are performed badly when done simultaneously
Multi-tasking / divided attention’s location in the brain
Imaging shows it to be in the DLPFC
TMS studies show impaired divided attention when DLPFC is impaired - appears to distribute resources
Question surrounding visual search
How does the brain search for all the features of the object it is tasked for all at once and so well?
Feature integration theory of visual search (FIT) and implications
Features of an object are encoded in parallel, prior to attention. Making them separable from the object itself when visually searching
Meaning if an object has a unique feature, it can be detected without attention. If not unique, attention/visual search is needed
Stages of visual search according to Feature integration theory of visual search (FIT)
1) Rapid initial parallel process to identify features (no attention)
2) Slower, serial process of spatial attention to form objects from the features (give meaning) - top down influence
Evidence for Feature integration theory of visual search (FIT) (2)
Search time for items with a unique feature is not effected by the number of distractors
Illusory conjunctions
Illusory conjunctions
Showing two objects briefly in periphery means they often experience a combination of the two object’s features - often highly confident of experience, not just guessing
When do Illusory conjunctions occur (5)
Focused attention is absent Relevant stored knowledge is absent Spatial attention absent In peripheral vision Not temporally, just spatially (exact same time)
Evidence against Feature integration theory of visual search (FIT)
Negative priming tasks show unattended stimuli are semantically processed (processed early - stage 1?)
Neglect patients have problems with both conjunctive and single feature visual search targets, indicating they are not in separate systems
Guided search theory (dual path model) of visual search
Emphasising top-down processing, it proposes a mix of serial and parallel processing is used. Pre-attention processing gives an activation map of how ‘promising’ each stimuli is (the more promising the more prioritised to pass through the attentional bottleneck)
Balint’s syndrome
Damage to the bilateral occipito-parietal cortex causing simultanagnosia (could not focus on one object at a time, and could not combine features to form objects (constant conjunction errors
Brain damage that causes problems with feature binding of visual objects (2)
Parietal lesions cause spatial binding problems and Thalamus lesions cause binding problems linked to top-down processing
Brain areas that influence feature binding in visual search (conjunction) tasks
Posterior temporal cortex (and parietal cortex) activated in tasks
Intraparietal sulcus reduces illusory conjunctions, indicating its role in conjunction of objects (activation gives higher performance)
Hemispatial neglect cause
Usually from stroke, lesions to a specific portion of the parietal lobe in one hemisphere
Symptoms of hemispatial neglect
Lack of awareness of stimuli presented to contralesional (other side from brain damage) side of space causing: inability to copy, imagine/remember (even pre-injury memories) or attend to objects on that side of space
Extinction attention disorder
Often detect stimuli in ipsilesional side of space (same as brain damage) but not contralesional - showing a bias
Most hemispatial neglect patients also have this
How much processing of contralesional field takes place for hemispatial neglect patients
A lot of basic in the visual cortices but much less than controls by the point of the dorsal parietal lobe
Evidence for hemspatial neglect patients’ attention being one of object deficit rather than space
Often seem to neglect the contralesional side of all objects in the scene, not their contralesional side
Evidence for strong processing of contralesional field in hemispatial neglect patients
Has a strong priming effect (faster reaction time) when an associated object is later presented in the ipsilesional field (must have been processed through ‘what’ stream)
Most common lesion for hemispatial neglect patients and evidence for it
On the right inferior pariental lobe (contralesional side on the left most often)
TMS on area causes temporary neglect symptoms
Is hemispatial neglect an attention or perception disorder
Attention
Evidence for an intact endogenous attention system in neglect patients (2)
They benefit from valid cues (arrow indicating direction of stimuli) when doing covert attention tasks
Patients are most impaired when trying to disengage from their ipsilesional side
??
Is hemispatial neglect more an exogenous or endogenous attention disorder and what are the implications
Exogenous, they can attend much better when asked to deliberately but struggle with automatic attention
Hemispatial neglect without brain lesions
Occurs when very drowsy, attention tends to shift to right side of visual field. Suggesting a left hemisphere attentional dominance for healthy people
Prevalence of ADHD
5-10% of children, 2-5% of adults, ratio of 3:1 boys:girls
Diagnostic subtypes of ADHD and how common they are
ADHD/IA: Predominantly inattentive (30%)
ADHD/HI: Predominantly hyperactive (9%)
ADHD/com: Combined (61%)
Inattention symptoms of ADHD (4)
Poor attention to detail
Difficulty persevering
Inability to follow instructions
Often forgetful
Hyperactivity symptoms of ADHD (3)
Tendency to fidget
Talks excessively, often before thinking
Tendency to interrupt
Requirements for ADHD diagnosis other than symptoms (2)
Present before aged 7 (a developmental disorder)
Impaired in two or more settings (school, home etc)
Risk factors for ADHD (4)
Genetics (4 times more likely if other family diagnosed)
Prenatal alcohol or tobacco exposure
Post natal pre-frontal damage
Premature births or low birthing weight
Neurocognitive deficits of ADHD (4)
3-4% reduced cortical volume (especially PFC)
Reduced cortical connectivity (axons) between hemispheres
Reduced grey matter and axons in fronto-parietal attention networks
hypoactivity (less) in DLPFC (the ‘choosing’ part of attention)
Imbalance in dopamine and noradrenaline circuits
MANY MORE - research xx
Medication for ADHD (2)
Methylphenidate (Ritalin, metadata etc)
Dextroamphetamine (Adderall)
How ADHD medication works (2)
Block reuptake of noradrenaline and dopamine, whilst facilitating their release
Enhance their availability in the PFC (noradrenaline) and Basal Ganglia (dopamine)