final Flashcards
fuck
MVPA or multi-variate pattern analysis
Predicts the stimulus someone is seeing or remembering based on their brain responses, this is done by considering the patterns across voxels or electrodes. Each voxel contains 600,000 neurons. MVPA decodes relationship between activity and remembered stimuli.
PFC has sustained activity during delay, but patterns of BOLD activity do not carry reliable information about stimulus. Visual cortex does not show elevated activity, but pattern allows you to decode stimulus held in STM, unclear whether pattern in visual cortex in STM is the same as during perception
prepotent response/stroop effect
When a stimulus has a response strongly associated with it, we call that a PREPOTENT response. We experience conflict when a prepotent response SHOULD NOT be enacted.
Example: the Stroop effect. Say the color the word is: GREEN
Environmental dependency
Patient dependent on environmental cues can’t help but mimic. can’t inhibit prepotent response… “distractor inhibition”
Perseveration: card sorting task
cards sorted with a rule in mind. After 10 correct trials, the rule is switched. Measure is to see if they change their strategy. If they continue to sort according to the old rule, they are perseverating. LFL damage doubled the rate of perseveration.
Effects of LFL(Lateral Frontal) damage
Suggestion: LFL damage causes a failure to inhibit prepotent incorrect responses OR a failure to inhibit distracting information OR a failure to boost the correct response
A not B error
perseveration is natural during development. Perseveration on recently rewarded response. Overcome through development or through functioning of the PFC.
Dopaminergic neurons in the Basal Ganglia
these signal subjective reward, error signal telling rest of brain if wrong or right
DA neurons in PFC
PFC has some of the highest density of DA neurons. PFC also has many more recurrent (self) connections than other areas. DA acts as a clamp, turning on PFC clamping into a pattern of activity, or turning off PFC and allowing a new pattern to form. PFC locks into a pattern of activity when a stimulus is rewarding.
what is a decision, why are decisions hard
A decision is a deliberative process that results in the commitment to a categorical proposition.
Decisions are made hard because of NOISE.
Signal Detection Theory
Momentary evidence only.
Assumes a single sample of evidence on every trial. Assumes noisy evidence (same stimulus will not always lead to same physical/neural response). Assumes two independent stages, sensory and decision/distribution and criteria. The amount of overlap in distributions determines the difficulty of the decision or the sensitivity of the system. Called d-prime. Placement of criteria determines willingness to have false alarms and misses.
perceptual decision making occurs where?
MT (medial temporal)
In signal detection theory, we can think that microstimulation to the MT area: _________?
biased the internal response to both null AND preferred motion
Motion coherence
the percentage of dots moving in same direction
Accumulated evidence about a response is represented where?
Accumulated evidence about a response is represented in LIP (Lateral Intraparietal)
MT (Middle Temporal) provides Momentary perceptual evidence about direction of motion
LIP goes to FEF (frontal eye fields) and SC (superior colliculus) as well as MT
The LIP (Lateral intraparietal sulcus) has perceptual and motor neurons
motor neurons and motor fields
Motor neurons have a ‘motor field’, a location in space where a monkey will make an eye movement when that neuron is stimulated. Experiment takes advantage of this by making the response be a Saccade either in or out of the LIP motor field. Motor fields are not stimulus dependent, they are response dependent
Beta oscillations in the human motor system are thought to also represent accumulated evidence for an action
Common Currency and the OFC (Orbitofrontal cortex)
transitivity, value transitivity, menu invariance
Rational decisions require:
Transitivity= A>B>C, so A>C
Value Transitivity= If A is worth twice as much as B, then 2B should be taken as often as A
Menu Invariance= The value of B is the same whether we’re comparing to A or C
If these properties are satisfied, then the item is in ‘common currency’
OFC (orbitofrontal) represents which type of rational decision property?
Menu invariance
Kluver-Busey syndrome symptoms
hypersexuality, visual agnosia, hyperappetite, etc
Amygdala damaged test with faces
First impression test with faces, how much do you trust this person? Ratings were different from sample, but this only applies to visual stimuli. When given verbal description, ratings same as controls
fMRI responses in amygdala correlate more to how a face is rated by a group than the specific individual being scanned
Why? Many idiosyncracies in determining whether or not a face is likable. Group average will not reflect such factors, and apparently, neither does the amygdala, responding based on inherent likability of the face. This is ‘evidence for implicit processing in the amygdala’
Effect went away when pictures were of ‘positively regarded’ black and white men, this suggests that implicit processing in the amygdala is actually learned, not innate/hardwired
Two types of learning in amygdala:
Pavlovian conditioning: pairing of neutral stimulus(CS) with noxious stimulus(US), caused the behavioral response associated with noxious stimulus to be associated with nuetral stimulus
Avoidance learning: Context dependent behavior that results in the avoidance of the CS.
Circuitry of amygdala
Lateral nucleus of the amygdala is the convergence of CS and US through LTP
Central nucleus accepts output of LA, so also critical for conditioning
Basal nucleus outputs to Basal Ganglia avoidance system and so critical in avoidance learning
Vigilance Theory
Seeing whites of eyes indicates how afraid someone is. Not alarming in itself, but says that there is danger nearby. If amygdala signals vigilance , it would be more active in response to the eyes-wide-open stimulus than others. And it is.
So the amygdala seems to do a quick and dirty analysis to tell the rest of the brain if there is anything that requires a state of vigilance.
Amygdala role in remembering emotional events.
Setup: Emotional events are usually remembered better. Amygdala lesion patients showed the same effect as those who were on beta-blockers in a study of emotional story recollection
Emotional response in the fusiform face area(FFA) is also conveyed by amygdala
vigilance signal learned by:
Vigilance signal learned by conditioning and other processes such as avoidance learning This vigilance signal has widespread effects and mediates how emotional memories are encoded
emotional response in the fusiform face area conveyed by
amygdala
Vegetative state or unresponsive wakefulness syndrome.
Associated with cortical damage. ARAS still intact, but patient unaware of themselves and their surroundings
Reticular activity or just arousal is not enough for consciousness. The other things that are needed are:
complex cortical activity and substantial cortico-cortical and cortico-thalamic connectivity.
The Lower Order Representation Theory
All you need to be conscious of something is for your brain to represent that information. I.e. V1(primary visual C) suffices for consciousness. V1 damage equals blindsight, eyes work but visual consciousness does not
Recurrent processing theory:
Feedback and feed-forward. Feedback from higher order brain areas to lesser is responsible for conscious perception. Also been used to explain visual masking
There are huge priming effects irrespective of visual overlap. Invisible or masked words still activate the visual cortex. The difference between visual and invisible is widespread activation in parietal and frontal cortices.
Global workspace theory
consciousness and reportable consciousness differ. Maybe the frontal/parietal activity is related to reporting/introspecting, not consciousness per se
Optokinetic nystagmus response(OKN) / no-report paradigm
Frontal activity went away when patients did not have to report their perceptions.
Short term memories not stored in PFC, so Stimulus info could be decoded from:
visual area, “sensory recruitment” account of STM
Action potential:
1 Resting membrane is hyperpolarized.
2 Depolarized by incoming signals. The voltage gated Na+ Channel opens only when a large depolarization is detected. Voltage gated K+ opens slightly slower. Push Na out and bring K in. 3 Membrane potential repolarized by K+, propagates by activating sequential Voltage gated calcium channels channels,
4 resting potential reached again by action of Na/K pumps
Laminar organization of V1
vertical and horizontal electrode penetration. IV is primary input layer, hypercolumn, ocular dominance columns left/right/left/right
Basilar membrane: Place code and rate code.
Base does not respond to bass.
Place code: Different frequencies of sound are represented in brain according to where along the basilar membrane is stimulated
Rate code: different intensities/amplitude of sound represented by firing rate of auditory nerve neurons.
Object recognition in temporal cortex: Reduction method
take parts of an image away. Neuron continue to respond until image gets too basic/simple. Suggests that response was not to e.g. a tiger’s head but rather simpler configuration of basic elements. Different IT neurons driven by different stimuli
Posner cue
Arrow tells person where to focus attention.
[X] [ ] Neutral cue
Demonstrates benefits of (covert spatial) attention. Valid is faster than neutral. Invalid is SLOWER than neutral, not the same. Supports the idea that attention can be drawn without moving one’s eyes
spatial attention feed-forward processing
PFC -> TRN (thalamic reticular nucleus) -> LGN (lateral geniculate nucleus)/ thalamus
Multivariate pattern analysis - faces/houses test.
This was evidence against localization of function/ evidence in favor of distributed processing. The different objects did not active discrete neurons.
Neurobiology of memory: 2 types of glutamate receptors, NMDA and AMPA. What about NMDA? (long term potentiation)
NMDA has magnesium ion that only opens when post-synaptic neuron already depolarized
NMDA receptor lets calcium ions into the cell, this triggers intercellular mechanisms that:
1 Produce more AMPA receptors in synapse
2 Create entirely new synaptic terminals.
This is called long-term potentiation
Reconsolidation
When memories retrieved, reconsolidation is thought to occur to return them to “labile state”? Make them stronger I guess. The rat fearing the tone test. Memory removing drug made the rat stop fearing the tone.
