Brain & Cognition 2 🧠Flashcards
the perception-action cycle
high level sensory cortex (hierarchical processing) -> meaningful features from the environment. -> motor outputs in reverse hierarchy,
overt orienting and attending
Moving your eyes, body, ears, nose, etc in the direction of a relevant stimulus (what the superior colliculus does).// •Eye & orienting movements
•Colliculus Superior: saccadic eye movements, orienting
•Pulvinar: attention shifts
•Frontal Eye Fields
covert attention
Shifting your attention towards something, without any external, overt signs, i.e. while maintaining fixation. This mechanism has evolved particularly in social animals, in which direction of gaze often has strong meaning (threat, aggression, sexual attraction)// •Pulvinar, FEF •Ventral Frontal cortex •Dorsolateral PreFrontalcortex •Superior Parietal Lobe (SPL) •Temporo-Parietal Junction (TPJ)
cocktail party effect
One may pretend to listen to someone in front of you, while actually focusing on what is said in another conversation.
attentional capture
while listening to the person in front of you, your attention may be suddenly captured by someone saying your name in another conversation:
top down attention
when subjects are instructedto focus their attention on some locationof the visual field (such as in the Posner cueing task). The behavioral effect typically is that reaction times to presented targets are faster at the attended location.10
bottom-up attention
a suddenly appearing stimulus will automatically ‘capture’ attention. Shorter reaction time to primed location. This happens even when subjects know the cue (prime) is mostly invalid (which shows captureis ‘automatic’ and not top down).
inhibition of return
when the temporal interval between prime and target > 300 ms.Now, reaction time is longerfor the cued location. The subject starts to actively suppress attention to the location of the (mostly invalid) cue.
object based attention
Instead of focusing on a particular location, attention can also focus on a particular object/ Attention can be directed towards objects that overlap in space.
feature based attention
shorter reaction times to objects with features
a potential label for assembly coding
Neurons of each assembly fire action potentials in synchrony. Assembly A and B code for different objects. The brain ‘knows’ which parts belong together because those that belong to an assembly fire action potentials in synchronyCross-correlation function reveals synchrony
feature integration theory
Features (like orientation or color) are detected in parallel across the visual field•Yet only at the location where attention is focused, these features are integrated•Can only occur for one or a few items at a time because of capacity limit of attention
crowding
inability to identify objects when surrounded by other objects (in peripheral vision)
biased competition model of attentional selectiong
- High level neurons have large receptive fields
- Multiple stimuli withinthe RF causes the response to be the average of the responses to poor (house) and optimal (face) stimuli that are obtained when these are presented in isolation: face detection (in this case) is hampered by the competing house stimulus
- Attention can biasthe competition, so that the response (here between 150-300ms) is what it would have been when the stimulus was presented alone.
- This resolves the competition, and allows for optimal subsequent processing, detection, reaction etc
things that cause attention
•Increase in fire rate and synchrony of attended locations, features and objects•(therefore) Feature binding and faster responses•A resolving of competition between responses falling with the same receptive field, hence better discrimination, less crowding
change blindness
the inability to notice changes that would be perfectly obvious once attention is directed to them
early vs late selection
1.At what moment during processing?2.At what level of processing in the visual hierarchy (V1, V4, higher?)3.In what pathways does selection occur (dorsal vs ventral)?
inattentional blindness
the inability to memorize and report salient stimuli (such as gorillas) when attention is diverted to some other task-relevant stimulus
early selection
Unattended words are not distinguished from non-words >
attentional blink
the inability to memorize and report a stimulus (T2) that is presented briefly after (up to ~500 ms) a stimulus (T1) that has tobe reported or memorized
late selection
Missed (unseen) T2 houses nevertheless evoke selective activation of the PPA (difference between red and blue). This activation is only amplified (green) when the target is seen
neglect
- No (conscious) percept of contralateral stimuli, that is not caused by a primary sensory deficit (hemianopsia) or a motor deficit (hemiparesis)
- Ignoring of contralateral stimuli•Slower reaction to contralateral stimuli
- Ignoring the ‘contralateral’ half of objects
- Much less eye, head or arm movements (exploration) towards contralateral side
allesthesia
stimuli are perceived at incorrect locations
extinction
- Typically end stage of neglect/ milder versionof neglect
•when both ipsi-and contralateralstimuli are present, only the ipsilateral stimuli are perceived
object based neglect
patients not so much ignore the left side of their visual space, but the left side of objects, regardless of their position in space. Only recognize and copy right sides.
balint syndrome
Very few eye movements: ‘gaze paralysis’. Note how the patient cannot follow the object the doctor is waving in front of her
simultanagnosia
inability to see more than one (part of) object at a time. Note how patient is focused on corner of bed.// inability to understand the spatial relationship between objects, and to see more than one object at a time, not seeing the big picture
unconscious priming
faster categorization of words when preceded by an unseen (extinguished) object of the same category. Yet unable to pick the unseen stimulus
3 guises of consciousness
state, device, sensation
polysomnography
simultaneous recording of EEG (brain) , EMG (muscle tone) and EOG (eye movements)
awake
Low amplitude, high frequency EEG•Saccadic eye movements•Muscle tone (high EMG)
asleep
•High amplitude, low frequency EEG•No saccadic eye movements (drifts)•Low muscle tone (low EMG), paralysis
rem sleep
Low amplitude, high frequency EEG•Saccadic eye movements•Low muscle tone (low EMG), paralysis
sleep paralysis
muscle tone stays flat because of muscle paralysis, yet person awake EEG and EOG like awake
narcolepsy
sudden rem sleep onset
sleep violence
rem sleep without muscle paralysis: violent movements acting out dreams
brain stem reticular system activating system & medial reticular formation
•Set of nuclei in the brain stem•Send fibersto the cortex with modulatory neurotransmitters
reticular activating system
is critical for maintaining the conscious state
brainstem reticular formation
critical for maintaining the conscious state//
projects to the cortex, either directly, or via the intralaminar nuclei of the thalamus
Effects of electrical stimulation of Medial Reticular Formation (MRF) in anesthetized cats
- More high frequency EEG (gamma) relative to low frequency EEG (delta)2.Firing rates variable3.Oscillations go up, more high frequency oscillations4.Synchrony goes up
- cat wakes up
thalamus
gates the info from the senses to the cortex
brain stem mrf
modulates the thalamic gating from arousal to sleep, allows or shuts down the inputs from the senses
utilization behaviour
The tendency to grasp common objects when presented, and perform the function commonly associated with the object.
imitation behaviour/mimicry
The tendency to imitate the gestures, actions, sentences of the person in front of you.
cortical
parietal, temporal, occipital lobe
subcortical
thalamus, basal ganglia, cerebellum, amygdala, hippocampus, brainstem nuclei
frontal
pre-motor, motor cortex
contra-lateral frontal lobe
pre-frontal, pre-motor, motor cortex
how does the pfc enable flexibility of reponses
- Workingmemory, so that longer stimulus response contingencies are possible, delayed responses
- inhibting direct response
- adding value to choice options, and updating these values on the basis of experience
different PFC neurons may encode object identity or location
Different strength of delay activity depending on identity (‘what’) of object (left neuron), Different strength of delay activity depending on location (‘where’) of object (right neuron)
internal value
generalized and automatic VALUE system It assigns value to items we are confronted with, dictates our choices., The PCC (posterior cingulate cortex), Hippocampus, VS (ventralStriatum/ nucleus Accumbens), ventromedialPFC
reward pathway in the brain
vmPFC, signals value for broad range of choices, including moral value, nucleus accumbent, signals value and motivation, dopamine releasing neurons in VTA signal reward or reward prediction
what would be needed for the PFC to perform a function of picking up the phone
reciprocal connections with sensory and motor cortex, neurons encoding rules between input and output, inputs from reward systems (dopamine), rapid learning of such rules, neurons encoding abstract concepts like ‘being at home’ , keeping info ‘on line (WM) because stimulus-response contingencies may span time
choices are determined by
a combination of low-and high-level versions of ‘greed’, ‘fear’, and ‘herd’ behavior•There is not one system that is ‘boss’, or in control. You are the combination of all these ‘drives
readiness potential
The actual movement is preceded by the subjective intent to actwith ~250 ms, But this subjective intent to act is itself precededby ~500 –1000 msof neural activity of the motor cortex (Cz): Our conscious intent to act is in fact the result of an unconscious process. Free will is an illusion
choice blindness
motivations do not lead our choices
post hoc rationalization
Subjects give motivations for ‘their’ choice(which was not their original choice) that vary from confabulation to motivations that pertain to the forced choice instead of the original one
Gazzaniga’s split brain experiments : the brain interpreter
The left hemisphere puts all information together into a final narrative, a story about the motivations and goals of our actions and thoughts
whole body rubber hand illusion
•Subjects (PS) sees himself (VF) in VR goggles•He is stroked on the back in sync with the dummy that is filmed (PF)•After a while, het feels an ‘out of body experience’ towards the VF copy•This does not happen when stroking is out of sync, or with non-corporeal objects
corpus callosum
connects two hemispheres to work together and connects the cortex to the two hemispheres. Connections between homotopicareas, also some between heterotopic areas•Together with Anterior Commisure(not always cut in surgery)•Posterior Commisureconnects subcortical nuclei
the WADA test
each hemisphere is temporarily anesthetized using amobarbital (or sodium amytal, etc).In most people, anesthesia of the left hemisphere results in aphasia, the inability to speak or comprehend languageBut some people have right hemisphere dominance for language, others bilateral language capabilities