Cognitive Neuroscience - Lectures (Utrecht University)
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Phonology: the study of the abstract sound patterns of a particular language, usually according to some system of rules.
Syntax: the rules for arranging items into their possible permissible combinations in a language.
Semantics: the analysis of the meaning of a language.
Language is a system of discrete infinity. There is a finite number of elements, but unbounded use of those elements.
Human language is grounded on a particular computational mechanism, realized neurally. Each expression is assigned an interpretation at two interfaces.
There is a sensitive period for learning a 2nd language:
Language wars:
Language has a hierarchical structure.
Aphasia: an impairment in language understanding and/or production that is caused by brain injury.
Damage to Broca’s area and Wernicke’s area is different and expresses itself differently. The damage is always on the left side of the brain, because language is lateralized.
Late 20th century view:
Contemporary view:
There are two networks; in the frontal and temporal lobes. They interact all the time. There are interactions through dorsal and to ventral pathways.
Neural mechanisms for syntax and hierarchical structures
Newborn’s Wernicke’s area is not yet connected to Broca’s area. But it is connected to the premotor cortex.
So there is a sensory-to-motor mapping system. And there is a dorsal system (syntax, hierarchical structures) and ventral system (processing of semantic information.
Ability to imitate sounds is necessary for language in humans. Not in monkeys.
Convergence: different species have come up with similar solutions for similar problems.
2 month old infants: the brain responds more to the sound of the mother than a stranger (is related to memory).
FOXP2 gene mutation causes aphasia to develop. Other animals can have this mutation as well. It is however not a language gene, because:
Conclusions:
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Franz Joseph Gall suggested that surface of the head depends on mental skills. He is one of the firsts linking the brain to cognition.
Can modern phrenology be seen as modern cognitive neuroscience?
Brodmann was the first to map the cortex based on cell types. More detailed maps followed later.
The structure of the brain has a reason: function.
You can measure brain activity using
Brain elements: neurotransmitter & hormones. You can add pharmacology and food supplements.
Brain computation: making models of the brain to improve applications (facebook, google).
Cognitive neuroscience defines steps/networks in information processes by using neuroscientific methods.
EEG (ElectroEncephaloGraphy):
When is the measurement good?:
32-64 electrodes are enough to measure time effects.
Advantages EEG:
EEG measures the voltage potentials and MEG measures the magnetic field. MEG is similar to EEG, but better localization and most sensitive to activity originating from sulci.
EEG = relatively cheap, measures more neurons.
MEG = expensive, better localization
EEG & MEG same temporal resolution, MEG better spatial resolution.
So slow waves = low arousal
Fast waves = high arousal
Gamma (32Hz>) = superlearning
Beta (16-31Hz) = processing information, analytical thinking
Alpha (8-15Hz) = Eyes closed or very relaxed
Theta (4-7Hz) = Sleep, REM, dreaming, deep meditation
Delta (<4Hz) = deep dreamless sleep
ADHD = hyperactive, but less cortical arousal
Treating ADHD = increase arousal with medicine
Each frequency reflects a different mental state.
Average ERP’s to cancel out the noise.
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Diffusion-weighted imaging – measures the direction of water movement by comparing responses to magnetic fields in different directions. Shows neural fibre bundles.
Functional MRI – measures how tissue magnetic interactions change over time. Examines the blood flow and oxygenation. Neural activity changes when subject is exposed to a stimulus.
MRI & fMRI advantages:
Disadvantages:
How does MRI work?
The signal depends on:
Deoxygenated blood causes signal loss.
Why does fmri work?:
Important: effect 2 does not compensate accurately for effect 1
So oxyhemoglobin concentration increases due to increased blood flow.
Relation between neural activity and BOLD (black is neural activity):
[note: deze afbeelding uit het college is door de WorldSupporter redactie verwijderd wegens vermoedelijke inbreuk op het auteursrecht]
LFP: synaptic activity = neural processing
fMRI is slightly better correlated with LFP. So BOLD signals reflect synaptic activity.
What limits the temporal resolution of fMRI?
Perception: a translation of the physical environment into a pattern of neural activity that can be used by our brain to guide behavior. Perception is a set of tricks to extract useful (not an accurate!!) information from the environment.
The ganglion cells look at change in color: contrast.
Visual convergence:
We need to match the details of the image to the properties of the (visual) cell:
So the top cell responds well to the first image and the bottom cell responds well to the third image. So we use the differently sized receptive field cells to perceive different properties in images.
The images we see is mapped in the visual cortex:
Orientation-cells only respond to cells in a specific orientation. This is the relation between preferred orientation and track distance:
There are two visual pathways:
V2 looks for patterns in the images it receives. V1 does not.
The middle stages of visual processing look at common
.....read moreThere are two types of movement:
The motor system has a hierarchical organization:
Motor sensor loop:
For rapid targeted movement, there is a primary fast ballistic movement, and then an error-correction movement.
Activating muscles through acetylcholine release. Then the muscle contracts.
Motor neurons are controlled by the central nervous system through the spinal cord. They are relatively large and are arranged in antagonistic (opposite) pairs.
Reflex arc: simple and short circuit for fast response. A reflex happens in the spinal cord and spinal neurons can generate an entire sequence of movements without feedback or input.
What happens when the sensory nerves are destroyed, but motor nerves are spared? No error-correction --> errors accumulate during sequences of automatic actions.
Summary peripheral motor system:
Central nervous system: there are different tracts responsible for different motoric functions:
Primary motor cortex:
Pre-motor cortex:
Posterior Parietal Cortex
Supplementary Motor Area (SMA)
Attention is selective. Selective attention refers to the allocation of processing resources, generally at the expense of resources allocated to other stimuli.
Neuroscientific concept: attention is the manipulation of activity of population of cells that process sensory information.
Advantages of attention:
Disadvantage: opposite effect for unattended stimuli.
Arousal is not attention. Arousal modulates all sensory signals baseline effect
Attention selects and modulates specific sensory signals selection effect
Two forms of attention:
Internal manipulation of attention: you decide yourself what you attend. This is endogenous, top-down or controlled attention.
External manipulation of attention: sensory stimulus characteristics decide what you attend. This exogenous, bottom-up, reflexive attention. The sensory area is shaped by experience over years. It responses to most relevant things due to experience.
--> Salience models: models that predict what you attend automatically.
Attentional blindness
Attentional blink
Attentional cueing
Cocktail party
Visual search
Neural mechanisms are strengthened when attention is given to it.
Question 1 can be answered using EEG: great temporal resolution.
Attention is necessary for similarity analysis.
Mismatch negativity (MMN): oddball paradigm.
Feature attention: the amplitude is increased for attended stimuli and the sensitivity is narrowed.
--> Attention acts in the brain area that codes the target feature.
Spatial attention: attention to location in a visual field. Could be an auditory source.
Receptive field: area of interest to the neuron. A neuron responds when a stimulus is shown in its receptive field.
Each cell has a receptive field: responses only to a specific
.....read moreShifts of attention are useful for many daily tasks, such as finding your keys, playing video games, learning, personality and flexibility and efficiency.
Patients with attentional deficits have damage to the frontoparietal network, causes:
Neglect
Neglect is different from hemianopia (V1 damage). Difficult to differentiate though (but hemianopia patients often know something is wrong).
Balint’s syndrome
Parietal lobe damage: deficits in attention and changing the allocation of attention
Frontal lobe damage: deficits in control & initiating the changes in attention
Frontalparietal network = attentional control
There is first activity in frontal areas, then in parietal areas.
The TPJ (temporo-parietal junction) is specifically important for bottom-up processing of attention.
During visual search you use a lot of bottom-up attention.
When searching for something, you are always driven by both pop-out and conjunction search. Reorienting during both types of visual search is coded in the intraparietal sulcus (IPS).
Default-mode network: active in rest. Decreased activity in the frontoparietal network means increased activity in the default-mode network (inverse coupling) --> Posterior cingulate cortex
EEG reflects sleep stages:
Sleep neurotransmitters:
Representations: somehow the world is represented in the mind and the brain.
Churchland & Sejnowski: the defining function of nervous systems is representational.
Stored representations are believed to depend on the configuration of weights between units. In neural terms, these weights are the strength of synaptic connections between neurons.
Some memory functions are intact in amnesic patients.
Non-declarative (implicit) memory: memory without awareness. Skill learning, priming, classical conditioning.
Priming tests consist of:
Classical conditioning: before conditioning, the animal responds to the US, but not to the CS. At this stage, this is called the unconditioned response or UCR. During the conditioning the CS and the US are paired repeatedly. Conditioning leads to a conditioned response.
Delay vs trace conditioning in amnesic patients
Anterograde amnesia: amnesia for events after the trauma
Retrograde amnesia: amnesia for events before trauma
Hebb: there is simultaneous activity in two neurons.
Changes in the effectiveness of synaptic transmission take place as a result of simultaneous pre- and postsynaptic activity.
There are two research strategies for neurobiology of learning and memory:
Top-down approach of LTP (long term potentiation) and memory.
NMDA receptor: neurotransmitter can bind to this. But there is a (Magnesium) block. This can be removed by depolarizing the cell. So it requires two simultaneous events: 1. Depolarization 2. Glutamate in the cleft.
Bottom-up approach: imprinting. The formation of early social preference for the mother or another stimulus.
Memory formation involved structural changes in the connections between neurons. Such structural changes involve protein synthesis.
Conclusions:
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The hippocampus plays a big role in declarative memory: it is the ‘hub’ of memory.
Medial temporal lobe lesions lead to severe and global amnesia. Remote memories are spared after MTL lesions.
Within the hippocampus, there is spatial encoding by place cells.
Recollection: hippocampus
Familiarity: perirhinal cortex
Three-process theory of medial temporal lobe functions:
Semantic knowledge in the brain:
Semantic dementia: semantic memory loss due to dementia. Damage to the temporal cortex
[note: deze afbeelding uit het college is door de WorldSupporter redactie verwijderd wegens vermoedelijke inbreuk op het auteursrecht]
Distributed-only view & Distributed-plus-hub view are two models of the cortical semantic network.
There is a lot of evidence for the distributed-plus-hub view.
Memories can become independent (outside of hippocampus).
How are retrieval memories reactivated and becoming available again? So how are episodic memories reactivated?
Role prefrontal cortex --> different parts are active for semantic and phonological pairs of words.
Damage to frontal lobe lesions: source errors.
Multiple trace theory of consolidation: hippocampus is always involved, and has multiple memory traces explanation of complete retrograde amnesia.
Memory is consolidated during sleep.
Filial imprinting – the formation (through learning) of an early social preference for the mother or another stimulus.
You need to sleep fairly soon after the learning experience for it to enhance memory.
Conclusions:
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Emotion has a signaling function, for example for a threat to integrity.
Emotions trigger adaptive responses. From evolutionary perspective: we use it for responses that are adaptive.
Emotions are universal, the basic emotions are: happiness, surprise, fear, anger, disgust and sadness.
3 biosystems from evolutionary perspective:
Limbic system = the emotional brain.
ANS controls the involuntary muscles.
When you encounter a threat, your autonomic nervous system responds:
Hormones: HPA-axis. Releases glucocorticoids, which regulates stress.
Fear response: LeDoux model. The amygdala is the important structure. He proposed there are different routes, a fast route and a slow route.
The information enters the BLA (basolateral) amygdala. Then projections are sent to the central amygdala, from where the projections run to the (hypo)thalamus.
‘Emotion’ areas of PFC:
Amygdala is involved in fear conditioning.
The CS will elict conditioned (fear) response:
The ACC and the anterior insula are consistently activated in response to threat.
In a study, no constant amygdala activation was found during fear. Why?
A fearful expression will slow down the reaction time in a stroop task. Also when the face is masked and the face is no longer recognizable.
There is no amygdala activation when the attention to the fearful stimulus was explicitely directed away.
There is no anatomical evidence for the fast route of LeDoux. There is however some evidence, such as affective blindsight, binocular rivalry.
Evidence that non-attended or unconsciously processed information can activate amygdala does not necessarily mean that this information has been processed (exclusively) through subcortical channels.
There should also be focus on networks, not only on isolated brain areas. Such as the salience network.
Summary:
Questions? Let me know in the contribution
.....read moreOur brains may have grown in size because we are social animals.
The orbitofrontal cortex plays a role in social functioning.
Somatic marker hypothesis
vmOFC: associates a ‘gut-feeling’ with each choice – helps sort through available options.
Patients with vmOFC damage: the somatic marker does not cause the SCR reflects to be a learned association.
The somatic marker occurs when you’re about to do something risky.
The default mode network may be involved in self-referential processing.
Most people think they are better than average: the better than average effect.
Processing others’ thoughts (theory of mind) can be measured using the false-belief test.
The TPJ is specifically involved in processing stories on other people’s thoughts. Why is this active?
Mirror neurons and mimicry also play a role.
These mechanisms may be deficient in autism. For example, the higher the autism quotient, the lower the mimicry.
People with autism look at the eyes way less than healthy controls.
High testosterone prenatally: low scores on the reading the eyes in the mind task.
Oxytocin: bonding hormone. Oxytocin enhances fixations on eye region and improves reading mind from eye.
Summary:
Questions? Let me know in the contribution section!
Follow me for more summaries / lecture notes!
Phonology: the study of the abstract sound patterns of a particular language, usually according to some system of rules.
Syntax: the rules for arranging items into their possible permissible combinations in a language.
Semantics: the analysis of the meaning of a language.
Language is a system of discrete infinity. There is a finite number of elements, but unbounded use of those elements.
Human language is grounded on a particular computational mechanism, realized neurally. Each expression is assigned an interpretation at two interfaces.
There is a sensitive period for learning a 2nd language:
Language wars:
Language has a hierarchical structure.
Aphasia: an impairment in language understanding and/or production that is caused by brain injury.
Damage to Broca’s area and Wernicke’s area is different and expresses itself differently. The damage is always on the left side of the brain, because language is lateralized.
Late 20th century view:
Contemporary view:
There are two networks; in the frontal and temporal lobes. They interact all the time. There are interactions through dorsal and to ventral pathways.
Neural mechanisms for syntax and hierarchical structures
Newborn’s Wernicke’s area is not yet connected to Broca’s area. But it is connected to the premotor cortex.
So there is a sensory-to-motor mapping system. And there is a dorsal system (syntax, hierarchical structures) and ventral system (processing of semantic information.
Ability to imitate sounds is necessary for language in humans. Not in monkeys.
Convergence: different species have come up with similar solutions for similar problems.
2 month old infants: the brain responds more to the sound of the mother than a stranger (is related to memory).
FOXP2 gene mutation causes aphasia to develop. Other animals can have this mutation as well. It is however not a language gene, because:
Conclusions:
Utility: psychological value assigned to an outcome.
Prospect theory
Primary reinforcer: rewards that have a direct benefit for fitness
Secondary reinforcer: neutral outcome that has been turned into a positive one
Substantial nigra and ventral tegmental area are the dopamine nuclei.
In rats, the dopaminergic system was removed, and the rats still liked certain tastes. This indicates wanting instead of liking: motivation to pursue a reward.
Nucleus accumbens: activated by wide range of motivationally relevant stimuli. Reinforcement of a desirable association.
DA neurons signal changes in information:
Reward prediction error (RPE): the actual outcome differs from what was expected.
Actor-critic models: the brain has 2 systems
Damage to reward pathways:
Pathological gamblers’ brains ‘learn’ from near-misses. Males 14-22 years old, prefrontal cortex not fully developed yet.
Salience can lead to dopaminergic increase.
Uncertainty: psychological state of having a lack of information.
Risk: decision has multiple potential outcomes with known probabilities
Brain regions risk taking:
[note: deze afbeelding uit het college is door de WorldSupporter redactie verwijderd wegens vermoedelijke inbreuk op het auteursrecht]
Ambiguity: probabilities of the outcomes cannot be known. OFC and PFC are involved.
Dual system: two separate processes
Social stimuli are rewarding. How rewarding depends on the social relationship.
Two theories:
Parietal cortex: social cognition
mPFC: thinking about other people’s mental states
Game theory studies how decisions are made in complex situations.
Altruistic punishment: censuring people who violate social norms.
Currency signal: neurons tracking subjective value, regardless of category.
Drift-diffusion models: assume that decision making is a random drift from neural states towards thresholds for action.
Modality-indepenent value signals:
.....read moreDevelopment of traits:
Key factor is selection pressure
Are we dealing with common descent or with convergence?
False dichotomies in evolution studies:
What is innate? Different opinions:
Lorenz: behavior can be dissected in innate and acquired/learned components.
Lehrman: behavior is the result of a complex interaction between the individual and its internal and external environment.
No new neurons are generated after birth.
At birth there are (too) many synaptic connections, so pruning takes place.
Does absolute size matter? No, if the body is bigger, the brain is too. So look at relative size.
Cortex size does matter. Forebrain complexity is characterized by cell groups.
Brains tend to get bigger and bigger. Why? 3 hypotheses:
Group size does not covary with primate general intelligence score.
Summary:
Misinterpretations of the view of evolution:
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