Emotion and Biological Psychology

epistemic emotions

closely tied to knowledge, learning, and cognitive processes – drive the doubt-certainty cycle

arise in response to situations involving uncertainty, curiosity, insight, or the pursuit of understanding

crucial in motivation for learning, problem-solving, and critical thinking – signal that something needs to be understood or resolved, prompting further cognitive effort

• curiosity = the desire to acquire new knowledge

• confusion = a reaction to conflicting or unclear information

• surprise = a response to unexpected information

• interest = engagement with novel or complex stimuli

• wonder = a deep sense of awe or fascination, often about something vast or mysterious

(course introduction)

general definition of emotional episode

an event-focused, two-step, fast process consisting of

a) elicitation mechanisms that

b) shape multiple responses (e.g. behavioral, physiological, and subjective feeling)

provides us with information about the environment and prepare us to handle it and reach our goals

(course introduction)

action tendency responses

approach – avoidance/withdrawal

the internal motive states that are hypothesized to underlie a felt urge, that urge’s direction (towards or away), and the urge’s aboutness (fear is about threat, sadness about loss, etc). underlies over behavior

have connections between amygdala and motor-related areas (and also others), such as motor cingulate and primary motor cortices

(the emotional brain)

volitional control as emotional respons component

the conscious capacity to regulate actions, emotions, and impulses to align with personal goals or values

(course introduction & the emotional brain)

functions/adaptive purposes of emotions

inform us about the environment and prepare us to handle it and reach our goals, e.g. increasing survival (although it gets out of hand sometimes…) and well-being

guide behavior

facilitate decision-making

prioritize attention and memory

regulate physiological states

support social communication

(course introduction)

emotions as functional states

Adolphs & Anderson’s idea that emotions are functional, in terms of relation to stimuli and behaviors, evolutionary, and in many other ways

defines emotion states by what they do (their causal relations), rather than how they are implemented

• example: a clock is defined as something that shows the time, rather than by the multiple implementations it can have
  
  

emotion states are typically caused by certain events (stimuli), and in turn cause other events (e.g. behaviors)

• many different stimuli can cause the same type of emotion state, and that state orchestrates many different behaviors

evolution only “sees” functional effects in why an emotion is adaptive, and how it evolved, relative to the environment and ecological challenges → emotions evolved are evolutionary functional

(course introduction & chapter 2)

brain state

an instance of an emotion corresponds to a brain state (but all brain states are not instances of emotions)

not all instances of the same emotion have an identical brain state

(course introduction)

properties/characteristics of emotion states

scalability: emotion intensity weak-strong (roughly like arousal)

valence: evaluation, will it be good/bad? does it feel positive/negative?

persistence: emotional states usually lasts longer than the trigger stimulus

generalization over stimuli and behavior: emotion states may be elicited by stimuli or contexts that were associates with the initial trigger stimulus

global coordination: engages the whole organism – coordinate multiple behavioral, bodily, biochemical, and cognitive changes

priority/automaticity: emotion states grain priority over many ongoing proxesses, such as behavior or volitional actions

social communication: signals to other organisms

can be used to separate instances of emotion states, distinguish emotion states from other behavioral states or reflexes, and identify states across diverse species

(the emotional brain & chapter 3)

necessities of emotion causation theories

should explain:

1. elicitation: why a given event evokes an emotion

2. differentiation: why the evoked emotion is of a specific kind

and the psychological mechanism, i.e. the process through which this is achieved

(emotion theory)

evolutionary origin of emotions

originally served to guide action

all living organisms share some fundamental characteristics:

1. they are autonomous systems

2. they can produce self-initiated movements

3. their movements show direction: they move towards some things and away from other

to determine the direction, some type of evaluative process is needed → the forerunner of our emotions

(emotion theory)

emerging consensus among emotion researches

emotions…

• are complex phenomena

• have evolutionary origins, but are shaped by cultural factors

• serve as an “interface” between the organism and its environment

• are elicited by some type of “information processing”

• have a number of important functions (usually of social nature)

• include several components (e.g. expression, physiology, action tendencies)

• involve changes in mental and bodily components that are centrally represented as feelings (which can be labeled)

(emotion theory)

dominant approaches in emotion theory

categorical

• basic emotion theories

• cognitive appraisal theories

• associative theories

dimensional

• unidimensional models

• multidimensional models

hybrid

• constructionist theories

  • multilevel theories

(emotion theory)

categorical approaches

theories that assume that people experience emotions as categories, which are distinct from each other

agrees on that learning is involved to some extent

(emotion theory)

basic emotion theories (BET)

categorical approach, assumes that there are a limited number of innate and universal emotion categories

there’s a set of survival problems that most living organisms have in common → these problems require adaptive responses → these responses are seen as the “prototypes” of human emotion

some say that basic emotions may combine with other emotions or cognitive contents to create more complex emotions

have their roots in Darwin’s work on emotional expression

(emotion theory)

examples of adaptive responses in basic emotion theories (BET)

fear, to avoid danger

interest, to search for food

joy, to cooperate with others

anger, to compete for resources

desire, to procreate

disgust, to avoid toxic substances and potential sources of disease

tender love, to care for offspring

(emotion theory & Malezieux et al. 2023)

possible support for basic emotion theories (BET)

early development

phylogenetic continuity

cross-cultural consistencies in the antecedent conditions

cross-cultural agreement in judgments of facial and vocal expression

categorical perception of emotional expressions (doesn’t require lexical categories)

distinct patterns of psychophysiological changes

distinct brain networks

vocal expressions developing without auditory and/or visual learning

(emotion theory & Juslin 2025)

Panksepp’s seven emotional systems

well-known model in basic emotion theories (BET), that defines emotions as fixed biological building blocks, not psychological constructions – strong view against most of constructed emotion ideas

argues that we are born with seven fixed, subcortical circuits:

• SEEKING: generalized motivational arousal

• RAGE: affective attech

• FEAR

• LUST: sexuality

• CARE: nurturance/maternal

• PANIC: separation distress, social bonding

• PLAY: social joy and affection

learning only conditions what triggers them and how we regulate the behavioral output

(emotion theory & chapter 10)

criticism against basic emotion theories (BET)

little agreement about how many emotions are basic, which emotions are basic, and why they are basic – if there really are basic emotions, how can there be so much disagreement?

can’t explain the variety of emotions people experience in life

not that much distinct patterns in expressions, physiology, or neural activity – more variability than the theories would predict

(emotion theory & Juslin 2025)

cognitive appraisal theories (CAT)

categorical theories, focus on how specific profiles of appraisal outcomes determine the emotion – assume “emotion specificity” in the response: each emotion is caused by a unique pattern

says that emotions are elicited and differentiated on the basis of a person’s subjective evaluation, of the personal significance (usually related to goals, motives, and plans) of a situation, object, or event on a number of dimensions or criteria

example: fear can be predicted to involve a profile of high suddenness, low predictability, goal incongruence, high urgency, low power, and an external agent

can be helpful for modern neurobiological accounts of emotion!

(emotion theory, Juslin 2025 & chapter 10)

comparison of basic emotion theories (BET) and cognitive appraisal theories (CAT)

similarities:

• assume “emotion specificity” in the response

• assume that emotions involve some interdependent and synchronized changes in multiple emotion components

• categorical approaches

differences:

• (most) CAT assume that emotions will reflect the outcomes of individual criteria in even more specific ways – presume distinct patterns not only for broad categories but also for each appraisal profile

• CAT often postulate a much larger number (even infinite) of emotions

• BET assume that cognitive appraisals result in nuances within categories, rather than adding additional categories

(emotion theory, Juslin 2025 & chapter 10)

criticism against cognitive appraisal theories (CAT)

numbers and identity of criteria: disagreement among researchers about the exact number and identity of the criteria required to account for emotions. some say the criteria are derived primarily from intuition of researcher rather than objective data

• appraisal profile for each emotion: even if they agree on the criteria, they may not predict the same appraisal profile for the emotion

non-testable assumption: virtually impossible to confirm if there are infinite numbers of emotions

only focused on humans and the experience of emotion

verbal self-reports: appraisals have mainly been studied with verbal self-reports (recalled emotional episodes) – critics argue that this is studying what people think causes their emotions rather than the actual causes

inconsistent view of subconsciousness: responds with “appraisals may occur subconsciously” when accused of being too cognitive, but at the same time assuming that subjects can self-report upon their appraisal processes (which is not possible if it’s outside consciousness)

conceptual confusion: sometimes the evaluations of the criteria is said to constitute the psychological mechanism that causes emotions. other times they suggest that it can be accomplished via different mechanisms

• hard to distinguish from associative (conditional) theory

nomothetic approach: rarely examines individual differences in everyday emotional episodes

not just one mechanism: appraisal may not be the only mechanism

• when trying to predict specific emotions based on ratings of criteria, only 40-50% of episodes are classified correctly

(emotion theory, Juslin 2025 & chapter 10)

associative theories (AT)

categorical approaches, range from simple condition theories to complex semantic networks

emotions are recorded in memory → activation of these memories is the most frequent cause of emotions in daily life

claim that most stimuli evoke emotions as a result of learning and emotional conditioning

• theorist agree that an association can be activated without awareness, but debate whether conscious awareness is needed for an association to be formed (i.e. for learning)

not all of them are focusing on how emotions are caused. some just investigate the link to memory

neo-behavioristic

(emotion theory, Juslin 2025 & chapter 10)

emotional conditioning

learning processes in LeDoux’s Higher-Order Theory of Emotional Consciousness (associative theory, AT)

a new neutral stimulus acquires “emotional power” via repeated pairings with another stimulus that is already stored in memory as part of an “emotion schema” → previously neutral stimulus will eventually evoke that emotion on its own

very similar to classical conditioning

(emotion theory)

Rolls’ emotion classification scheme

associative theory (AT), similar to operant conditioning/instrumental learning

we are born with unlearned primary reinforcers (e.g. pain), and learn secondary reinforcers (e.g. money) by associations throughout life – any stimulus may have several different associations

emotions = states produced by instrumental reinforcing stimuli

elicited by rewards and punishments (reinforcers), and by the omission or termination of such reinforcers. categorizes emotion in terms of:

a. whether the reinforcer is positive (reward) or negative (punishment)

b. by the contingency relationship between the response and the reinforcer

dimensional in reinforcer-contingency relationships, BUT SPECIFIC EMOTIONS AS OUTCOMES

(Juslin 2025)

criticism against associative theories (AT)

elicitation problem: not very informative about which stimuli cause emotions

differentiation problem: not very informative about which stimuli lead to which emotions

underestimates innately prepared responses: any stimulus should be capable of eliciting any emotion, but this is not really true – we learn some associations easier than others, e.g. easier to develop a phobia of snakes than lightbulbs

circular reasoning: the emotion (e.g. joy) could be the reward and the elicited emotion. no clear distinction between emotion and motivation

no justice for the diversity of emotions: involve a minimal level of meaning analysis, there appears to be a limit to what kind of emotions they can explain

sneaks in some cognitive interpretation elements: acknowledgement that associations alone can’t explain the full range of emotions experienced by people

neglect evidence of multiple emotion systems within the brain

little effort to analyze cultural differences in emotions (probably because mostly animal studies) even though most emotional responses are said to be learned

unlearnd reinforcers (e.g. smile, aggressive vocalization) kinda similar to the innate affect programs in BET

(emotion theory & Juslin 2025)

dimensional approaches

conceptualize emotions based on their placement along broad and continuous affective dimensions (such as valence, activation, or potency) that are believed to be more fundamental than categories formed by emotion terms

focus on the subjective feeling component, as measured through verbal self-report

not usually regarded as theories of emotion causation – the goal is rather to describe the structure of emotional experience (feelings) – but often part of hybrid theories

come in many different forms: one-dimensional, two-dimensional, three-dimensional

(emotion theory & Juslin 2025)

circumplex model of emotions/core affect (Russell)

two-dimensional model that illustrates that emotions vary in their similarity to each other

says that we are always experiencing some core affect – at a given moment, the conscious experience is a single integral blend of two dimensions

economic way of representing affective responses

supported by evidence of valence and arousal being pan-cultural and present in young children

(emotion theory & Juslin 2025)

criticism against the circumplex model

blurs important psychological distinctions: emotions placed roughly at the same position can be quite different

• e.g. angry and afraid are both high in arousal and unpleasantness, but very different in terms of their implications for the individual, such as different action tendencies

people actually don’t seem to experience a feeling all of the time, in fact maybe only 25% of the time

confuse emotions (intense, short-lived responses to events) with moods (weaker, more floating, without a specific object)

methodological problems: the model might just be random from the factor analyses

mixed emotions: we can experience opposite emotions at the same time, this model doesn’t acknowledge that

• valence not necesarily bipolar

two-dimensional space: emotions can’t be reduced onto two dimensions

• two activation dimensions reflecting different physiological systems are found. these may be manipulated independently in opposite directions

there might be two arousal dimensions reflecting different physiological systems

(emotion theory & Juslin 2025)

hybrid approaches

combine categorical and dimensional aspects

come in different forms: constructionist and multilevel

(emotion theory)

theory of constructed emotion (TCE) (Feldman Barrett)

hybrid approach constructionism theory, says that emotions aren’t in principle distinct from cognitions and perceptions – no brain systems/core neural circuit dedicated/unique to emotions at all

the brain uses concepts to give meaning to both internal and external sensations – if the concept happens to be about emotion, the brain is constructing an emotion

emotions arise from predictive regulation (allostasis) and the categorization of interoceptive and sensory inputs using our emotion concepts (required – without a concept for fear, you can’t experience fear)

hybrid model: interpretative layer for emotion categories/concepts, affect layer with biological dimensions/core affect

focus on the feeling component of emotions

basically: “the brain categorizes the present moment of affect, by means of interoceptive predictions and emotion concepts from one’s culture, to construct an instance of an emotion”

(emotion theory, Juslin 2025, the emotional brain & chapter 10)

criticism against theory of constructed emotion (TCE)

circumplex problems remain

mental states as conceptualizations and core affect: if all mental states are conceptualizations, core affect should be too, but it’s seen as a biological primitive

domain-general system: emotions feel very different from other mental states, which contradicts the idea of the same domain-general core systems for all mental states

language-dependent: the focus on language forces an awkward position. it there’s no swedish word for an english term of emotion X, do swedes not experience emotion X?

• labeling constitutes the emotion → no emotion label, no emotion (this is an extreme position)

difficult to test: no clear hypotheses on how the brain relates to emotions, unclear distinction between emotions being triggered vs created, “predicts variability” but there’s always variability (i.e. impossible to falsify)

point of accuracy: says that accuracy has no scientific meaning, but at the same time says that a person can’t be “wrong” about his or her feeling

• emotions aren’t only created in the self but also in others (e.g. I perceive you as afraid and you perceive yourself as afraid). a single organism can have multiple simultaneous distinct emotions for different perceivers, without a theoretical limit to how many. if accuracy has no meaning, all these percepts are equally valid, but at the same time a person can’t be wrong about his or her own perception.

• → although all percepts are valid, some percepts are more valid than others

requiring concepts: if concepts are absolutely necessary, how can we create the concept of fear without experiencing fear? no infant or animal could never have emotions – fails to explain how emotions evolved

doesn’t differentiate feelings from emotions – emotions are labeled feelings

(emotion theory, Juslin 2025 & chapter 10)

multilevel theories (MLT)

many different causes of human behavior and emotions, i.e. emotions are multiply determined – a single emotion mechanism is unable to account for all emotions

these theories can resolve some of the problems associated with other theories

• reflect both universal and culture-specific aspects

• accounts for variability and individual differences

• can explain that more than one emotion can occur at the same time (occurance of mixed emotions)

• cover emotions not addressed by traditional theories

• more consistent with neuropsychological findings

• incorporates both dimensional and categorical aspects

• different events may activate different mechanisms, and different mechanisms have different emotions related to them (?)

(emotion theory)

the BRECVEMAC theory

different types of emotions are aroused by different types of mechanisms at different levels of the brain. the lowest levels may involve mainly the arousal dimension and proto-emotions (e.g. surprise), whereas the highest levels may involve more complex and even aestethic emotions

features nine mechanisms, which involve more or less distinct brain networks, thought to have evolved sequentially/gradually through evolution

Brain stem reflex

Rhythmic entrainment

Evaluative conditioning

Contagion

Visual imagery

Episodic memory

Musical expectancy

Aesthetic judgment

Cognitive appraisal

(emotion theory – Patrik’s theory :)

main problems for emotion theories

emotions are a less perfectly homogenous class of phenomena

• instead of agreeing on criteria distinguishing different emotions from each other, it might be easier to converge on a set of criteria that distinguish emotions from non-emotional phenomena

disconnection between psychological emotion theories and empirical studies in neuroscience

• no shortage of either one, but they aren’t exactly working toghether

  • few neuropsycholocigal studies try to test theories of emotion, although there are a lot of neuroscience data on emotions

(emotion theory)

emotional perception vs emotional induction

observing and understanding vs internally experiencing

cognitive and sensory ability to detect and decode emotional signals in others or environment (e.g., looking at a sad face or listening to sad music and logically realizing it represents sadness)

vs

actual activation of your own subcortical circuits and autonomic nervous system, causing you to genuinely experience the emotion yourself (e.g. crying and feeling sad while listening to that music)

components of the central nervous system (CNS)

brain

spinal cord

(neurobiology – repetition)

afferent signals

goes to the brain (or intended brain region)

(neurobiology – repetition)

efferent signals

goes from the brain (or intended brain region)

(neurobiology – repetition)

gross division of the nervous system

central nervous system (CNS)

peripheral nervous system

(neurobiology – repetition)

components of the peripheral nervous system

networks of nerves and ganglia outside the brain and the spinal cord

divides into somatic and autonomic nervous system

(neurobiology – repetition)

neuron

nerve cells that handle/process/transfer information in the nervous system

consists of a cell body with a nucleus, dendrites, and an axon (surrounded by myelin sheath) ending in an axon terminal

(neurobiology – repetition)

glial cells

non-neuronal helper sells in the nervous system

don’t carry nerve impulses (action potential), but help with e.g. cleaning waste, digest parts of dead neurons, provide insulation (i.e. myelin) to the neurons’ axons, and regulate synaptic transmission

several different types, for example: astrocytes, schwann cells, and oligodendrocytes

(neurobiology – repetition)

autonomic nervous system

part of the peripheral nervous system that controls and regulates internal organs without us consciously recognising it

both reflexes and central regulation

divides into two major divisions that act complementary: the sympathetic and parasympathetic nervous system, sometimes also enteric and intrinsic cardiac nervous system

(neurobiology – repetition)

visceral nervous system

sometimes used as a synonym to the autonomic nervous system

sometimes seen as a system specifically for the afferents (input) from the viscera (internal organs), i.e. for interoception. the autonomic nervous system is then seen as the motor (efferent) component

(neurobiology – repetition)

insula

brain structure very important for the autonomic nervous system. primary interoceptive cortex that integrates bodily signals, tracking the state of the body

also activates when we experience/anticipate fear/anxiety:

• awareness of bodily reactions like increased heart rate

• integrates threat cues and negative feedback signals from the body

• assisting the cortical interpretation of emotional stimuli

(neurobiology – repetition & treatment of affective disorders)

sympathetic nervous system

quick and mobilizing part of the autonomic nervous system that controls our “fight or flight” response

regulates vital organ functions

activates in “times of need”, especially under stress or danger

increases heart rate/blood flow, releases glucose to give us a quick burst of energy, and slows down enteric activity to save energy for immediate physical action, among other things

(neurobiology – repetition)

parasympathetic nervous system

slower and dampening part of the autonomic nervous system that controls “rest and digest”

helps to control body responses during times of rest

increases digestion rate, lowers heart rate, and calls for insulin release, among other things

(neurobiology – repetition)

ways of dividing the brain

gross anatomy

hemispheres

lobes

structures/regions

cytoarchitecture

(neurobiology – repetition)

(neurobiology – repetition)

cerebrum

(neurobiology – repetition)

cerebellum

(neurobiology – repetition)

brain stem

1

(neurobiology – repetition)

frontal lobe

2

(neurobiology – repetition)

temporal lobe

3

(neurobiology – repetition)

brain stem

4

(neurobiology – repetition)

cerebellum

5

(neurobiology – repetition)

occipital lobe

6

(neurobiology – repetition)

parietal lobe

1

(neurobiology – repetition)

corpus callosum

2

(neurobiology – repetition)

orbitofrontal cortex

3

(neurobiology – repetition)

hypothalamus

4

(neurobiology – repetition)

amygdala

5

(neurobiology – repetition)

ventral-medial prefrontal cortex (important for emotion regulation)

6

(neurobiology – repetition)

hippocampus

7

(neurobiology – repetition)

thalamus

8

(neurobiology – repetition)

cingulate gyrus

frontal lobe tasks

planning/reasoning

problem-solving

recognising and regulating emotion

social skills

(neurobiology – repetition)

temporal lobe tasks

understanding language

processing auditory information

organising information

memory

learning

(neurobiology – repetition)

brain stem tasks

regulate breathing, body temperature, heart activity etc

(neurobiology – repetition)

cerebellum tasks

control balance and muscle co-ordination

(neurobiology – repetition)

occipital lobe tasks

integrating and processing visual information (colour, shape, distance)

(neurobiology – repetition)

parietal lobe tasks

recognising sensations and body position

recognising objects

spatial judgments

understanding time

(neurobiology – repetition)

amygdala tasks

integrate information from different parts of the brain

salience detection

essential for the processing of emotional responses (not necessary for fear though! patient SM)

(neurobiology – repetition)

1

(neurobiology – repetition)

cerebral cortex

2

(neurobiology – repetition)

basal ganglia

3

(neurobiology – repetition)

hippocampus

4

(neurobiology – repetition)

amygdala

brief history of (thought) localisation of psychological functions

the brain was not originally seen as responsible, instead the heart, liver, blood, pineal gland, and humidity (among other things)

(neurobiology – repetition)

phrenology

idea that the mind is based in the brain, that is not seen as a unity but as distinct organs with distinct functions

the brain was said to be composed of different muscles – the bigger ones are those we use the most

believed that personality traits can be predicted by measuring contours of the brain

discredited pseudoscience

(neurobiology – repetition)

division of the brain in functional areas

(neurobiology – repetition)

holistic view of the brain (Flourens, Lashley)

early form of distributed processing saying that the whole cerebrum contributes to higher functions

no specific place has a specific function → the location of brain damage doesn’t matter, only the size of the injury

equipotentiality: intact parts of the brain can take over functions from damaged areas

(neurobiology – repetition)

ideas of early connectionism/interactionism

Forms of distributed processing

Wernicke: basic functions localized to specific brain regions – complex cognitive functions involve connections between regions

Luria: block model where localized functions work in functional systems across three blocks

• block 1: basal parts of the brain. wakefulness, basal attention, and affect

• block 2: posterior cortex. receive, analyze, store information from the outside

• block 3: frontal lobe. motor function, planning, executive functions

(neurobiology – repetition)

modern distributed processing in networks

networks are the basic building blocks for brain functions. they operate within the connectome (the brain's functional network)

it processes information by combining local specialization, where specialized functions are handled within network modules (functional segregation), and global coordination, where network hubs integrate that information across the brain (functional integration)

this topology is dynamic and meta-stable, meaning the networks can reorganize fast depending on the functional requirements

which parts are communicating at a timepoint changes → the network also changes over time

(neurobiology – repetition)

default mode network (DMN)

resting network of the triple network model

deals with self-reflection, memories, planning, inner focus

medial prefrontal cortex, posterior cingulate cortex, lateral and medial paretial lobe

(neurobiology – repetition)

salience network (SN)

network in the triple network model that deals with behavioral relevance

detects what is important in the flow of information and deals with switches between default mode network and central executive network

anterior insula and cingulate cortex

(neurobiology – repetition)

central executive network (CEN)

network in the triple network model that deals with goal oriented behavior, working memory, problem-solving, outer focus

dorsolateral prefrontal cortex, posterior paretial cortex

(neurobiology – repetition)

triple network model

model illustrating how distributed processing operates through three different networks

(neurobiology – repetition)

contents of networks

circuits, which consist of cells (neuron and glia) that communicate mostly through chemical processes at synapses, but sometimes also electrochemical

(neurobiology – repetition)

electrochemical neural communication

how a signal travels from one end of a neuron to the other (i.e. communication within cells)

resting potential → reaching threshold due to stimulation from another neuron → depolarization → action potential → repolarization → hyperpolarization → signal to next neuron

(neurobiology – repetition)

action potential

at rest, the inside of the neuron is more negatively charged (i.e. the resting potential is negative) because of an imbalance in the concentrations of ions – mostly in natrium (Na+) and potassium (K+) – and proteins

when a neuron receives signals from another neuron, the membrane potential is no longer in rest and gets less negative. when the charge reach the threshold (often -55 mV), action potential begins. the neuron is depolarised by Na+ entering through ion channels opened due to the action potential, making the charge inside the neuron positive. the Na+ channels are then closed and K+ channels opened, causing K+ to exit the neuron. these channels are a bit slow, so “too much” K+ exits. this makes the neuron hyperpolarized with an extremely negative charge, which makes it impossible for the potential to travel in any other direction than “forward”. when it reaches the axon terminal (the end of the neuron), the voltage change opens calcium channels

(neurobiology – repetition)

effects of the action potential on the presynaptic site

potential reaches voltage-sensitive terminal → opens calcium channels → calcium ions enter and bind to the protein calmodulin, forming a complex → the complex binds to vesicles → releases some of the vesicles and induces vesicles to bind to the presynaptic membrane and to empty their contents exocytosis

(neurobiology – repetition)

effects on the action potential on the postsynaptic site

the neurotransmitters released from the presynaptic site bind to receptors on the postsynaptic site

what happens next depends on the type of the receptor:

• ionotropic receptors quickly open and close ion-channels, which can lead to depolorization or hyperpolarization in the receiving neuon

• metabotrobic receptors don’t open channels directly. instead they affect cellular mechanisms, which leads to slower but widespread effects (domino effect kinda!) binding to a metabotropic receptor activates a protein that can trigger thousands of internal chemical messages

and on the type of neurotransmitter, e.g.:

• glutamate (major excitatory transmitter) typically binds to receptors opening channels for positive ions, leading to depolarization

• GABA (major inhibitatory transmitter in adults. excitatory in children due to opposite chloride concentrations) typically binds to receptors that influx negative ions by increasing the frequency of opening of Ci- channel, making it harder for the neuron to fire

• e.g. serotonin, dopamin, noradrenalin, endocannabois, and adenosine can act both excitatory and inhibitory depending on the type of receptor they bind to

(neurobiology – repetition)

benzodiazepines

group of medications used for anxiolytic (anxiety reducing), sedative, and amnesia

binds to the same receptor as the GABA neurotransmitters (GABAa receptor) and typically help to influx negative ions by increasing the frequency of opening of Cl^- channel, making it harder for the neuron to fire

basically: boosts the effect of the body’s own GABA

(neurobiology – repetition)

GABA

major inhibitory transmitter in adults. excitatory in children.

binds to GABA-receptors that open the chloride (CI^-) channels and hyperpolarize the neuron, which makes it harder for it to fire

fun fact: small children lack a few ion pumps, which causes them to have high Cl^- concentration inside the neuron. when the receptor opens the Cl^- channels, Cl^- therefore exits (instead of enters as in adults) which causes depolarization (instead of hyperpolarization as in adults)

(neurobiology – repetition)

glutamate

the brain’s primary excitatory transmitter. typically triggers the influx of positive ions, causing depolarization

can bind to both ionotropic (e.g. AMPA, NMDA) and metabotropic receptors (e.g. mGluR)

important transmitter for learning and memory

crucial role in the brain and involved in an absolute majority of excitatory functions

needed to make GABA

(neurobiology – repetition)

NMDA receptor

ionotropic receptor that glutamate binds to

kinda unique since it’s both chemically and voltage-gated

to open it, both glutamate and glycine must bind to the receptor, and it must be free from blockage. magnesium ions and dissociative anaestethics such as ketamine can “mechanically” block the channel by polarising the channel. alcohol, for example, can make it harder to open the channel by binding to another site on the receptor

• fun fact: “blackouts” from heavy drinking can be due to the brain not being able to open the ion channels needed to form memories

(neurobiology – repetition)

serotonin

transmitter that works as a modulator rather than inhibitor/excitator, and has multiple different functions depending on the receptor it binds to

can bind to at least 14 different subtypes of receptors, mostly metabotropic but one ionotropic in the enteric system

impacts a lot! for example, mood, memory, appetite, motor control, circadian rythm, body temperature, gastric emptying, pain and nocioception, guarding reflex

only 1% is in the brain, produced in raphne nuclei. the absolute majority is produced and used in the enteric system

(neurobiology – repetition)

selective serotonin reuptake inhibitors (SSRIs)

group of medications commonly used to treat mental disorders such as depression and different anxiety disorders, e.g. escitalopram, sertraline, paroxetine

we don’t know how they work (invented by accident…), but generally said to work by blocking the serotonin transporters (SERT) and preventing the released serotonin to be re-uptaken from the synaptic cleft

• normally, serotonin that has been released by the sender neuron but not absorbed by the receiver neuron will be absorbed back from the synaptic cleft and reused by the sender neuron. these medications help with blocking this re-absorbation, leading to more serotonin being left in the synaptic cleft to bind to receptors

HOWEVER, hard to find correlation between SERT occupancy and clinical improvement. they might actually work more due to effects on dopamine interactions, and expectancy effects seems to contribute to improvement (maybe partly because expectancy might affect dopamine signaling)

(neurobiology – repetition, treatment of affective disorders)

examples of serotonergic drugs

SSRIs

TCAs

MAOIs

Buspirone

Triptans

Atypical antipsychotics (e.g. quetiapine, aripiprazole, olanzapine)

Fenfluramine

(neurobiology – repetition)

dopamine

important for controlling movements, motivation, and for the reward system

transmitter that mostly works as a modulator. can bind to multiple receptor types – but all of them are metabotrophic – and have both excitatory and inhibitory effects

can affect:

• presynaptic release of neurotransmitters by binding to autoreceptors on the sending neuron to regulate the release (it binds to the same neuron it was just released from and signals that release should stop)

• postsynaptic detection sensitivity by making the receiver cell more or less responsive to glutamate

• synaptic integration and excitability by altering the neuron’s membrane potential and changing the neuron’s ability to fire

in the brain it’s primarily produced in substantia nigra and VTA, but it functions outside the central nervous system as well (e.g. by reducing insulin production in the pancreas)

(neurobiology – repetition)

dopamine pathways

structural "highway" or bundles consisting of thousands of individual neurons running parallel to each other

a vast cluster of neuron cell bodies sits in a starting hub (e.g. the VTA). each of these cells shoots out an incredibly long axon (a projection neuron), bundled together into a single highway

when an electrical action potential travels down these massive axon cables, it triggers the simultaneous release of neurotransmitters (like dopamine) at the final destination (e.g. nucleus accumbens)

the main ones are: mesolimbic, mesocortical, nigrostriatal, tuberoinfundibular