MARCH 18 Flashcards
1
Q
paper: “affective valence in the brain: ______ or ______?”
A
modes
modules
2
Q
question that the paper asks
A
how do brain systems evaluate the AFFECTIVE VALENCE of a stimulus?
that is, its quality of being GOOD or BAD
3
Q
2 possibilities for how brain encodes valence
A
- module
- mode
4
Q
module
A
a neural subsystem that’s PERMANENTLY DEDICATED to mediate ONLY ONE AFFECTIVE FUNCTION
or at least only one specific valence
5
Q
module could be…
A
subregion of the brain
projection pathway
neuronal population
individual neuron
6
Q
mode
A
a given neural module can exist in MULTIPLE NEUROBIOLOGICAL STATES
that give it DIFFERENT AFFECTIVE FUNCTIONS
suggests that affective function/valence mediated by a neural module need not remain permanently stable
it can CHANGE DYNAMICALLY ACROSS VARIOUS SITUATIONS
7
Q
affective valence
A
quality of being perceived as ‘good’ or ‘bad’
8
Q
how can affective valence be further decomposed
A
into HEDONIC and MOTIVATIONAL aspects
9
Q
hedonic aspects (of affective valence)
A
POSITIVE: ‘pleasure’
NEGATIVE: ‘displeasure’ or ‘pain’
10
Q
motivational aspects (of affective valence)
A
POSITIVE (APPETITIVE): functions that promote reward pursuit
NEGATIVE (AVERSIVE): functions that promote threat avoidance
11
Q
positive (appetitive) motivation
A
functions that promote reward pursuit
ie. incentive salience
12
Q
negative (aversive) motivation
A
functions that promote threat avoidance
ie. fearful salience
13
Q
how do we commonly experience valence?
A
as a SUBJECTIVE FEELING
14
Q
other than subjective feeling, how can valence be inferred?
A
from OBJECTIVE BEHAVIOURAL and PHYSIOLOGICAL MEASURES
15
Q
T/F: behavioural measures can isolate hedonic and motivation components of affective valence
A
T
16
Q
facial expressions
A
facial expressions to APPETITIVE and AVERSIVE stimuli induce DISTINCT facial expressions
can be interpreted as measure of the objective hedonic properties
(found reliable facial expressions for liking in response to sweet tastes and disgust in response to bitter tastes, in mice, monkeys and humans)
17
Q
what can hedonic affective reactions be modulated by?
A
by factors that alter hedonic impact
- PHYSIOLOGICAL STATE (hunger/satiety)
- PSYCHOLOGICAL FACTORS (learned preferences/aversions)
- NEUROBIOLOGICAL MANIPULATIONS (neural inhibition or stimulation)
18
Q
objectively measuring motivational properties
A
POSITIVE motivational impacts can be seen in APPETITIVE FOOD SEEKING and EATING behaviours
^ seen as “wanting”
NEGATIVE motivational impacts can be seen in various ‘FEARFUL’ reactions to threatening stimuli
19
Q
what’s seen as wanting? (objective measurements)
A
appetitive food seeking and eating
(positive motivational aspect of valence)
20
Q
what’s seen as a negative motivational valence? (objective measurements)
A
‘fearful’ reactions to threatening stimuli
21
Q
how can ‘liking’ and ‘wanting’ be separated?
A
- behaviourally
- in their neural mechanisms
22
Q
example of how LIKING and WANTING can be independently modulated
A
in substance use disorders, ‘WANTING’ but NOT ‘LIKING’ is increased
to drive continued drug seeking
even in face of harmful consequences
23
Q
dominant view of how brain systems evaluate the affective valence of a stimulus
A
affective modules
but Berridge proposes an alternative: affective modes
24
Q
are affective modes and nodules mutually exclusive?
A
no
and the likely answer is a MIX of BOTH
25
"affective modules" hypothesis
specific neural systems ('modules) are RELIABLY and PERMANENTLY dedicated to generating a SINGLE AFFECTIVE FUNCTION
the neurobiological 'units' can be represented across a range of SCALES/LEVELS
26
possible range of scales/levels of neurobiological units (affective modules hypothesis)
brain region
subnuclei
group of neurons
single neuron
neurotransmitter signal
27
affective modules view treats modules as ______ ______, with each carrying...
labelled lines
each carrying a SPECIFIC VALENCE SIGNAL
(they have definitive functions in terms of determining valence)
28
what's a labelled line?
refers to coding mechanism whereby a SINGLE NEURON encodes a SPECIFIC FEATURE
it's 'labelled' for a specific type of sensory input, and only responds to that input
29
what kinds of systems use the 'labelled lines' arrangement?
sensory systems
ie. taste, auditory perception
they use this arrangement to distinguish diff sensory inputs
30
affective 'labelled lines'
labelled lines concept = in traditional views of valence coding that seek to ASSIGN A STABLE VALENCE CODING PROPERTY to a DISCRETE NEUROBIOLOGICAL UNIT
this is an assumption about how the brain works, and it hasn't been tested widely
31
the "affective modes" hypothesis
a given neural module may not be permanently dedicated to JUST ONE affective function
but rather have MULTIPLE NEUROBIOLOGICAL AFFECTIVE MODES
that it can occupy to mediate different affective valence-related functions
32
what could an affective mode correspond to?
1. particular pattern of NEUROCHEMICAL stimulation
2. pattern of GENOMIC activation
3. temporal pattern of ELECTRICAL EXCITATION of the module
4. particular NEUROBIOLOGICAL STATE of the larger circuitry within which the module is embedded
33
when might affective modes shift?
with changes in:
1. INTERNAL PHYSIOLOGICAL STATES (hunger, stress)
2. EXTERNAL STIMULI/ENVIRONMENTS
34
anatomical gradient in affective modules
sagittal slice of brain (front to back)
module 1 (FRONT): LIKING
module 2: WANTING
module 3: FEAR
module 4: DISGUST
^ distinct anatomical substrates mediate fixed functions
35
anatomical gradient in affective modes
liking, wanting, fear, digust are dispersed among the modules
module 1: LIKING and WANTING
module 2: WANTING and FEAR
module 3: WANTING and FEAR
module 4: WANTING, FEAR and DISGUST
36
while affective modules are static and fixed, affective modes are...
dynamic and variable
37
what anatomical distinction is important in within the nucleus accumbens?
medial and lateral
the core versus the shell - these 2 subregions of the NA vary in the inputs they received and the outputs they send
38
in evaluating existence of modules or modes, we also must consider what distinction?
distinction between the HEDONIC and MOTIVATIONAL aspects of affective valence
there's evidence of BOTH hedonic and motivational 'modules' in the nucleus accumbens
39
evidence for existence of both hedonic and motivational modules in the nucleus accumbens comes from what?
dopamine signalling
it mediates WANTING (but not liking)
40
what does disrupting dopamine signalling affect? and what does it not affect?
it affects PURSUIT and CONSUMPTION of REWARDS
but it DOESN'T affect liking
41
increased dopamine in the NAc increases _______ but doesn't change _________
increases WANTING
but doesn't change LIKING
42
because activation of dopamine neurons amplifies incentive salience, we can consider dopamine signalling in the NAc a WHAT?
'wanting module'
43
example of a wanting module in the NAc
dopamine signalling
(it's a neurobiological unit whose function is to encode wanting)
44
hedonic hotspots
(totally separate to the role of the NAc in wanting)
hedonic hotspots were discovered that control the LIKING of sweet tastes
they are SMALL REGIONS that play a PREDOMINANT ROLE in controlling LIKING
45
where are the hedonic hotspots in the brain?
there are many of them, distributed THROUGHOUT the brain
46
NT signalling at hedonic hotspots does what? and from which NTs?
enhances liking
from these NTs:
- opioids
- endocannabinoids
- orexins
(but NOT dopamine)
47
network of hedonic hotspots may rep WHAT?
a 'LIKING MODULE'
48
stimulating the NAc hedonic hotspot reliably does what?
increases POSITIVE REACTIONS
even stimulating kappa-opioid receptors (which are aversive in other brain regions) increases liking
49
kappa opioid receptors and hedonic hotspots
in the hedonic hotspot of the NAc, stimulating kappa-opioid receptors INCREASES POSITIVE REACTIONS
despite the fact that kappa-opioid stimulation is aversive in other parts of the brain outside the hedonic hotspot`
50
beyond the hedonic hotspot, the NAc appears to be organized HOW to MEDIATE WHAT?
organized along a ROSTROCAUDAL GRADIENT
to mediate APPETITIVE-DEFENSIVE reactions (motivational aspect)
(so NAc = implicated in both liking and wanting)
51
NAc circuitry - NAc neurons are mostly what?
GABAergic projection neurons (inhibitory)
increasing their activity inhibits the regions they project to
52
2 projection pathways from the NAc
1. DIRECT: to the VTA
2. INDIRECT: to the ventral pallidum (VP)
53
direct pathway - increasing this pathway's activity does what?
this pathway goes to VTA
increasing this activity SUPPRESSES VTA ACTIVITY
(VTA is major source of dopamine)
54
indirect pathway - increasing activity of this pathway does what?
this pathway goes to ventral pallidum (VP)
because VP normally inhibits the VTA, increasing activity of these NAc neurons INCREASES VTA ACTIVITY by inhibiting the inhibition of the VTA
55
what does increased activity in the direct and indirect pathways do to VTA activity?
direct: decreases VTA activity
indirect: increases VTA activity
56
NAc projection neurons receive GLUTAMATERGIC PROJECTIONS from PFC, hippocampus, amygdala - what does disrupting these projections do?
disrupting these projects SILENCES the NAc projection neurons
57
GABA agonists can do what to NAc projection neurons?
directly inhibit them
58
2 ways to inhibit NAc projection neurons
1. disrupting glutamatergic projections from PFC, hippocampus, amygdala
2. introducing GABA agonists
59
depending on the _____ _____ _____ of a manipulation of either glutamatergic or GABAergic signaling in NAc, what happens?
depending on the ROSTRAL-CAUDAL LOCATION
of a manipulation of either glutamatergic or GABAergic signalling in the NAc
INTENSIVE APPETITIVE (eating food) of AVERSIVE (defensive burying) is elicited
60
what do rostral manipulations do?
1. increase APPETITIVE EATING
2. can induce PLACE PREFERENCE
61
what do caudal manipulations do?
1. generate intense DEFENSIVE BEHAVIOURS (burying, distress calls, attacking)
2. can induce PLACE AVERSION
62
what does the fact that rostral manipulations induce appetitive behaviours, while caudal manipulations induce defensive behaviours, suggest?
could suggest that the ROSTRAL and CAUDAL NAc function as DISTINCT and OPPOSING appetitve and aversive motivational modules
63
caudal manipulation equals
aversive
(negative motivation)
64
rostral manipulation equals
appetitive
(positive motivation)
65
differentiating between affective modules and modes necessitates what kinds of experiments?
experiments that examine affective function and coding ACROSS A RANGE OF CONDITIONS
because a criterion for modules is stability, and a criterion for modes is diversity
(a single snapshot doesn't provide evidence as to whether functions of certain areas are stable or variable)
66
do NAc 'motivational modules' maintain invariance across conditions?
non
the rostral-caudal gradient is modified by ENVIRONMENTAL conditions
to bias the function of INTERMEDIATE 'MODULES' towards appetitive or aversive motivational behaviours
67
what was the rostral-caudal gradient established under?
stable conditions
(so finding of rostral = appetitive and caudal = aversive was the result of stable conditions)
68
in a more comfortable, low stress testing environment, appetitive behaviours can be elicited where?
at more caudal locations
(more caudal than when compared to the stable condition findings)
69
in a high-stress, bright testing environment, aversive behaviours can be elicited where?
at more rostral locations
(more rostral than when compared to the stable condition findings)
70
across testing conditions, the rostral and caudal poles maintain their distinctive coding, but...
but most of the NAc is HIGHLY SENSITIVE to ENVIRONMENTAL MANIPULATIONS
such that the VALENCE of the response is REVERSED
^ this looks like modes in action
71
the fact that most of NAc is highly sensitive to environmental manipulations, to extent that valence of responses can be reversed, demonstrates what?
this demonstrates that by and large,
affective modules in the NAc are NOT dedicated to a singular valence
but they DYNAMICALLY ENCODE valence in MULTIPLE MODULES
72
majority of research on amygdala focuses on what?
negative valence (fear/threat)
research focuses on BLA and CeA (central amygdala)
73
BLA and CeA also involve what behaviours?
appetitive motivation and positive emotions
74
what have neuroscientists done to reconcile proposal that amygdala is involved in POSITIVE and NEGATIVE valence?
proposed amygdala is divided into TWO OPPOSING MODULES
2 main ways this has been considered:
1. amygdala projection modules
2. neuronal population modules in the amygdala
75
2 main ways it's been considered that amygdala is divided into 2 opposing modules (one for pos valence, other for neg valence)
1. amygdala projection modules
2. neuronal population modules in the amygdala
76
amygdala projection modules hypothesis
hypothesis that distinct projections send axons from specific brain region to SOME SUBREGION OF AMYGDALA mediate POSITIVE or NEGATIVE VALENCE
ie. projections from distinct parts of GUSTATORY CORTEX that encode SWEET or BITTER taste to BLA or CeA
77
evidence inconsistent with the modules account: stimulation of BLA projections to NAC has been linked to...
both REWARD and SUPPRESSION of REWARD
78
neuronal population modules in the amygdala hypothesis
variety of DISTINCT VALENCE-RELATED SUBPOPULATIONS have been proposed
with same general idea that ONE NEURON TYPE MEDIATES POSITIVE VALENCE, while another type mediates NEGATIVE valence
(ie. CeA neurons that release corticotropin releasing factor may mediate negative valence)
79
is there a clear unifying principle for how valence is parsed in the amygdala?
no, not yet
there are many diff proposals
(ie. amygdala projection modules and distinct neuronal population modules)
80
evidence for affective modes in the amygdala
optogenetic stimulation ACROSS CeA increases positive incentive motivation
manipulations were broad - and they all increased appetitive behaviour
if there was specialization, there shouldn't have been this effect
if there were dedicated negative-valence modules in the CeA, how could stimulation across CeA have this pro-reward effect?
81
so is it modes or modules?
some evidence for affective modules (ie. neural subunits with differing capacity to mediate positive or negative valence)
also considerable evidence that's inconsistent with a strict modules hypothesis (ie. putative valence modules can have diff effects in diff conditions)
82
is it modes or modules? what could be an answer?
is the answer to define SMALLER and SMALLER modules?
this still assumes there's a level at which stable valence encoding will be identified
testing this would require experiments that test across a range of experimental conditions
