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Module BIO00009I
Neuroscience
Lecture 6
Anatomy of neural circuits underlying behaviour
Sangeeta Chawla
sangeeta
...
ac
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Neuronal cell signalling
Intracellular signalling
- GPCR and Ca2+ signalling
- Modulation of synaptic transmission

L6
...
Pharmacology of reward pathways
-The reward pathway
-Synaptic targets of dependence-producing drugs

L8
...
Understand how intracellular signalling contributes to
neurotransmission and its modulation
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Relate major anatomical regions of the brain to their
function and neural circuits to behavioral responses
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Understand how small molecules can interact with neuronal
proteins to modify connectivity within neural circuits and alter
behaviour
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Appreciate the mechanisms by which behaviour is
synchronized to day-night cycles
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Explain and evaluate how our understanding of behaviour
and neural circuits has been inferred from particular
experiments
...
Anatomy and neural circuits
Gross views of Brain

The Human Brain
- 1011 neurons (and 3x1011 glia)
- 1014 synapses
- 102 transmitters
- blood vessels

Purves

Human brain is big! Number of features varies
depending on the individual and between the sexes
(more in male)
...
3Kg 15cm across
Top is cerebral cortex, 80% of brain volume
...

It’s the newest (evolutionary) part of the brain
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Slide 5

Shows different ways you can cut brain
...


L6
...
Anatomy and neural circuits
Overview of CNS

CNS
Cerebral hemisphere/
Forebrain

Hindbrain

PNS
Motor
Nerves

CNS= spinal cord+ brain
Area of brain towards spinal cord is the hind brain- most
evolutionary significant/old part of brain as well as midbrain
...
Eg Midbrain, pons, cerebellum, medulla
perform vital functions, breathing heartrate
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Purves

Slide 7

L6
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MRI uses a very
strong magnetic field to align protons (hydrogen atoms)
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Hydrogen in different types of tissue (gray
vs white matter vs CSF) has slightly different realignment rates
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But in humans we image using
magnetic resonance imaging
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Sides are
structurally same but responsible for different
functions
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MRI uses a very strong magnetic field to
align protons (hydrogen atoms)
...
)
- Allows to do imaging
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Gray matter- cell bodies
of neurones- GREY
White matter- axons, have less water than gray
CSF- all the different H20 lipid contents, most waterDARK
Contrast in the realignment rates makes the images

Slide 8

L6
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Does this also due to feedback

Brain stem- ancient part of brain
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The nerves from the eye inhinge on the brainstem,
pupls reflex action is only a reflex! Mediates arousal
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Slide 9

L6
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Amount of distortion different in
oxygenated and deoxygenated blood
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Activation of Cerebellum during a
bilateral finger tapping task- touch
thumb with each finger,

Purves

MRI image with
fMRI activity
superimposed

Slide 10

L6
...
The haemoglobin in the blood
distorts the magnetic resonance of the nearby H atoms
basec on the H ability to align to magnetic field to be
pushed out and realign
...

Lighter colour is higher activity, although artificial
colour scale
...

Motor Cortex- Controls movement but has to receive
information/signals from prefrontal cortex
...
Ie
visual
Occipital lobe: vision and projects to the motor
cortex so it can intiate movement
Basal ganglia- fine tuned motor response,
defective in parkinsons, gets tremors, neurons are
damaged
Cerebellum- 40% of all brain neurons, even though
much smaller structure than rest of brain
...
Anatomy and neural circuits
Cellular organization of cortex

Cerebral cortex organised into cell layers

Layers organize
inputs and outputs

Visual cortex (occiptal) motor cortex (frontal lobe)

Purves

Slide 12

How inputs/outputs are organised
Different layers communicate with different other
regions
...
Anatomy and neural circuits
The Amygdala

EMOTIONS
Emotional state
(example Fear)
-Physical sensation
-increased heart rate, sweating
-Conscious feeling (subjective)
-consciously feel afraid

1
...

2
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Experience physically and
emotionally
Emotional state- Cant localise it to a region of braincerebral cortex
Find something pleasurable, seek to do it again

Emotions influence motivational behaviours- form memroy of a stimuli

Slide 13

L6
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Anatomy and neural circuits
The Amygdala

Neutral stimulus
Sound

Rodents with lesions in amygdala lack
conditioned response

Joseph LeDoux

Fear conditioning in ratsa learned emotional response

Neutral stimulus
Paired with
Aversive foot shock

Learned fear response to
Neutral stimulus

Blood Pressure
Freezing response

Physical expression of
fear orchestrated
by projections of amygdala to
hypothalamus and brain stem

Amygdala- behind temporal lobe
Receives input and gives output allowing you to
experience a response and form a memory of it
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Slide 15

L6
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Did another experiment: divided cage into two
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Other has nothing
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This is explicit conscious processing

Visceral motor effector systems
freezing and blood pressure

Purves

Slide 16

Patient cant experience fear due to damaged amygdala
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Initially in amygdala
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Her hippocampus was in tact
and could remember still though
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L6
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M
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Failed to recognise fear when
compared to control patients
Purves

Slide 17

L6
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Anatomy and neural circuits
The reward pathway

YES

LEARNED FEAR
OF COLORS
YES

YES

NO

NO

YES

NO

NO

Motivation and Reward

1
...

Hypothalamic neurons have receptors for the hormone,
leptin (produced by fat tissue) that suppresses appetite and stimulates
metabolic rate
...
Motivational states driven by rewarding/pleasureable and
reinforcing effects of a stimulus
Feeding behavior- We tend to eat much more of “palatable food” than
bland diet

L6
...

Activates in a VTA area which sends axons to nucleus
accumbens
...

The Mesolimbic Dopamine System

Slide 19

Emotions are responsible for driving motivational
behaviours

The REWARD circuit

Nuc Acc-Forebrain

Dopamine
VTA -Midbrain
Purves

Slide 20

-Activity in the Nucleus
Accumbens correlated with
higher bids
...
How rewarding it is
is measured by the activity in the nucleus accumbens
Music- tuned to their taste but not heard before and
imaged their brain whilst
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Found activity correlated with how
much theyd pay
...
Anatomy and neural circuits
The reward pathway

Activation of the Nucleus Accumbens
predicts “Reward value”
-Participants listened to
previously unheard music
excerpts while undergoing
fMRI scanning

-Assessed reward value by
asking participants to bid
with their own money ($0-$2)

Also other bits light up eg hearing etc

Slide 21

Learning outcomes
Lecture 6 summary
2
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Neural circuits underlying emotional responses and reward
Ventral tegmental area (VTA) and the nucleus accumbens:
Assigns reward value “Rheostats” of rewardhow rewarding/pleasurable is an experience?
Amygdala: assigns an emotion to stimuli -pleasurable/rewarding or aversive
-makes connection between experience and other cues
-directs autonomic responses via hypothalamus

Hippocampus: records memory of experience and context
Frontal regions of cortex: process and coordinate information
and determine conscious behavior to obtain reward and avoid punishment
5
...

Functional brain imaging and behavioral experiments on
human patients with lesions and on experimental animals

Slide 22

Overview
Lectures 5 to 8

L5
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Anatomy of neural circuits underlying behaviour
-Anatomical organisation of the brain
-Neural circuits underlying emotional responses and reward

L7
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Synchronizing behaviour with the environment
-Sleep/wake cycles
-Circadian rhythms



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