Neural Basis of Motivation and Learning (NEUR0014)
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Orbitofrontal Cortex: Emotion, Learning & Value
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Neural Basis of Motivation and Learning (NEUR0014)
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University College London (UCL)
Orbitofrontal Cortex: Emotion, Learning & Value (Lecture 12 of 16 in NEUR0014: Neural Basis of Motivation and Learning)
Thorough review of the proposed functions of the orbitofrontal cortex including the somatic marker hypothesis, response inhibition and the encoding of value and expected reward...
Neural Basis of Motivation and Learning (NEUR0014)
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Voorbeeld van de inhoud
Lecture 12: The Orbitofrontal Cortex: Emotion,
Learning and Value
OFC is a very important brain area in neuroeconomics
This is a broader overview of the OFC, with theories proposed about what it does and why we think
some of these theories are not very strong (with evidence to disprove them):
• Domasio’s somatic marker hypothesis (early, emotion)
• OFC and reversal learning – response inhibition? Rapid and flexible learning?
• The coding of value of stimuli and rewards in OFC
• The OFC and encoding expected rewards
Anatomy and Phineas Gage
OFC is part of the limbic system is the sense that, even though its neocortex, it shares a lot of very
strong connections with other brain areas that are considered part of the limbic system or
“emotional brain”
The OFC is defined in humans strictly as the portion of the cortex which receives projections from
the magnocellular nucleus of the mediodorsal thalamus
But, the important functional projections of the OFC are to the:
• Amygdala
• Striatum
• All areas of sensory neocortex (encoding all sorts of different sensory modalities)
OFC refers to the brain area sitting above the eye. The OFC as defined today is Brodmann’s areas 11l,
12r, 12m and 13l/m/b. Defining these different regions of neocortex is a scientific research question
in itself, thus over recent history of modern neuroscience the exact definitions of which areas have
included in the OFC have changes
Remember!; when we talk about clinical cases we can never exactly control or be
completely be aware of where exactly the damage is. Often you have cases where lesions overlap
with the OFC area but not exactly, and may affect other neighbouring regions
Homologous areas in Macaque Monkey are similar to humans
Homologous areas in rodents are harder to find; these prefrontal parts of the neocortex are one of
the parts of the brain that is most different between primates and other animals, thus we struggle to
define exactly what is rat OFC. Rats do have prefrontal cortex, so an area has been defined
,Which information reaches the OFC?
Functional connections
(Rolls and Grabenhorst, 2008)
Inputs
One of the critical characteristics of the OFC is that it receives sensory inputs from all the different
sensory modalities:
• Vision
• Taste
• Olfaction
• Touch
All of these sensory inputs converge onto the OFC by their various pathways and associated cortices
The OFC also has very strong connections to the amygdala
Outputs
OFC has output connections onto a variety of brain areas important in learning and motivated
behaviour:
• Striatum
• Lateral hypothalamus
o (Petrovich, 2018) – LH as a motivation-cognition interface in the control of feeding
behaviour
o (Hurley et al. 2014) – LH model for translation of past experience and sensed deficits
into motivated behaviours
• Cingulate cortex
• Medial pre-frontal cortex
The OFC is a brain area which, on the basis of its anatomical connections, is very well positioned to
take all sorts of incoming sensory data and use that information to inform the emotive or
motivational state of the animal
Phineas Gage
• Accidental injury; iron bar went through eye and took out a large portion of frontal cortices,
including OFC Commented [IM236]: Need to remember that is was more
than just the OFC that was damaged, thus this case study can only
o Resulted in emotional disturbances provide supporting evidence to theories so far
o Although in many senses he could still operate cognitively, he demonstrated Or just guide the future direction of research into OFC function
problems with:
§ Emotion
§ Correct display of emotion in the social context
§ Forward planning (being able to make a plan and stick with it)
, § Motivation
• Observations of Gage’s ‘uninhibited’ behaviour was one of the first pieces of evidence
supporting the theory that OFC is responsible for ‘response inhibition’
A lesser known part of the history of Gage is that some contemporary accounts seem to indicate that
actually this damage was relatively temporary and Gage went on to have a fairly successful second
half of his life (i.e. moved to South America and set up a successful business as a coachman)
Conclusion Therefore, although his deficits are very interesting and inform modern neuroscience, he
is also an interesting case that demonstrates the ability of the brain to heal in a cognitive sense – for
the remaining brain tissue to flexibly adapt and take over the functions of tissue that is damaged
Also, interestingly, reconstructions of his skull post-accidence indicate that Gage may have only
suffered unilateral damage and therefore what may have happened is that the remaining
hemisphere may have been able to slowly take over/compensate for the initially lost function
Gage is one of many cases in the history of clinical neuropsychology in which it was noticed that
damage to the frontal cortices can produce ‘Acquired Sociopathy,’ a syndrome which includes Commented [IM237]: Remember!: in human patients you
cannot control which parts of the brain get damaged, therefore
disturbances of emotion/affect. Other characteristics: most case studies involving damage to the OFC often show wider
damage to the other frontal cortices. Damage is often diffuse and
• General dampening of emotional experience large.
• Poorly modulated emotional reactions
• Disturbances in decision-making
• Disturbances in goal-directed behaviour
• Disturbances in social behaviour
• Marked lack of insight into acquired changes
This sets us up for the neuroscientific investigation of what the exact function of the OFC is, mainly
using animal models.
The specific theory that the OFC is required to encode a neural representation of emotion:
The OFC and emotion: the somatic marker hypothesis
This is a theory that most people accept is incorrect; the theory has been falsified
But it is a very important theory in the modern field of neuroscience because it got people thinking
about the role of OFC (and prefrontal cortices more generally) in the processing of emotion, and
how that emotion signal might interact with other brain area
The story of the theory, the evidence for it and how it came to be falsified is an interesting one. A
commonly discussed, though not-believed theory.
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