Summary: Switching off activity in the anterior cingulate cortex prevented marmoset monkeys from making an association between behavior and a particular outcome.
Source: University of Cambridge
Researchers have discovered a specific brain region underlying ‘goal-directed behaviour’ – that is, when we consciously do something with a particular goal in mind, for example going to the shops to buy food.
The study, published today in the journal Neuron, found that marmoset monkeys could no longer make an association between their behaviour and a particular outcome when a region of their brain called the anterior cingulate cortex was temporarily switched off.
This finding is important because the compulsive behaviours in OCD and addiction are thought to result from impairments in the ‘goal-directed system’ in the brain. In these conditions worrying, obsessions or compulsive behaviour such as drug seeking may reflect an alternative, habit-based system at work in the brain in which behaviours are not correctly linked with their outcomes.
It also sheds more light on how healthy people behave in a goal-directed way, which is needed to respond to changing environments and goals.
“We have identified the very specific region of the brain involved in goal-directed behaviour. When we temporarily turned this off, behaviour became more habitual – like when we go onto autopilot,” said Lisa Duan in the University of Cambridge’s Department of Psychology, first author of the report.
Marmosets were used because their brains share important similarities with human brains, and it is possible to manipulate specific regions of their brains to understand causal effects.
In the experiment, marmosets were first taught a goal-directed behaviour: by tapping a coloured cross when it appeared on a touchscreen, they were rewarded with their favourite juice to drink. But this connection between action and reward was randomly uncoupled so that they sometimes received the juice without having to respond to the image. They quickly detected this change and stopped responding to the image, because they saw they could get juice without doing anything.
Using drugs, the researchers temporarily switched off the anterior cingulate cortex including its connections with another brain region called the caudate nucleus. Repeating the experiment, they found when the connection between tapping the cross and receiving juice was randomly uncoupled, the marmosets did not change their behaviour but kept tapping the cross when it appeared.
Such habitual responding to the coloured cross was not observed when several other neighbouring regions of the brain’s prefrontal cortex – known to be important for other aspects of decision-making – were switched off. This shows the specificity of the anterior cingulate region for goal-directed behaviour.
A similar effect has been observed in computer-based tests on patients with Obsessive Compulsive Disorder (OCD) or addiction – when the relationship between an action and an outcome is uncoupled the patients continue to respond as though the connection is still there.
Previous evidence from patients suffering brain damage, and from brain imaging in healthy volunteers, shows that part of the brain called the prefrontal cortex is involved in goal-directed behaviour. However, the prefrontal cortex is a complex structure with many regions, and it has not previously been possible to identify the specific part responsible for goal-directed behaviour from human studies alone.
“We think this is the first study to have established the specific brain circuitry that controls goal-directed behaviour in primates, whose brains are very similar to human brains,” said Professor Angela Roberts in the University of Cambridge’s Department of Physiology, Development and Neuroscience, joint senior author of the report.
“This is a first step towards identifying suitable molecular targets for future drug treatments, or other forms of therapy, for devastating mental health disorders such as OCD and addiction,” added Professor Trevor Robbins in the University of Cambridge’s Department of Psychology, joint senior author of the report.
Funding: This research was conducted in the University of Cambridge’s Behavioural and Clinical Neuroscience Institute, and was funded by Wellcome.
About this neuroscience research news
Source: University of Cambridge Contact: Press Office – University of Cambridge Image: The image is credited to University of Cambridge
Controlling one’s world: identification of sub-regions of primate PFC underlying goal-directed behavior
•Monkey pgACC-24 is necessary for detecting causal control of actions over outcomes
•Its projection target in the caudate nucleus is also implicated
•Three other subregions of the ventromedial prefrontal cortex are not necessary
•Anterior OFC-11 may mediate Pavlovian influences on goal-directed behavior
Impaired detection of causal relationships between actions and their outcomes can lead to maladaptive behavior. However, causal roles of specific prefrontal cortex (PFC) sub-regions and the caudate nucleus in mediating such relationships in primates are unclear.
We inactivated and overactivated five PFC sub-regions, reversibly and pharmacologically: areas 24 (perigenual anterior cingulate cortex), 32 (medial PFC), 11 (anterior orbitofrontal cortex, OFC), 14 (rostral ventromedial PFC/medial OFC), and 14-25 (caudal ventromedial PFC) and the anteromedial caudate to examine their role in expressing learned action-outcome contingencies using a contingency degradation paradigm in marmoset monkeys.
Area 24 or caudate inactivation impaired the response to contingency change, while area 11 inactivation enhanced it, and inactivation of areas 14, 32, or 14-25 had no effect. Overactivation of areas 11 and 24 impaired this response.
These findings demonstrate the distinct roles of PFC sub-regions in goal-directed behavior and illuminate the candidate neurobehavioral substrates of psychiatric disorders, including obsessive-compulsive disorder.