Navigating life can be complicated with numerous decisions to make. Thankfully, the orbitofrontal cortex and hippocampus assist us in this process. According to researchers at UC Santa Barbara, these brain regions collaborate to help us handle tasks that involve interpreting ambiguous situations—those in which the meaning of stimuli varies based on context.
UCSB neuroscientist Ron Keiflin, who studies the neural circuits involved in valuation and decision-making, explained, “I would argue that that’s the foundation of cognition. That’s what distinguishes us from simple robots that react identically to every stimulus. Our capacity to recognize that the significance of certain stimuli depends on context provides us with flexibility; it enables us to act appropriately depending on the situation.”
For example, while your phone may be ringing, your decision to answer it will rely on several factors such as your current activity, location, the time, the caller’s identity, and various details. “It’s the same stimulus,” Keiflin noted, “but depending on the surrounding situation, it will be interpreted differently, and you may respond in distinct ways.”
This research, published in the journal Current Biology, is the first to directly examine how the orbitofrontal cortex and hippocampus contribute to this process of contextual clarification.
Understanding Meaning
The orbitofrontal cortex (OFC) is located at the front of the brain, right above the eyes, and is linked to reward evaluation, planning, decision-making, and learning. In contrast, the dorsal hippocampus (DH) is situated further back within the brain and plays a role in spatial navigation and episodic memory.
Keiflin shared, “Historically, studies of the orbitofrontal cortex and hippocampus have generally progressed independently, but ultimately, the findings from these different research areas have pointed to similar conclusions regarding these regions.”
“The concept is that these brain regions construct a ‘cognitive map’ of the world’s structure,” he explained, clarifying that this doesn’t need to be strictly spatial. “It’s a map detailing the causal framework of the environment; this map assists you in mentally simulating the outcomes of your actions and selecting the optimal course of action.”
This cognitive map is critical for understanding that a cue’s significance can vary based on context. However, previous studies did not explicitly investigate the roles these brain areas play in contextual clarification.
To delve into how the OFC and DH contribute to contextual clarification, researchers designed an experiment where rats were exposed to short auditory signals in either a bright or dark setting (adjusted by toggling a light bulb on or off). These auditory signals sometimes indicated a reward (a bit of sugar water) but not always; sometimes, the same signals led to no reward, rendering them ambiguous as predictors. Eventually, the rats figured out that one sound indicated a reward only in the light setting, while the opposite was true for the other sound. Essentially, they learned that the cues’ meanings depended on the context.
The researchers could tell that the rats had learned to differentiate between the two contexts when they approached and licked the sugar water cup in anticipation of the reward in one scenario but not in another.
To analyze the involvement of the orbitofrontal cortex and hippocampus in this process of contextual clarification, the scientists employed “chemogenetics,” a technique that allowed them to temporarily deactivate either brain region during the experiment.
The results showed that deactivating the OFC significantly impacted the rats’ performance. Without a functional OFC, the rats could not utilize the context to inform their expectations or adjust their reward-seeking behavior. Surprisingly, the DH appeared to be largely unnecessary for this particular task; the rats maintained high accuracy even when their hippocampus was inactive.
Does this imply that the DH isn’t involved in contextual clarification? Not necessarily. A pivotal realization for the researchers was that knowledge is not only crucial for recalling past experiences but also vital for future learning.
Keiflin stated, “If I walked into an advanced math lecture, I would grasp — and learn — very little. However, someone with a stronger foundation in mathematics would comprehend the material, which would greatly enhance their learning.”
In relation to their experiment, the researchers believed that previous knowledge of context-dependent relationships would ease the learning of new context-dependent relationships, which is precisely what they observed.
It took over four months for the rats to master the initial context-dependent pairs, but once they had a cognitive map of these relationships, they could learn new pairs in just a few days.
Using the same chemogenetic method, the researchers explored the roles of the OFC and DH in this accelerated learning based on knowledge. They discovered that both structures were crucial; without the OFC and DH, the rats couldn’t apply their previous knowledge to draw conclusions about new context-dependent relationships.
The findings suggest that the OFC and DH both contribute to contextual clarification, but they do so in somewhat different ways: the OFC is essential for utilizing contextual knowledge to drive behavior, whereas the DH is more significant for using that knowledge to aid in new contextual learning.
Although the influence of prior knowledge on learning is well recognized in psychology and known among educators, it is often overlooked in neuroscience studies, Keiflin highlighted.
“A deeper neurobiological understanding of this rapid learning and inference of context-dependent relations is essential, as this learning style likely mirrors the human learning experience more closely.”
