Brain Assignment of Values Varies with Context

This morning as you opened the refrigerator door, you looked at the food options for breakfast and asked yourself, “What shall I have for breakfast? Cereal topped with bananas? Sausage and eggs? Pancakes? Fruit bowl? Bagel? Each option has a value, which changes from morning to morning. Each morning, the brain you assess the relative values and decides which food choice counts the most for that particular moment. How does the brain determine that value?

Whether it is in the home, workplace, the school, or in inter-personal relationships, we typically face experiences to which we assign value. Often, we must weigh the relative values of several competing experiences in order to choose a single option to act upon.

In humans, it seems clear that value assignment depends heavily upon function in the prefrontal cortex (PFC). But how does this circuitry assign value? Two possibilities come to mind: 1) the neural response to the stimuli associated with an experience may be consistent across different contexts, or 2) the encoding may be relative, depending on the experience’s context. Relative coding seems likely for the breakfast choice example mentioned above. Any morning’s choice will not be the same every morning. The choice depends, among other things, on how you feel, your level of appetite, and your recent breakfast choices.

Also, value assignment can be thought of as a learning experience. If we have never tasted bananas, for example, our first exposure entails a value assessment on how good it tastes, which we then learn to apply to our future decisions about whether we want to have banana for breakfast or any other time. Clearly, feedback is important. How did it taste and how did that taste compare with other kinds of food that we have eaten, especially eaten recently? If you have had bananas every morning for a week, you may be tired of eating bananas. Then, there is the issue of the context in which perception occurs. Bananas might have more appeal for breakfast that they do for supper.

Research a decade or so ago revealed that our perception is stable across multiple contexts. For example, we can see a banana in the light or dark. We see a green banana or a ripe yellow banana, and still know it is a banana. We can even shut our eyes and feel the shape and still conclude it is a banana.

Assigning value to what we perceive could be another matter. Does value depend on the choice context, rather than being invariant across contexts? That is, do neural circuits re-scale value assignment depending on the context? Earlier fMRI brain-scan studies showed that context is important to value assessment in several areas (mPFC, orbitofrontal cortex (OFC), and cingulate cortex). A recent study has examined whether context-depending coding occurs in all PFC regions and how it is affected by feedback information. Twenty-eight human participants (both sexes) performed an instrumental learning task in which they were trained to maximize their monetary payoff. Choice options produce either reward (adding money to their account) or punishment (subtracting money). Subjects performed four learning trials while in the fMRI scanner in which they were repeatedly were presented with a pair of abstract symbols. For each run, they were presented eight different symbols pairs to produce four choice contexts (i.e., reward/partial feedback, reward/complete, punishment/partial, and punishment/complete). In each trial, they chose between two symbols associated with a certain outcome of money reward. Thus, the contexts were defined based on the possible outcome (either reward or punishment of receiving or losing a specified amount of money). Half of the trials presented complete feedback in which the outcome of the unchosen option was displayed as well, while in the other half of trials subjects were informed of only the value payoff of chosen options.

As repeated learning trials progressed, subjects were learning to optimize their payoffs. MRI signal change reflecting differences between good and bad outcomes was higher for chosen than for unchosen outcomes, with no difference between the chosen outcomes in terms of whether the feedback was partial or complete.

Increased activity in all of the PFC regions and cingulate cortex confirmed their role in encoding and processing value assessment. Anterior PFC activity increased for chosen outcomes, but decreased by unchosen outcome processing. Activity patterns also varied depending on whether partial or complete feedback was given. How does the brain assign different values according to situational context? The explanation is that the neurons must rescale their impulse discharge response to the perceived value of object properties relative to the specific context.

The amount of feedback, partial or complete, greatly affected context-dependent value learning, as revealed by brain activation in multiple regions of PFC and the cingulate cortex. Complete feedback produced the best learning and also caused a switch to assigning value depending on the context. Overall, the subjects learned equally well in reward and punishment context.

The authors used a complicated way to show what we already know from personal experience. We learn what we value from the feedback we receive from our choices, and the value we assign depends on situational context. We readily learn to like bananas on breakfast cereal, but bananas have much less value on pizza at dinner.

The demonstration of the role of prefrontal cortex is important. These results tell us that concussion, stroke, or other damage that affects this part of the brain will impair our ability to make reasoned judgments about the choices we make.

The take-home message is that value assessment occurs in multiple PFC areas in multiple ways, and neural activity does depend on situational context. The coding process is learned by experience and the comprehensiveness of feedback. This learning is consistent with what has been learned over decades of learning and memory research, as I summarize in my books on memory.

Sources:

Doris Pischedda, Stefano Palminteri and Giorgio Coricelli (2020).The effect of counterfactual Information on outcome value coding in medial prefrontal and cingulate cortex: from an absolute to a relative neural code. Journal of Neuroscience 15 April 2020, 40 (16) 3268-3277; DOI: https://doi.org/10.1523/JNEUROSCI.1712-19.2020

Klemm, W. R. (2012).  Memory Power 101. New York: Skyhorse.

Memory and Location, Location, Location

When you remember first meeting the love of your life, do you also have a strong memory of where you both were and also where you were in relation to objects in the scene? When I first met my wife, Doris, it was at a party and she was at a piano surround by “bird dog” males, who I saw from an adjacent room. In my mind’s eye, I still see both rooms and where everybody was.

Do you remember where you were on 9/11? I was in the waiting room of a hospital, looking over a series of lounge chairs at a large-screen TV program that was reporting the news.

It seems that many people remember not only events but where they were at the time of the event. But how does this happen? We do know that a new experience may be “consolidated” into a lasting memory, especially if it stirs emotion and you replay it in your mind. That is certainly the case when you meet the love of your life or see a terrible event.

If you were there, you would surely remember what you were doing.

Back in the 1970s I was studying the part of the brain known as the hippocampus, and it was known at the time that this structure is crucial for consolidating memories. I and others were focused on an EEG rhythm (theta rhythm of 4-7 waves per second) that was especially prominent when an animal moves around in an enclosure EEG signals are summed over dozens of neurons, and therefore to get more precise data some investigators put microelectrodes into the hippocampus so they could monitor the nerve impulse activity of single neurons as the animal moved around.

It was quickly discovered that some hippocampal neurons fired impulses selectively when an animal was in a special location within the enclosure. Collectively, these “place” neurons were actually mapping the enclosure space and tracking the animal’s position as it moved around in this space.

New insight on an additional role for place neurons has come from a new research report on human epileptics with electrodes implanted in their hippocampus to locate the diseased tissue. These patients played a virtual-reality game in which their avatar drove through a virtual town and delivered items to stores. Their task was to memorize the layout and what was delivered at each store. Meanwhile, place cells in the hippocampus were monitored and their place coding was noted. Then when participants were asked to recall the memory of what went where, the place-responsive activity was reinstated even though the subjects were not actually playing the game but recalling it from memory. And the activity of place cells was similar to that during the learning stage.

In other words, neural representations of the content of the experience had become linked with the spatial and temporal context. Such evidence provides strong evidence for the theory that memory formation and recall involve association of event with context, especially spatial and temporal context. This linkage creates a mutually reinforcing interaction of event and location. We tend to remember both or neither.

Can we apply these findings to improving everyday learning and memory situations? Of course, we can. The key elements for making it easier to learn something new are to:

1.  Identify a context that stirs emotions, preferably positive emotions like meeting someone you are attracted to.

2.  Be especially aware of where you are at the time and where you are in relation to the location of various objects.

The hippocampus uses these emotional and spatial cues to facilitate the consolidation of memory. We know that memory is promoted by making associations. Emotions and spatial cues are probably the most effective kinds of cues.

Sources: Miller, J. F. et al. (2013) Neural activity in human hippocampal formation reveals the spatial context of retrieved memories. Science. 342, 1111-1114

END NOTE: If you find these posts helpful, you are not alone. I am gratified to have so many readers. My reader views here and at a cross-posting site now total over 800,000. Thank you so much for wanting to read what I write. You might also want to read some of my books: see http://thankyoubrain.com