Cognitive Control: Working Memory Gating (Part 1)

If you are successful in controlling yourself in the car, then you must have in some way used a representation of your context, i.e., driving your car, to choose an appropriate action over the more habitual, but inappropriate one. To do so, you likely held this context in your working memory. Working memory is a system for maintaining a limited amount of information in an active state so that it can be used for on-going processing. Thus, maintaining your car-driving-context in working memory allows it to provide internal state support for choosing the appropriate action.

Consider an example of an everyday act of control. You are driving your car when your cell phone buzzes to notify you of an incoming message or call. For many people, that buzz is a strong cue that elicits the act of checking your phone. And if you were relaxing in your home, this might be an appropriate action to take. Indeed, you might even check your phone without having set a goal to do so. However, cell phone use while driving is dangerous, and in some places, it’s illegal. Thus, in this context, you need to override your tendency to check your phone and do something else, like redirect your attention to the road or click a mute button.
Figure 1. Working Memory Gating. Modified with permission from Badre, D., and Nee, D. E. (2018), Frontal cortex and the hierarchical control of behavior. Trends in Cognitive Science, 22(2), 170-188.

Thus, to carry out a new task or unfamiliar rule, we need to quickly identify the right gating policies for that task. These gating policies will specify what information should be input our output from working memory and under what conditions. Returning to our cell phone example, our gating policy should update the context of driving as a context, and set conditions so we access this context for support when our phone buzzes. Thus, our gating policies realize our rule about using phones while driving within the complex dynamics of our actual drive.  
We also need a way to control output from working memory. In general, for any on-going behavior, we are not constantly monitoring what we are doing with respect to our internal goals. Indeed, with a well-learned action, like a practiced piece of music or a tennis serve, attending to the details of our actions can disrupt rather than help. Conversely, if a context support is needed, but we fail to apply it, we are susceptible to errors and slips of action. In our example, failing to exert control at the right moment might result in us checking our phones before we realize we are doing so. So, there are moments when control is needed, and it is crucial to align our use of information in memory with those moments.
In today’s post, I will introduce an example of one proposed mechanism of cognitive control that is discussed in detail in my book, On Task. This is the mechanism of working memory gating.
This simple and widely held conception of how control operates places working memory at the center of successful control. However, in practice, this notion is complicated by the fact that the world is complex and dynamic. We have access to lots of potential contextual information we might maintain that changes from moment-to-moment. Meanwhile, our working memory capacity is limited. Thus, we need a means of controlling the input to working memory to select what information to maintain versus what information to ignore and when to do so.

Working Memory Gating Policies

Mechanisms that control the input and output of working memory are sometimes conceptualized by computational cognitive neuroscientists using the metaphor of gates on memory. These gates control the flow of information. Thus, an input gate can open to allow information encountered at an arbitrary time to be placed in a state such that it is accessible at a later time. Conversely, when this input gate is closed, it can prevent transition to this state, protecting against distracting information. On the other end, an output gate can be opened to allow contextual information held in memory to be accessed at the right moment and used as a control signal.
Selective working memory gating is particularly important because we often have multiple contexts that are relevant to our behavior and evolve over different time scales. Consider, for example, that most everyday sequential behavior is hierarchical in nature, with goals and subgoals at different levels of abstraction. For instance, when I make a cup of coffee, I have an overall goal of making coffee, but also various subgoals like filling a carafe or adding grounds. I will update the subordinate goals while the superordinate one rides along in the background. Further, I may need to update subgoals contingent on my superordinate goal. Selective gating helps manage these complex dynamics among multiple elements of context.

In my next post tomorrow, I will discuss mechanisms for working memory gating in the brain, and how they help us address some of the basic challenges for cognitive control theory.
In sum, finding the right working memory gating policies is part of how we are able to connect our goals with our behavior. Experimental evidence indicates that the efficiency with which we acquire and perform new tasks partly depends on our ability to locate and apply the right working memory gating policies, independent of the task rules that specify which stimulus cues what response. People’s behavior shows that they are capable of both transferring and generalizing gating policies to new tasks, leveraging their prior experience to behave flexibly. Thus, successfully controlling ourselves can depend not only on our general capacity for control but also on how well we have matched our policies for working memory gating with the task at hand.
To be useful for control, working memory gates should also be selective, allowing content addressable access to memory. Thus, if more than one piece of contextual information is maintained at a time, a selective gate can update and access specific information in memory, rather than gating everything or nothing.