Working Memory

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Function: Working Memory

Describe the Function

Working memory denotes that part of the memory system which allows for temporary storage of a limited amount of information and simultaneous manipulation of that information. The much older notion of “short-term” memory is included in the more widely accepted concept of that part of working memory which provides limited, temporary information storage.

It was once believed that the capacity of an individual’s working memory is limited to seven items, plus or minus two, that could be stored. However a growing body of research is demonstrating that working memory capacity can be deepened, broadened, and made more flexible. Moreover, research is demonstrating that increased working memory capacity has immediate far-reaching effects beyond remembering items or engaging in a conversation. For example, working memory development, when done therapeutically, can alter neural processes and stimulate neuroplastic change in the frontoparietal, dorsal-lateral prefrontal cortex, anterior cingulate, and striatum. Such changes are clinically observable and, if it is a clinical goal as may be the case for individuals undergoing SUD treatment, result in a marked increase in an individual’s cognitive control over their impulsivity.

Models of Working Memory

From a cognitive function development perspective, several models of working memory may be useful for developing therapeutic procedures.

Multicomponent Model

The multicomponent model of working memory was the leading view from 1974, when it was first presented by Baddeley and Hitch, to the early 2000s.<a href="#_edn1" name="_ednref1">[1]</a> Within this model, working memory is conceived of as having four primary components, each of which have capacities for information storage and manipulation, and which can communicate with one another and with long-term memory:

• Phonological Loop – A “relatively modular system” comprised of a transitory storage and a means of refreshing information in storage through vocal or subvocal rehearsal (i.e. repeating a grocery list to yourself on the way to the store).<a href="#_edn2" name="_ednref2">[2]</a> It is believed that the phonological loop supports the acquisition of language through the temporary storage of new words until they can be stored in phonological long term memory. The phonological loop is involved in receiving and processing auditory information, such as a list of digits. It also plays a role in reasoning, hence it popular pastime of talking to oneself while working out a difficult problem.
• Visuospatial Sketchpad – The purpose of this component of working memory is to represent, maintain, and allow for understanding of information that can be represented visually and/or specially, and to do so in a way that persists across an individual’s irregular pattern of eye movements as he or she scans the visual world. For example, whereas the phonological loop is used directly to receive and process verbal directions to a location, the visuospatial sketchpad would be employed in translating the verbal description into a mental map. Alternatively, the sketchpad would be employed in interpreting a printed map relative to observed landmarks and topographical reliefs. As with verbal rehearsing to keep items in the phonological loop fresh, items stored in the visuospatial sketchpad may be refreshed by “covert motor performance that serves to reactivate the memory traces residing in sensory stores,” such as eye movements. Thus, by rehearsing the eye movements one might need to observe a physical object, the memory of the object is refreshed in the sketchpad.<a href="#_edn3" name="_ednref3">[3]</a>
• Episodic Buffer – A passive component of working memory that allows “binding” of small chunks of multidimensional information – or episodes – from long term memory, sensory inputs, and other working memory components. The episodic buffer seems to play an important role in consciousness.<a href="#_edn4" name="_ednref4">[4]</a> However, there is still ongoing academic discussion as to the operation, role, nature, and even existence of this component.
• Central Executive – Within the multicomponent model, the central executive is believed to be an attentional control system. While this component is believed to have limited processing capacity, it is crucial in overall control of an individual’s actions. The central executive function may be divided into two attentional subsystems: an automatic system responsible for handling well-learned or habitual behaviors, and the so-called Supervisory Attentional System which freely draws from long-term memory and other working memory components to postulate on possible outcomes to a given situation, and then chooses the solution deemed most desirable.

Global Workspace Theory

The Global Workspace Theory postulates that the brain is comprised of a highly interconnected network of specialized processes, what Baars denoted as “a brainweb.”<a href="#_edn5" name="_ednref5">[5]</a> Coordination and control of this web takes place through an individual’s consciousness – via an architecture similar to, but not necessarily identical to the multicomponent model’s episodic buffer. This theory allows for multiple, distinct, and separately acting conscious activities – e.g. auditory and visual consciousness, each capable of being willfully activated, each located in a different part of the brain. Similar to the central executive component of the multicomponent model, an individual’s activation of conscious functions requires utilization of the selective attention system under control of both the frontal executive cortex and automated centers such as the amygdala.

Recently functional connectivity analyses have lent support to the Global Workplace Theory. Based on such analyses, researchers are beginning to understand the way functional neural networks can be reorganized based on higher cognitive loads, particularly when stimulated with n-back working memory tasks.<a href="#_edn6" name="_ednref6">[6]</a>

Bayesian Probabilistic Inference

Also termed “The Bayesian Brain,” this model builds off the Global Workspace Theory to describe how unconscious backstage processes can guide decision-making processes under conditions of uncertainty. Three main principles are worth noting:

• Activation of prefrontal cortex and hippocampus neural networks allow the individual to determine, albeit without conscious awareness, a prediction error and to infer an evaluation of current experience based on prior experiences.
• Neural systems with in prefrontal cortex, basal ganglia, and insular cortex derive or interpret familiarity with a given stimuli based on the stimuli’s salience, and thereby merge prior experiences with current beliefs about that stimuli