Working memory is a cognitive system with a limited capacity that can hold information temporarily. It is important for reasoning and the guidance of decision-making and behavior. Working memory is often used synonymously with short-term memory. Still, some theorists consider the two forms of memory distinct, assuming that it allows for the manipulation of stored information. In contrast, short-term memory only refers to the short-term storage of information. It is a theoretical concept central to cognitive psychology, neuropsychology, and neuroscience.
Working memory is one of the brain’s executive functions. It’s a skill that allows us to work with information without losing track of what we’re doing. Think of it as a temporary sticky note in the brain. It holds new information in place so the brain can work with it briefly and connect it with other information.
What is the role of Working memory?
The capacity of Working memory
Cowan proposed that it has a capacity of about four chunks in young adults (and fewer in children and old adults). In the visual domain, some investigations report no fixed capacity limit concerning the total number of items that can be held in working memory. Instead, the results argue for a limited resource that can be flexibly shared between items retained in memory, with some items in the focus of attention being allocated more resources and recalled with greater precision.
Whereas most adults can repeat about seven digits in the correct order, some individuals have shown impressive enlargements of their digit span—up to 80 digits. This feat is possible through extensive training on an encoding strategy by which the digits in a list are grouped (usually in groups of three to five) and these groups are encoded as a single unit (a chunk).
Working memory Development
The capacity increases gradually over childhood and declines gradually in old age.
Childhood Working memory
Measures of performance on tests increase continuously between early childhood and adolescence, while the structure of correlations between different tests remains largely constant. Starting with work in the Neo-Piagetian tradition, theorists have argued that the growth of capacity is a major driving force of cognitive development.
Although neuroscience studies support the notion that children rely on the prefrontal cortex for performing various tasks, an fMRI meta-analysis on children compared to adults performing the n-back task revealed a lack of consistent prefrontal cortex activation in children, while posterior regions including the insular cortex and cerebellum remain intact.
Working memory is among the cognitive functions most sensitive to decline in old age. Several explanations for this decline have been offered. One is the processing speed theory of cognitive aging by Tim Salthouse. Drawing on the finding that cognitive processes generally slow as people grow older, Salthouse argues that slower processing leaves more time for working memory content to decay, thus reducing effective capacity. However, the decline of its capacity cannot be entirely attributed to slowing because capacity declines more in old age than speed.
Age-related decline can be briefly reversed using low-intensity transcranial stimulation to synchronize rhythms in prefrontal and temporal areas.
Working memory training
Some studies on the effects of training, including the first by Torkel Klingberg, suggest that working memory in those with ADHD can improve through training. This study found that a period of training increases a range of cognitive abilities and increases IQ test scores.
Another study by the same group has shown that, after training, measured brain activity related to working memory increased in the prefrontal cortex, an area that many researchers have associated with its functions. One study has shown that its training increases the density of prefrontal and parietal dopamine receptors in test subjects. However, subsequent experiments with the same training program have shown mixed results, with some successfully replicating, and others failing to replicate the beneficial effects of training on cognitive performance.
Working Memory in the Brain
Localization in the brain
Localization of brain functions in humans has become much easier with the advent of brain imaging methods (PET and fMRI). This research has confirmed that areas in the PFC are involved in functions. During the 1990s much debate has centered on the different functions of the ventrolateral (i.e., lower areas) and the dorsolateral (higher) areas of the PFC.
A human lesion study provides additional evidence for the role of the dorsolateral prefrontal cortex in working memory. One view was that the dorsolateral areas are responsible for spatial working memory and the ventrolateral areas for non-spatial working memory. Another view proposed a functional distinction, arguing that ventrolateral areas are mostly involved in the pure maintenance of information, whereas dorsolateral areas are more involved in tasks requiring some processing of the memorized material. The debate is not entirely resolved but most of the evidence supports the functional distinction.
One approach to modeling the neurophysiology and the functioning is the prefrontal cortex basal ganglia working memory (PBWM). In this model, the prefrontal cortex works hand-in-hand with the basal ganglia to accomplish the tasks.
Many studies have shown this to be the case. One used ablation techniques in patients who had had seizures and had damage to the prefrontal cortex and basal ganglia. Researchers found that such damage resulted in a decreased capacity to carry out executive functions. Additional research conducted on patients with brain alterations due to methamphetamine use found that training increases volume in the basal ganglia.
Effects of Stress on Neurophysiology
Working memory is impaired by acute and chronic psychological stress. This phenomenon was first discovered in animal studies by Arnsten and colleagues, who have shown that stress-induced catecholamine release in PFC rapidly decreases PFC neuronal firing and impairs working memory performance through feedforward, intracellular signaling pathways.
Exposure to chronic stress leads to more profound working memory deficits and additional architectural changes in PFC, including dendritic atrophy and spine loss, which can be prevented by inhibition of protein kinase C signaling. fMRI research has extended this research to humans and confirms that reduced working memory caused by acute stress links to reduced activation of the PFC, and stress increased levels of catecholamines. Mood states (positive or negative) can influence the neurotransmitter dopamine, which in turn can affect problem solving.
Effects of Alcohol on Neurophysiology
Excessive alcohol use can result in brain damage which impairs working memory. Alcohol affects the blood-oxygen-level-dependent (BOLD) response. The BOLD response correlates increased blood oxygenation with brain activity, which makes this response a useful tool for measuring neuronal activity. The BOLD response affects regions of the brain such as the basal ganglia and thalamus when performing a task.
Adolescents who start drinking at a young age show a decreased BOLD response in these brain regions. Alcohol-dependent young women in particular exhibit less of a BOLD response in parietal and frontal cortices when performing a spatial working memory task. Binge drinking, specifically, can also affect one’s performance on tasks, particularly visual working memory. Additionally, there seems to be a gender difference regarding how alcohol affects working memory. While women perform better on verbal working memory tasks after consuming alcohol compared to men, they appear to perform worse on spatial working memory tasks as indicated by less brain activity. Finally, age seems to be an additional factor. Older adults are more susceptible than others to the effects of alcohol.
Working memory role in Academic Achievement
The capacity is correlated with learning outcomes in literacy and numeracy. Initial evidence for this relation comes from the correlation between capacity and reading comprehension, as first observed by Daneman and Carpenter (1980) and confirmed in a later meta-analytic review of several studies.
Subsequent work found that its performance in primary school children accurately predicted performance in mathematical problem solving. One longitudinal study showed that a child’s memory at 5 years old is a better predictor of academic success than IQ.
Working memory relation to Attention
There is some evidence that optimal performance links to the neural ability to focus attention on task-relevant information and to ignore distractions, and that practice-related improvement is due to increasing these abilities.
One line of research suggests a link between the capacities of a person and their ability to control the orientation of attention to stimuli in the environment. Such control enables people to attend to information important to their current goals, and to ignore goal-irrelevant stimuli that tend to capture their attention due to their sensory saliency (such as an ambulance siren).
Working memory relationship with Neural Disorders
An impairment of working memory functioning is normally seen in several neural disorders:
Several authors have proposed that symptoms of ADHD arise from a primary deficit in a specific executive function (EF) domain such as working memory, response inhibition, or a more general weakness in executive control. A meta-analytical review cites several studies that found significantly lower group results for ADHD in spatial and verbal tasks and in several other EF tasks. However, the authors concluded that EF weaknesses neither are necessary nor sufficient to cause all cases of ADHD.
Patients with Parkinson’s show signs of reduced verbal function. They wanted to find out if the reduction is due to a lack of ability to focus on relevant tasks or a low amount of memory capacity.
As Alzheimer’s disease becomes more serious, fewer functions. In addition to deficits in episodic memory, Alzheimer’s disease is associated with impairments in visual short-term memory, assessed using delayed reproduction tasks. These investigations point to a deficit in visual feature binding as an important component of the deficit in Alzheimer’s disease.
There is one study that focuses on neural connections and fluidity in mice brains. The study helps answer questions about how Alzheimer’s can deteriorate it and ultimately obliterate memory functions.
A group of researchers hosted a study that researched the function and connectivity of working memory over a 30-month longitudinal experiment.
Working memory relationship with Uncertainty
A recent study by Li and colleagues showed evidence that the same brain regions responsible are also responsible for how much humans trust those memories. In the past, studies have shown that individuals can evaluate how much they trust their memories, but how humans can do this was largely unknown.
How to enhance Working memory?