Short-Term Memory Impairment

What is Short-Term Memory Impairment?

Short-term memory, also known as active memory, keeps pieces of information or chunks of memory for a relatively short period, usually up to 30 seconds. On the other hand, long-term memory can keep information indefinitely. But the difference between these two isn’t just in the time they store information; they also function differently. Regardless, they are closely connected.

Think of short-term memory like a temporary notepad, usually holding around 7 items based on psychologist George Miller’s concept. It gets its items from what we sense and pay attention to. On the other hand, long-term memory stores knowledge and memories of actions, skills, events, facts, and rules. There are two types of these memories. One is called procedural memories (knowing how to do things), and the other is declarative memories (knowing facts). Declarative memory includes knowing general facts and personal experiences.

Although short-term memory is related to working memory, the two are not the same. Short-term memory is a set of storage systems, while working memory is about organizing and manipulating information. Despite this, people often use the terms interchangeably. Furthermore, we need to differentiate short-term memory from sensory memory, which stores raw sensory information for a brief moment—a fraction of a second and depends on the way the information was originally perceived.

Over time, several models have been proposed to explain the complex dynamics of memory. A prevalent model is the Atkinson and Shiffrin model from the 1960s. Research findings have led to debates about whether short- and long-storage are separate systems or part of a single system. However, the Atkinson and Shiffrin model remains a fundamental approach to understanding memory.

Short-term memory can be divided into several subsystems with limited capacity. This limitation actually acts as an advantage because it allows us to focus on essential information and ignore the rest—imagine a prey having to keep an eye on its surroundings for a possible attack. The subsystems of short-term memory process sensory information and are therefore closely related to our different sensory modalities.

In the 1970s, another memory model was developed by Baddeley and Hitch, known as the working memory model. This model includes short-term memory but expands on it. Working memory is the set of processes that allow us to use and manipulate stored information. This system is responsible for understanding new information, solving problems, and forming arguments and is key to achieving short-term goals. Deficits in working memory have been related to several learning disorders like ADHD, dyslexia, and certain language impairments.

Research has shown that children with ADHD often have inadequate brain responses in areas related to working memory. Workings memory hitches and lapses have also been considered common characteristics in psychotic disorders.

Short-term and long-term memory can be distinguished based on how long information is stored and the amount of information that can be held. Unlike short-term memory, long-term memory has an almost limitless capacity and can contain memories for years. How memories progress from being part of short-term memory to becoming part of long-term memory is a topic of ongoing discussions in neurocognitive science. Advanced brain imaging techniques have also shown that different parts of the brain are activated when we learn and remember different things. For instance, motor skills learning is linked to the activation of the cerebellum and brainstem nuclei. Cognitive learning associated with problem-solving involves the medial temporal lobes.

What Causes Short-Term Memory Impairment?

Several medical conditions, such as strokes, brain injuries, aneurysms, tumors, and infectious diseases may affect short-term memory – the ability to keep a small amount of information in mind and use it within a few seconds. However, it’s rarely the case that only short-term memory is affected. For instance, bleeding from an aneurysm – a bulge in the wall of a blood vessel – can cause both short-term and long-term memory loss. A variety of other health conditions like infections throughout the body, thyroid issues, surgery, certain psychiatric conditions like depression, traumatic experiences, and even cancer treatments can influence short-term memory.

A study showed that nearly 21% of college athletes have had concussions which are linked with long-term cognitive (brain-based) impairments, notably in working memory – the brain’s system for temporarily storing and managing information. Boxing training for a year can also affect working memory, short-term and long-term memory. This suggests that boxers should use better head protection during training to prevent frequent blows to the head. Diseases that progressively damage the brain’s nerve cells, like dementia, are major causes of memory impairment. Short-term memory loss might be an early sign of dementia.

Mild cognitive impairment, where memory loss doesn’t hinder everyday life or independence, is the stage between normal cognitive aging and severe decline seen in Alzheimer’s disease. Changes in different memory domains have also been observed in Parkinson’s disease, Huntington’s disease, and primary progressive aphasia – a group of related disorders that affect language abilities.

Executive functions -cognitive processes that regulate thought and action- in primary progressive aphasia might also be impaired. Changes in these functions such as shifting attention, inhibiting actions, and updating working memory, might influence cognitive control of behaviour. A study also described progressive loss of understanding of words’ meanings in one type of primary progressive aphasia, which can be improved through learning therapy.

Other factors that may affect memory include substance abuse (like alcohol, drugs, and heavy cigarette smoking), sleep deprivation, high stress levels, and deficiency of vitamin B12. Chronic alcohol consumption can lead, over time, to Korsakoff syndrome – a memory disorder caused by vitamin B1 deficiency. Vitamin B1 deficiency could also be caused by dietary deficiencies, prolonged vomiting, and eating disorders health issues. Memory disorders similar to Korsakoff syndrome have also been seen after brain injuries that impact the thalamus and hippocampus – both crucial for memory.

Recent studies also shed light on the important role of the prefrontal cortex, a part of the brain involved in decision making and behavior, especially under stress. Stress activates a system in the body which, in turn, releases certain chemicals in the brain, affecting memory and thought processing.

Other treatments like electroconvulsive therapy – a procedure that involves passing small electric currents through the brain to trigger a brief seizure – may cause short-term memory alterations during treatment. Memory loss can also be triggered by certain medications, including drugs for epilepsy, pain, depression, and even some types of cholesterol drugs. Although some of these drugs impair memory processing, so far, mostly observational data and case reports are available about these effects, indicating that more research is needed.

Risk Factors and Frequency for Short-Term Memory Impairment

Memory impairment can be caused by various conditions. For example, in relation to diseases that cause the brain to degenerate, around 15% to 20% of people aged 65 or older have a condition called mild cognitive impairment. About one-third of these individuals will develop Alzheimer’s disease within five years. Currently, there are about 5.8 million Americans living with Alzheimer’s. Furthermore, the number of new cases of all types of dementia is expected to double by 2050.

Mild cognitive impairment is a condition where memory is impacted, but daily life activities are normal. This can precede dementia for several years. Studies show that between 5% to 15% of individuals with mild cognitive impairment advance to dementia each year.

The occurrence of dementia is almost twice as high in Black people compared to White people. Also, China’s aging population, which is expected to rise from 12% in 2010 to 33% by 2050, will likely cause Alzheimer’s disease to affect around 27.7 million people there by 2050.

Parkinson’s disease affects approximately 1% of the population over 60, while the occurrence of Huntington’s disease is 0.38 per 100,000 people per year. However, for conditions that don’t cause brain degeneration, it’s difficult to estimate numbers as memory decline isn’t always noticeable in patients.

Signs and Symptoms of Short-Term Memory Impairment

Short-term memory loss involves forgetting recently learned information. For example, someone with short-term memory loss might repeatedly ask the same questions, forget where they are, not remember recent events, or forget something they’ve just read or seen. This is also called fixation amnesia. The symptoms and severity can vary, based on what’s causing the memory changes. Short-term memory encompasses different aspects like remembering words or visual information, which could be affected to different degrees. Generally, these memory changes last as long as the condition behind them or fade away over a few weeks or months, like in the case of cognitive dysfunction following surgery.

In diseases like dementia, short-term memory typically worsens progressivley, affecting various aspects of memory. However, in mild cognitive impairment, memory loss can stay the same, get worse, or improve. For example, about a third of brain aneurysm cases experience memory problems that go away over time, even though this recovery may take a few weeks. In most instances of psychogenic amnesia, which is memory loss caused by a psychological reason rather than a physical cause, memories can often be restored through psychological treatments. However, if this amnesia has been lasting for months or years, recovery becomes unachievable and the person starts a new life journey (known as a fugue state).

Sometimes, short-term memory loss is part of a more extensive set of symptoms. For instance, those with alcohol-induced Korsakoff syndrome often struggle with memory loss (both anterograde and retrograde), create false memories to fill memory gaps, and have related psychiatric symptoms. A recent research study described Korsakoff syndrome as an episodic memory loss due to damage in the brain region known as the medial diencephalic structure. One specific pattern of memory problems was found: impaired learning and application of new tasks due to complexity. Interestingly, similar issues were previously observed in patients with amnesia related to another brain area, the medial temporal lobe. Coupling Korsakoff syndrome with problems recalling specific personal memories was also noted. Sometimes, Korsakoff syndrome can come with complications related to a lack of Vitamin B1 (or thiamine deficiency) known as Wernicke encephalopathy, and together they are referred to as Wernicke-Korsakoff syndrome.

Testing for Short-Term Memory Impairment

Various methods are used to evaluate short-term memory. For example, simple tests that ask you to recall words or numbers assess verbal memory. Other tests might examine how well you store verbal (spoken or written language) or visuospatial (understanding the relationships between objects in space) information. More complex methods involve remembering the order of items presented to you. Special tests are also used for children.

Recent reviews have highlighted the use of an automated system known as the Cambridge Neuropsychological Test Automated Battery (CANTAB) to assess working memory. Working memory is your ability to hold and manipulate information over short periods. This tool could be helpful in diagnosing mild cognitive impairment, a condition that causes slight but noticeable and measurable declines in cognitive abilities, including memory and thinking skills. CANTAB has specific tests like spatial span, spatial working memory, and rapid visual information processing that could prove useful in a clinical setting.

There are other tools that are specifically designed to test short-term memory impairment and provide information about how severe the memory impairment is. The Short-Term Memory Recall Test and its simplified version are some such tools. They can be particularly useful in identifying memory impairment in its early stages, before dementia sets in. On the other hand, the Temple Assessment of Language and Short-term Memory in Aphasia (TALSA) focuses on short-term impairment after stroke-related aphasia, a condition that impairs your ability to process language. Different tools are used to assess memory changes in various conditions that cause a gradual decline in cognitive function. For instance, the California Verbal Learning Test-3 (CVLT-3) helps distinguish memory disorders of Alzheimer’s disease from those of Huntington’s disease.

There are also screening procedures available to identify patients with early Alzheimer’s disease. These procedures include performance on the Free and Cued Selective Reminding Test (FCSRT) and Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). Further tests focus on finding the cause of memory decline. These could include imaging procedures like magnetic resonance imaging (MRI) or computed tomography (CT) scans, or laboratory tests like checking for Vitamin B12 levels. Past studies have shown that MRI can rule out other causes of cognitive decline and reveal patterns of brain shrinkage that could predict certain types of dementia. While these patterns are not specific to each disease, they can help confirm a diagnosis or identify certain processes.

Treatment Options for Short-Term Memory Impairment

Various techniques have been suggested to improve memory tasks, including behavioral approaches and other non-behavioral methods. Behavioral strategies focus on repetitive learning and association of new information with already stored knowledge. Some of these methods even include Tai Chi movements and controlled breathing, but more research is needed to determine their effectiveness.

Pharmacological treatments like Alzheimer’s disease medications have been used, but they have not shown significant benefits in slowing down or preventing the progression of mild cognitive impairment to Alzheimer. The use of simple learning aids like rhymes can be beneficial, especially for children memorizing numbers or sequences. This strategy works by associating a word, phrase, or image with an object.

In more specific situations, such as in the face of neurodegenerative conditions like Alzheimer’s, or when memory impairment is mild and can be slowed down or stopped, more complex non-drug approaches are necessary. Computer-based memory training programs are used in cases of mild cognitive impairment when no FDA-approved medication is available. These computer programs can also be combined with wellness education and physical exercises like yoga. A study has even shown that Kundalini yoga training could improve memory by supporting better sensory integration in the hippocampal region (part of your brain that is key for memory and learning) in women with subjective memory decline and cardiovascular risk factors.

Moreover, other studies have focused on the impact of exercise on cognitive function in older adults with mild cognitive impairment. The findings suggest that regular exercise can significantly improve cognitive function, particularly mind-body exercise.

Web-based cognitive training can beneficially modify memory processing in Parkinson’s disease and can improve executive function – the set of cognitive abilities that control and manage other cognitive processes – in older adults with mild cognitive impairment through virtual reality. Music therapy and specific exercises like Wuqinxi (a type of Qigong exercise) have shown promising results in enhancing memory and possibly delaying or preventing the progression to Alzheimer’s disease.

Non-behavioral strategies can include things like transcranial direct current stimulation for short term memory loss due to primary progressive aphasia, a neurological syndrome in which language capabilities become slowly and progressively impaired.

There’s also research being conducted on the effects of certain food nutrients, like thymoquinone found in black seeds or green tea, in battling Alzheimer’s disease-related short-term memory decline, and certain peptides found in foods such as cheese and milk to mitigate stress-induced memory alterations. Lastly, a study has shown promising results on moxibustion treatment, a form of heat therapy in traditional Chinese medicine, for improving memory in patients with mild cognitive impairment. However, it’s important to note that the effectiveness of these treatments requires further research and validation.

What else can Short-Term Memory Impairment be?

When trying to determine the cause of memory loss, doctors use a process called differential diagnosis. Here are some conditions that may cause similar symptoms:

• Alzheimer’s disease: This is the most common type of dementia, and it’s known for causing issues with short-term memory initially, with long-term memory staying intact. Over time, the patient also develops problems with problem-solving, judgment, motivation, organization, and thinking abstractly.
• Creutzfeldt-Jakob disease: This is a fast-acting and fatal disease that affects the brain. It commonly presents with issues like short-term memory loss, decreased concentration, and rapidly progressing dementia. This condition is usually confirmed via MRI.
• Dementia with Lewy bodies: This brain disease causes a range of cognitive, behavioral and motor symptoms. However, it often presents more management challenges and has a worse prognosis than other forms of dementia.
• Frontotemporal dementia: This is the second most common form of dementia that typically presents before old age. It’s known for causing significant changes in behavior, language, and cognitive abilities and has a notable genetic component.
• Progressive supranuclear palsy: This is a progressive disease that impacts the brain. It presents with motor, behavior, and cognitive issues, such as postural instability, cognitive decline, and abnormal eye movements.
• Semantic dementia: This form of dementia is associated with the decay of the anterior temporal regions of the brain, and it causes a significant impairment of semantic memory. Sometimes this condition might be misdiagnosed as Alzheimer’s disease or frontotemporal dementia.
• Traumatic brain injury: After experiencing a brain injury, the patient might face cognitive issues and behavioral changes due to diffuse axonal injury. These changes can include slowed processing of information, long-term memory impairment, difficulty paying attention, loss of self-awareness, and mental fatigue.
• Depression and other psychiatric illnesses: These can affect concentration and damage short-term memory.
• Vitamin deficiencies: Being deficient in vitamins like B12 and B1 can negatively affect short-term memory.
• Medication use: Some medications, like narcotics, can impair memory.
• Thyroid disorders: Problems with the thyroid, like hypothyroidism, can lead to memory impairment and a sense of being “foggy”.

What to expect with Short-Term Memory Impairment

The overall outlook for short-term memory loss can significantly vary and largely depends on the underlying cause. For instance, temporary memory loss due to a serious heart condition known as transposition of the great arteries often improves and returns to normal without requiring comprehensive treatment. Similarly, memory loss as a result of hypothyroidism (an underactive thyroid), lack of certain vitamins, or depression can also be reversed once the initial issue is treated.

However, the majority of cases of short-term memory loss are due to progressive conditions such as Alzheimer’s disease. Other common reasons include stroke or traumatic brain injuries, which might only be partially reversible, depending on the extent of the damage and the brain’s remaining healthy tissue. These deficiencies typically don’t change much, but they might seem more apparent as the patient ages and their brain’s healthy tissue decreases.

Possible Complications When Diagnosed with Short-Term Memory Impairment

Short-term memory loss can range in severity and can considerably disrupt a person’s social life. Common examples of this can be missing important appointments, forgetting past conversations, and generally becoming distant from friends and family. This can often lead to people feeling isolated from society without proper support. As the memory loss progresses, it can also affect a person’s ability to do daily chores like grocery shopping and paying bills. This often leads to the need for extra help.

For more severe cases, memory loss could actually be dangerous. For instance, a person might forget to switch off the stove or lose their way even in familiar surroundings, making it challenging to get home. This situation becomes even more critical when a person has other health issues. They might forget to take their medicines or get confused and end up taking their medicine multiple times, which can lead to severe health risks.

Memory loss might also affect daily routines like eating, bathing, or getting dressed as a person may forget these tasks. In extreme cases, individuals may lose their independence and need to shift to a nursing home for proper care.

Common Impacts of Memory Loss:

• Forgetting appointments and conversations
• Declining communication with friends and family
• Difficulties with complex tasks like grocery shopping and bill payments
• Possibility of dangerous situations (like forgetting to turn off the stove)
• Forgetting to take medication or overdosing due to forgetfulness
• Difficulty with daily routines (eating, bathing, dressing)
• Potential need for relocation to a nursing home

Preventing Short-Term Memory Impairment

In most cases where a sudden loss of memory occurs, like with a stroke or a brain injury, doctors can usually diagnose the problem easily. However, there aren’t many treatment options available. But in conditions like vitamin deficiencies, depression, or an underactive thyroid (hypothyroidism), the diagnosis might take longer. That’s because these conditions come on gradually and the patient’s ability to function normally usually decreases in the later stages of the disease. In such situations, it’s important to educate the patient about their condition. Screenings also play a key role and should be conducted at the doctor’s office, especially for patients at risk of these conditions.