5c Flashcards
Autobiographical events
Episodic memory is often associated with autobiographical events, which refer to personally lived experiences. Examples of autobiographical events may include:
• your first day of school
• memories from a family vacation
• a birthday party.
These autobiographical events are stored in long-term memory and are retrieved every time you think or speak about them.
However, studies have found that the retrieval of autobiographical events involves the activation of both these brain areas, suggesting that autobiographical events involve an overlap of episodic and semantic memory (Burianova et al., 2010).
This may occur because autobiographical events contain information that is semantic, such as the date or location of the event. Additionally, autobiographical events also contain episodic components, which are more specifically related to the personal experience of the event, such as recalling the feeling of being nervous or happy during the event. The episodic component of autobiographical events allows for the event to be remembered in rich detail
Hippocampus and lobe roles
Research shows that the hippocampus is primarily involved in the retrieval of episodic memories and that the frontal and temporal lobes are involved in the retrieval of semantic memories (Tulving et al., 1991).
Role of episodic and semantic memory in cinstructing possible imagined futures
Episodic and semantic memory are also involved in constructing possible imagined futures, which refer to hypothetical experiences and situations that an individual has the ability to create and conceptualise in their mind.
The brain regions that are involved in the retrieval of autobiographical memories are also activated when people construct possible imagined futures. Schacter et al. (2008) found
that patients who sustained damage to their hippocampus not only experienced difficulty remembering past events, but also struggled to imagine future scenarios. This is because when individuals attempt to mentally construct a possible imagined future, they draw on elements of past experiences from their semantic and episodic memory.
Semantic memory is involved in the construction of possible imagined futures as individuals must be able to envision possible scenarios that are consistent and fit in with what they already know about the world. Episodic memory is also involved by allowing individuals to construct a possible imagined future that is subjective and includes more richly detailed elements, such as the people involved or emotional reactions. An example of how episodic and semantic memory influence the construction of a possible imagined future is depicted in figure 2.
Reality of possible imagined futures
It’s important to note that possible imagined futures do not always become a reality and are often a mental simulation of a hypothetical event. Despite this, the ability to imagine futures is very important as mentally ‘trying out’ different scenarios can guide our future behaviours. For example, being able to imagine future scenarios can help us anticipate potential consequences of our behaviour and decide whether or not we avoid or approach certain situations (Addis et al., 2007).
What is alzeimers
Neurodegenerative diseases are diseases characterised by the progressive loss of neurons in the brain. Alzheimer’s disease is an example of a neurodegenerative disease that is characterised by memory decline.
Some symptoms of Alzheimer’s disease include:
• a decrease in cognitive functions, such as the ability to plan, problem-solve, and think logically.
• personality change.
• changes in mood and emotion.
• frequently becoming confused or disoriented.
• difficulty with language and communication.
How does alzeimers affect the brain
Despite the presentation of these symptoms, a conclusive diagnosis of Alzheimer’s disease can only be made through a post-mortem examination. A post-mortem examination is an assessment of a dead body that occurs to determine the cause of death. From a post-mortem examination, lesions, which refer to an area of tissue that has been damaged due to disease or injury, can be examined through neuroimaging. Therefore, what we know about the biological markers of Alzheimer’s disease largely stems from brain imaging and post-mortem studies.
In these studies, lesions are predominantly identified in the hippocampus. The two primary lesions associated with Alzheimer’s disease are:
• amyloid plaques, which are fragments of the protein beta-amyloid that accumulate into insoluble plaques that inhibit communication between neurons.
• neurofibrillary tangles, which are an accumulation of the protein tau that forms insoluble tangles within neurons, which then inhibit the transportation of essential substances and eventually kill the neuron entirely.
At the later stages of Alzheimer’s disease, the brain can be observed as having significantly reduced in size due to a loss of brain matter which is attributed to the progressive loss of neurons. This is evident in figure 6, which compares an MRI of a normal brain to a brain with Alzheimer’s disease.
How does alzeimers effect episodic and semantic memory
As damage can be associated with the hippocampus, patients with Alzheimer’s disease may struggle to remember semantic and episodic components of personally experienced events. Additionally, a study found that individuals with Alzheimer’s disease lacked the capacity to draw on episodic and semantic memories in order to plan and construct new future scenarios. In this study, they found that this inability to imagine futures compromised their social interactions, ability to plan and carry out these plans, as well as impairing their sense of identity (El Haj et al., 2015).
Aphangasia
Aphantasia is a phenomenon in which individuals lack the capacity to generate mental imagery. Mental imagery refers to the visual representations and experiences of sensory information without the presence of sensory stimuli. Mental imagery can vary in details
and vividness, however, those with aphantasia describe themselves as not having the power
to generate mental imagery altogether
It is important to understand that there is no known cause for aphantasia; individuals can be born with it or suddenly acquire it during life.
Creating mental images aphantasia
When creating mental imagery, individuals use sensory information that has been organised in short-term memory and then transferred to long-term memory to recreate perceptual experiences. This sensory information can be stored in both our semantic and episodic memories.
People without aphantasia are likely to draw on both episodic and semantic memory when creating mental imagery. For example, if an individual imagines themselves on a beach, they might picture themselves sitting on the grainy sand, looking out onto the blue water, and feeling the warmth of the sun on their skin. For these individuals, these mental representations are in the form of images, which rely heavily on episodic memory of past experiences at the beach, as well as semantic memory of what a beach is.
By contrast, people with aphantasia may not be able to visualise richly detailed and vivid episodic memories due to their inability to generate mental imagery. Additionally, while semantic memories may remain intact, the visual component of these memories may also be lacking. Returning to the beach example, an individual with aphantasia would still be able to anticipate what going to a beach involves, without forming a mental image, by drawing on other (non-visual) information from their episodic and semantic memory, such as the knowledge that beaches generally consist of sand and large bodies of water.
Aphantasia research
Research shows that people with aphantasia struggle to retrieve autobiographical events and construct possible imagined futures (Dawes et al., 2020). Firstly, it is difficult for people with aphantasia to retrieve personally lived experiences as they cannot generate vivid, detailed mental imagery of past autobiographical events from their long-term memory. Secondly, this makes
it difficult for people with aphantasia to construct possible imagined futures. For example, people with aphantasia may struggle to generate mental imagery of a past holiday at the beach (retrieving autobiographical events), which may prevent them from generating mental imagery of a future holiday at a similar location (constructing possible imagined futures). Although people with aphantasia are still able to apply non-visual components of autobiographical memories to future events, their lack of mental imagery makes this process more difficult and less vivid than those without the condition.
