Retrospective memory
Retrospective memory is the memory of people, words, and events encountered or experienced in the past. It includes all other types of memory including episodic, semantic and procedural. It can be either implicit or explicit. In contrast, prospective memory involves remembering something or remembering to do something after a delay, such as buying groceries on the way home from work. However, it is very closely linked to retrospective memory, since certain aspects of retrospective memory are required for prospective memory.
Relationship with prospective memory
Early research on prospective memory and retrospective memory has demonstrated that retrospective memory has a role in prospective memory. It was necessary to create more accurate terms in order to explain the relationship fully. Prospective memory describes more accurately an experimental paradigm, therefore, the term prospective remembering was subsequently used. A review by Burgess and Shallice described studies where patients had impaired prospective memory, but intact retrospective memory, and also studies where the impaired retrospective memory caused an impact on prospective memory. A double dissociation for the two has not been found, therefore concluding they are not independent entities. The role of retrospective memory in prospective memory is suggested to be minimal, and takes the form of the information required to make plans. According to Einstein & McDaniel the retrospective memory component of the prospective remembering task refers to the ability to retain the basic information about action and context. An example used in the reviews explains this in the following scenario:The basic information of the retrieval context includes time, location and objects, which in combination form the required retrieval context. Each individual representation required is a form of retrospective memory. Despite all the research this issue is still debatable within the scientific community.
Episodic memory
Retrospective episodic memory is recollection of past episodes. Significant research in this field looks at the phenomenon of mental time travel.Mental time travel
is defined as the ability to mentally project oneself backwards in time to re-live past personal experiences, or forward in time to pre-live possible events in the future. It is a concept created by Canadian psychologist Endel Tulving. It does not simply refer to knowing an event happened, but requires conscious awareness that the individual is indeed reliving the episode. Due to this, it is certain that mental time travel requires central executive functioning, and most often a conscious ability. However new research has found many cases in which mental time travel occurs involuntarily without consciousness. Specifically research shows this occurs for autobiographical events, and as a result these cases are more specific and detail oriented. An example of this would be the phenomenon of scent: How a particular scent can send an individual back to a specific event in their lifetime. There is also evidence that involuntary and voluntary mental time travel differ on activation levels in areas of the brain suggesting that they have different retrieval mechanisms. Current research has moved away from the retrospective portion and towards the prospective aspect of mental time travel. There is also extensive research on whether mental time travel is unique to humans as there has been some evidence that it may be possible to occur in animalsEpisodic
Retrospective episodic memory is the memory of moments from the past. It is frequently used in studies of Alzheimer patients and testing their dementia. A study by Livner et al. compared the effect of the disease on both prospective and retrospective memory. In this case the episodic memory being tested was the ability to remember the testing instructions. To test retrospective memory participants were presented with a list of nouns that had been divided into four categories. The results of retrospective memory were divided into three sections: number of categories, number of items remembered and forgetting ratio, in order to look at the three separate process in creating memory. Using their results and knowledge of episodic memory the researchers were able to find a pattern of functional impairments in the brain.Autobiographical
Retrospective autobiographical memory is recalling specific events from your own past. Testing of this type of memory has been used when researching the effect of emotion and context on memory. Abenavoli and Henkel conducted a study looking at childhood events, context and metamemory. They wanted to see if the participants memory of remembering childhood events was accurate. The results showed that when context was recreated metamemory improved as did vividness of the actual event. Besides these topics, it is also used in studying mental time travel and age-related factors.Semantic memory
Retrospective semantic memory refers to the collection of knowledge, meaning and concepts that have been acquired over time. It plays a significant role in the study of priming. Jones researched a pure mediated priming effect and wanted to discover which model accounted for it. Pure priming refers to the connection between two concepts that have a weak or no association with each other. Each of three potential models were tested with the results concluding that retrospective semantic matching model creates the pure priming effect. This study shows pure priming has more applications than previously thought.Retrograde amnesia
is defined as the loss of memory of events and experiences occurring prior to an illness, accident, injury, or traumatic experience such as rape or assault. The amnesia may cover events over a longer or only a brief period. Typically, it declines with time, with earlier memories returning first.There are many possible causes of amnesia. The most common include Alzheimer's disease, traumatic brain injury, brain infection, dementia, seizures, and stroke. Less common causes include a brain tumor or psychiatric disorders. Psychogenic amnesia usually happens in close association with a stressful event that involves serious threat to life or health.
There are two types of retrograde amnesia, one dealing with episodic memory, and one dealing with semantic memory.
Semantic retrograde amnesia involves loss of generic, lifelong knowledge, as in the various forms of aphasia or agnosia, and also loss of learned motor skills, as in the various types of apraxia. Its primary focus is on retrograde amnesia for specific, usually time-limited, knowledge. In the case of semantic retrograde amnesia, memory for public events and memory for people have formed the primary corpus of research.
Neuroanatomy
Medial prefrontal cortex
A study was conducted by Kesner on retrospective memory involving rats. Lesions made to the medial prefrontal cortex of rats led to impairment of retrospective memory, as well as strong impairment to prospective memory on a radial arm task.Medial temporal lobe
Different brain regions in the medial temporal lobe play a unique role in memory. The medial temporal lobe seems to function as a memory system for consciously available events and facts, and is important for the acquisition of new episodic and semantic memory. There is also evidence that the medial temporal lobe automatically encodes memories.The role of the medial temporal lobe for retrospective memory was assessed by Okuda et al. using Positron Emission Tomography. The PET found that thinking about past events increased blood flow to the medial temporal lobes, emphasizing that this brain area contributes to the activation of retrospective memory. Also, the medial temporal lobe displayed activation levels associated with prospective memories. This finding gives support for the belief that thinking about the future to an extent relies upon thinking about the past, showing a close relationship between retrospective memory and prospective memory.
Hippocampus
The hippocampus plays an important role for remembering specific personal experiences in humans, as well as memory for sequence of events.A series of lesion studies assessed the role of the hippocampus on retrospective memory. In the first delayed response task, nonhuman primates were shown two food wells. For the primates to get a reward, they had to remember which food well was baited. However, the primate had to retain the information about the two prospects until an apparatus was lowered and raised after a delay interval. The results showed that lesions to the hippocampus impaired performance on this task. In a variation of the study, the primates were required to approach the food well that was empty after a delay. It was found that damage to the thalamus also caused impaired performance on both tasks, but at longer delay intervals. These studies confirmed that damage to the hippocampus and thalamus impaired the recall for episodic memory of previously experienced events.
In a lesion study involving rats, Ferbinteanu and Shapiro found the importance of the hippocampus for correctly remembering past events. In the study, rats with fornix lesions displayed poor choice accuracy in a spatial task requiring memory for temporal context, which was seen as evidence for impaired retrospective memory.
In an earlier study, Kametani and Kesner found that rats with lesions in the hippocampus made a large number of errors on a radial arm maze, indicating impaired retrospective memory for points of interpolation within the maze.
Thalamus
It is known that the thalamus plays a crucial role in memory.While investigating stroke-patients with damage to the thalamus, Cipolotti et al. found that the stroke victims had poor recognition and recall memory on verbal and non-verbal tests. The poor recall identified that the retrospective memory of the patients was being effected by the damage on the thalamus due to stroke.
Lesions to the thalamus have been found to impair the recognition memory of monkeys. In a study conducted by Aggleton and Mishkin, they found that monkeys with lesions to the anterior thalamus and the posterior thalamus had an impaired ability for recognition and associative memory on matching tests. The researchers also suggested that combined damage to both regions of the thalamus can lead to amnesia.