Memory Distortion & Source Amnesia: Formation & Neuroscience of False Memories, Lecture notes of Psychology

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Abstract

Our memory is prone to distortions which in everyday life can lead to mistaken memories. This thesis investigates memory distortion. In addition, one might recall (e.g. an event) correctly but misremember the source of the event (e.g. place or time of the event); this particular type of memory distortion is called source amnesia. Here, an overview of cognitive theories of memory distortion as well as the neuroscience behind memory distortion is provided. In addition, the particular memory distortion of source amnesia where one is unable to acquire when or where a fact was learned is further investigated. Results indicate that an overlap of qualities related to the information being learned causes information to be linked to wrong sources, thus creating distorted memories. Misinformation is also indicated to produce impairment in memory. In memory distortions, memory impairments are representative in various areas of the brain, including the hippocampus and the amygdala in the medial temporal lobes as well as in the frontal cortex and in the visual cortex. These key areas are also closely related to brain aging in Alzheimer´s disease and in schizophrenia, depression, posttraumatic stress disorder (PTSD) and in drug and alcohol abuse. Individuals inflicted with these disease symptoms seem to be more prone to source amnesia compared to controls. The limitations and future directions of what we can study regarding memory distortion and source amnesia are also presented in this thesis.

Keywords : memory distortion, source amnesia, misattribution, memory impairment

Table of Contents

• 1. Introduction
• 2. Memory
  • 2.1 Memory systems
  • 2.2 Memory and diagnostic tests
• 3. Memory distortion
  • 3.1 Cognitive theories of memory distortion
  • 3.2 The neuroscience of memory distortion
• 4. Source amnesia
  • 4.1 Neurobiological aspects of source amnesia
  • 4.2 Psychiatric diseases and addiction and source amnesia
• 5. Discussion
  • 5.1 Limitations and future directions
  • 5.2 Conclusion
• References

memory distortion and source amnesia such as drugs, dementia, psychiatric illnesses, and old age, all which will be further described in this paper. The aim of this thesis is to investigate why our memories can be badly mistaken by answering the question:

1. What are the neural correlates of memory distortion and in particular source amnesia? Initially, memory and different memory systems will be explained in order to better understand how memories are formed. In addition, diagnostic tests that are used to test memory function are presented in this thesis since these can be used to test memory function and source amnesia. The cognitive theories of memory distortion explain why one might experience distorted memories whereas the neuroscience of memory distortion explains how memory distortion can be manifested in the brain. One particular type of memory distortion called source amnesia is provided and explained, using neurobiological and psychiatric aspects. Finally, the results of the research of memory distortion and source amnesia are discussed followed by a presentation of limitations and suggested future research. 2. Memory Since this essay investigates memory distortion, a shorter explanation of different types of memory will now be presented.

Different models of memory distinguish between memories of shorter length, for example, sensory memory which contains a time-lapse of milliseconds to seconds. Memories that are of short to medium-lived persistence are defined as short-term, whereas working memory have a time-lapse of seconds to minutes and long-term memory which have a memory persistence of decades (Gazzaniga, Ivry, & Mangun, 2013).

Additionally, learning and memory can be divided into three extensive stages of processing. Encoding , which processes information that comes in and consequently creates memory traces which is then stored. The stage of encoding consists of two phases; the first phase is called acquisition. An extensive amount of stimuli are constantly attacking sensory systems, which in majority produce a very short and temporary sensory response that quickly fades, with a response of 1000 milliseconds after presentation, never reaching short-term memory. In this stage stimuli are able to process, a phase called sensory buffer. A limited amount of these stimuli are then good for a continuance to the short-term memory (Gazzaniga, Ivry, & Mangun, 2013). Consolidation is the second phase of encoding in which the brain makes changes in order to maintain a memory over time, creating a memory of long- term. The consolidation gets stronger over time and has a time lapse of days to months and years. The second stage of learning and memory processing is the representation of a permanent record of the information, called storage , which is the result of both acquisition and consolidation. The third stage, called retrieval , deals with the access to information stored, creating a representation carrying out a learned behaviour (e.g. motor act) (Gazzaniga, Ivry, & Mangun, 2013).

2.1 Memory systems

2.1.1 Short-term memory In sensory memory, memory lasts (at most) for a couple of seconds. For hearing, sensory memory is called echoic memory and as for vision, it is called iconic memory. In principle, these forms of memories can retain extensive information, however only for a very short time. In addition, in short-term memory, the course of time last from seconds to minutes compared to sensory memory. The capacity of short-term memory is limited. (Gazzaniga, Ivry, & Mangun, 2013).

appropriately. If one is able to recollect contextual details of previous experiences one is also setting the foundation of forming an important distinction between semantic memory and episodic memory (Tulving, 1983). According to Tulving (1983), the semantic memory is our general knowledge of the world e.g. rules, meanings, and factual details. We, for instance, know that Paris is the capital of France and that 7 x 6 = 42. These types of knowledge are useful even though we cannot usually remember when and where we learned them. The episodic memory, in contrast, is the recollection of personally-experienced events. This type of memory includes knowledge about something that has occurred and also some recollection of the time and place of what has occurred. If one has to recollect for instance the memory of a car crash, contextual details of the place, time, and sequence are of great importance (Tulving, 1983).

2.2 Memory and diagnostic tests Several diagnostic tests could be used in order to test prefrontal function and source memory function in participants with source amnesia; some of them are explained next.

2.2.1 The verbal fluency test In the verbal fluency test which is a short test of verbal functioning two tasks is typically consisted (Shao, Janse, Visser, & Meyer, 2014). One task tests category fluency and one letter fluency (sometimes called phonemic fluency). Participants have one minute to produce as many unique words as possible within a semantic category (category fluency) or starting with a given letter (letter fluency) in the standard versions of the task. In each task, the participant's score is the number of unique correct words. Verbal fluency tasks are often included in clinical practice, neuropsychological assessment and in research. The verbal fluency tasks have for instance been used to support diagnoses of attention- deficit/hyperactivity disorder and in cognitive impairment in persons who have neurodegenerative diseases, such as Parkinson’s disease or Alzheimer's disease (Shao, Janse,

Visser, & Meyer, 2014). Verbal fluency tasks have also been used in research on groups that are non-clinical to measure verbal ability which includes lexical retrieval and lexical knowledge and as a test of the ability of executive control. The participants have to retrieve words of their language, which require them to access their mental lexicon, they have to focus on the task, the words and its constraints as well as avoiding repetition and this involves executive control processes. Thus, serious deficits in either verbal ability or executive control should indicate a poor performance in the fluency tasks (Shao, Janse, Visser, & Meyer, 2014).

2.2.2 Wisconsin Card Sorting Test To test prefrontal function, one can use the Wisconsin Card Sorting Test. First, different stimulus cards are presented to the subject. Then the participant has to match the cards, but the subject is not told how to match the cards, however, the subject is told if a particular match is right or wrong. The Wisconsin Card Sorting Test can e.g. consist of four key cards and 128 response cards with geometric figures that vary in form, colour or number, they are then sorted thereafter. Subjects have to find the correct classification by trial and error and examiner feedback. After 10 following correct matches, the classification rules changes without warning. The test is not timed and the subject continues to sort the cards until all cards are sorted (Nyhus & Barceló, 2009).

2.2.3 The Stroop Color and Word Test The Stroop Color and Word Test (SCWT), often used in clinical and experimental settings, is a neuropsychological test that deals with cognitive interference. In this task, subjects are told to name what colour of which the ink of an incongruent word is (e.g. the word RED is printed in green ink). Reading a word is told to be more of an automatic cognitive process compared to colour naming. The participant has to solve this cognitive interference and hinder themselves to respond incorrectly. SCWT may be possible to use in

knowledge, social context, goals and motives, features of which can be composed together during a specific event (Johnson et al., 2012). Mental experiences can be divided into perceptual information (e.g. sound, colour) contextual information (e.g. temporal and spatial characteristics), emotion, semantic concepts, cognitive activities (e.g. imaging, retrieving added information) as well as recency and familiarity which are less specific qualities. All qualities judge the root of the mental experience due to the fact that different sources differ on dimensions (e.g. we ought to have very strange content in dreams compared to real life). The overlap of qualities from different sources creates misattribution, for instance, one having a specific vivid imagination from the past, claiming it to be a previous perception (Johnson et al., 2012). The outcome of a source monitoring process is labelled memory attribution , a process of which collects evidence from different mental experiences. The amount of information which the process considers depends on e.g. past experience, motives, and task content. Furthermore, our cognitive system can work in systematic processes of which enable the possibility to retrieve extra information, examining plausibility with given knowledge and how consistent a memory is in a narrative. The processes function as a correcting system which creates doubt about clear but doubtful memories or about believable but faulty memories (Johnson et al., 2012).

Doubt can be very practical in that it assists in further efforts to seek proof, to remember, plant judgment, or enabling the option to live in uncertainty. Source monitoring processes are affected by beliefs (e.g. the quality of a memory source), knowledge and an evaluation and consultation about a social/cultural context in memories. The social and cultural context is proposed as the deciding mechanism behind what we remember and how often we do so, as well as what we consider good evidence in recalling an event (Johnson et al., 2012).

3.1.2 The misinformation effect The misinformation effect (or misinformation paradigm) refers to the notion of impairment in memory of the past that appears after one is exposed to information of which is misleading (Loftus, 2005). Loftus, Miller, & Burns (1978) evoked false memories of a traffic sign in a series of five experiments. The three-stage procedure applied was named the misinformation paradigm and has since been used by various research groups. The misinformation paradigm contains three standard stages: first, one is experiencing an event, secondly one is receiving misinformation about the event, and third, one is being tested in regards to a memory of the specific event (Loftus, 2005).

With the misinformation paradigm in mind, subjects first see a complex event, e.g. a fake automobile accident (Loftus, 2005). Thereafter, one-half of the subjects receive information which is misleading about the accident while the other half receives no misinformation. Finally, all subjects try to remember the original accident. In one study using the misinformation paradigm, subjects saw an accident and thereafter some of them received misinformation about the type of traffic sign used to control the traffic. Subjects of which got mislead received the false suggestion that they actually had seen a yield sign, not a stop sign. Later when asked what kind of traffic sign they remembered seeing at the intersection, the subjects who were given the false suggestion were likely to accept it as their memory; consequently claiming seeing a yield sign. Subjects who did not receive the misinformation had memories of which were much more accurate (Loftus, 2005).

In addition, when talking to other people, seeing biased coverage in media about an event or when we are interrogated in a suggestive manner, misinformation can contaminate our memories. Furthermore, it can be stated that it is easier to modify memories when the passage of time manage the original memory to fade. While faded and weakened, memories become vulnerable to contamination (Loftus, 2005).

different but still, they share several characteristics. The term delusion is usually used to describe false beliefs that are: consistent over time, farfetched or bizarre and held with conviction. Confabulation, however, is argued to not meet these criteria’s, thus one should be treating the term separately from delusion (Turner & Coltheart, 2010). According to Fotopoulou, Conway and Solms (2007), confabulation can be defined as the production of distorted, misinterpreted or fabricated memories concerning oneself or the world. This is done without the conscious intention to deceive. Furthermore, serious misattributions can occur and thus create confabulation if the frontal cortex (ventromedial prefrontal cortex in particular) gets damaged (Damasio et al., 1985; Johnson, 1990; Johnson et al., 2000; Moscovitch, 1995; Schnider, 2008). In a study, Mercer, Wapner, Gardner, & Benson, (1977) examined if confabulation can reflect a patient’s suggestibility. The patients were made to believe that they previously had given a response concerning some questions of which they, in fact, had answered ―I don’t know‖, they were then asked to reproduce their answer. Mild and severe confabulators both generally stood by their previous answer of ―I don’t know‖ and there was no inclination of answering the questions concerned.

3.1.4 The Deese-Roediger-McDermott Paradigm In the Deese-Roediger-McDermott (DRM) task, lists of words which associate with one another (e.g., hospital, nurse) are presented to subjects (Pardilla-Delgado & Payne, 2017). After sufficient time has passed, the participants are asked to recognize or recall the words from the list. Furthermore, participants are asked in the recognition memory version of the DRM task if they remember the words which were presented in the list as well as related words (which were not presented) e.g. critical lure words (e.g. doctor, a word related to hospital and nurse). The critical word is usually identified by the subject with high confidence (Pardilla-Delgado & Payne, 2017). According to Pardilla-Delgado & Payne (2017) the delay

between encoding and the memory test of the false memory effect has been shown for a shorter time (e.g., directly, 20 min) and a longer delay of (e.g., one, seven or 60 days).

Originally, Deese (1959) made a report about the illusion and in addition, Roediger and McDermott (1995) connected the illusion to memory distortion. Furthermore, Roediger and McDermott (1995) argued that the DRM task was a reliable way to study distorted memories under carefully controlled laboratory conditions. Roediger and McDermott (1995) induced false recognition and false recall for words that were not presented in lists. Subjects had to study 24 lists of 15 words that were related to a common word (critical target or critical lure) that was not on the list. False recognition and false recall of the critical lure occurred frequently in response to the lists presented.

Knowingly, the memories of a list of words are more limited and less complicated than memories which are of autobiographical character (e.g., social context, perceptual details, personal relevance, etc.). It can be stated that the DRM illusion can be applied broadly (Gallo, 2010). Roediger (1996) suggest that the DRM illusion enable one to be informed about one’s memory and its basic understanding (Roediger, 1996). Furthermore, the DRM illusion is advantageous compared to other approaches concerning memory distortion in that it provides a simple way of demonstrating memory distortion (Gallo, 2010).

According to Gallo, (2010), the DRM illusion mirrors the phenomena of memory distortion and wrongful recall. Miller and Wolford (1999) proceed from the so-called signal detection theory and implies that the illusion of DRM may be the result of a response bias concerning any word which appeared to be similar or related to the study list, participants might assume or guess that the related bait word did exist in the list due to strongly being associated with the studied words.

mainstream neuropsychology (brain mechanisms) (Brainerd & Reyna, 2004). FTT has concerning true and wrong memory reports integrated these approaches by initially doing several developmental studies which evolved into adult experimentation to furthermore continue into investigations of neurophysiological character (Brainerd & Reyna, 2004).

Brainerd & Reyna, (2004) continues to describe the explanatory principles of FTT. There are two approaches to memory development in relation to FTT. First, the explanation of memory development can be described by how information is represented in memory followed by how these representations later are retrieved and preserved. FTT makes a distinct difference between representations of which apprehend the surface of an experience and representations of which apprehend the gist of an experience. Secondly, the focus lies on securing tests of which are strong, this is done by generating new predictions concerning memory development, in particular, predictions of which are counterintuitive (Brainerd & Reyna, 2004).

The human brain enables a distinction between verbatim and gist traces of experiences. Verbatim traces are representations of which are integrated of a memory targets surface, also associated with item-specific information such as contextual cues (Brainerd & Reyna, 2004). Traces that are of verbatim character are shallow but accurate representations which can be forgotten quickly (Reyna, 2012). On the other hand, gist traces represents elaborative information about a memory target such as semantic and relational information, the essential meaning of the situation (Reyna, 2012). Together, representations of gist and verbatim are formed in parallel, representing a variety of qualities of a stimulus. In order to make accurate calculations for instance; adding numbers, using logic or computing probability, one is acquired to use the representations of verbatim. It is assumed that people rather work with gist-based representations due to verbatim representations being more difficult to work with (Reyna, 2012).

One major difference between information which is verbatim and information which is gist information is that the verbatim information could be found in the memory targets which subjects experience (e.g., the fonts used in the words which are printed on a study list), whereas in the gist information the information is accessed by the rememberer himself by using retrieval cues in form of gist traces in one’s index experience (Brainerd & Reyna, 2004). Furthermore, traces of verbatim memory are representations of the rememberers actual experience, and traces of gist can be thought as the representation of what the rememberers understand of their experience (Brainerd & Reyna, 2004). FTT suggest that gist-based memory errors occur when people falsely recognize or recall a new word, picture or other types of items that are either conceptually or perceptually related to an item that they did previously encounter (Schacter, Guerin, & Jacques, 2011). Individuals fail to recollect specific details of the experience and instead general information or the gist of what happened is remembered. According to FTT, the memory distortion in gist-based memory can be produced in the DRM-paradigm, a paradigm earlier explained (Schacter, Guerin, & Jacques, 2011).

3.2 The neuroscience of memory distortion Due to numerous developments in neuroimaging, especially in functional resonance imaging (fMRI), one is able to track cognitive processes of which partake in memory retrieval, encoding, and error (Johnson et al., 2012). The focus of the research field is not solely on understanding neural correlates in regards to cognitive processes but also studying what someone currently is thinking by analysing neural activity and patterns (Haynes & Rees, 2006). Consequently, one is able to e.g. study honest and deceptive responses (Abe et al., 2008).

called true items , new words in close relation to the studied words, called wrong items , and new unrelated words, called new items. The result showed that activity in the regions of the anterior medial temporal lobe did not distinguish true from false, whereas activity in the posterior medial temporal lobe regions did. This suggests that there is a specific subconscious mechanism for true and wrong memories (Cabeza, Rao, Wagner, Mayer, & Schacter, 2001).

3.2.2 The amygdala The amygdala, a part of the limbic system located in the medial temporal lobe near the hippocampus is representing the process of emotion (LeDoux, 2000). It is suggested that during encoding in participants of which are healthy, the activity of the amygdala is greater for emotional cues compared to cues which are neutral e.g. (Cahill et al., 1996). In addition, greater activity in the amygdala can be shown during encoding for remembered compared to emotional items of which are forgotten (Dolcos, LaBar, & Cabeza, 2004).

3.2.3 The frontal cortex Serious misattributions can occur and thus create confabulation if areas in the frontal cortex (ventromedial prefrontal cortex in particular) - are damaged either through trauma or neurodegeneration (Damasio, Graff-Radford, Eslinger, Damasio, & Kassell, 1985; Johnson, 1990 ; Johnson, Hayes, D’Esposito, & Raye, 2000; Moscovitch, 1995; Schnider, 2008).

3.2.4 The visual cortex In regions associated with visual processing, a greater local activity was attributed to true memories compared to subsequent false memories, thus indicating that visual processing is important in the encoding and retrieval of true memories (Baym & Gonsalves, 2010). Greater activity in the right frontal cortex and bilateral medial temporal lobe was on the other hand more indicated in both true and wrong memories compared to forgetting. The results presented by neuroimaging suggest that wrong memories need at least some information

about the original event to be encoded in order for the misinformation to have an effect on later memory (Baym & Gonsalves, 2010). Strong encoding of the general contextual frame of an event, in combination with a weaker encoding of specific important details, such as identity or features of objects present during the event, are important factors for the construction of distorted memories (Baym & Gonsalves, 2010).

4. Source amnesia Source amnesia is about one recognizing a person or recalling a fact, however one is not able to remember where or when this information about the fact or person was originally learned (Donaldson & Tulving, 1972). It is suggested that source amnesia occurs due to a disconnection that is between the semantic memory and the episodic memory. Knowledge that is semantic is kept by the individual, but one is missing the episodic knowledge to show the context in which the knowledge was obtained (Donaldson & Tulving, 1972). Furthermore, observations suggest that patients with signs of frontal lobe dysfunction have difficulties remembering the episodes of which information has been acquired (Craik, Morris, Morris, R. G., & Loewen, 1990).

4.1 Neurobiological aspects of source amnesia Source amnesia can appear in everyday life. There are both normal and more serious examples of source amnesia which can be caused by numerous aspects, these aspects are explained next.

4.1.1 The aging brain Cognitive decline which is age related is a well-documented phenomenon in episodic memory tasks. During the course of normal aging, the structural integrity of the medial temporal lobe and the prefrontal cortex, as well as one’s ability to recall episodic memories correctly, is greatly compromised (Berron, Neumann, Maass, Schütze et al., 2018). Since