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Approaches to memory in autism
Autism is a Spectrum Disorder and therefore presents many challenges to the study of autism and memory function. It has been important for researchers to be able to collect data across the spectrum: developing experimental designs to study both individuals with High Functioning Autism (HFA) and those with Moderate-Low Functioning Autism (M-LFA). Methodology has developed to effectively classify individuals on the spectrum. Many of these methods include various tests of Verbal IQ (VQ), Nonverbal/Performance Quotients (PQ) and Full-Scale IQ (FSIQ). Research initiatives are then able to make methodical comparisons and analyses between HFA and M-LFA individuals. Although, in recent years, “mixed” studies of both HFA and M-LFA participants are emphasized as well.

Memory difficulty is not part of the diagnostic criteria for Autism Spectrum Disorder (ASD), but it is a common difficulty experienced by many individuals in the spectrum. Multiple studies suggest that memory deficit observed in ASD has a biological explanation linked to abnormalities in the hippocampus and other neural regions responsible for strategic regulation, such as the amygdala and and the frontal cortex. Some of the earliest references to research on the topic of autism and memory date back to the 1960’s and ‘70’s when several studies appeared proposing that autism should be classified as an Amnesic Disorder (Boucher & Warrington, 1976). What is now diagnosed as autism, was formerly diagnosed as Developmental Amnesia. However, this theory was counteracted by studies like that conducted by Bennetto. In comparing results of memory tasks for subjects with autism and subjects with frontal lobe lesions, he found that even though individuals with autism and those with frontal lobe lesions have similar behavior patterns, they have different memory functions. Particularly, the study revealed that the autism subjects had intact declarative memory functions that are normally impaired for individuals with amnesia, thereby showing that autism is not an amnesic disorder.

Meanwhile other theories emerged. Hughes and Russel (1993) proposed that individuals with autism experienced executive function memory impairments, explaining why planning, organizing and strategizing can be difficult for individuals on the autism spectrum. A study conducted by Renner et al. suggested that individuals with autism employ different organizational strategies during encoding and retrial from memory.

This page emphasizes declarative and non-declarative memory theories associated with autism and memory. For further information about implicit and explicit memory function for individuals with autism, see autism and working memory.

Explicit/Declarative memory and autism
Although little research has been conducted on M-LFA individuals and memory function, there is some evidence that declarative memory impairment is consistently greater for M-LFA individuals than for HFA individuals. There are definitely some similarities between M-LFA and HFA memory, but the majority of comparative studies suggest that differences between them are largely occurring within components of declarative memory.

Autobiographical memory
In 1988, Neisser defined self-concept as a set of beliefs about oneself. In 2001 Tulving emphasized that episodic memory is directly connected to the self and one's self-concept. Howe and Courage argued that autobiographical memories could not be understood or without a developed self-concept. Multiple research initiatives have used this knowledge about the self and developing self-concept to dive deeper into autobiographical memory function in ASD individuals. The data from the aforementioned researchers suggests a pattern of impaired future thinking in ASD, which diminishes self-concept development. This reduced self-concept results in a reduced self-reference effect and impaired autobiographical memory.

Other research shows that impaired psychological self-knowledge and the intact physical self-knowledge for ASD individuals also supports the hypothesis that ASD individuals have an underdeveloped self-concept. The evidence of intact physical self-awareness and knowledge has prompted further research into questions of what specifically causes the difference in self-awareness for ASD individuals. Studies on this topic have proposed that ASD subjects have difficulty encoding self-relevant information because encoding psychological autobiographical knowledge like this depends on social factors. The researchers argue that these social factors are limited for ASD individuals because of impaired social communication skills. Impaired memory binding may also play a role but more evidence is needed. Individuals with ASD are able to encode events at perceptual and objective levels, but they are unable to encode events in a subjective manner.

A 2012 study conducted by Laura Crane et al., like previous studies, suggests that adults with ASD experienced a reduction in the speed of recall of the autobiographical memory as well as the detail of memory in comparison to typical adults. However, the study results suggest that when adults with ASD were able to retrieve these memories their accounts were qualitatively similar to typical adults.

Prospective memory
The landmark study conducted by Jones et al. in 2010 is the first one to examine evidence-based prospective memory impairment for ASD individuals. The primary findings of this study provide evidence suggesting that poor social and communication skills in ASD individuals have an affect on their prospective memory function.

With these demonstrated connections between social communication skills and prospective memory, several hypotheses have arisen concerning what specific aspects of diminished social skills are influencing prospective memory impairment. Prospective memory relies heavily upon social motivation--like the desire to be socially included, insight and perception into other people’s emotions, and the ability to read social cues. Individuals with ASD are largely tuned out to these types of social motivation, which then affects their prospective memory. Difficulty reflecting upon one’s own mental state and the mental state of others, self-awareness and self-monitoring deficiencies likely also play a role in impaired prospective memory.

A recent study conducted by Altgassen et al. in 2012 also suggested that even though there are differences between individuals with ASD and typical adults when it comes to planning performance and organizational skills, there is no significant difference between individuals with ASD and typical participants when it comes to rule adherence. In fact, ASD individuals tend to follow rules very closely once they have been learned.These findings suggest that everyday organizational task rules are not always evident ASD people, and if they were targeted as rules it would be easier for them to follow. Prospective memory in autism has not been widely studied, so further research needs to be conducted in this field in order to investigate if there is supporting evidence to this claim.

Cued recall
Cued recall, research has been conducted primarily with HFA individuals, but some studies have shown common weakness on cued recall tests for both groups of HFA and M-LFA individuals. In another study, testing a HFA group and a control group of non-ASD individuals revealed that the ASD group made more intrusion errors on recall trials. This evidence also supports the hypothesis that ASD individuals may have a deficit in cued recall. Studies about temporal order memory and ASD participants also indicate that temporal order memory for verbal information is impaired in ASD individuals. However, there is also contradictory evidence for these claims. A 2001 study conducted by Mottron et al. found that ASD individuals, unlike typical individuals, do not benefit more from semantic rather than phonological cues. ASD individuals do not always conform to the Levels of Processing principle, since they benefit the same from deep and superficial recall cues.

In a recency judgment task study conducted by Gras-Vincendon et al., evidence suggested that temporal context memory is not impaired in individuals with HFA. The study proposes this is due largely because the recency judgment task involves more automatic than organizational processing. The researchers proposed that the supposedly impaired temporal order memory for verbal information found in Bennetto’s work is actually due to difficulty with general complex verbal stimuli.

Recognition
Recognition in HFA individuals has been widely studied. Overall, these studies conclude that the majority of HFA individuals have intact recognition ability. Non-social stimuli recognition is often superior, or “robustly intact”, although there is some evidence suggesting that HFA individuals have difficulty with complex scenes and color combinations. For example, HFA individuals exhibit intact recognition of non-social stimuli such as written words, spoken sentences, pictures of common objects, and meaningless patterns or shapes. For HFA individuals impaired recognition have been found in object-location and object-color recognition tests, and recognition of words encoded self-referentially. For more information regarding recognition of social stimuli for individuals with autism, see the facial recognition page.

Contrary to the plethora of HFA recognition memory studies, the study of recognition for M-LFA individuals is considerably lacking. The studies that do exist predominantly point to impaired recognition of pictures, words to name objects and other non-social stimuli. Four delayed recognition studies reported recognition impairment for M-LFA participants. Additionally, four of the seven primary studies of non-social stimuli recognition revealed significant impairment of non-social stimuli for M-LFA individuals. The other three studies were less reliable because of methodology. Boucher, Lewis and Collis gathered data supporting poor facial recognition, something widely observed for M-LFA individuals.

Implicit/Non-declarative memory
Research suggests that both HFA and M-LFA individuals show strong implicit memory function. HFA individuals display intact implicit memory for non-social stimuli, unimpaired classical conditioning and performance on other implicit learning tasks. HFA individuals displayed normal perceptual and conceptual priming. Studies concerning implicit memory in M-LFA individuals are sparse and further study is needed.

As mentioned above, there are very few reliable studies of non-declarative memory for M-LFA. However, there are some speculations. Some consider that the impaired motor skills evident in many cases of M-LFA may suggest impaired procedural learning. Other studies, including Walenski (2006) and Romero-Muguia (2008), also think that ASD behavior is indicative of implicit memory function. For example, many ASD individuals have exceptional implicit perceptual processing abilities in mathematics, the arts and in musical improvisation. Furthermore, there is speculation that because M-LFA individuals are often characterized by habit and routine, habit formation is likely unimpaired. Behavioral treatments and therapies used with M-LFA individuals are usually very helpful, suggesting that implicit knowledge can be acquired and conditioning is intact.

Further research
Across the board, it is agreed that there is an urgent need for more research concerning M-LFA memory function. Specifically, there are about half as many M-LFA studies on memory compared to HFA. It should be noted that very few studies of implicit/non-declarative memory exist and almost no brain studies. Almost all of the M-LFA studies are conducted with school-aged children, so there is a great need for a wider age range in memory studies. Very little mapping of the developmental process of ASD has happened, so there is an overall need for longitudinal studies of individuals with ASD across their lifetime. Replication and extension of prospective memory research is needed as well as further cross-sectional and comparison studies for HFA and M-LFA. Recently a specific call has been issued for the investigation of total loss of declarative memory in significantly low-functioning, nonverbal individuals with ASD.

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Course Page
 * Education Program:Davidson College/Cognitive Psychology (2013 Q1)