Autism and memory
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This relationship between autism and memory, specifically memory functions in relation to Autism Spectrum Disorder (ASD), has been an ongoing topic of research. ASD is a
Although memory difficulty is not part of the diagnostic criteria for autism spectrum disorder (ASD), it is a common symptom experienced by many autistic people.[2]
Overview
Some of the earliest references to the topic of autism and memory dated back to the 1960s and 1970s, when several studies appeared proposing that autism should be classified as amnesia. What is now diagnosed as autism was formerly diagnosed as developmental amnesia.[3] Although the views of autism as an amnesia of memory have now been rejected, there are still many studies done on the relationship between memory functions and autism.[4]
Long-term memory
There are two types of long-term memory; both of which have been studied in relation to autism. Declarative memory is memory that can be consciously recalled, such as facts and knowledge.[5] Declarative memory includes semantic and episodic memory. Semantic memory involves the recollection of facts, and episodic memory involves the recollection of previous experiences in life.[6] Studies on autistic people have shown impairments in their episodic memory but relative preservation of their semantic memory.[6] The brain regions that play a major role in declarative learning and memory are the hippocampus and regions of the medial temporal lobe.[6]
Long-term memory (LTM) is a complex and integral component of the human memory system, responsible for the storage and retention of information over extended periods, ranging from hours to a lifetime. It constitutes one of the three primary stages of memory, alongside sensory memory and short-term memory, and plays a pivotal role in shaping our cognitive experiences.[7]
Declarative memory and autism
Autobiographical memory
Autobiographical memory is an example of declarative memory. One aspect of autobiographical memory is the self-reference effect, which means that typically people have a stronger memory for information that is relevant to themselves.[8] It has been theorized that autistic people have diminished psychological self-knowledge but intact physical self-knowledge. As a result, these individuals show impaired autobiographical episodic memory and a reduced self-reference effect (which may each rely on psychological aspects of the self-concept), but do not show specific impairments in memory for their own rather than others' actions (which may rely on physical aspects of the self-concept).[8]
Explicit memory retrieval and recognition
Autistic people do not always conform to the
Recognition in HFA (highly functioning autistic) individuals has been widely studied. Overall, these studies conclude that the majority of HFA individuals have intact recognition abilities.
Contrary to the plethora of HFA recognition memory studies, the study of recognition for M-LFA individuals is considerably lacking.[3] 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 impairments for M-LFA participants.[3] Additionally, four of the seven primary studies of non-social stimuli recognition revealed significant impairment of non-social stimuli for M-LFA individuals.[3] The other three studies were less reliable because of their methodology.[3] Boucher, Lewis, and Collis gathered data supporting poor facial recognition, something widely observed for M-LFA individuals.[3]
Implicit/Non-declarative memory
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),
Working memory and autism
Working memory, a cognitive system with limited capacity[9] that retains and manipulates multiple pieces of transient information, has been found to be affected in individuals with ASD. Certain studies have suggested that deficits in working memory performance exist in individuals with ASD, especially when it comes to verbally mediated working memory tasks.[10][11] One reason for this impairment is due to the working memory which is a part of the executive functions (EF), an umbrella term for cognitive processes that regulate, control, and manage other cognitive processes,[12] for instance planning and attention.
A majority of the research has found that individuals with autism perform poorly on measures of
Global working memory
Beversdorf finds that autistic individuals are not as reliant on contextual information (i.e. comparing typically related schemas) to aid in memory consolidation, they are less likely to rely on semantically similar cues (ex. Doctor-Nurse vs. Doctor-Beach). Thus, an autistic individual would fare well on discriminating and recalling accurate items from false items.[17]
Bennetto, Pennington and Rogers investigated the degree of cognitive impairment in autistic individuals with an emphasis on illuminating the latency in executive functioning. Findings suggested a hindrance in temporal order, source, free recall and working memory. However, their participants did exhibit capable short and long-term memory, cued recall and the capacity to learn new material. In sum, they suggested that there is both a general deficit in global working memory and a specific impairment in social intelligence where the former is exacerbated by the latter and vice versa.[13]
Other evidence points towards unique
Central executive or executive functioning
It is believed that a dysfunction in working memory significantly influences the symptoms associated with autism spectrum disorders.
Category integration
Given these findings, it would appear that autistic individuals have trouble
The idea that autistic individuals learn differently than those without autism can account for the delay in their ability to categorize. However, once they begin categorizing they are at an average level of cognitive ability as compared to those without autism.[26] This, however, is only applicable to higher functioning individuals within the spectrum as those with lower IQ levels are notoriously difficult to test and measure.[27]
In part with a different style of learning, individuals within the spectrum have also been proposed[by whom?] to have a weak central coherence. This theory meshes well with the general traits of individuals within the spectrum. Again though, this is explained through different learning styles. As opposed to viewing a forest as a collection of trees, those with autism see one tree, and another tree, and another tree and thus it takes an immense amount of time to process complex tasks in comparison with non-autistic people.[27] Weak central coherence can be used to explain what is viewed as a working memory deficit in attention or inhibition, as autistic individuals possess an intense focus on single parts of a complex, multi-part concept and cannot inhibit this in order to withdraw focus and direct it on the whole rather than a singular aspect. Thus, this suggests that the decrement in working memory is partially inherited which is then exacerbated by further genetic complications leading to a diagnosis of autism.
Visual and spatial memory
Deficits in spatial working memory appear to be familial in people with autism, and probably even in their close relatives.[28] Replication of movements by others, a task that requires spatial awareness and memory capacities, can also be difficult for autistic children and adults.[29]
People with Asperger's Syndrome were found to have spatial working memory deficits compared with control subjects on the Executive-Golf Task, although these may be indicative of a more general deficit in non-verbal intelligence in people with ASD.[30] Despite these results, autistic children have been found to be superior to typically developing children in certain tasks, such as map learning and cued path recall regarding a navigated real-life labyrinth.[31] Steele et al. attempts to explain this discrepancy by advancing the theory that the performance of autistic people on spatial memory tasks degrades faster in the face of increasing task difficulty, when compared with normally developed individuals.[32] These results suggest that working memory is related with an individual's ability to solve problems, and that autism is a hindrance in this area.[32]
Autistic people appear to have a local bias for visual information processing, that is, a preference for processing local features (details, parts) rather than global features (the whole).[33] One explanation for this local bias is that people with autism do not have the normal global precedence when looking at objects and scenes. Alternatively, autism could bring about limitations in the complexity of information that can be manipulated in short-term visual memory during graphic planning.[33]
The difficulties that individuals with ASD often have in regards to facial recognition has prompted further questions. Some researches have shown that the fusiform gyrus in ASD individuals act differently from in non-ASD individuals which may explain the aforementioned troubles regarding facial recognition.[34]
Research by Baltruschat et al. has shown that improvement in spatial working memory for autistic individuals may be possible.[35] Adapting a behaviorist approach by using positive reinforcement could increase WM efficiency in young children with ASD.[35]
Auditory and phonological memory
The research on phonological working memory in autism is extensive and at times conflicting. Some research has found that, in comparison with spatial memory, verbal memory and inner speech use remain relatively spared,[36][37] while other studies have found limitations on the use of inner speech by autistic people.[38][39] Others have found a benefit to phonological processing in autism when compared with semantic processing,[24] and attribute the results to a similar developmental abnormality to that in savant syndrome.[40]
In particular, Whitehouse et al.[38] have found that autistic children, when compared with typically developing (TD) children of a similar mean verbal age and reading ability, performed better when asked to recall a set of pictures presented to them, but not as well when asked to recall a set of printed words presented interspersed with the pictures; a competing verbal task given to both sets of participants also worsened performance on control children more than it did on autistic children. They also reported that word length effects were greater for the control group. These results are contested by Williams, Happé, and Jarrold, who contend that it may be verbal IQ, rather than verbal ability, that is at issue, and Whitehouse et al.'s subjects were not matched on chronological age. Williams, Happé, and Jarrold[37] themselves found no difference between autistic children and controls on a serial recall task where phonological similarity effects, rather than word length effects, were used as an alternate measure of inner speech use.
Joseph et al.
Gabig et al.[40] discovered that children with autism, regarding verbal working memory and story retelling, performed worse than a control group of TD children. In three separate tasks designed to test verbal working memory, the autistic children scored well below the expected levels for their age. While results do show lower scores for autistic children, there was also information that suggested lack of vocabulary contributed to the lower scores, rather than working memory itself.[40]
There is some evidence from an fMRI study that autistic individuals are more likely to use visual cues rather than verbal cues on some working memory tasks, based on the differentially high activation of right parietal regions over left parietal regions in an N-back working memory task with letters.[41]
Opposing results
Some data has shown that individuals with ASD may not have WM impairments and that this supposed impairment observed is a result of testing. Nakahachi et al. argue that the vagueness of many tests measuring WM levels in people with ASD is the cause. They found that people with ASD only performed worse on WM tests if the test itself could have interfered with the completion of the test. These findings show that the type of test and the way it is presented to individuals with ASD can strongly affect the results, therefore much caution should be taken in choosing the design of a study focusing on WM in people with ASD.[42]
Ozonoff et al. have found similar results in their studies on working memory in individuals with ASD. Their research showed no significant difference between individuals with ASD and those without ASD in tests designed to measure various aspects of working memory.[15] This supports the notion that Autism does not inhibit WM. Results from experiments that have shown lower WM facilities in ASD individuals may be due to the human interaction nature of these experiments as individuals with ASD exhibit low social functioning skills.[15] Experiments utilizing computer rather than human interaction remove this problem and may head more accurate findings.[15]
Further research by Griffith et al. also indicates that WM may not be impaired in those with autism. There may be some executive function impairments in these individuals, but not in working memory and rather in social and language skills, which can effect education early in life.[43][44][45] Other research conducted by Griffith et al. on young autistic individuals did not measure verbal working abilities, but nonetheless found no significant difference between the executive functions in autistic and non-autistic individuals.[43] Though there has been much research that alludes to low WM abilities in those with autism, these recent data weaken the argument that autistic individuals have little WM facilities.
Working memory refers to the cognitive system responsible for temporarily holding and manipulating information needed for various cognitive tasks. It plays a crucial role in activities such as problem-solving, language comprehension, and learning. In the context of autism spectrum disorder (ASD), individuals may exhibit differences in working memory, which can impact their cognitive abilities and daily functioning.
Research suggests that working memory deficits are common among individuals with autism. These deficits can manifest in difficulties with tasks that require information to be held in mind while simultaneously processing or manipulating other information. For example, individuals with autism may struggle with following multi-step instructions, organizing thoughts, or completing tasks that involve complex sequences.
Several studies have explored the relationship between working memory and autism, shedding light on the nuances of this cognitive aspect in the autism population. One such study by Barendse et al. (2013) investigated working memory performance in children with autism compared to typically developing children. The findings indicated that children with autism exhibited impairments in both verbal and visuospatial working memory tasks.[46] [47]
Physiological underpinnings
The physical underpinnings of the cause for differences in the memory of autistic people has been studied. Bachevalier suggests a major dysfunction in the brain of an autistic individual resides in the neural mechanisms of the structures in the
Further evidence suggests that there is abnormal circuitry in what Brothers calls the neural basis for social intelligence, or holistically interpreting people's expressions and intentions.[51][52] The interaction between the amygdala, the orbitofrontal cortex (OFC), and the superior temporal sulcus and gyrus (STG) enables one to process social information for personal interaction. In the case of autistic individuals there seems to be a limitation in these structures such that facial expressions, body language and speech expressions (ex. sarcasm) go consciously unnoticed, it is theorized that this could have something to do with the sagittal stratum, which is sometimes referred to as the "sarcasm center".[53] However, Frith and Hill suggest that through 'remediation' or training that attends to specific traits in expressions, social understanding can be partially improved.[54] The possibility of training in social understanding has given hope that there is a path that can be taken to reduce the social divide that is between children with autism and children who are neurotypical.[55]
Physiological underpinnings form the biological bedrock sustaining essential functions within the human body, crucial for overall health. These intricate mechanisms encompass molecular regulation, cellular signaling, and the dynamic interplay between organ systems. Understanding these foundations offers a unique perspective, revealing how disruptions in one system impact others, influencing health outcomes.
The personalized dimension adds complexity, acknowledging genetic variations, epigenetic factors, and environmental influences. Recognizing individual diversities enables the tailoring of interventions, ushering in a new era of precision medicine.
Additionally, studying the adaptive nature of physiological processes highlights the body's resilience in maintaining internal stability amid external challenges. This exploration provides insights for interventions that enhance resilience and optimize health outcomes.
In essence, delving into physiological underpinnings is a journey into the intricate tapestry of biological mechanisms, empowering researchers and healthcare professionals to deepen their understanding, promote health, prevent diseases, and embrace the era of personalized medicine.[56]
Memory strengths
Although many people who have been diagnosed with autism have some memory difficulties, there are some who excel with memory. Some individuals with HFA have been diagnosed with Savant syndrome. Those who are considered savants have abilities, usually related to memory, that are far above average, while also experiencing mental disabilities. Savants can also excel in a range of skills other than memory, including math, art, and music.[57]
Memory strength is a multifaceted cognitive function, with individual variations in key factors that contribute to its effectiveness. Here are some distinctive memory strengths:
Effective Encoding and Retrieval: Creating robust neural connections during information processing enhances later retrieval.
Associative Memory: Strong ability to link new information with existing knowledge, forming a network of interconnected memories.
Spatial Memory: Exceptional recall and navigation skills, beneficial in fields like architecture and navigation.
Emotional Memory: Vivid recollection of emotionally charged events, contributing to richer personal memories.
Visual Memory: Strong ability to recall images and details, useful in art, design, and face recognition.
Working Memory Capacity: Processing and remembering more information simultaneously, aiding complex problem-solving.
Long-Term Memory Consolidation: Efficient transfer of information from short-term to long-term memory for lasting retention.
Multisensory Integration: Excelling in incorporating information from various sensory modalities for robust memory formation.
Adaptability and Plasticity: High neuroplasticity facilitates easier learning of new information and adaptability to change.
Metacognition: Awareness of one's cognitive processes for effective monitoring and regulation of learning and memory.
These memory strengths are diverse, and a combination of factors contributes to an individual's overall memory abilities. For further reading, refer to articles by Tulving, Schacter, Baddeley, and Squire for in-depth exploration of memory.[58] [59] [60]
Further research
Few studies of implicit/non-declarative memory exist. Almost all of the M-LFA studies were conducted with school-aged children (children from ages 3-18).[3] Recently[when?] a specific call has been issued for the investigation of total loss of declarative memory in significantly low-functioning, nonverbal autistic people.[3]
See also
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