Memory traces and autism

The ability to multitask is of great importance in present day society. Our environment bombards each of us with important cues and signals from both the external and internal world. Nature has found it adaptive to constantly store this information and to process the same for its potential importance. If the information is deemed important it will then generate a memory trace enabling the same to be pulled back again to our conscious or attentive selves in order to make comparisons and thus enable us to take appropriate actions. This is an important executive ability born, in part, from our need to shift our focus of attention. It may be that focusing intently our attention overloads our processing systems and that for the most part our central nervous system can best handle information coming from one sensory channel at a time.

Sensory memory is very short-term memory that allows us to recall things that were said or happened but to which we had not initially paid attention. Think of it as a memory buffer that holds information in it and compensates for our inability to think about more than one thing at the same time. In essence it provides a time delay or replay option for prior events much like a VCR or DVR allows us to replay scenes from a movie. In electronics this reminds me of the recording ability of an oscilloscope and its ability to portray information before a triggered event. Electronic engineers have enabled such a feature because sometimes the events leading to, for example, a glitch may help elucidate the cause of the same.

sensory-memory

Sensory memory allows us to pay attention to one sensory modality and then to examine what went along with it in another sensory modality (e.g., visual with auditory), thus combining the same and giving us a complete and detailed representation of an event. Without this ability we would be distracted by all of life’s stimuli and our ability to encode information into long-term memory would be impaired. In effect, a defect in sensory memory would make us live our life short-changed of deeply processed information.

working-memory-two-processes

If the sensory memory of an individual was affected there would be a recognizable cascading series of abnormalities or symptoms. To start with, our visual recall or iconic memory would be altered. Iconic memory helps us keep our visual interpretation of the world intact and seemless (note: echoic memory would be something similar but for auditory memory). Iconic memory allows for the integration of parts into a whole and therefore it is related to both working memory and the binding phenomenon, i.e., the ability to piece together different aspects of a sensory phenomenon into a cognitive whole, see http://bit.ly/1pkw1SA. Sparse sampling of a phenomenon could cause different signals to become indistinguishable (aliases of each other, or an “aliasing effect”). There could be difficulties in categorization, that is, in how objects in our world are differentiated and understood, e.g., why are a Chihuahua and Dalmatian classed together as dogs? Attempts at overcoming difficulties in sensory memory could entail mindless automatic repetitions of events in the form of echolalia (repetition of vocalizations). In addition, defective or inadequate information when displayed in the sketchpad of our working memory would limit the capacity to bring into focus different constructs in order to take a decision or solve a problem. Sensory memory problems could therefore be manifested as abnormalities of theory of mind.

Although we all share in this inability to simultaneously absorb all sensory aspects of an experience, it may be more evident in some individuals and under certain circumstances. Have you ever had the experience of zoning-out while watching TV and not paying attention to the surrounding environment? This natural phenomenon is exaggerated in autistic individuals. Unfortunately many of the tests used when screening for iconic memory necessitate the cooperation of high functioning individuals. In this regard results from a small preliminary study testing iconic memory in autistic individuals was understandably negative (McMorris et al., Autism Dev Dis 43(8):1956-66, 2013). More research into this area is needed.

Sometime in 2005 Dinah Murray wrote an article describing the phenomenon of “monotropism” in autism. The article was co-written by our good friend Wen Lawson. Monotropism was meant to underline the restricted range of interests in autism, but more importantly, the fact that they could only pay attention to whatever was on their attention tunnel. In a previous blog Wen stated, “I suggest that an individual with an autism spectrum condition (ASC) fails to note what might be said to them because their ‘attention system’ which needs to include ‘interest’ to be triggered sufficiently, may be off line. Then, even if their ‘attention’ and ‘interest’ are triggered, they will still process the information slowly, piece by piece due to their information processing being single channeled. With us, it’s one thing at a time and our ‘interest’ system needs to be on board. If not, we can be overwhelmed with too much information (noise) and we either switch off or close down. Using our ‘interest’ (passion) to build a connection to understanding is a better way to go. This allows us to feel valued as well as give us an opportunity to notice (see http://bit.ly/1G4cvg7 )”. Although somewhat similar to the defects of sensory memory previously quoted, the two theories are clearly different.

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