Spatial Memory

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Spatial Memory

Post by Cr6 on Thu Dec 25, 2014 11:56 pm

Short-term spatial memory

Short-term memory (STM) can be described as a system allowing one to temporarily store and manage information that is necessary to complete complex cognitive tasks.[1] Tasks which employ short-term memory include learning, reasoning, and comprehension.[1] Spatial memory is a cognitive process that enables a person to remember different locations as well as spatial relations between objects.[1] This allows one to remember where an object is in relation to another object;[1] for instance, allowing someone to navigate through a familiar city. Spatial memories are said to form after a person has already gathered and processed sensory information about her or his environment.[1]

Spatial working memory

Working memory (WM) can be described as a limited capacity system that allows one to temporarily store and process information.[2] This temporary store enables one to complete or work on complex tasks while being able to keep information in mind.[2] For instance, the ability to work on a complicated mathematical problem utilizes one's working memory.

One highly influential theory of WM is the Baddeley and Hitch multi-component model of working memory.[2][3] The most recent version of this model suggests that there are four subcomponents to WM, namely the phonological loop; the visuo-spatial sketchpad; the central executive; and the episodic buffer.[2] One component of this model, the visuo-spatial sketchpad, is said to be responsible for the temporary storage, maintenance, and manipulation of both visual and spatial information.[2][3]

Baddeley and Hitch's multi-component model of working memory.

In contrast to the multi-component model, some researchers believe that STM should be viewed as a unitary construct.[3] In this respect, visual, spatial, and verbal information are thought to be organized by levels of representation rather than the type of store to which they belong.[3] Within the literature, it is suggested that further research into the fractionation of STM and WM be explored.[3][4] However, much of the research into the visuo-spatial memory construct have been conducted in accordance to the paradigm advanced by Baddeley and Hitch.[2][3][4][5][6]

The role of the central executive

Research into the exact function of the visuo-spatial sketchpad has indicated that both spatial short-term memory and working memory are dependent on executive resources and are not entirely distinct.[2] For instance, performance on a working memory but not on a short-term memory task was affected by articulatory suppression suggesting that impairment on the spatial task was caused by the concurrent performance on a task that had extensive use of executive resources.[2] Results have also found that performances were impaired on STM and WM tasks with executive suppression.[2] This illustrates how, within the visuo-spatial domain, both STM and WM require similar utility of the central executive.[2]

Additionally, during a spatial visualisation task (which is related to executive functioning and not STM or WM) concurrent executive suppression impaired performance indicating that the effects were due to common demands on the central executive and not short-term storage.[2] The researchers concluded with the explanation that the central executive employs cognitive strategies enabling participants to both encode and maintain mental representations during short-term memory tasks.[2]

Although studies suggest that the central executive is intimately involved in a number of spatial tasks, the exact way in which they are connected remains to be seen.[7]

Long-term spatial memory

Spatial memory recall is built upon a hierarchical structure. That is to say that people remember the general layout of a particular space and then "cue target locations" located within that spatial set.[8] This paradigm includes an ordinal scale of features that an individual must attend to in order to inform his or her cognitive map.[9] Recollection of spatial details is a top-down procedure that requires an individual to recall the superordinate features of a cognitive map, followed by the ordinate and subordinate features. Thus, two spatial features are prominent in navigating a path: general layout and landmark orienting (Kahana et al., 2006).

People are not only capable of learning about the spatial layout of their surroundings, but they can also piece together novel routes and new spatial relations through inference. Yet, this field has traditionally been hampered by confounding variables, such as cost and the potential for previous exposure to an experimental environment. Thankfully, technological leaps have opened a new, albeit virtual, world to psychologists.

A cognitive map is "a mental model of objects’ spatial configuration that permits navigation along optimal path between arbitrary pairs of points."[10] This mental map is built upon two fundamental bedrocks: layout, also known as route knowledge, and landmark orientation. Layout is potentially the first method of navigation that people learn to utilize; it’s workings reflect our most basic understandings of the world.

Hermer and Spelke (1994) determined that when toddlers begin to crawl, around eighteen months, they navigate by their sense of the world’s layout. Indeed, it would seem that a sojourning toddler’s world is a place of axial lines and contrasting boundaries. McNamara, Hardy and Hirtle identified region membership as a major building block of anyone’s cognitive map (1989). Specifically, region membership is defined by any kind of boundary, whether physical, perceptual or subjective (McNamara et al, 1989). Boundaries are among the most basic and endemic qualities in the world around us. These boundaries are nothing more than axial lines which are a feature that people are biased towards when relating to space; for example one axial line determinant is gravity (McNamara & Shelton, 2001; Kim & Penn, 2004). Axial lines aid everyone in apportioning our perceptions into regions. This parceled world idea is further supported items by the finding that items that get recalled together are more likely than not to also be clustered within the same region of one’s larger cognitive map.[9] Clustering shows that people tend to chunk information together according to smaller layouts within a larger cognitive map.

Boundaries, though, are not the only determinants of layout. Clustering also demonstrates another important property of our relation to spatial conceptions. This is that spatial recall is a hierarchical process. When someone recalls an environment or navigates terrain, that person implicitly recalls the overall layout at first. Then, due to the concept’s "rich correlational structure," a series of associations become activated .[8] Eventually the resulting cascade of activations will awaken the particular details that correspond with the region being recalled. This is how people encode many entities from varying ontological levels, such as the location of a stapler; in a desk; which is in the office .. Alas, layout has its flaws too. One can recall from only one at region at a time (a bottleneck).

A bottleneck in a person's cognitive navigational system could be disastrous, for instance if there were need for a sudden detour on a long road trip. And yet, people are still capable of getting place to place functionally. Lack of experience in a locale, or simply sheer size, can disorient one’s mental layout, especially in a large and unfamiliar place with lots of overwhelming stimuli. In these environments people are still able to orient themselves, and even find their way around using landmarks. This ability to "prioritize objects and regions in complex scenes for selection (and) recognition" was labeled by Chun and Jiang in 1998. Landmarks give people guidance by activating "learned associations between the global context and target locations."[8] Mallot and Gillner (2000) showed that subjects learned an association between a specific landmark and the direction of a turn, thereby furthering the relationship between associations and landmarks.[11] Shelton and McNamara (2001) succinctly summed up why landmarks, as markers, are so helpful: "location...cannot be described without making reference to the orientation of the observer."

It is fairly clear that people use both the layout of a particular space, as well as the presence of orienting landmarks in order to navigate. Yet, psychologists have yet to explain whether layout affects landmarks or if landmarks determine the boundaries of a layout. Thus, this concept suffers from a chicken and the egg paradox. In fact, McNamara has found that subjects use "clusters of landmarks as intrinsic frames of reference," which only confuses the issue further.[10]
People perceive objects in their environment relative to other objects in that same environment. In other words, landmarks and layout are complimentary systems for spatial recall. However, it is unknown how these two systems interact when both types of information are available. Thus, we have to make certain assumptions about the interaction between these two systems. For example, cognitive maps are not "absolute" but rather, as anyone can attest, are "used to provide a default...(which) modulated according to...task demands."[8] Psychologists also think that cognitive maps are instance based, which accounts for "discriminative matching to past experience."[8]

These assumptions could soon be validated. Advances in virtual reality technology have pried open the door to this enigmatic field. Now experimenters find themselves creating scenarios that were impossible to imagine fifteen years ago. Virtual reality affords experimenters the luxury of extreme control over their test environment. Any variable can be manipulated, including things that would not be possible in reality.


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