Spatial Memory

"Spatial memory"

In cognitive psychology and neuroscience, spatial memory is the part of memory responsible for recording information about one's environment and spatial orientation. For example, a person's spatial memory is required in order to navigate around a familiar city, just as a rat's spatial memory is needed to learn the location of food at the end of a maze. Spatial memory has representations within working, short-term memory and long-term memory. Research indicates that there are specific areas of the brain associated with spatial memory. Many methods are used for measuring spatial memory in children, adults, and animals.

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 tasks.^[1]Tasks which employ short-term memory include learning, reasoning, and comprehension.^[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.

Long-term spatial memory:

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.

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.

Hippocampus:

The hippocampus provides animals with a spatial map of their environment.^[22] It stores information regarding non-egocentric space (egocentric means in reference to one's body position in space) and therefore supports viewpoint independence in spatial memory.^[23] This means that it allows for viewpoint manipulation from memory. It is however, important for long-term spatial memory of allocentric space (reference to external cues in space).^[24] Maintenance and retrieval of memories are thus relational or context dependent.^[25] The hippocampus makes use of reference and working memory and has the important role of processing information about spatial locations.^[26]

Blocking plasticity in this region results in problems in goal-directed navigation and impairs the ability to remember precise locations.^[27]Amnesic patients with damage to the hippocampus cannot learn or remember spatial layouts and patients having undergone hippocampal removal are severely impaired in spatial navigation.^[23][28] Monkeys with lesions to this area cannot learn object-place associations and rats also display spatial deficits by not reacting to spatial change.^[23][29] In addition, rats with hippocampal lesions were shown to have temporally ungraded (time-independent) retrograde amnesia that is resistant to recognition of a learned platform task only when the entire hippocampus is lesioned, but not when it is partially lesioned.^[30] Deficits in spatial memory are also found in spatial discrimination tasks.^[28]

Brain slice showing areas CA1 and CA3 in the hippocampus

Large differences in spatial impairment are found among the dorsal and ventral hippocampus. Lesions to the ventral hippocampus have no effect on spatial memory, while the dorsal hippocampus is required for retrieval, processing short-term memory and transferring memory from the short term to longer delay periods.^[31][32][33] Infusion of amphetamine into the dorsal hippocampus has also been shown to enhance memory for spatial locations learned previously.^[34] These findings indicate that there is a functional dissociation between the dorsal and ventral hippocampus.

The hippocampus is known to contain two separate memory circuits. One circuit is used for recollection-based place recognition memory and includes the entorhinal-CA1 system,^[36] while the other system, consisting of the hippocampus trisynaptic loop (entohinal-dentate-CA3-CA1) is used for place recall memory^[37] and facilitation of plasticity at the entorhinal-dentate synapse in mice is sufficient to enhance place recall.^[38]

Place cells are also found in the hippocampus.

References:

1.       ^ Jump up to:^{a b c d e} Johnson, E.; Adamo-Villani, N. (2010). "A Study of the Effects of Immersion on Short-term Spatial Memory". Engineering and Technology. 71: 582–587.

2.       ^ Jump up to:^{a b c d e f g h i j k l} Ang, S. Y.; Lee, K. (2008). "Central executive involvement in children's spatial memory". Memory. 16 (8): 918–933. doi:10.1080/09658210802365347. PMID 18802804.

3.       ^ Jump up to:^{a b c d e f} Jones, D.; Farrand, P.; Stuart, G.; Morris, N.; et al. (1995). "Functional equivalence of verbal and spatial information in serial short-term memory". Journal of Experimental Psychology: Learning, Memory, and Cognition. 21 (4): 1008–1018. doi:10.1037/0278-7393.21.4.1008.

4.       ^ Jump up to:^{a b c d e} Della Sala, S.; Gray, C.; Baddeley, A.; Allamano, N.; Wilson, L.; et al. (1999). "Pattern span: a tool for unwelding visuo-spatial memory". Neuropsychologia. 37 (10): 1189–1199. doi:10.1016/S0028-3932(98)00159-6. PMID 10509840.

5.       ^ Jump up to:^{a b c d e} Mammarella, I. C.; Pazzaglia, F.; Cornoldi, C.; et al. (2008). "Evidence for different components in children's visuospatial working memory". British Journal of Developmental Psychology. 26 (3): 337–355. doi:10.1348/026151007X236061.