4 Types of Memory

The 3-stage (or multi-store) model of memory is a traditional yet prevailing model of memory. Yet, it should be noted that it is also a model that is still under development by cognitive (neuro)scientists. In the model, there are three types of memory: (1) Sensory memory, (2) Short-term (working) memory (STM), (3) Long-term memory (LTM).

 

Figure 4.1. 3-stage or multi-store model of memory (source: Wikipedia)

Sensory Memory

Sensory memory is an automatic process related to perception. “Sensory memory refers to the automatic, transient storage of the sensory features of incoming stimuli for subsequent integration with previously presented stimuli and or recalled information” (Alain, Woods & Knight, 1998). Our senses are constantly collecting information from our environment. This information is always available to us. When we move our attention (focus) or our attention is pulled to one of the senses, then we become consciously aware of that information. This awareness signals that sensory information has moved into our working memory (which is part of STM). At any time we can move our attention to any one of our senses to check the incoming information. Short-term memory (STM) “reflect faculties of the human mind that can hold a limited amount of information in a very accessible state temporarily” (Cowan, 2008).

Figure 4.2. We collect information from our senses and encode it in short-term memory.

Working Memory

Working memory “is short-term maintenance of information in the absence of sensory input” (Eriksson, Vogel, Lansner, Bergström & Nyberg, 2015). “Working memory includes short-term memory and other processing mechanisms that help to make use of short-term memory” (Cowan, 2008). In other words, working memory is a part of short-term memory and refers to the information held in STM that we are actively keeping and manipulating.

Figure 4.3. A depiction of working memory

Long-term Memory

Long-term memory (LTM) is “a vast store of knowledge and a record of prior events” (Cowan, 2008). “Long- and short-term memory could differ in two fundamental ways, with only short-term memory demonstrating (1) temporal decay and (2) chunk capacity limits.” (Cowan, 2008). In other words, LTM does not decay as quickly as STM nor is there a clear limit to how much information can be stored in LTM (see Table 1 for a comparison of STM and LTM characteristics).

Figure 4.4. A depiction of long-term memory

How do we know short-term and long-term memory are distinct? Scientists can selectively block long-term or short-term memory formation without affecting the other (Cammarota, M., Bevilaqua, Medina & Izquierdo, 2007). For example, by blocking the receptors for neurotransmitters, STM can be disrupted but LTM are still updated. Also, by interfering with protein synthesis, STM can form but LTM are not created or updated. The distinction in types of memory is also evidenced by the different types of amnesia (Squire et al., 2015). “Anterograde amnesia is a loss of the ability to create new memories after the event that caused amnesia, leading to a partial or complete inability to recall the recent past, while long-term memories from before the event remain intact. This is in contrast to retrograde amnesia, where memories created prior to the event are lost while new memories can still be created” (“Anterograde amnesia,” n.d.).

Table 1. Short-term memory and Long-term memory characteristics
Short-term (working) memory (STM) characteristics (Kukushkin & Carew, 2017; Eriksson et al., 2015; Kandel, Dudai, & Mayford, 2014)

  • Duration: 10-15 s unless rehearsed
  • Capacity: 4 units or chunks of information
  • Formation (the speed in which they form): fast (milliseconds)
  • Region: prefrontal cortext – hippocampus
  • Mechanism: neurotransmitters
Long-term memory (LTM) characteristics (Kukushkin & Carew, 2017; Eriksson et al., 2015; Kandel, Dudai, & Mayford, 2014)

  • Duration: from minutes to a lifetime
  • Capacity: no known limit
  • Formation (the speed in which they form): slow (minutes to days)
  • Region: neocortex (distributed across the neocortex)
  • Mechanism: new protein synthesis, gene expression

The Purpose of STM and LTM

Why does our brain have distinct short-term and long-term memory systems? STM and LTM serve different purposes in our survival system (Fuster & Bressler, 2015). Short-term memory enables us to rapidly adapt to novel experiences. As we live in a dynamic and uncertain environment and regularly encounter novel information this is a critical ability. On the other hand, long-term memory enables us to effectively preadapt to future experiences. “The biological utility of memory stems from its ability to modify future behavior based on past experience” (Kukushkin & Carew, 2017). We can identify patterns in our environment and improve the efficiency and effectiveness of our reactions (Schacter, Addis & Buckner, 2007)

References

Sensory Memory
  • Alain, C., Woods, D. L., & Knight, R. T. (1998). A distributed cortical network for auditory sensory memory in humans. Brain research, 812(1-2), 23-37.
  • Cowan, N. (2008). What are the differences between long-term, short-term, and working memory?. Progress in brain research, 169, 323-338.
Working Memory
  • Eriksson, J., Vogel, E. K., Lansner, A., Bergström, F., & Nyberg, L. (2015). Neurocognitive architecture of working memory. Neuron, 88(1), 33-46.
  • Cowan, N. (2008). What are the differences between long-term, short-term, and working memory?. Progress in brain research, 169, 323-338.
Long-term Memory
  • Cowan, N. (2008). What are the differences between long-term, short-term, and working memory?. Progress in brain research, 169, 323-338.
  • Cammarota, M., Bevilaqua, L. R., Medina, J. H., & Izquierdo, I. (2007). 10 Studies of Short-Term Avoidance Memory. Neural plasticity and memory: from genes to brain imaging, 193.
  • Squire, L. R., Genzel, L., Wixted, J. T., & Morris, R. G. (2015). Memory consolidation. Cold Spring Harbor perspectives in biology, 7(8), a021766.
  • Anterograde amnesia. (n.d.). In Wikipedia. Retrieved May 15, 2020, from https://en.wikipedia.org/wiki/Anterograde_amnesia)
  • Hunkin, N., Parkin, A., Bradley, V., Burrows, E., Aldrich, F., Jansari, A., & Burdon-Cooper, C. (1995) Focal retrograde amnesia following closed head injury: A case study and theoretical account, Neuropsychologia, 33(4) 509-523. doi:10.1016/0028-3932(94)00136-D
The Purpose of STM and LTM
  • Kukushkin, N. V., & Carew, T. J. (2017). Memory Takes Time. Neuron, 95(2), 259-279.
  • Eriksson, J., Vogel, E. K., Lansner, A., Bergström, F., & Nyberg, L. (2015). Neurocognitive architecture of working memory. Neuron, 88(1), 33-46.
  • Kandel, E. R., Dudai, Y., & Mayford, M. R. (2014). The molecular and systems biology of memory. Cell, 157(1), 163-186.
  • Fuster, J. M., & Bressler, S. L. (2015). Past makes future: role of pFC in prediction. Journal of cognitive neuroscience, 27(4), 639-654.
  • Fuster, J. M. (2009). Cortex and memory: emergence of a new paradigm. Journal of cognitive neuroscience, 21(11), 2047-2072.
  • Schacter, D. L., Addis, D. R., & Buckner, R. L. (2007). Remembering the past to imagine the future: the prospective brain. Nature reviews neuroscience, 8(9), 657-661.

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