Memory has the ability to encode, store and recall information. Memories give an organism the capability to learn and adapt from previous experiences as well as build relationships. Encoding allows a perceived item of use or interest to be converted into a construct that can be stored within the brain and recalled later from long-term memory. Working memory stores information for immediate use or manipulation, which is aided through hooking onto previously archived items already present in the long-term memory of an individual.
History
Encoding is still relatively new and unexplored but the origins of encoding date back to age-old philosophers such as Aristotle and Plato. A major figure in the history of encoding is Hermann Ebbinghaus (1850–1909). Ebbinghaus was a pioneer in the field of memory research. Using himself as a subject he studied how we learn and forget information by repeating a list of nonsense syllables to the rhythm of a metronome until they were committed to his memory.Ebbinghaus, H. (1885). Memory: A Contribution to Experimental Psychology. These experiments led him to suggest the learning curve. He used these relatively meaningless words so that prior associations between meaningful words would not influence learning. He found that lists that allowed associations to be made and semantic meaning to be apparent were easier to recall. Ebbinghaus' results paved the way for experimental psychology in memory and other mental processes.
During the 1900s, further progress in memory research was made. Ivan Pavlov began research about classical conditioning. His research demonstrated the ability to create a semantic relationship between two unrelated items. In 1932, Frederic Bartlett proposed the idea of mental schemas. This model proposed that whether new information would be encoded was dependent on its consistency with prior knowledge (mental schemas).Bartlett, F. C. (1932). Remembering: A study in experimental and social psychology. Cambridge, England: Cambridge University Press. This model also suggested that information not present at the time of encoding would be added to memory if it was based on schematic knowledge of the world. In this way, encoding was found to be influenced by prior knowledge. With the advance of Gestalt theory came the realization that memory for encoded information was often perceived as different from the stimuli that triggered it. It was also influenced by the context in which the stimuli were embedded in.
With advances in technology, the field of neuropsychology emerged and with it a biological basis for theories of encoding. In 1949, Donald Hebb looked at the neuroscience aspect of encoding and stated that "neurons that fire together wire together," implying that encoding occurred as connections between neurons were established through repeated use. The 1950s and 60s saw a shift to the information processing approach to memory based on the invention of computers, followed by the initial suggestion that encoding was the process by which information is entered into memory. In 1956, George Armitage Miller wrote his paper on how short-term memory is limited to seven items, plus-or-minus two, called The Magical Number Seven, Plus or Minus Two. This number was appended when studies done on chunking revealed that seven, plus or minus two could also refer to seven "packets of information". In 1974, Alan Baddeley and Graham Hitch proposed their model of working memory, which consists of the central executive, visuo-spatial sketchpad, and phonological loop as a method of encoding. In 2000, Baddeley added the episodic buffer. Simultaneously Endel Tulving (1983) proposed the idea of encoding specificity whereby context was again noted as an influence on encoding.
Types There are two main approaches to analyzing how the brain encodes information: the physiological approach, and the mental approach. The physiological approach looks at how a stimulus is represented by neurons firing in the brain, while the mental approach looks at how the stimulus is represented in the mind.
There are many types of mental encoding that are used, such as visual, elaborative, organizational, acoustic, and semantic. However, this is not an extensive list.
Visual encoding Visual encoding is the process of converting images and visual sensory information to memory stored in the brain. This means that people can convert the new information that they stored into mental pictures (Harrison, C., Semin, A.,(2009). Psychology. New York p. 222) Visual sensory information is temporarily stored within our iconic memoryBaddeley, A., Eysenck, M.W., & Anderson, M.C. (2009). Memory. London: Psychology Press. p. 27, 44-59 and working memory before being encoded into permanent long-term storage.Sperling, G. (1963). A model for visual memory tasks. Human Factors, 5, 19-31.Sperling, G. (1967). Successive approximations to a model for short term memory. Acta Psychologica, 27, 285-292. Baddeley's model of working memory suggests that visual information is stored in the visuo-spatial sketchpad. The visuo-spatial sketchpad is connected to the central executive, which is a key area of working memory. The amygdala is another complex structure that has an important role in visual encoding. It accepts visual input in addition to input, from other systems, and encodes the positive or negative values of conditioned stimuli.Belova, M.A., Morrison, S.E., Paton, J.J., & Salzman, C.D. (2006). The primate amygdala represents the positive and negative value of visual stimuli during learning. Nature; 439(7078): 865-870.
Elaborative encoding
Elaborative encoding is the process of actively relating new information to knowledge that is already in memory. Memories are a combination of old and new information, so the nature of any particular memory depends as much on the old information already in our memories as it does on the new information coming in through our senses. In other words, how we remember something depends on how we think about it at the time. Many studies have shown that long-term retention is greatly enhanced by elaborative encoding.Brown and Craik (2000)
Semantic encoding Semantic encoding is the processing and encoding of sensory input that has particular meaning or can be applied to a context. Various strategies can be applied such as chunking and mnemonics to aid in encoding, and in some cases, allow deep processing, and optimizing retrieval.
Words studied in semantic or deep encoding conditions are better recalled as compared to both easy and hard groupings of nonsemantic or shallow encoding conditions with response time being the deciding variable.Demb, JB., Desmond, JE., Gabrieli, JD., Glover, GH., Vaidya, CJ., & Wagner, AD. Semantic encoding and retrieval in the left inferior prefrontal cortex: a functional MRI study of task difficulty and process specificity. The Journal of Neuroscience; 15, 5870-5878. Brodmann's areas 45, 46, and 47 (the left inferior prefrontal cortex or LIPC) showed significantly more activation during semantic encoding conditions compared to nonsemantic encoding conditions regardless of the difficulty of the nonsemantic encoding task presented. The same area showing increased activation during initial semantic encoding will also display decreasing activation with repetitive semantic encoding of the same words. This suggests the decrease in activation with repetition is process specific occurring when words are semantically reprocessed but not when they are nonsemantically reprocessed. Lesion and neuroimaging studies suggest that the orbitofrontal cortex is responsible for initial encoding and that activity in the left lateral prefrontal cortex correlates with the semantic organization of encoded information.Frey, S., & Petrides, M. (2002). Orbitofrontal cortex and memory formation. Neuron, 36(1), 171-176.
Acoustic encoding Acoustic encoding is the encoding of auditory impulses. According to Baddeley, processing of auditory information is aided by the concept of the phonological loop, which allows input within our echoic memory to be sub vocally rehearsed in order to facilitate remembering. When we hear any word, we do so by hearing individual sounds, one at a time. Hence the memory of the beginning of a new word is stored in our echoic memory until the whole sound has been perceived and recognized as a word. Studies indicate that lexical, semantic and phonological factors interact in verbal working memory. The phonological similarity effect (PSE), is modified by word concreteness. This emphasizes that verbal working memory performance cannot exclusively be attributed to phonological or acoustic representation but also includes an interaction of linguistic representation.Acheson, D.J., MacDonald, M.C., & Postle, B.R. (2010). The Interaction of Concreteness and Phonological Similarity in Verbal Working Memory. Journal of Experimental Psychogy: Learning, Memory and Cognition; 36:1, 17-36. What remains to be seen is whether linguistic representation is expressed at the time of recall or whether the representational methods used (such as recordings, videos, symbols, etc.) participate in a more fundamental role in encoding and preservation of information in memory. The brain relies primarily on acoustic (aka phonological) encoding for use in short-term storage and primarily semantic encoding for use in long-term storage.
Other senses Tactile encoding is the processing and encoding of how something feels, normally through touch. Neurons in the primary somatosensory cortex (S1) react to vibrotactile stimuli by activating in synchronization with each series of vibrations.Crawley, AP., Davis, KD., Mikulis. DJ. & Kwan, CL. (1998). Function MRI study of thalamic and cortical activation evoked by cutaneous heat, cold, and tactile stimuli. Journal of Neurophysiology: 80 (3): 1533–46 Odors and tastes may also lead to encode.
Organizational encoding is the course of classifying information permitting to the associations amid a sequence of terms.
Long-term potentiation
Encoding is a biological event that begins with perception. All perceived and striking sensations travel to the brain's thalamus where all these sensations are combined into one single experience.Mohs, Richard C. "How Human Memory Works." 8 May 2007. HowStuffWorks.com. <http://health.howstuffworks.com/human-memory.htm> 23 February 2010. The hippocampus is responsible for analyzing these inputs and ultimately deciding if they will be committed to long-term memory; these various threads of information are stored in various parts of the brain. However, the exact way in which these pieces are identified and recalled later remains unknown.