Intermediate-term memory (ITM) is a stage of

memory Memory is the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If past events could not be remembered, ...

distinct from

sensory memory During every moment of an organism's life, sensory information is being taken in by sensory receptors and processed by the nervous system. Sensory information is stored in sensory memory just long enough to be transferred to short-term memory. Hum ...

working memory Working memory is a cognitive system with a limited capacity that can hold information temporarily. It is important for reasoning and the guidance of decision-making and behavior. Working memory is often used synonymously with short-term memory, ...

short-term memory Short-term memory (or "primary" or "active memory") is the capacity for holding a small amount of information in an active, readily available state for a short interval. For example, short-term memory holds a phone number that has just been recit ...

, and

long-term memory Long-term memory (LTM) is the stage of the Atkinson–Shiffrin memory model in which informative knowledge is held indefinitely. It is defined in contrast to short-term and working memory, which persist for only about 18 to 30 seconds. Long-t ...

. While sensory memory persists for several milliseconds, working memory persists for up to thirty seconds, and long-term memory persists from thirty minutes to the end of an individual's life, intermediate-term memory persists for about two to three hours. This overlap in the durations of these memory processes indicates that they occur simultaneously, rather than sequentially. Indeed, intermediate-term facilitation can be produced in the absence of long-term facilitation. However, the boundaries between these forms of memory are not clear-cut, and they can vary depending on the task. Intermediate-term memory is thought to be supported by the

parahippocampal cortex The parahippocampal gyrus (or hippocampal gyrus') is a grey matter cortical region of the brain that surrounds the hippocampus and is part of the limbic system. The region plays an important role in memory encoding and retrieval. It has been inv ...

. In 1993, Rosenzweig and colleagues demonstrated that, in chicks conditioned with an aversive stimulus, percent avoidance of the stimulus (and, by implication, memory of the aversive nature of the stimulus) reached relative minima at one minute, fifteen minutes, and sixty minutes. These dips were theorized to correspond to the time points in which the chicks switched from working memory to intermediate-term memory, from intermediate-term memory to the early phase of long-term memory, and from the early phase of long-term memory to the late phase of long-term memory, respectively—thus demonstrating the presence of a form of memory that exists between working memory and long-term memory, which they referred to as "intermediate-term memory". Though the idea of intermediate-term memory has existed since the 1990s, Sutton ''et al.'' introduced a novel theory for the neural correlates underlying intermediate-term memory in ''

Aplysia ''Aplysia'' () is a genus of medium-sized to extremely large sea slugs, specifically sea hares, which are one clade of large sea slugs, marine gastropod mollusks. These benthic herbivorous creatures can become rather large compared with most ...

'' in 2001, where they described it as the primary behavioral manifestation of intermediate-term facilitation.

Characteristics

In 2001, Sutton and colleagues proposed that intermediate-term memory possesses the following 3 characteristics: * Its induction requires

translation Translation is the communication of the Meaning (linguistic), meaning of a #Source and target languages, source-language text by means of an Dynamic and formal equivalence, equivalent #Source and target languages, target-language text. The ...

, but ''not''

transcription Transcription refers to the process of converting sounds (voice, music etc.) into letters or musical notes, or producing a copy of something in another medium, including: Genetics * Transcription (biology), the copying of DNA into RNA, the fir ...

* Its expression requires the persistent activation of

protein kinase A In cell biology, protein kinase A (PKA) is a family of enzymes whose activity is dependent on cellular levels of cyclic AMP (cAMP). PKA is also known as cAMP-dependent protein kinase (). PKA has several functions in the cell, including regulatio ...

and

protein kinase C In cell biology, Protein kinase C, commonly abbreviated to PKC (EC 2.7.11.13), is a family of protein kinase enzymes that are involved in controlling the function of other proteins through the phosphorylation of hydroxyl groups of serine and t ...

* It declines completely before the onset of long-term memory

Mechanism

Induction

Because intermediate-term memory does not involve transcription, it likely involves the translation of mRNA transcripts already present in neurons.

Comparison with short-term/working memory

Unlike short-term memory and working memory, intermediate-term memory requires changes in translation to occur in order to function.

Comparison with long-term memory

While ITM requires only changes in translation, induction of long-term memory requires changes in transcription as well. The change from short-term memory to long-term memory is thought to dependent on

CREB CREB-TF (CREB, cAMP response element-binding protein) is a cellular transcription factor. It binds to certain DNA sequences called cAMP response elements (CRE), thereby increasing or decreasing the transcription of the genes. CREB was first des ...

, which regulates transcription, but because ITM does not involve a change in transcription, it is thought to be independent of CREB activity. According to the definition of ITM proposed by Sutton ''et al.'' in 2001, it disappears completely before long-term memory is induced.

References

{{Memory Memory