Associative memory (psychology)

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In psychology, associative memory is defined as the ability to learn and remember the relationship between unrelated items. This would include, for example, remembering the name of someone or the aroma of a particular perfume. [1] This type of memory deals specifically with the relationship between these different objects or concepts. A normal associative memory task involves testing participants on their recall of pairs of unrelated items, such as face-name pairs. [2] Associative memory is a declarative memory structure and episodically based. [3]

Contents

Conditioning

Two important processes for learning associations, and thus forming associative memories, are operant conditioning and classical conditioning. Operant conditioning refers to a type of learning where behavior is controlled by environmental factors that influence the behavior of the subject in subsequent instances of the stimuli. In contrast, classical conditioning is when a response is conditioned to an unrelated stimulus.

Location and circuitry

The neuroanatomical structures that govern associative memory are found in the medial temporal lobe and functionally connected cortical areas. The main locations are the hippocampus and its surrounding structures of the entorhinal, perirhinal, and parahippocampal cortices. More recently, the parietal-hippocampal network has been identified as a key circuit for associative memory [4] Humans with large medial temporal lobe lesions have shown to have impairments in recognition memory for different types of stimuli. [5] The hippocampus has also shown to be the main location for memory consolidation, especially related to episodic memory. The inputs from these unrelated stimuli are collected in this location and the actual synaptic connections are made and strengthened. [6] Additionally, involvement from the prefrontal cortex, [7] [8] frontal motor areas, [9] and the striatum has been shown in the formation of associative memories. Associative memory is not considered to be localized to a single circuit, with different types of subsets of associative memory utilizing different circuitry. [7]

Biological basis

The associations made during the learning process have a biological basis that has been studied by neuroscientists for the last few decades. The convergence of the biologically important information drives the neural plasticity that is the basis of associative memory formation. [7]

Research and future work

Associative memory becomes poorer in humans as they age. Additionally, it has been shown to be non-correlational with a single item (non-associative) memory function. [10] Non-invasive brain stimulation techniques have emerged as promising tools for the improvement of associative memory. Transcranial direct-current stimulation over prefrontal cortex has improved performance on associative memory tasks, [2] but recent studies that stimulated posterior parietal cortex showed more reliable effects. [11] [12] Patients with Alzheimer's disease have been shown to be poorer in multiple forms of associative memory. [13]

Mathematical models

Starting from Hopfield’s work, [14] mathematical modeling of memory formation and retrieval has been in the center of attention. For a long time, the ability to establish the relationship between unrelated items has been considered as an emergent feature of the nonlinear dynamics of large neural networks. [15] More recent experimental discovery of the so-called concept or grandmother cells ascribes some functions in episodic memory to single neurons. [16] Mathematical modeling of grandmother cells confirms that single neurons can indeed implement associative memory. [17] The associative property emerges in large assemblies of single neurons receiving a multidimensional synaptic input from afferent populations and synaptic plasticity obey the Hebbian rule.

See also

Related Research Articles

<span class="mw-page-title-main">Entorhinal cortex</span> Area of the temporal lobe of the brain

The entorhinal cortex (EC) is an area of the brain's allocortex, located in the medial temporal lobe, whose functions include being a widespread network hub for memory, navigation, and the perception of time. The EC is the main interface between the hippocampus and neocortex. The EC-hippocampus system plays an important role in declarative (autobiographical/episodic/semantic) memories and in particular spatial memories including memory formation, memory consolidation, and memory optimization in sleep. The EC is also responsible for the pre-processing (familiarity) of the input signals in the reflex nictitating membrane response of classical trace conditioning; the association of impulses from the eye and the ear occurs in the entorhinal cortex.

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. LTM is commonly labelled as "explicit memory" (declarative), as well as "episodic memory," "semantic memory," "autobiographical memory," and "implicit memory".

<span class="mw-page-title-main">Long-term potentiation</span> Persistent strengthening of synapses based on recent patterns of activity

In neuroscience, long-term potentiation (LTP) is a persistent strengthening of synapses based on recent patterns of activity. These are patterns of synaptic activity that produce a long-lasting increase in signal transmission between two neurons. The opposite of LTP is long-term depression, which produces a long-lasting decrease in synaptic strength.

<span class="mw-page-title-main">Olfactory bulb</span> Neural structure

The olfactory bulb is a neural structure of the vertebrate forebrain involved in olfaction, the sense of smell. It sends olfactory information to be further processed in the amygdala, the orbitofrontal cortex (OFC) and the hippocampus where it plays a role in emotion, memory and learning. The bulb is divided into two distinct structures: the main olfactory bulb and the accessory olfactory bulb. The main olfactory bulb connects to the amygdala via the piriform cortex of the primary olfactory cortex and directly projects from the main olfactory bulb to specific amygdala areas. The accessory olfactory bulb resides on the dorsal-posterior region of the main olfactory bulb and forms a parallel pathway. Destruction of the olfactory bulb results in ipsilateral anosmia, while irritative lesions of the uncus can result in olfactory and gustatory hallucinations.

<span class="mw-page-title-main">Temporal lobe</span> One of the four lobes of the mammalian brain

The temporal lobe is one of the four major lobes of the cerebral cortex in the brain of mammals. The temporal lobe is located beneath the lateral fissure on both cerebral hemispheres of the mammalian brain.

<span class="mw-page-title-main">Fear conditioning</span> Behavioral paradigm in which organisms learn to predict aversive events

Pavlovian fear conditioning is a behavioral paradigm in which organisms learn to predict aversive events. It is a form of learning in which an aversive stimulus is associated with a particular neutral context or neutral stimulus, resulting in the expression of fear responses to the originally neutral stimulus or context. This can be done by pairing the neutral stimulus with an aversive stimulus. Eventually, the neutral stimulus alone can elicit the state of fear. In the vocabulary of classical conditioning, the neutral stimulus or context is the "conditional stimulus" (CS), the aversive stimulus is the "unconditional stimulus" (US), and the fear is the "conditional response" (CR).

Semantic memory refers to general world knowledge that humans have accumulated throughout their lives. This general knowledge is intertwined in experience and dependent on culture. New concepts are learned by applying knowledge learned from things in the past.

<span class="mw-page-title-main">Dopaminergic pathways</span> Projection neurons in the brain that synthesize and release dopamine

Dopaminergic pathways in the human brain are involved in both physiological and behavioral processes including movement, cognition, executive functions, reward, motivation, and neuroendocrine control. Each pathway is a set of projection neurons, consisting of individual dopaminergic neurons.

Neural coding is a neuroscience field concerned with characterising the hypothetical relationship between the stimulus and the individual or ensemble neuronal responses and the relationship among the electrical activity of the neurons in the ensemble. Based on the theory that sensory and other information is represented in the brain by networks of neurons, it is thought that neurons can encode both digital and analog information.

Repetition priming refers to improvements in a behavioural response when stimuli are repeatedly presented. The improvements can be measured in terms of accuracy or reaction time, and can occur when the repeated stimuli are either identical or similar to previous stimuli. These improvements have been shown to be cumulative, so as the number of repetitions increases the responses get continually faster up to a maximum of around seven repetitions. These improvements are also found when the repeated items are changed slightly in terms of orientation, size and position. The size of the effect is also modulated by the length of time the item is presented for and the length time between the first and subsequent presentations of the repeated items.

<span class="mw-page-title-main">Reward system</span> Group of neural structures responsible for motivation and desire

The reward system is a group of neural structures responsible for incentive salience, associative learning, and positively-valenced emotions, particularly ones involving pleasure as a core component. Reward is the attractive and motivational property of a stimulus that induces appetitive behavior, also known as approach behavior, and consummatory behavior. A rewarding stimulus has been described as "any stimulus, object, event, activity, or situation that has the potential to make us approach and consume it is by definition a reward". In operant conditioning, rewarding stimuli function as positive reinforcers; however, the converse statement also holds true: positive reinforcers are rewarding.

<span class="mw-page-title-main">Posterior parietal cortex</span>

The posterior parietal cortex plays an important role in planned movements, spatial reasoning, and attention.

The neuroanatomy of memory encompasses a wide variety of anatomical structures in the brain.

Recognition memory, a subcategory of declarative memory, is the ability to recognize previously encountered events, objects, or people. When the previously experienced event is reexperienced, this environmental content is matched to stored memory representations, eliciting matching signals. As first established by psychology experiments in the 1970s, recognition memory for pictures is quite remarkable: humans can remember thousands of images at high accuracy after seeing each only once and only for a few seconds.

<span class="mw-page-title-main">Nonsynaptic plasticity</span> Form of neuroplasticity

Nonsynaptic plasticity is a form of neuroplasticity that involves modification of ion channel function in the axon, dendrites, and cell body that results in specific changes in the integration of excitatory postsynaptic potentials and inhibitory postsynaptic potentials. Nonsynaptic plasticity is a modification of the intrinsic excitability of the neuron. It interacts with synaptic plasticity, but it is considered a separate entity from synaptic plasticity. Intrinsic modification of the electrical properties of neurons plays a role in many aspects of plasticity from homeostatic plasticity to learning and memory itself. Nonsynaptic plasticity affects synaptic integration, subthreshold propagation, spike generation, and other fundamental mechanisms of neurons at the cellular level. These individual neuronal alterations can result in changes in higher brain function, especially learning and memory. However, as an emerging field in neuroscience, much of the knowledge about nonsynaptic plasticity is uncertain and still requires further investigation to better define its role in brain function and behavior.

The lateral intraparietal cortex is found in the intraparietal sulcus of the brain. This area is most likely involved in eye movement, as electrical stimulation evokes saccades of the eyes. It is also thought to contribute to working memory associated with guiding eye movement, examined using a delayed saccade task described below:

  1. A subject focuses on a fixation point at the center of a computer screen.
  2. A target is presented at a peripheral location on the screen.
  3. The target is removed and followed by a variable-length delay period.
  4. The initial focus point in the middle of the screen is removed.
  5. The subject's task is to make a saccade to the location of the target.
<span class="mw-page-title-main">Sleep and memory</span> Relationship between sleep and memory

The relationship between sleep and memory has been studied since at least the early 19th century. Memory, the cognitive process of storing and retrieving past experiences, learning and recognition, is a product of brain plasticity, the structural changes within synapses that create associations between stimuli. Stimuli are encoded within milliseconds; however, the long-term maintenance of memories can take additional minutes, days, or even years to fully consolidate and become a stable memory that is accessible. Therefore, the formation of a specific memory occurs rapidly, but the evolution of a memory is often an ongoing process.

Malleability of intelligence describes the processes by which intelligence can increase or decrease over time and is not static. These changes may come as a result of genetics, pharmacological factors, psychological factors, behavior, or environmental conditions. Malleable intelligence may refer to changes in cognitive skills, memory, reasoning, or muscle memory related motor skills. In general, the majority of changes in human intelligence occur at either the onset of development, during the critical period, or during old age.

While the cellular and molecular mechanisms of learning and memory have long been a central focus of neuroscience, it is only in recent years that attention has turned to the epigenetic mechanisms behind the dynamic changes in gene transcription responsible for memory formation and maintenance. Epigenetic gene regulation often involves the physical marking of DNA or associated proteins to cause or allow long-lasting changes in gene activity. Epigenetic mechanisms such as DNA methylation and histone modifications have been shown to play an important role in learning and memory.

Many experiments have been done to find out how the brain interprets stimuli and how animals develop fear responses. The emotion, fear, has been hard-wired into almost every individual, due to its vital role in the survival of the individual. Researchers have found that fear is established unconsciously and that the amygdala is involved with fear conditioning.

References

  1. ↑ Suzuki, Wendy A. (February 2005). "Associative Learning and the Hippocampus". Psychological Science Agenda. American Psychological Association.
  2. 1 2 Matzen, Laura E., Michael C. Trumbo, Ryan C. Leach, and Eric D. Leshikar. "Effects of Non-invasive Brain Stimulation on Associative Memory". Brain Research 1624 (2015): 286-296.
  3. ↑ Dennis, Nancy A., Indira C. Turney, Christina E. Webb, and Amy A. Overman. "The Effects of Item Familiarity on the Neural Correlates of Successful Associative Memory Encoding". Cognitive, Affective, & Behavioral Neuroscience 15.4 (2015): 889-900.
  4. ↑ Wagner AD, Shannon BJ, Kahn I, Buckner RL. "Parietal lobe contributions to episodic memory retrieval". Trends in Cognitive Sciences 9.9 (2005): 445-53.
  5. ↑ Ranganath, Charan, and Maureen Ritchey. "Two Cortical Systems for Memory-guided Behaviour". Nature Reviews Neuroscience 13.10 (2012): 713-26.
  6. ↑ Cohen, Neal J., Jennifer Ryan, Caroline Hunt, Lorene Romine, Tracey Wszalek, and Courtney Nash. "Hippocampal System and Declarative (relational) Memory: Summarizing the Data from Functional Neuroimaging Studies". Hippocampus 9.1 (1999): 83-98.
  7. 1 2 3 Fanselow, Michael S.; Poulos, Andrew M (2004-08-30). "The Neuroscience of Mammalian Associative Learning". Annual Review of Psychology . 56 (1): 207–234. doi:10.1146/annurev.psych.56.091103.070213. ISSN   0066-4308. PMID   15709934.
  8. ↑ Becker, Nina, Erika J. Laukka, Grégoria Kalpouzos, Moshe Naveh-Benjamin, Lars Bäckman, and Yvonne Brehmer. "Structural Brain Correlates of Associative Memory in Older Adults". NeuroImage 118 (2015): 146-53.
  9. ↑ Brasted P. J., Bussey TJ, Murray EA, Wise SP (2002). "Fornix transection impairs conditional visuomotor learning in tasks involving nonspatially differentiated responses". Journal of Neurophysiology 87: 631-633.
  10. ↑ Becker, Nina, Erika J. Laukka, Grégoria Kalpouzos, Moshe Naveh-Benjamin, Lars Bäckman, and Yvonne Brehmer. "Structural Brain Correlates of Associative Memory in Older Adults". NeuroImage 118 (2015): 146-153.
  11. ↑ Bjekić, J., Vulić, K., Živanović, M., Vujičić, J., Ljubisavljević, M., & Filipović, S. R. "The immediate and delayed effects of single tDCS session over posterior parietal cortex on face-word associative memory. Behavioural brain research, 2019 366: 88-95."
  12. ↑ Bjekić, J., Čolić, M. V., Živanović, M., Milanović, S. D., & Filipović, S. R. "Transcranial direct current stimulation (tDCS) over parietal cortex improves associative memory."Neurobiology of Learning and Memory, 2019, 157: 114-120.
  13. ↑ Bastin, Christine, Mohamed Ali Bahri, Frédéric Miévis, Christian Lemaire, Fabienne Collette, Sarah Genon, Jessica Simon, Bénédicte Guillaume, Rachel A. Diana, Andrew P. Yonelinas, and Eric Salmon. "Associative Memory and Its Cerebral Correlates in Alzheimer's Disease: Evidence for Distinct Deficits of Relational and Conjunctive Memory". Neuropsychologia 63 (2014): 99-106.
  14. ↑ Hopfield J.J. Neural networks and physical systems with emergent collective computational abilities. Proc Natl Acad Sci USA 79, 2554-2558 (1982)
  15. ↑ Gurney K. An introduction to neural networks, Taylor & Francis, London, New York, 2014.
  16. ↑ Quian Quiroga R. Concept cells: the building blocks of declarative memory functions. Nat Rev Neurosci 13, 587 (2012).
  17. ↑ Gorban, Alexander N.; Makarov, Valeri A.; Tyukin, Ivan Y. (July 2019). "The unreasonable effectiveness of small neural ensembles in high-dimensional brain". Physics of Life Reviews. 29: 55–88. arXiv: 1809.07656 . Bibcode:2019PhLRv..29...55G. doi: 10.1016/j.plrev.2018.09.005 . PMID   30366739.
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