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==History==
The difference between procedural and [[declarative memory]] systems were first explored and understood with simple [[semantics]].
Psychologists and [[philosophers]] began writing about memory over two centuries ago. "Mechanical memory" was first noted in 1804 by [[Maine de Biran]]. [[William James]], within his famous book: ''[[The Principles of Psychology]]'' (1890), suggested that there was a difference between memory and habit. [[Cognitive psychology]] disregarded the influence of learning on memory systems in its early years, and this greatly limited the research conducted in procedural learning up until the 20th century.<ref>{{cite journal | last1 = Bullemer | first1 = P. | last2 = Nissen | first2 = MJ. | last3 = Willingham | first3 = D.B. | year = 1989 | title = On the Development of Procedural Knowledge | url = | journal = Journal of Experimental Psychology: Learning, Memory, and Cognition | volume = 15 | issue = 6| pages = 1047–1060 | doi=10.1037/0278-7393.15.6.1047| pmid = 2530305 }}</ref> The turn of the century brought a clearer understanding of the functions and structures involved in procedural memory acquisition, storage, and retrieval processes.
McDougall{{who|date=November 2018}} (1923) first made the distinction between [[explicit memory|explicit]] and implicit memory. In the 1970s procedural and declarative knowledge was distinguished in literature on [[artificial intelligence]]. Studies in the 1970s divided and moved towards two areas of work: one focusing on animal studies and the other to amnesic patients. The first convincing experimental evidence for a dissociation between [[declarative memory]] ("knowing what") and non-declarative or procedural ("knowing how") memory was from Milner (1962), by demonstrating that a severely amnesic patient, [[Henry Molaison]], formerly known as patient H.M., could learn a hand–eye coordination skill (mirror drawing) in the absence of any memory of having practiced the task before. Although this finding indicated that memory was not made up of a single system positioned in one place in the brain, at the time, others agreed that motor skills are likely a special case that represented a less cognitive form of memory. However, by refining and improving experimental measures, there has been extensive research using amnesic patients with varying locations and degrees of structural damage. Increased work with amnesic patients led to the finding that they were able to retain and learn tasks other than motor skills. However, these findings had shortcomings in how they were perceived as amnesic patients sometimes fell short on normal levels of performance and therefore [[amnesia]] was viewed as strictly a retrieval deficit. Further studies with amnesic patients found a larger ___domain of normally functioning memory for skill abilities. For example, using a mirror reading task, amnesic patients showed performance at a normal rate, even though they are unable to remember some of the words that they were reading. In the 1980s much was discovered about the anatomy physiology of the mechanisms involved in procedural memory. The [[cerebellum]], [[hippocampus]], [[neostriatum]], and [[basal ganglia]] were identified as being involved in memory acquisition tasks.<ref>{{cite journal | last1 = Squire | first1 = L.R. | year = 2004 | title = Memory systems of the brain: A brief history and current perspective | url = | journal = Neurobiology of Learning and Memory | volume = 82 | issue = 3| pages = 171–177 | doi=10.1016/j.nlm.2004.06.005| pmid = 15464402 | citeseerx = 10.1.1.319.8326 | s2cid = 9008932 }}</ref>
== Working memory ==
=== Practice and the power law of learning ===
[[Practice (learning method)|Practice]] can be an effective way to learn new skills if knowledge of the result, more commonly known as [[Corrective feedback|feedback]], is involved.<ref>{{Cite book|title=How People Learn: Brain, Mind, Experience, and School: Expanded Edition|last=Council|first=National Research|date=1999-08-23|isbn=9780309070362|___location=|pages=177|language=en|doi=10.17226/9853}}</ref><ref>{{Cite book|title=Learning and memory : from brain to behavior|last1=Eduardo.|first1=Mercado|last2=E.|first2=Myers, Catherine|date=2014-01-01|publisher=Worth Publishers|isbn=9781429240147|___location=|pages=311|oclc=900627172}}</ref> There is an observed phenomenon known as the [[Power law of practice|power law of learning]], which predicts the rate of skill acquisition over practice time. The power law of learning says that learning occurs at the fastest rate in the beginning then drastically tapers off. The rate at which practice loses its ability to sharpen execution is independent from the skill being practiced and the type of animal learning the skill. For example, participants in a reading speed study made the greatest leap in the first days of the experiment, while additional days of practice saw only slight improvement.<ref>{{Cite book|title=Learning and memory : from brain to behavior|last1=Eduardo.|first1=Mercado|last2=E.|first2=Myers, Catherine|year=2014|isbn=9781429240147|___location=|pages=311–312|oclc=961181739}}</ref>
The power law of learning can be overcome if the subject is shown a more effective way to accomplish the task. A study subject was shown a film comparing his task performance, kicking a target as rapidly as possible, with that of a known way of minimizing kicking time. Though the subject had reached the limit of his ability to improve through practice as predicted by the power law of learning, viewing the film resulted in a breakthrough in his ability that defied the power law of learning. Viewing the film is an example of [[observational learning]], which effectively gives the viewer new memories of a technique to draw upon for his or her future performances of the task.<ref>{{Cite book|title=Learning and memory : from brain to behavior|last1=Eduardo.|first1=Mercado|last2=E.|first2=Myers, Catherine|year=2014|isbn=9781429240147|___location=|pages=312|oclc=961181739}}</ref>
==Tests==
===Pursuit rotor task===
A device used to study visual-motor tracking skills and [[hand–eye coordination]] by requiring the participant to follow a moving object with a [[cursor (computers)|cursor]]<ref name="Cognitive Atlas">{{Cite web | url=http://www.cognitiveatlas.org | title=Cognitive Atlas}}</ref> or use a [[stylus]] to follow the target on a computer screen or a turntable.<ref>{{cite web |url=http://149.142.158.188/phenowiki/wiki/index.php/Pursuit_Rotor_Task |title=Archived copy |accessdate=2012-02-27 |url-status=dead |archiveurlarchive-url=https://web.archive.org/web/20130927220537/http://149.142.158.188/phenowiki/wiki/index.php/Pursuit_Rotor_Task |archivedatearchive-date=27 September 2013 |df=dmy-all }}</ref> With the computer screen version, the participant follows a dot on a circular path like the one shown below.<ref>{{Cite web | url=http://peblblog.blogspot.com/2010/04/pursuit-rotor-task.html | title=PEBL Blog: The Pursuit Rotor Task| date=2010-04-24}}</ref> [[File:PursuitRotor.png|thumb|Screenshot of a computerized version of the pursuit rotor task.]]
The pursuit rotor task is a simple pure visual-motor tracking test that has consistent results within age groups.<ref name="Lang">{{cite journal | url = | doi=10.1016/0191-8869(81)90025-8 | volume=2 | issue=3 | title=Learning and reminiscence in the pursuit rotor performance of normal and depressed subjects | journal=Personality and Individual Differences | pages=207–213 | year=1981 | last1 = Lang | first1 = Rudie J.}}</ref> This displays a measurement of procedural memory as well as demonstrates the participant's [[fine motor skill]]s. The pursuit rotor task tests the fine-motor skills which are controlled by the motor cortex illustrated by the green section below. [[File:Cerebral lobes.png|thumb]]<ref name="Allen">{{cite journal | last1 = Allen | first1 = J.S. | last2 = Anderson | first2 = S.W. | last3 = Castro-Caldas | first3 = A. | last4 = Cavaco | first4 = S. | last5 = Damasio | first5 = H. | year = 2004 | title = The scope of preserved procedural memory in amnesia | url = | journal = Brain | volume = 127 | issue = 8| pages = 1853–67 | doi = 10.1093/brain/awh208 | pmid = 15215216 | doi-access = free }}</ref> The results are then calculated by the participant's time-on and time-off the object. Amnesic participants show no impairment in this motor task when tested at later trials. It does however seem to be affected by lack of sleep and drug use.<ref name="Dotto">{{cite journal | last1 = Dotto | first1 = L | year = 1996 | title = Sleep Stages, Memory and Learning | url = | journal = Canadian Medical Association | volume = 154 | issue = 8| pages = 1193–6 | pmid = 8612256 | pmc = 1487644 }}</ref>
===Serial reaction time task===
===Weather prediction task===
Specifically, this task uses experimental analysis of weather prediction. As a probability learning task, the participant is required to indicate what strategy they are using to solve the task. It is a cognitively-oriented task that is learned in a procedural manner.<ref name="Acquisition of Mirror Tracing"/> It's designed using multidimensional stimuli, so participants are given a set of cards with shapes and then asked to predict the outcome. After the prediction is made participants receive feedback and make a classification based on that feedback.<ref name="Multiple memory systems competition">{{cite journal | last1 = Packard | first1 = M.G. | last2 = Poldrack | first2 = R.A. | year = 2003 | title = Competition among multiple memory systems: converging evidence from animal and human brain studies | url = | journal = Neuropsychologia | volume = 41 | issue = 3| pages = 245–251 | doi=10.1016/s0028-3932(02)00157-4| pmid = 12457750 | s2cid = 1054952 }}</ref> For example, the participant can be shown one pattern and then asked to predict whether the pattern indicates good or bad weather. The actual weather outcome will be determined by a probabilistic rule based on each individual card. Amnesic participants learn this task in training but are impaired in later training control.<ref name="Multiple memory systems competition"/>
=== Choice reaction task ===
===Divided attention===
There are several factors that contribute to the exceptional performance of a skill: memory capacities,<ref>{{cite journal | last1 = Chase | first1 = W. G. | last2 = Simon | first2 = H. A. | year = 1973 | title = Perception in chess | url = | journal = Cognitive Psychology | volume = 4 | issue = | pages = 55–81 | doi=10.1016/0010-0285(73)90004-2}}</ref><ref>Starkes, J. L., & Deakin, J. (1984). Perception in sport: A cognitive approach to skilled performance. In W. F. Straub & J. M. Williams (Eds.), Cognitive sport psychology (pp. 115–128). Lansing, MI: Sport Science Associates.</ref> knowledge structures,<ref>{{cite journal | last1 = Chi | first1 = M. T. | last2 = Feltovich | first2 = P. J. | last3 = Glaser | first3 = R. | year = 1981 | title = Categorization and representation of physics problems by experts and novices | url = | journal = Cognitive Science | volume = 5 | issue = 2| pages = 121–152 | doi=10.1207/s15516709cog0502_2}}</ref> problem-solving abilities,<ref>Tenenbaum, G., & Bar-Eli, M. (1993). Decision-making in sport: A cognitive perspective. In R. N. Singer, M. Murphey, & L. K. Tennant (Eds.), Handbook of research on sport psychology (pp. 171–192). New York: Macmillan.</ref> and attentional abilities.<ref name="attention">{{cite journal | last1 = Beilock | first1 = S.L. | last2 = Carr | first2 = T.H. | last3 = MacMahon | first3 = C. | last4 = Starkes | first4 = J.L. | year = 2002 | title = When Paying Attention Becomes Counterproductive: Impact of Divided Versus Skill-Focused Attention on Novice and Experienced Performance of Sensorimotor Skills | url = https://semanticscholar.org/paper/3bbd5a432c08263b0bebcc888d9592ffe4bec50f| journal = Journal of Experimental Psychology: Applied | volume = 8 | issue = 1| pages = 6–16 | doi=10.1037/1076-898x.8.1.6| pmid = 12009178 | s2cid = 15358285 }}</ref> They all play key roles, each with its own degree of importance based on the procedures and skills required, the context, and the intended goals of the performance. Using these individualized abilities to compare how experts and novices differ regarding both cognitive and sensorimotor skills has provided a wealth of insight into what makes an expert excellent, and conversely, what sorts of mechanisms novices lack. Evidence suggests that an often overlooked condition for skill excellence is attentional mechanisms involved in the effective utilization and deployment of procedural memory during the real-time execution of skills. Research suggests that early in skill learning, execution is controlled by a set of unintegrated procedural steps that are held in working memory and attended to one-by-one in a step-by-step fashion.<ref>Anderson, J. R. (1983). The architecture of cognition. Cambridge, MA: Harvard University Press.</ref><ref name="Anderson, J. R. 1993">Anderson, J. R. (1993). Rules of mind. Hillsdale, NJ: Erlbaum.</ref><ref>Proctor, R. W., & Dutta, A. (1995). Skill acquisition and human performance. Thousand Oaks, CA: Sage.</ref> The problem with this is that attention is a limited resource. Therefore, this step-by-step process of controlling task performance occupies attentional capacity which in turn reduces the performer's ability to focus on other aspects of the performance, such as decision making, fine motor-skills, self-monitoring of energy level and "seeing the field or ice or court". However, with practice, procedural knowledge develops, which operates largely outside of working memory, and thus allows for skills to be executed more automatically.<ref name="Anderson, J. R. 1993"/><ref name="Langer, E. 1979">{{cite journal | last1 = Langer | first1 = E. | last2 = Imber | first2 = G. | year = 1979 | title = When practice makes imperfect: Debilitating effects of overlearning | url = | journal = Journal of Personality and Social Psychology | volume = 37 | issue = 11| pages = 2014–2024 | doi=10.1037/0022-3514.37.11.2014| pmid = 521900 }}</ref> This, of course, has a very positive effect on overall performance by freeing the mind of the need to closely monitor and attend to the more basic, mechanical skills, so that attention can be paid to other processes.<ref name="attention"/>
===Choking under pressure===
It is well established that highly practiced, over-learned skills are performed automatically; they are controlled in real time, supported by procedural memory, require little attention, and operate largely outside of [[working memory]].<ref>{{cite journal | last1 = Anderson | first1 = J. R. | year = 1982 | title = Acquisition of a cognitive skill | journal = Psychological Review | volume = 89 | issue = 4| pages = 369–406 | doi=10.1037/0033-295x.89.4.369| s2cid = 18877678 | url = https://semanticscholar.org/paper/eb324f42d42dc29d9f89e044a76516227e4e2c66 }}</ref> However, sometimes even experienced and highly skilled performers falter under conditions of stress. This phenomenon is commonly referred to as choking, and serves as a very interesting exception to the general rule that well-learned skills are robust and resistant to deterioration across a wide range of conditions.<ref name="choking">{{cite journal | last1 = Beilock | first1 = S.L. | last2 = Carr | first2 = T. | year = 2001 | title = On the Fragility of Skilled Performance: What Governs Choking Under Pressure? | url = | journal = Journal of Experimental Psychology: General | volume = 130 | issue = 4| pages = 701–725 | doi=10.1037/e501882009-391| citeseerx = 10.1.1.172.5140 }}</ref> Although not well understood, it is widely accepted that the underlying cause of choking is performance pressure, which has been defined as an anxious desire to perform very well in a given situation.<ref name="choking"/> Choking is most often associated with motor skills, and the most common real-life instances are in sports. It is common for professional athletes who are highly trained to choke in the moment and perform poorly. However, choking can occur within any ___domain that demands a high level of performance involving complex cognitive, verbal or motor skills. "Self-focus" theories suggest that pressure increases anxiety and self-consciousness about performing correctly, which in turn causes an increase in attention paid to the processes directly involved in the execution of the skill.<ref name="choking"/> This attention to the step-by-step procedure disrupts the well-learned, automatic (proceduralized) performance. What was once an effortless and unconscious retrieval execution of a procedural memory becomes slow and deliberate.<ref name="Langer, E. 1979"/><ref>{{cite journal | last1 = Lewis | first1 = B. | last2 = Linder | first2 = D. | year = 1997 | title = Thinking about choking? Attentional processes and paradoxical performance | url = | journal = Personality and Social Psychology Bulletin | volume = 23 | issue = 9| pages = 937–944 | doi=10.1177/0146167297239003| pmid = 29506446 | s2cid = 3702775 }}</ref><ref>{{cite journal | last1 = Kimble | first1 = G. A. | last2 = Perlmuter | first2 = L. C. | year = 1970 | title = The problem of volition | url = | journal = Psychological Review | volume = 77 | issue = 5| pages = 361–384 | doi=10.1037/h0029782| pmid = 4319166 }}</ref><ref>{{cite journal | last1 = Masters | first1 = R. S. | year = 1992 | title = Knowledge, knerves and know-how: The role of explicit versus implicit knowledge in the breakdown of a complex motor skill under pressure | url = | journal = British Journal of Psychology | volume = 83 | issue = 3| pages = 343–358 | doi=10.1111/j.2044-8295.1992.tb02446.x}}</ref> Evidence suggests that the more automated a skill is the more resistant it is to distractions, performance pressure, and subsequent choking. This serves as a good example of the relative durability of procedural memory over episodic memory. In addition to deliberate practice and automization of skills, self-consciousness training has been shown to help with reducing the effect of choking under pressure.<ref name="choking"/>
====Rising to the occasion====
== Genetic influence ==
Genetic makeup has been found to impact skill learning and performance, and therefore plays a role in achieving expertise. Using the pursuit rotor task, one study examined the effects of [[Practice (learning method)|practice]] in identical and fraternal twins raised in separate homes. Because identical twins share 100% of their genes while fraternal twins share 50%, the impact of genetic makeup on skill learning could be examined. The results of the pursuit rotor task test became more identical with practice over time for the identical twins, whereas the results for the fraternal twins became more disparate with practice. In other words, the performance of the skill by the identical twins became closer to 100% identical, while the fraternal twins' skill performance became less identical, suggesting the 50% difference in genetic makeup is responsible for the difference in skill performance. The study shows that more practice leads to a closer representation of a person's innate capability, also known as [[Aptitude|talent]]. Therefore, some of the differences people show after extended practice increasingly reflects their genetics. The study also confirmed the idea that practice improves skill learning by showing that, in both the identical and fraternal groups, more practice aided in shedding ineffective tendencies in order to improve execution of a given skill.<ref>{{Cite journal|last1=Fox|first1=Paul W.|last2=Hershberger|first2=Scott L.|last3=Bouchard|first3=Thomas J.|date=1996-11-28|title=Genetic and environmental contributions to the acquisition of a motor skill|journal=Nature|language=en|volume=384|issue=6607|pages=356–358|doi=10.1038/384356a0|pmid=8934520|bibcode=1996Natur.384..356F|s2cid=4354381|url=https://www.semanticscholar.org/paper/afa191e4026af47dbe915c19349046eba4c4c1e3}}</ref><ref>{{Cite book|title=Learning and memory : from brain to behavior|last1=Eduardo.|first1=Mercado|last2=E.|first2=Myers, Catherine|date=2014-01-01|publisher=Worth Publishers|isbn=9781429240147|___location=|pages=307–308|oclc=900627172}}</ref> Currently, the link between [[learning]] and genetics has been limited to simple task learning, while a link to more complex forms of learning, such as the learning of [[cognitive skill]]s, has not been confirmed.<ref>{{Cite journal|last1=Wulf|first1=Gabriele|last2=Shea|first2=Charles H.|date=2002-06-01|title=Principles derived from the study of simple skills do not generalize to complex skill learning|journal=Psychonomic Bulletin & Review|language=en|volume=9|issue=2|pages=185–211|doi=10.3758/BF03196276|pmid=12120783|issn=1069-9384|doi-access=free}}</ref>
==Anatomical structures==
{{details|topic=the basal ganglia|Basal ganglia}}
[[File:Basal ganglia and related structures (2).svg|thumb|right|Basal ganglia (red) and related structures (blue) shown within the brain]]
The [[dorsolateral]] striatum is associated with the acquisition of habits and is the main neuronal cell nucleus linked to procedural memory. Connecting excitatory [[afferent nerve fiber]]s help in the regulation of activity in the basal ganglia circuit. Essentially, two parallel information processing pathways diverge from the striatum. Both acting in opposition to each other in the control of movement, they allow for association with other needed functional structures<ref>{{cite journal | last1 = Alexander | first1 = GE | last2 = Crutcher | first2 = MD | year = 1990 | title = Functional architecture of basal ganglia circuits; neural substrates of parallel processing | url = | journal = Trends Neurosci | volume = 13 | issue = 7| pages = 266–271 | doi=10.1016/0166-2236(90)90107-l | pmid=1695401| s2cid = 3990601 }}</ref> One pathway is direct while the other is indirect and all pathways work together to allow for a functional neural feedback loop. Many looping circuits connect back at the striatum from other areas of the brain; including those from the emotion-center linked limbic cortex, the reward-center linked [[ventral striatum]] and other important motor regions related to movement.<ref>{{cite journal | last1 = Haber | first1 = SN | last2 = Fudge | first2 = JL | last3 = McFarland | first3 = NR | year = 2000 | title = Striatonigrostriatal pathways in primates form an ascending spiral from the shell to the dorsolateral striatum | url = | journal = J. Neurosci. | volume = 20 | issue = 6| pages = 2369–2382 | doi = 10.1523/JNEUROSCI.20-06-02369.2000 | pmid = 10704511 | doi-access = free }}</ref> The main looping circuit involved in the motor skill part of procedural memory is usually called the cortex-basal ganglia-thalamus-cortex loop.<ref>{{cite journal | last1 = Parent | first1 = A | year = 1990 | title = Extrinsic connections of the basal ganglia | url = | journal = Trends Neurosci | volume = 13 | issue = 7| pages = 254–258 | doi=10.1016/0166-2236(90)90105-j| pmid = 1695399 | s2cid = 3995498 }}</ref>
The striatum is unique because it lacks the [[glutamate]]-related neurons found throughout most of the brain. Instead, it is categorized by a high concentration of a special type of [[GABA]] related inhibiting cell known as the [[medium spiny neuron]].<ref>{{cite journal | last1 = Smith | first1 = Y. | last2 = Raju | first2 = D. V. | last3 = Pare | first3 = J. F. | last4 = Sidibe | first4 = M. | year = 2004 | title = The thalamostriatal system: a highly specific network of the basal ganglia circuitry | url = https://www.semanticscholar.org/paper/99588f5770f5388d0c260eb6b70b9c88ebff0171| journal = Trends Neurosci | volume = 27 | issue = 9| pages = 520–527 | doi=10.1016/j.tins.2004.07.004| pmid = 15331233 | s2cid = 22202019 }}</ref> The two parallel pathways previously mentioned travel to and from the striatum and are made up of these same special medium spiny neurons. These neurons are all sensitive to different neurotransmitters and contain a variety of corresponding receptors including dopamine receptors ([[DRD1]], [[DRD2]]), [[muscarinic receptors]] (M4) and [[adenosine receptors]] (A2A). Separate interneurons are known to communicate with striatal spiny neurons in the presence of the [[somatic nervous system]] neurotransmitter [[acetylcholine]].<ref>{{cite journal | last1 = Zhou | first1 = FM | last2 = Wilson | first2 = CJ | last3 = Dani | first3 = JA | year = 2002 | title = Cholinergic Interneuron characteristics and nicotinic properties in the striatum | url = | journal = J. Neurobiol. | volume = 53 | issue = 4| pages = 590–605 | doi=10.1002/neu.10150 | pmid=12436423}}</ref>
Current understanding of brain anatomy and physiology suggests that striatal neural plasticity is what allows basal ganglia circuits to communicate between structures and to functionally operate in procedural memory processing.<ref>{{cite journal | last1 = Kreitzer | first1 = AC | year = 2009 | title = Physiology and pharmacology of striatal neurons | url = | journal = Annual Review of Neuroscience| volume = 32 | issue = | pages = 127–47 | doi=10.1146/annurev.neuro.051508.135422| pmid = 19400717 }}</ref>
===Cerebellum===
{{details|topic=the cerebellum|Cerebellum}}
[[File:Cerebellum.png|thumb|right|The cerebellum is highlighted red]]
The [[cerebellum]] is known to play a part in correcting movement and in fine-tuning the motor agility found in procedural skills such as painting, instrument playing and in sports such as golf. Damage to this area may prevent the proper relearning of motor skills and through associated research it has more recently been linked to having a role in automating the unconscious process used when learning a procedural skill.<ref>{{cite journal | last1 = Saywell | first1 = N | last2 = Taylor | first2 = D | date = Oct 2008 | title = The role of the cerebellum in procedural learning – are there implications for physiotherapists' clinical practice?. | url = | journal = Physiotherapy: Theory and Practice | volume = 24 | issue = 5| pages = 321–8 | doi=10.1080/09593980701884832| pmid = 18821439 | s2cid = 205654506 }}</ref> New thoughts in the scientific community suggest that the cerebellar cortex holds the holy grail of memory, what is known to researchers as "[[the engram]]" or the biological place where memory lives. The initial memory trace is thought to form here between parallel fibers and [[Purkinje cells|Purkinje cell]] and then travel outwards to other cerebellar nuclei for consolidation.<ref>{{cite journal | last1 = Nagao | first1 = S | last2 = Kitazawa | first2 = H | year = 2008 | title = Role of the cerebellum in the acquisition and consolidation of motor memory | url = | journal = Brain Nerve | volume = 60 | issue = 7| pages = 783–90 | pmid = 18646618 }}</ref>
===Limbic system===
{{details|topic=the limbic system|Limbic system}}
The [[limbic system]] is a group of unique brain areas that work together in many interrelated processes involved in emotion, motivation, learning and memory. Current thinking indicates that the limbic system shares anatomy with a component of the neostriatum already credited with the major task of controlling procedural memory. Once thought to be functionally separate, this vital section of the brain found on the striatum's back border has only recently been linked to memory and is now being called the marginal division zone (MrD).<ref>{{cite journal | last1 = Shu | first1 = S.Y. | last2 = Bao | first2 = X.M. | last3 = Li | first3 = S.X. | last4 = Chan | first4 = W.Y. | last5 = Yew | first5 = D. | year = 2000 | title = A New Subdivision, Marginal Division, in the Neostriatum of the Monkey Brain | url = | journal = Biomedical and Life Sciences | volume = 25 | issue = 2| pages = 231–7 | doi = 10.1023/a:1007523520251 | pmid = 10786707 | s2cid = 11876741 }}</ref> A special membrane protein associated with the limbic system is said to concentrate in related structures and to travel towards the basal nuclei. To put things simply, the activation of brain regions that work together during procedural memory can be followed because of this limbic system associated membrane protein and its application in molecular and [[immunohistochemistry]] research.<ref>{{cite journal | last1 = Yun Shu | first1 = Si | last2 = Min Bao | first2 = Xin | last3 = Ning | first3 = Qun | last4 = Ming Wu | first4 = Yong | last5 = Wang | first5 = Jun | last6 = Leonard | first6 = Brian E. | year = 2003 | title = New component of the limbic system; Marginal division of the neostriatum that links the limbic system to the basal nucleus of Meynert | url = | journal = Journal of Neuroscience Research | volume = 71 | issue = 5| pages = 751–757 | doi=10.1002/jnr.10518| pmid = 12584733 }}</ref>
==Physiology==
===At the synapse===
Recent findings could help explain the relationship between procedural memory, learning and [[synaptic plasticity]] at the level of the molecule. One study used small animals lacking normal levels of [[CREB]] family transcription factors to look at the processing of information in the striatum during various tasks. Although poorly understood, results show that CREB function is needed at the synapse for linking the acquisition and storage of procedural memory.<ref>{{cite journal | last1 = Pittenger | first1 = C | last2 = Fasano | first2 = S | last3 = Mazzocchi-Jones | first3 = D | last4 = Dunnett | first4 = SB | last5 = Kandel | first5 = ER | last6 = Brambilla | first6 = R | year = 2006 | title = Impaired bidirectional synaptic plasticity and procedural memory formation in striatum-specific cAMP response element-binding protein-deficient mice | url = | journal = J Neurosci | volume = 26 | issue = 10| pages = 2808–13 | doi=10.1523/jneurosci.5406-05.2006 | pmid=16525060| pmc = 6675171 }}</ref>
==Disorders==
===Human immunodeficiency virus (HIV)===
{{details|topic=human immunodeficiency virus|HIV}}
Neural systems used by procedural memory are commonly targeted by [[Human Immunodeficiency Virus]]; the striatum being the structure most notably affected.<ref>{{cite journal | last1 = Reger | first1 = M | last2 = Welsh | first2 = R | last3 = Razani | first3 = J | last4 = Martin | first4 = DJ | last5 = Boone | first5 = KB | year = 2002 | title = A meta-analysis of the neuropsychological sequelae of HIV infection | url = | journal = Journal of the International Neuropsychological Society | volume = 8 | issue = 3| pages = 410–424 | doi=10.1017/s1355617702813212| pmid = 11939699 }}</ref> MRI studies have even shown white matter irregularity and basal ganglia subcortical atrophy in these vital areas necessary for both procedural memory and motor-skill.<ref>{{cite journal | last1 = Chang | first1 = L | last2 = Lee | first2 = PL | last3 = Yiannoutsos | first3 = CT | last4 = Ernst | first4 = T | last5 = Marra | first5 = CM | last6 = Richards | first6 = T | display-authors = etal | year = 2004 | title = A multicenter in vivo proton-MRS study of HIV-associated dementia and its relationship to age | url = https://www.semanticscholar.org/paper/f773811cd3929a13639cb15fa8cedcf5f0e01212| journal = NeuroImage | volume = 23 | issue = 4| pages = 1336–1347 | doi=10.1016/j.neuroimage.2004.07.067 | pmid=15589098| s2cid = 2664814 }}</ref> Applied research using various procedural memory tasks such as the Rotary pursuit, Mirror star tracing and Weather prediction tasks have shown that HIV positive individuals perform worse than HIV negative participants suggesting that poorer overall performance on tasks is due to the specific changes in the brain caused by the disease.<ref>{{cite journal | last1 = Gonzalez | first1 = R | last2 = Jacobus | first2 = J | last3 = Amatya | first3 = AK | last4 = Quartana | first4 = PJ | last5 = Vassileva | first5 = J | last6 = Martin | first6 = EM | year = 2008 | title = Deficits in complex motor functions, despite no evidence of procedural learning deficits, among HIV+ individuals with history of substance dependence | url = | journal = Neuropsychology | volume = 22 | issue = 6| pages = 776–86 | doi=10.1037/a0013404| pmid = 18999351 | pmc = 2630709 }}</ref>
===Huntington's disease===
{{details|topic=Huntington's disease|Huntington's disease}}
[[File:Huntington.jpg|thumb|left|Coronal FSPGR through the brain of Huntington's patient]]
Despite being a disorder that directly affects striatal areas of the brain used in procedural memory, most individuals with [[Huntington's disease]] don't display the same memory problems as other people with striatum related brain diseases.<ref>{{cite journal | last1 = Sprengelmeyer | first1 = R | last2 = Canavan | first2 = AG | last3 = Lange | first3 = HW | last4 = Hömberg | first4 = V | date = Jan 1995 | title = Associative learning in degenerative neostriatal disorders: contrasts in explicit and implicit remembering between Parkinson's and Huntington's diseases | url = | journal = Mov Disord | volume = 10 | issue = 1| pages = 51–65 | doi=10.1002/mds.870100110| pmid = 7885356 }}</ref> In more advanced stages of the disease, however, procedural memory is affected by damage to the important brain pathways that help the inner subcortical and prefrontal cortex parts of the brain to communicate.<ref>Saint-Cyr JA, Taylor AE, Lang AE. (1988) "Procedural learning and neostriatal dysfunction in man" ''Brain'' 1988 Aug;111 ( Pt 4):941-59.</ref>
===Obsessive compulsive disorder===
{{details|topic=obsessive–compulsive disorder|OCD}}
Neuroimaging studies show that [[OCD]] patients perform considerably better on procedural memory tasks because of noticeable over-activation of the striatum brain structures, specifically the frontostriatal circuit. These studies suggest that procedural memory in OCD patients is unusually improved in the early learning stages of procedural memory.<ref>{{cite journal | last1 = Roth | first1 = RM | last2 = Baribeau | first2 = J | last3 = Milovan | first3 = D | last4 = O'Connor | first4 = K | last5 = Todorov | first5 = C | date = Sep 2004 | title = Procedural and declarative memory in obsessive-compulsive disorder | url = | journal = J Int Neuropsychol Soc | volume = 10 | issue = 5| pages = 647–54 | doi=10.1017/s1355617704105018| pmid = 15327712 }}</ref> Individuals with OCD do not perform significantly different on procedural working memory tasks than healthy controls.<ref name="Shahar 197–204"/>
===Parkinson's disease===
{{details|topic=Parkinson's disease|Parkinson's disease}}
[[Parkinson's disease]] is known to affect selective areas in the frontal lobe area of the brain. Current scientific information suggests that the memory performance problems notably shown in patients are controlled by unusual frontostriatal circuits.<ref>{{cite journal | last1 = Sarazin | first1 = M | last2 = Deweer | first2 = B | last3 = Pillon | first3 = B | last4 = Merkl | first4 = A | last5 = Dubois | first5 = B | date = Dec 2001 | title = Procedural learning and Parkinson disease: implication of striato-frontal loops | url = | journal = Rev Neurol | volume = 157 | issue = 12| pages = 1513–8 | pmid = 11924447 }}</ref> Parkinson's patients often have difficulty with the sequence-specific knowledge that is needed in the acquisition step of procedural memory.<ref>{{cite journal | last1 = Muslimovic | first1 = D | last2 = Post | first2 = B | last3 = Speelman | first3 = JD | last4 = Schmand | first4 = B | date = Nov 2007 | title = Motor procedural learning in Parkinson's disease | url = | journal = Brain | volume = 130 | issue = 11| pages = 2887–97 | doi=10.1093/brain/awm211| pmid = 17855374 | doi-access = free }}</ref> Further evidence suggests that the frontal lobe networks relate to executive function and only act when specific tasks are presented to the patient. This tells us that the frontostriatal circuits are independent but able to work collaboratively with other areas of the brain to help with various things such as paying attention or focusing.<ref>{{cite journal | last1 = Sarazin | first1 = M | last2 = Deweer | first2 = B | last3 = Merkl | first3 = A | last4 = Von Poser | first4 = N | last5 = Pillon | first5 = B | last6 = Dubois | first6 = B | date = Mar 2002 | title = Procedural learning and striatofrontal dysfunction in Parkinson's disease | url = | journal = Mov Disord | volume = 17 | issue = 2| pages = 265–73 | doi=10.1002/mds.10018| pmid = 11921111 }}</ref>
===Schizophrenia===
{{details|topic=schizophrenia|Schizophrenia}}
MRI studies have shown that [[schizophrenic]] patients not currently taking related medication have a smaller putamen; part of the striatum that plays a very important role in procedural memory.<ref>{{cite journal | last1 = Lang | first1 = DJ | last2 = Kopala | last3 = Smith | first3 = GN | display-authors = etal | year = 1999 | title = MRI study of basal ganglia volumes in drug-naive first-episode patients with schizophrenia | url = | journal = Schizophr Res | volume = 36 | issue = | page = 202 }}</ref> Further studies on the brain reveal that schizophrenics have improper basal ganglia communication with the surrounding extrapyramidal system that is known to be closely involved with the motor system and in the coordination of movement.<ref>A Chatterjee, M Chakos, A Koreen, S Geisler, B Sheitman, M Woerner, JM Kane J Alvir and Ja (1995). "Prevalence and clinical correlates of extrapyramidal signs and spontaneous dyskinesia in never-medicated schizophrenic patients" ''Am J Psychiatry'' 1995 Dec; 152 (12); 1724-9.</ref> The most recent belief is that functional problems in the striatum of schizophrenic patients are not significant enough to seriously impair procedural learning, however, research shows that the impairment will be significant enough to cause problems improving performance on a task between practice intervals.<ref>{{cite journal | last1 = Schérer | first1 = H | last2 = Stip | first2 = E | last3 = Paquet | first3 = F | last4 = Bédard | first4 = MA | date = Winter 2003 | title = Mild procedural learning disturbances in neuroleptic-naive patients with schizophrenia | url = | journal = Journal of Neuropsychiatry| volume = 15 | issue = 1| pages = 58–63 | doi=10.1176/appi.neuropsych.15.1.58| pmid = 12556572 }}</ref>
==Drugs==
===Cocaine===
{{details|topic=cocaine|Cocaine}}
It is evident that long-term [[Cocaine]] abuse alters brain structures. Research has shown that the brain structures that are immediately affected by long-term cocaine abuse include: cerebral [[hypoperfusion]] in the frontal, periventricular and temporal-parietal.<ref name="cocaine abuse">{{cite journal | last1 = Strickland | first1 = T. L. | last2 = Mena | first2 = I. | last3 = Villanueva-Meyer | first3 = J. | last4 = Miller | first4 = B. L. | last5 = Cummings | first5 = J. | last6 = Mehringer | first6 = C. M. | last7 = Satz | first7 = P. | last8 = Myers | first8 = H. | year = 1993 | title = Cerebral perfusion and neuropsychological consequences of chronic cocaine use | url = | journal = The Journal of Neuropsychiatry and Clinical Neurosciences| volume = 5 | issue = 4| pages = 419–427 | doi=10.1176/jnp.5.4.419| pmid = 8286941 }}</ref> These structures play a role in various memory systems. Furthermore, the drug cocaine elicits its desirable effects by blocking the DRD1 dopamine receptors in the striatum, resulting in increased dopamine levels in the brain.<ref name="cocaine abuse"/> These receptors are important for the consolidation of procedural memory. These increased dopamine levels in the brain resultant of cocaine use is similar to the increased dopamine levels in the brain found in schizophrenics.<ref>{{cite journal | last1 = Serper | first1 = M. R. | last2 = Bermanc | first2 = A. | last3 = Copersinoa | first3 = M. L. | last4 = Choub | first4 = J. C. Y. | last5 = Richarmea | first5 = D. | last6 = Cancrob | first6 = R. | year = 2000 | title = Learning and memory impairment in cocaine-dependent and comorbid schizophrenic patients | url = | journal = Psychiatry Research | volume = 93 | issue = 1| pages = 21–32 | doi=10.1016/s0165-1781(99)00122-5| pmid = 10699225 | s2cid = 44527373 }}</ref> Studies have compared the common memory deficits caused by both cases to further understand the neural networks of procedural memory. To learn more about the effects of dopamine and its role in schizophrenia see: [[dopamine hypothesis of schizophrenia]]. Studies using rats have shown that when rats are administered trace amounts of cocaine, their procedural memory systems are negatively impacted. Specifically, the rats are unable to effectively consolidate motor-skill learning.<ref>Willuhn I, Steiner H. (2008) Motor-skill learning in a novel running-wheel task is dependent on D1 dopamine receptors in the striatum. ''Neuroscience'', 22 April; 153 (1); 249-58. Epub 2008 Feb 6.</ref> With cocaine abuse being associated with poor procedural learning, research has shown that abstinence from cocaine is associated with sustained improvement of motor-skill learning (Wilfred et al.).
===Psychostimulants===
{{details|topic=psychostimulants|Psychostimulant}}
Most [[psychostimulant]]s work by activating dopamine receptors causing increased focus or pleasure. The usage of psychostimulants has become more widespread in the medical world for treating conditions like [[ADHD]]. Psychostimulants have been shown to be used more frequently today amongst students and other social demographics as a means to study more efficiently or have been abused for their pleasurable side effects.<ref>McCabe, S. E., Knight, J. R., Teter, C. J., Wechsler, H. (2004). Non-medical use of prescription stimulants among US
college students: prevalence and correlates from anational survey. Research Report.</ref> Research suggests that when not abused, psychostimulants aid in the acquisition of procedural learning. Studies have shown that psychostimulants like [[d-amphetamine]] facilitates lower response times and increased procedural learning when compared to control participants and participants who have been administered the [[antipsychotics|antipsychotic]] [[haloperidol]] on procedural learning tasks.<ref>Kumari, V., Gray, J.A., Corr, P.J., Mulligan, O.F., Cotter, P.A., Checkley, S.A. (1997). Effects of acute administration of d-amphetamine and haloperidol on procedural learning in man. ''Journal of Psychopharmacology'' 129(3); 271–276</ref> While improvements in procedural memory were evident when participants were administered traces of psychostimulants, many researchers have found that procedural memory is hampered when psychostimulants are abused.<ref>{{cite journal | last1 = Toomey | first1 = R. | last2 = Lyons | first2 = M. J. | last3 = Eisen | first3 = S. A. | last4 = Xian | first4 = Hong | last5 = Chantarujikapong | first5 = Sunanta | last6 = Seidman | first6 = L. J. | last7 = Faraone | first7 = S. | last8 = Tsuang | first8 = M. T. | year = 2003 | title = A Twin Study of the Neuropsychological Consequences of Stimulant Abuse | url = | journal = Arch Gen Psychiatry | volume = 60 | issue = 3| pages = 303–310 | doi=10.1001/archpsyc.60.3.303| pmid = 12622664 | doi-access = free }}</ref> This introduces the idea that for optimal procedural learning, dopamine levels must be balanced.
==Sleep==
Practice is clearly an important process for learning and perfecting a new skill. With over 40 years of research, it is well established in both humans and animals that the formation of all forms of memory are greatly enhanced during the brain-state of sleep. Furthermore, with humans, sleep has been consistently shown to aid in the development of procedural knowledge by the ongoing process of memory consolidation, especially when sleep soon follows the initial phase of memory acquisition.<ref>{{cite journal | last1 = Karni | first1 = A. | last2 = Tanne | first2 = D. | last3 = Rubenstein | first3 = B.S. | last4 = Askenasy | first4 = J.J. | last5 = Sagi | first5 = D. | year = 1994 | title = Dependence on REM sleep of overnight improvement of a perceptual skill | url = | journal = Science | volume = 265 | issue = 5172| pages = 679–682 | doi=10.1126/science.8036518| pmid = 8036518 | bibcode = 1994Sci...265..679K }}</ref><ref>{{cite journal | last1 = Gais | first1 = S. | last2 = Plihal | first2 = W. | last3 = Wagner | first3 = U. | last4 = Born | first4 = J. | year = 2000 | title = Early sleep triggers memory for early visual discrimination skills | url = https://www.semanticscholar.org/paper/ba7d00d764e18b32c63b0eae5a5edf9854b09c28| journal = Nat. Neurosci. | volume = 3 | issue = 12| pages = 1335–1339 | doi=10.1038/81881| pmid = 11100156 | s2cid = 2075857 }}</ref><ref>{{cite journal | last1 = Stickgold | first1 = R. | last2 = James | first2 = L. | last3 = Hobson | first3 = J.A. | year = 2000a | title = Visual discrimination learning requires sleep after training | url = | journal = Nat. Neurosci. | volume = 3 | issue = 12| pages = 1237–1238 | doi=10.1038/81756| pmid = 11100141 | doi-access = free }}</ref><ref>{{cite journal | last1 = Stickgold | first1 = R. | last2 = Whidbee | first2 = D. | last3 = Schirmer | first3 = B. | last4 = Patel | first4 = V. | last5 = Hobson | first5 = J.A. | year = 2000b | title = Visual discrimination task improvement: A multi-step process occurring during sleep | url = https://www.semanticscholar.org/paper/f635eb5e63eff7dc17c1b0b9548f80b1b35b76cf| journal = J. Cogn. Neurosci. | volume = 12 | issue = 2| pages = 246–254 | doi=10.1162/089892900562075| pmid = 10771409 | s2cid = 37714158 }}</ref><ref>{{cite journal | last1 = Walker | first1 = M.P. | last2 = Brakefield | first2 = T. | last3 = Morgan | first3 = A. | last4 = Hobson | first4 = J.A. | last5 = Stickgold | first5 = R. | year = 2002 | title = Practice with sleep makes perfect: Sleep dependent motor skill learning | url = | journal = Neuron | volume = 35 | issue = 1| pages = 205–211 | doi=10.1016/s0896-6273(02)00746-8 | pmid=12123620| s2cid = 7025533 }}</ref> Memory consolidation is a process that transforms novel memories from a relatively fragile state to a more robust and stable condition. For a long time it was believed that the consolidation of procedural memories took place solely as a function of time,<ref>{{cite journal | last1 = Brashers-Krug | first1 = T. | last2 = Shadmehr | first2 = R. | last3 = Bizzi | first3 = E. | year = 1996 | title = Consolidation in human motor memory | url = | journal = Nature | volume = 382 | issue = 6588| pages = 252–255 | doi=10.1038/382252a0| pmid = 8717039 | citeseerx = 10.1.1.39.3383 | bibcode = 1996Natur.382..252B | s2cid = 4316225 }}</ref><ref>{{cite journal | last1 = McGaugh | first1 = J.L. | year = 2000 | title = Memory—A century of consolidation | url = https://semanticscholar.org/paper/4599cc62e637a5619b3f9ee8dd2326d7288cbb1c| journal = Science | volume = 287 | issue = 5451| pages = 248–251 | doi=10.1126/science.287.5451.248 | pmid=10634773| bibcode = 2000Sci...287..248M | s2cid = 40693856 }}</ref> but more recent studies suggest, that for certain forms of learning, the consolidation process is exclusively enhanced during periods of sleep.<ref>{{cite journal | last1 = Fischer | first1 = S. | last2 = Hallschmid | first2 = M. | last3 = Elsner | first3 = A.L. | last4 = Born | first4 = J. | year = 2002 | title = Sleep forms memory for finger skills | url = | journal = Proc. Natl. Acad. Sci. USA | volume = 99 | issue = 18| pages = 11987–11991 | doi=10.1073/pnas.182178199| pmid = 12193650 | pmc = 129381 | bibcode = 2002PNAS...9911987F }}</ref> However, it is important to note that not just any type of sleep is sufficient to improve procedural memory and performance on subsequent procedural tasks. In fact, within the ___domain of motor skill, there is evidence showing that no improvement on tasks is shown following a short, [[non-rapid eye movement]] (NREM; stages 2–4) sleep, such as a nap.<ref>{{cite journal | last1 = Siegel | first1 = J. M. | year = 2001 | title = The REM sleep-memory consolidation hypothesis | url = | journal = Science | volume = 294 | issue = 5544| pages = 1058–1063 | doi=10.1126/science.1063049| pmid = 11691984 | bibcode = 2001Sci...294.1058S | s2cid = 2214566 }}</ref> [[REM sleep]] following a period of [[slow-wave sleep]] (SWS; combined stage 3 and 4 and the deepest form of NREM sleep), has shown to be the most beneficial type of sleep for procedural memory enhancement, especially when it takes place immediately after the initial acquisition of a skill. So essentially, a full night (or day) of uninterrupted sleep soon after learning a skill will allow for the most memory consolidation possible. Furthermore, if REM sleep is disrupted, there is no gain in procedural performance shown.<ref>{{cite journal | last1 = Karni | first1 = A. | last2 = Meyer | first2 = G. | last3 = Rey-Hipolito | first3 = C. | last4 = Jezzard | first4 = P. | last5 = Adams | first5 = M.M. | last6 = Turner | first6 = R. | last7 = Ungerleider | first7 = L.G. | year = 1998 | title = The acquisition of skilled motor performance: Fast and slow experience-driven changes in primarymotor cortex | url = | journal = Proc. Natl. Acad. Sci. USA | volume = 95 | issue = 3| pages = 861–868 | doi=10.1073/pnas.95.3.861| pmid = 9448252 | pmc = 33809 | bibcode = 1998PNAS...95..861K }}</ref> However, equal improvement will take place whether the sleep after practice was at night or during the daytime, as long as SWS is followed by REM sleep. It has also been shown that the enhancement in memory is specific to the learned stimulus (i.e., learning a running technique will not cross over to improvements in biking performance).<ref>{{cite journal | last1 = Mednick | first1 = S.C. | display-authors = etal | year = 2003 | title = Sleep-dependent learning: a nap is as good as a night | url = https://www.semanticscholar.org/paper/ee698a6866fc21686c4e6798f0c3dbc13e568d2d| journal = Nat. Neurosci. | volume = 6 | issue = 7| pages = 697–698 | doi=10.1038/nn1078 | pmid=12819785| s2cid = 16348039 }}</ref> Subject performance in the Wff 'n Proof Task,<ref>Smith C. REM sleep and learning: some recent findings. In: Moffit A, Kramer M, Hoffman H, editors. The functions of dreaming. Albany:SUNY; 1993.</ref><ref>{{cite journal | last1 = Smith | first1 = C | last2 = Fazekas | first2 = A | year = 1997 | title = Amount of REM sleep and Stage 2 sleep required for efficient learning | url = | journal = Sleep Res | volume = 26 | issue = | page = 690 }}</ref><ref>{{cite journal | last1 = Smith | first1 = C | last2 = Weeden | first2 = K | year = 1990 | title = Post training REMs coincident auditory stimulation enhances memory in humans | url = | journal = Psychiatr J Univ Ott | volume = 15 | issue = 2| pages = 85–90 | pmid = 2374793 }}</ref> the [[Tower of Hanoi]],<ref>{{cite journal | last1 = Smith | first1 = CT | last2 = Nixon | first2 = MR | last3 = Nader | first3 = RS | year = 2004 | title = Post training increases in REM sleep intensity implicate REM sleep in memory processing and provide a biological marker of learning potential | url = | journal = Learn Mem | volume = 11 | issue = 6| pages = 714–9 | doi=10.1101/lm.74904| pmid = 15576889 | pmc = 534700 }}</ref> and the Mirror Tracing Task<ref>Conway J, Smith C. REM sleep and learning in humans: a sensitivity to specific types of learning tasks. In: Proceedings of the 12th Congress of the European Sleep Research Society. 1994.</ref> has been found to improve following REM sleep periods.
Whether a skill is learned explicitly (with [[attention]]) or implicitly, each plays a role in the offline consolidation effect. Research suggests that explicit awareness and understanding of the skill being learned during the acquisition process greatly improves the consolidation of procedural memories during sleep.<ref>{{cite journal | last1 = Robertson | first1 = E.M. | display-authors = etal | year = 2004 | title = Awareness modifies skill-learning benefits of sleep | url = | journal = Curr. Biol. | volume = 14 | issue = 3| pages = 208–212 | doi=10.1016/s0960-9822(04)00039-9| pmid = 14761652 | doi-access = free }}</ref> This finding is not surprising, as it is widely accepted that intention and awareness at time of learning enhances the acquisition of most forms of memory.
==Language==
One study used patients with [[Korsakoff’s syndrome]] to show that procedural memory subserves [[syntactic priming]]. Although Korsakoff’s patients have deficits in declarative memory, their nondeclarative memory is preserved, allowing them to successfully complete syntactic priming tasks, as in the study. This result proves syntactic priming is a nondeclarative memory function. These patients were also capable of forming proper grammatical sentences, suggesting that procedural memory is responsible for grammatical processing in addition to syntactic priming.<ref>{{cite journal|last1=Heyselaar|first1=Evelien|last2=Segaert|first2=Katrien|last3=Walvoort|first3=Serge J.W.|last4=Kessels|first4=Roy P.C.|last5=Hagoort|first5=Peter|year=2017|title=The role of nondeclarative memory in the skill for language: Evidence from syntactic priming in patients with amnesia|url=http://pure-oai.bham.ac.uk/ws/files/40798978/HSWKH_Neuropsychologia_revised_2.pdf|journal=Neuropsychologia|volume=101|pages=97–105|doi=10.1016/j.neuropsychologia.2017.04.033|pmid=28465069|hdl=11858/00-001M-0000-002D-4D0D-1|s2cid=4109634}}<!--http://pure-oai.bham.ac.uk/ws/files/40798978/HSWKH_Neuropsychologia_revised_2.pdf--></ref>
Another study’s results support the hypothesis that procedural memory subserves grammar. The study involved a series of tests for two groups: one typically developing (TD) group and one group with developmental language disorder (DLD). Those with DLD have difficulty with proper grammar usage, due to deficits in procedural memory function. Overall, the TD group performed better on each task and displayed better speed in grammatical processing than the DLD group. Therefore, this study shows that grammatical processing is a function of procedural memory.<ref>{{cite journal | last1 = Clark | first1 = Gillian M. | last2 = Lum | first2 = Jarrad A.G. | title = Procedural memory and speed of grammatical processing: Comparison between typically developing children and language impaired children | journal = Research in Developmental Disabilities | volume = 71 | year = 2017 | pages = 237–247 | doi = 10.1016/j.ridd.2017.10.015 | pmid = 29073489 | url = }}</ref>
According to a study carried out in 2010 by [[Dalhousie University]] researchers, spoken languages which require the use of helping words or suffixes, rather than word order, to explain subject-object relationships rely on procedural memory. Word-order dependent languages rely on short-term memory for equivalent tasks.<ref>[http://www.sciencenews.org/view/generic/id/57944/title/Languages_use_different_parts_of_brain Languages use different parts of brain]</ref>
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