Editing Caudate nucleus (section)

==Cognitive functions==

===Goal-directed action===
A review of neuroimaging studies, anatomical studies of caudate connectivity, and behavioral studies reveals a role for the caudate in executive functioning. A study of Parkinson's patients (see below) may also contribute to a growing body of evidence.

A two-pronged approach of neuroimaging (including [[positron emission tomography|PET]] and [[fMRI]]) and anatomical studies expose a strong relationship between the caudate and cortical areas associated with executive functioning: "non-invasive measures of anatomical and functional connectivity in humans demonstrate a clear link between the caudate and executive frontal areas."<ref name="Grahn 2009 146"/>

Meanwhile, behavioral studies provide another layer to the argument: recent studies suggest that the caudate is fundamental to goal-directed action, that is, "the selection of behavior based on the changing values of goals and a knowledge of which actions lead to what outcomes."<ref name="Grahn 2009 146"/> One such study presented rats with levers that triggered the release of a cinnamon flavored solution. After the rats learned to press the lever, the researchers changed the value of the outcome (the rats were taught to dislike the flavor either by being given too much of the flavor, or by making the rats ill after drinking the solution) and the effects were observed. Normal rats pressed the lever less frequently, while rats with lesions in the caudate did not suppress the behavior as effectively. In this way, the study demonstrates the link between the caudate and goal-directed behavior; rats with damaged caudate nuclei had difficulty assessing the changing value of the outcome.<ref name="Grahn 2009 146"/> In a 2003-human behavioral study, a similar process was repeated, but the decision this time was whether or not to trust another person when money was at stake.<ref>{{cite journal | vauthors = Elliott R, Newman JL, Longe OA, Deakin JF | title = Differential response patterns in the striatum and orbitofrontal cortex to financial reward in humans: a parametric functional magnetic resonance imaging study | journal = The Journal of Neuroscience | volume = 23 | issue = 1 | pages = 303–7 | date = January 2003 | pmid = 12514228 | pmc = 6742125 | doi = 10.1523/JNEUROSCI.23-01-00303.2003 }}</ref> While here the choice was far more complex––the subjects were not simply asked to press a lever, but had to weigh a host of different factors––at the crux of the study was still behavioral selection based on changing values of outcomes.

In short, neuroimagery and anatomical studies support the assertion that the caudate plays a role in executive functioning, while behavioral studies deepen our understanding of the ways in which the caudate guides some of our decision-making processes.

===Memory===
The dorsal-prefrontal cortex subcortical loop involving the caudate nucleus has been linked to deficits in working memory, specifically in [[schizophrenic]] patients.  Functional imaging has shown activation of this subcortical loop during working memory tasks in primates and healthy human subjects.  The caudate may be affiliated with deficits involving working memory from before illness onset as well.  Caudate nucleus volume has been found to be inversely associated with [[Perseveration|perseverative]] errors on spatial working memory tasks.<ref name="Hannan 2010 223–230">{{cite journal | vauthors = Hannan KL, Wood SJ, Yung AR, Velakoulis D, Phillips LJ, Soulsby B, Berger G, McGorry PD, Pantelis C | title = Caudate nucleus volume in individuals at ultra-high risk of psychosis: a cross-sectional magnetic resonance imaging study | journal = Psychiatry Research | volume = 182 | issue = 3 | pages = 223–30 | date = June 2010 | pmid = 20488675 | doi = 10.1016/j.pscychresns.2010.02.006 | s2cid = 35678217 }}</ref><ref name="Levitt 2002">{{cite journal|vauthors=Levitt JJ, McCarley RW, Dickey CC, Voglmaier MM, Niznikiewicz MA, Seidman LJ, Hirayasu Y, Ciszewski AA, Kikinis R, Jolesz FA, Shenton ME|date=July 2002|title=MRI study of caudate nucleus volume and its cognitive correlates in neuroleptic-naive patients with schizotypal personality disorder|journal=The American Journal of Psychiatry|volume=159|issue=7|pages=1190–7|doi=10.1176/appi.ajp.159.7.1190|pmc=2826363|pmid=12091198}}<!--|access-date=10 February 2015--></ref>

The [[amygdala]] sends direct projections to the caudate nucleus.  Both the [[amygdala]] and the caudate nucleus have direct and indirect projections to the [[hippocampus]].  The influence of the [[amygdala]] on memory processing in the caudate nucleus has been demonstrated with the finding that lesions involving the connections between these two structures "block the memory-enhancing effects of [[oxotremorine]] infused into the caudate nucleus".  In a study involving rats given water-maze training, the caudate nucleus was discovered to enhance memory of visually cued training after [[amphetamine]] was infused post-training into the caudate.<ref>{{cite journal | vauthors = McGaugh JL | title = The amygdala modulates the consolidation of memories of emotionally arousing experiences | journal = Annual Review of Neuroscience | volume = 27 | pages = 1–28 | year = 2004 | pmid = 15217324 | doi = 10.1146/annurev.neuro.27.070203.144157 }}</ref>

===Learning===
In a 2005 study, subjects were asked to learn to categorize visual stimuli by classifying images and receiving feedback on their responses. Activity associated with successful classification learning (correct categorization) was concentrated to the body and tail of the caudate, while activity associated with feedback processing (the result of incorrect categorization) was concentrated to the head of the caudate.<ref>{{cite journal | vauthors = Seger CA, Cincotta CM | title = The roles of the caudate nucleus in human classification learning | journal = The Journal of Neuroscience | volume = 25 | issue = 11 | pages = 2941–51 | date = March 2005 | pmid = 15772354 | pmc = 6725143 | doi = 10.1523/jneurosci.3401-04.2005 | series = 11 }}</ref>

===Sleep===
Bilateral lesions in the head of the caudate nucleus in cats were correlated with a decrease in the duration of deep [[slow wave sleep]] during the sleep-wakefulness cycle.  With a decrease in total volume of deep slow wave sleep, the transition of [[short-term memory]] to [[long-term memory]] may also be affected negatively.<ref>{{cite journal | vauthors = Gogichadze M, Oniani MT, Nemsadze M, Oniani N |title=Sleep disorders and disturbances in memory processing related to the lesion of the caudate nucleus |journal=Parkinsonism and Related Disorders |volume=15 |year=2009 |pages=S167–S168 |doi=10.1016/S1353-8020(09)70639-X }}</ref>

However, the effects of caudate nuclei removal on the sleep–wakefulness pattern of cats have not been permanent.  Normalization occurs by three months after caudate nuclei [[ablation]].  This discovery may be due to the inter-related nature of the roles of the caudate nucleus and the [[frontal cortex]] in controlling levels of [[central nervous system]] activation.  The cats with caudate removal, although permanently hyperactive, had a significant decrease in [[rapid eye movement sleep]] (REMS) time, which lasted about two months.  However, afrontal cats had a permanent decrease in REMS time and only a temporary period of hyperactivity.<ref name="pmid15339255">{{cite journal | vauthors = Villablanca JR | title = Counterpointing the functional role of the forebrain and of the brainstem in the control of the sleep-waking system | journal = Journal of Sleep Research | volume = 13 | issue = 3 | pages = 179–208 | date = September 2004 | pmid = 15339255 | doi = 10.1111/j.1365-2869.2004.00412.x | doi-access = free }}</ref>

Contrasting with associations between "deep", REM sleep and the caudate nucleus, a study involving [[EEG]] and [[fMRI]] measures during human sleep cycles has indicated that the caudate nucleus demonstrates reduced activity during non-REM sleep across all sleep stages.<ref>{{cite journal | vauthors = Kaufmann C, Wehrle R, Wetter TC, Holsboer F, Auer DP, Pollmächer T, Czisch M | title = Brain activation and hypothalamic functional connectivity during human non-rapid eye movement sleep: an EEG/fMRI study | journal = Brain | volume = 129 | issue = Pt 3 | pages = 655–67 | date = March 2006 | pmid = 16339798 | doi = 10.1093/brain/awh686 | doi-access = free }}</ref>  Additionally, studies of human caudate nuclei volume in [[congenital central hypoventilation syndrome]] (CCHS) subjects established a correlation between CCHS and a significant reduction in left and right caudate volume.  CCHS is a genetic disorder that affects the [[sleep cycle]] due to a reduced drive to breathe.  Therefore, the caudate nucleus has been suggested to play a role in human sleep cycles.<ref>{{cite journal | vauthors = Kumar R, Ahdout R, Macey PM, Woo MA, Avedissian C, Thompson PM, Harper RM | title = Reduced caudate nuclei volumes in patients with congenital central hypoventilation syndrome | journal = Neuroscience | volume = 163 | issue = 4 | pages = 1373–9 | date = November 2009 | pmid = 19632307 | pmc = 2761724 | doi = 10.1016/j.neuroscience.2009.07.038 }}</ref>

===Emotion===

The caudate nucleus has been implicated in responses to visual beauty, and has been suggested as one of the "neural correlates of romantic love".<ref>{{cite journal | vauthors = Ishizu T, Zeki S | title = Toward a brain-based theory of beauty | journal = PLOS ONE | volume = 6 | issue = 7 | pages = e21852 | date = May 2011 | pmid = 21755004 | pmc = 3130765 | doi = 10.1371/journal.pone.0021852 | bibcode = 2011PLoSO...621852I | veditors = Warrant EJ | doi-access = free }}</ref><ref>{{cite journal | vauthors = Aron A, Fisher H, Mashek DJ, Strong G, Li H, Brown LL | title = Reward, motivation, and emotion systems associated with early-stage intense romantic love | journal = Journal of Neurophysiology | volume = 94 | issue = 1 | pages = 327–37 | date = July 2005 | pmid = 15928068 | doi = 10.1152/jn.00838.2004 | s2cid = 396612 }}</ref>

Approach-attachment behavior and affect are also controlled by the caudate nucleus.  Cats with bilateral removal of the caudate nuclei persistently approached and followed objects, attempting to contact the target, while exhibiting a friendly disposition by the elicitation of treading of the forelimbs and purring.  The magnitude of the behavioral responses was correlated to the extent of the removal of the nuclei.  Reports of human patients with selective damage to the caudate nucleus show unilateral caudate damage resulting in loss of drive, [[obsessive-compulsive disorder]], stimulus-bound [[perseveration|perseverative]] behavior, and hyperactivity.  Most of these deficits can be classified as relating to approach-attachment behaviors, from approaching a target to romantic love.<ref name="pmid20407491" />

===Language===
Neuroimaging studies reveal that people who can communicate in multiple languages activate exactly the same brain regions regardless of the language. A 2006 publication studies this phenomenon and identifies the caudate as a center for language control. In perhaps the most illustrative case, a trilingual subject with a lesion to the caudate was observed. The patient maintained language comprehension in her three languages, but when asked to produce language, she involuntarily switched between the three languages. In short, "these and other findings with bilingual patients suggest that the left caudate is required to monitor and control lexical and language alternatives in production tasks."<ref>{{cite journal | vauthors = Crinion J, Turner R, Grogan A, Hanakawa T, Noppeney U, Devlin JT, Aso T, Urayama S, Fukuyama H, Stockton K, Usui K, Green DW, Price CJ | s2cid = 10445511 | title = Language control in the bilingual brain | journal = Science | volume = 312 | issue = 5779 | pages = 1537–40 | date = June 2006 | pmid = 16763154 | doi = 10.1126/science.1127761 | bibcode = 2006Sci...312.1537C }}</ref><ref>{{cite web|url=https://www.newscientist.com/article/dn9304-how-bilingual-brains-switch-between-tongues.html|title=How bilingual brains switch between tongues |website=newscientist.com}}</ref>

Local shape deformations of the medial surface of the caudate have been correlated with verbal learning capacity for females and the number of perseverance errors on spatial and verbal fluency working memory tasks for males.  Specifically, a larger caudate nucleus volume has been linked with better verbal fluency performance.<ref name="Hannan 2010 223–230"/>

A neurological study of [[glossolalia]] showed a significant reduction in activity in the left caudate nucleus during glossolalia compared to singing in English.<ref>{{cite journal | vauthors = Newberg AB, Wintering NA, Morgan D, Waldman MR | title = The measurement of regional cerebral blood flow during glossolalia: a preliminary SPECT study | journal = Psychiatry Research | volume = 148 | issue = 1 | pages = 67–71 | date = November 2006 | pmid = 17046214 | doi = 10.1016/j.pscychresns.2006.07.001 | s2cid = 17079826 }}</ref>

===Threshold control===
The brain contains large collections of neurons reciprocally connected by [[excitatory synapses]], thus forming large network of elements with [[positive feedback]]. It is difficult to see how such a system can operate without some mechanism to prevent explosive activation. There is some indirect evidence<ref>Braitenberg V. (1984) Vehicles. Experiments in synthetic psychology.</ref> that the caudate may perform this regulatory role by measuring the general activity of [[cerebral cortex]] and controlling the [[threshold potential]].