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The dorsal nexus is composed by many executive brain networks that are responsible for the mantainance and manipulation of information that allow the control of behavior, memory, conflict resolution and other cognitive functions. An increased functionality in these netoworks are associated with two different types of depression (major depression and decreased depression).Patients with any of this two types of depression shows a recover using ketamine and electroconvulsive therapy (ECT). Although any of these treatments can develop side effects associated with loss of memory and confusion.Magnetic resonance imaging (MRI) and Positron emision tomography (PET) allow the identification of the abnormalities that these networks can present in a depression state associated with dorsal nexus. |
The dorsal nexus is composed by many executive brain networks that are responsible for the mantainance and manipulation of information that allow the control of behavior, memory, conflict resolution and other cognitive functions. An increased functionality in these netoworks are associated with two different types of depression (major depression and decreased depression).Patients with any of this two types of depression shows a recover using ketamine and electroconvulsive therapy (ECT). Although any of these treatments can develop side effects associated with loss of memory and confusion.Magnetic resonance imaging (MRI) and Positron emision tomography (PET) allow the identification of the abnormalities that these networks can present in a depression state associated with dorsal nexus. |
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==References== |
==References== |
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Revision as of 10:02, 8 May 2013
The dorsal nexus is composed by many executive brain networks that are responsible for the mantainance and manipulation of information that allow the control of behavior, memory, conflict resolution and other cognitive functions. An increased functionality in these netoworks are associated with two different types of depression (major depression and decreased depression).Patients with any of this two types of depression shows a recover using ketamine and electroconvulsive therapy (ECT). Although any of these treatments can develop side effects associated with loss of memory and confusion.Magnetic resonance imaging (MRI) and Positron emision tomography (PET) allow the identification of the abnormalities that these networks can present in a depression state associated with dorsal nexus.
Anatomy and functions
The brain’s intrinsic connections are divided into different networks that permit the establishment communication among different structures. These brain networks are: the cognitive control network or executive network, default mode network, and affective network or somatic network.[1]. The dorsal nexus, a region included in the dorsal medial prefrontal cortex (DMPFC), is an important component of them, because these networks are dependent on. [1]The executive network (EN) is located in the dorsolateral prefrontal cortex and lateral parietal cortex. It is responsible for the mantainance and manipulation of the information in the working memory, but it also plays an important role as support of adaptative, goal directed-behaviors so that is why is called the problema solver. [2]The affective network or salience network includes connections between the limbic area and subcortical areas .It is important not just in a fear or a vigilance state, but also in the autonomic and visceral regulation. [2] However this is not its only function, it also generates the somatic sensations that acompany emotions. [3]
In the other hand, the default mode is most active when the brain is at rest or when a person is having a social communication. Its activity decreases during the performance of an activity that involves cognitive demanding tasks. [1]
Dorsal nexus and depression
Neuroimaging studies proved that neurological diseases and psychiatric disorders are associated to problems in the functional connectivity of neural networks between healthy people and patients with a major depression . MRIs shows that the dorsal nexus is responsible for connecting these networks which explains how symptoms of depression are influenced by the condition of brain networks. [1] This increased connectivity can produce sympthoms such as decreased ability to focus, increased vigilance that can be presented as paranoia, rumination and an autonomic , viceral and emotional imbalance. [4]
In patients with depression exists an abnormal connectivity in the bilateral parahipocampal cortex and an increase in charge of hiperintesity of the white matter. Increased default-mode network connectivity, mediated via a region of the dorso medial prefrontal cortex may underline the characteristics of depression. In this pathology dorsal nexus is strongly connected to the task-positive, task-negative and affective networks. The function of this node is to allow enhanced “cross-talk” between networks and this may explain how the diverse symptoms seen in depression converge [5] The dorsal nexus can be related to two different types of depression, decreased and major depression. It is important to mention that there is a big difference between these two types of depression, in the first one the network connection between cingulated subgenual cortex and amígdala, pale striatum and medial thalamus is diminished and in the second one these are normal. This permits to explain how drugs and psycotherapy affect the mecanisms involved in this pathology.[4]
Diagnosis of depression involving dorsal nexus
Neuroimaging techniques allow the watching of images of the nervous system in vivo and that permit scientists explore the structures and functions of the human brain. In neuropsychiatry, neuroimaging techniques such as MRI and Positron Emission Tomography allow the identification of different networks that are implicated in various pathologies [3].
In the case of depression, portions of three different networks (the cognitive control network, the default mode network and the affective network) which are related with de conflict resolution, making decisions, behavior, regulate memory and future planning present increased function in MRI’s . These three increased connectivity networks converged specifically on the dorsal nexus .The dorsal nexus has extremely high connectivity with large regions including dorso lateral prefrontal cortex, dorso medial prefrontal cortex, ventral medial prefrontal cortex, pregenual an subgenual cortex, posterior cingulate, and precuneus . Because these networks can be determined for each individual based on the strength of correlation to an a priori seed location, group statistical differences in networks can be evaluated on an image – wide basis [6].
Treatment
Treating the symptoms of depression has the purpose of reduce and control the dysfunction that patients could have in any areas of their life. The choice of treatment is based on the needs of the patient and can include drugs, therapy and other similar treatments. Regardless of the chosen treatment , if is necessary to consider possible side effects .[7] In the case of depression associated with dorsal nexus and other associated structures, reducing the increased connectivity might play a critical role reducing depression symptomatology and thus represent a potential therapy target for affective disorders [8]
Since glutamate is the most abundant and mayor excitatory neurotransmitter in the brain, pathophysiological changes in glutamatergic signaling are likely to affect neurobehavioral plasticity, information processing and large-scales changes in functional brain connectivity. [8]Ketamine, a fast-acting general anesthetic derived from phencyclidine and use as a pediatric inductor, plays a non-well know role in the neural network dynamics at the healthy brain . The administration of ketamine in abnormal brain has the potential of reduce the increased function of the networks that are seen in depression. The therapeutic potential of ketamine may be explained by reversing disturbances in the glutamatergic system and restoring parts of a disrupted neurobehavioral homeostasis where several structural, metabolic, and functional abnormalities have taken place. [8] Long term ketamine treatments lead to cognitive impairment including problems of short-term memory, visual and verbal memory. On the other hand short term treatments are generally well tolerated and any damage may be reversible. [9]
Electroconvulsive therapy (ECT) significantly reduces functional connectivity between the dorsolateral prefrontal cortex (Dorsal nexus) and the anterior cingulate cortex , the medial prefrontal cortex, and other areas implicated in major depression [10]. Although electroconvulsive therapy has been used as a treatment for depression since 1930, it has several side effects as loss of memory, confusion and difficulties in forming new memories. Because of this reasons, this kind of treatment is limited to severely damaged patients [11]
References
- ^ a b c d Sheline, Yvette; Yan, Shizi (2010). "Resting-state functional MRI in depression unmasks increased connectivity between networks via the dorsal nexus". PNAS. Retrieved 16 April 2013.
- ^ a b Maletic, Vladimir (2012). /role-default-mode-network-depression=16 April 2013 "Role of Default Mode Network in Depression". TrendCong. 6: 290.
{{cite journal}}
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value (help) - ^ a b "Depression and the Brain". UHN rTMS Clinic. Retrieved 17 April 2013.
- ^ a b Lanfranco, Renzo (2011). Depresi%C3%B3n.pdf "Alteraciones de la conectividad funcional de la Default-Mode network en la depresión mayor:una breve mirada a la actividad intrínseca del cerebro" (PDF). Trastor. 7: 138147. Retrieved 16 April 2013.
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value (help) - ^ Norbury, R; Mannie, Z; Cowen, PJ (2011). April 2013 "Imaging vulnerability for depression". Molecular Psychiatry. 16: 1067–1068. doi:10.1038/mp.2011.4.
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value (help) - ^ Sheline, Yvette; Yan, Shizi (2010). "Resting-state functional MRI in depression unmasks increased connectivity between networks via the dorsal nexus". PNAS. Retrieved 16 April 2013.
- ^ Erowid Ketamine Vault: Dosage
- ^ a b c Scheidegger, Milan; Walter; Lehmann, Martin (2012). =16 April 2013 "Ketamine decreases resting state functional connectivity between networks via the dorsal nexus: implications for major depression". Reson. 20: 124.
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at position 119 (help) - ^ Erowid Ketamine Vault: Dosage
- ^ Valero, Tom (2012). "FMRI Data Offer Clues about the Brain Mechanism Behind ECT for Severe Depression". American Academy of Neurology. Retrieved 17 April 2013.
- ^ Norton, Elizabeth (2012). . "Insight Into a Shocking Therapy for Depression". Science. Retrieved 17 April 2013.
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