Nucleus accumbens

Nucleus accumbens

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The nucleus accumbens (NAcc), also known as the accumbens nucleus or as the nucleus accumbens septi (Latin for nucleus adjacent to the septum) is a region in the basal forebrain rostral to the preoptic area of the hypothalamus.

The nucleus accumbens and the olfactory tubercle collectively form the ventral striatum, which is part of the basal ganglia.

Each cerebral hemisphere has its own nucleus accumbens. It is located where the head of the caudate nucleus and the anterior portion of the putamen meet just lateral to the septum pellucidum.

The nucleus accumbens can be divided into two structures—the nucleus accumbens core and the nucleus accumbens shell. These structures have different morphology and function.


Cocaine use followed by withdrawal induces synaptic plasticity in the nucleus accumbens (NAc), which are thought to underlie subsequent drug-seeking behaviors and relapse. Previous studies suggest that cocaine-induced synaptic changes depend on acid-sensing ion channels (ASICs). Gupta et al. investigated the potential involvement of carbonic anhydrase 4 (CA4), an extracellular pH-buffering enzyme. They examined the effects of CA4 in mice on ASIC-mediated synaptic transmission in medium spiny neurons (MSNs) in NAc, as well as on cocaine-induced synaptic changes and behavior. They found that CA4 is expressed in the NAc and present in synaptosomes. Disrupting CA4 either globally, or locally, increased ASIC-mediated synaptic currents in NAc MSNs and protected against cocaine withdrawal-induced changes in synapses and cocaine-seeking behavior. These findings raise the possibility that CA4 might be a previously unidentified therapeutic target for addiction and relapse 1).


Research has indicated the nucleus accumbens has an important role in pleasure including laughter, reward, and reinforcement learning, as well as fear, aggression, impulsivity, addiction, and the placebo effect.


Previous imaging studies independently highlighted the role of the anterior thalamus (ANT) and nucleus accumbens (NAcc) in successful memory retrieval. While these findings accord with theoretical models, the precise temporal, oscillatory and network dynamics as well as the interplay between the NAcc and ANT in successfully retrieving information from long-term memory are largely unknown.

The University of HamburgLübeck and Magdeburg in Germany addressed this issue by recording intracranial electroencephalography in human epilepsy patients from the NAcc (n = 5) and ANT (n = 4) during an old/new recognition test.

The findings demonstrate that differences in event-related potentials between correctly classified old (i.e., studied) and new (i.e., unstudied) images emerged in the NAcc and ANT already between 200 and 600 ms after stimulus onset. Moreover, time-frequency analyses revealed theta (4-8 Hz) power decreases for old compared to new items in the NAcc and the opposite effect in the ANT. Importantly, Granger causality analyses revealed a directional communication from ANT to NAcc suggesting that entrainment from ANT drives successful memory retrieval.

Together, this findings show evidence for the notion that the NAcc and ANT receive memory signals, and that theta oscillations may serve as a mechanism to bind these distributed neural assemblies 2).

see Deep brain stimulation of the nucleus accumbens.


1)

Gupta SC, Ghobbeh A, Taugher-Hebl RJ, Fan R, Hardie JB, LaLumiere RT, Wemmie JA. Carbonic anhydrase 4 disruption decreases synaptic and behavioral adaptations induced by cocaine withdrawal. Sci Adv. 2022 Nov 18;8(46):eabq5058. doi: 10.1126/sciadv.abq5058. Epub 2022 Nov 16. PMID: 36383659.
2)

Bauch EM, Bunzeck N, Hinrichs H, Schmitt FC, Voges J, Heinze HJ, Zaehle T. Theta Oscillations underlie Retrieval Success Effects in the Nucleus Accumbens and anterior Thalamus: evidence from human intracranial recordings. Neurobiol Learn Mem. 2018 Jul 4. pii: S1074-7427(18)30154-0. doi: 10.1016/j.nlm.2018.07.001. [Epub ahead of print] PubMed PMID: 29981424.

Insula functions

Insula functions

The insula serves as an integration cortex for multimodal convergence of distributed neural networks such as the somesthetic-limbic, insulo-limbic, insulo-orbito-temporal and the prefrontal-striato-pallidal-basal forebrain 1).

Histologically, the insula is a part of the paralimbic cortex, as it bears in its antero-inferior part an allo and mesocortical area. The insula is functionally involved in cardiac rhythm and arterial blood pressure control, as well as in viscero-motor control and in viscero-sensitive functions. There is considerable evidence for the involvement of the insula as a somesthetic area, including a major role in the processing of nociceptive inputs.


The combined findings of many sleep-related studies have confirmed a close link between the insula and insomniasleep deprivationsleep disorders, and more. Although these results do not directly confirm that the insula is involved in sleep, an overall analysis of the results indicates that the insula may be a potential key brain region involved in sleep 2).


The insular lobe is involved in the gustatory, olfactory, auditory, and vestibular senses, motor integration, and motor planning of speech 3) 4).

Its possible role in some epilepsies may explain some failures of temporal lobectomy 5).

The insulae are believed to be involved in consciousness and play a role in diverse functions usually linked to emotion or the regulation of the body’s homeostasis. These functions include perception, motor control, self-awareness, cognitive functioning, and interpersonal experience. In relation to these, it is involved in psychopathology.

Recent neuroimaging studies have demonstrated that anterior insular cortex activation is associated with accessing interoceptive information and underpinning the subjective experience of emotional state. Only a small number of studies have focused on the influence of insular damage on emotion processing and interoceptive awareness. Moreover, disparate hypotheses have been proposed for the alteration of emotion processing by insular lesions. Some studies show that insular lesions yield an inability for understanding and representing disgust exclusively, but other studies suggest that such lesions modulate arousal and valence judgments for both positive and negative emotions.

In a study, Terasawa et al. examined the alteration in emotion recognition in three right insular and adjacent area damaged cases with well-preserved higher cognitive function. Participants performed an experimental task using morphed photos that ranged between neutral and emotional facial expressions (i.e., anger, sadness, disgust, and happiness). Recognition rates of particular emotions were calculated to measure emotional sensitivity. In addition, they performed heartbeat perception task for measuring interoceptive accuracy. The cases identified emotions that have high arousal level (e.g., anger) as less aroused emotions (e.g., sadness) and a case showed remarkably low interoceptive accuracy. The current results show that insular lesions lead to attenuated emotional sensitivity across emotions, rather than category-specific impairments such as to disgust. Despite the small number of cases, our findings suggest that the insular cortex modulates recognition of emotional saliency and mediates interoceptive and emotional awareness 6).


1)

Shelley BP, Trimble MR. The insular lobe of Reil–its anatamico-functional, behavioural and neuropsychiatric attributes in humans–a review. World J Biol Psychiatry. 2004 Oct;5(4):176-200. Review. PubMed PMID: 15543513.
2)

Wang Y, Li M, Li W, Xiao L, Huo X, Ding J, Sun T. Is the insula linked to sleep? A systematic review and narrative synthesis. Heliyon. 2022 Nov 5;8(11):e11406. doi: 10.1016/j.heliyon.2022.e11406. PMID: 36387567; PMCID: PMC9647461.
3)

Hugues D, Laurent C, Manuel L, et al. The insular lobes: Physiopathological and surgical considerations. Neurosurgery 2000; 4: 801-811
4)

Francesco S, Jacques G, Kost E, et al. Review of current microsurgical management of insular gliomas. Acta Neurochir 2010; 152: 19-26
5)

Guenot M, Isnard J, Sindou M. Surgical anatomy of the insula. Adv Tech Stand Neurosurg. 2004;29:265-88. Review. PubMed PMID: 15035341.
6)

Terasawa Y, Kurosaki Y, Ibata Y, Moriguchi Y, Umeda S. Attenuated sensitivity to the emotions of others by insular lesion. Front Psychol. 2015 Sep 1;6:1314. doi: 10.3389/fpsyg.2015.01314. eCollection 2015. PubMed PMID: 26388817.

3D imaging

3D imaging

The word stereoscopy derives from Greek στερεός (stereos), meaning “firm, solid”, and σκοπέω (skopeō), meaning “to look, to see”.

Stereoscopy (also called stereoscopics or 3D imaging) is a technique for creating or enhancing the illusion of depth in an image by means of stereopsis for binocular vision.

One of the primary restrictions of endoscopic or endoscope assisted surgery is the lack of binocular or stereoscopic vision. Monocular endoscopes and displays create a 2-dimensional (2-D) image that impairs depth perception, hand-eye coordination, and the ability to estimate size 1) 2).

Most stereoscopic methods present two offset images separately to the left and right eye of the viewer. These two-dimensional images are then combined in the brain to give the perception of 3D depth. This technique is distinguished from 3D displays that display an image in three full dimensions, allowing the observer to increase information about the 3-dimensional objects being displayed by head and eye movements.

Operating in a 2D environment requires surgeons to train their hand-eye coordination to respond to visual cues received by the interaction of the operative instruments with the environment to accurately understand the relative depth of structures in the 2-D projection. Surgeons will often move the endoscope in and out or side to side to gain a motion parallax depth cue. This lack of stereoscopic vision has contributed to the steep learning curve in the field of neuroendoscopy. The next obvious step in the evolution of minimal access endoscopic surgery is the development of high-definition stereoendoscopes that produce a 3-dimensional (3-D) image.

Although such stereoendoscopes exist their use in neurosurgery has been limited because of the larger diameter and poor resolution of earlier generations.

It is easy to make errors in estimating the exact size and positioning of neural structures, especially when only using tomographic methods, as a lot of imagination and little precision is required. Wu and Tang found that combining the use of sectional micro-anatomy and micro-stereoscopic anatomy is much more accurate. They believe that his study makes a significant contribution to the literature because they believe that using improved methods to examine the neural structure is vital in future research on the micro-stereoscopic brain anatomy 3)


In neurosurgery stereoscopy has been used very successfully to demonstrate microsurgical anatomy by Albert L. Rhoton and co-workers 4) and Shimizu et al in 2006 5) , explained the importance of 3D neuroanatomical imaging as a teaching tool in neurosurgical training and comprehensively described original techniques for their production.

The use of 3D imaging in neurosurgical training is not as widespread as it could be, partially due to the complexity of some techniques described in the past, the long preparation time in the pre- and post-operative phases and their interference with the operation, making it impractical in busy neurosurgical theatres.

Companies producing microscopes and endoscopes have developed integrated 3D technology making 3D recording and editing less complex, but these are still very expensive.


Abarca et al performed endoscopic dissection in cadaveric specimens fixed with formalin and with the Thiel technique, both prepared using the intravascular injection of colored material. Endonasal approaches were performed with conventional 2D endoscopes. Then they applied the 3D anaglyph technique to illustrate the pictures in 3D.

The most important anatomical structures and landmarks of the sellar region under endonasal endoscopic vision are illustrated in 3D images.

The skull base consists of complex bony and neurovascular structures. Experience with cadaver dissection is essential to understand complex anatomy and develop surgical skills. A 3D view constitutes a useful tool for understanding skull base anatomy 6).

Used effectively, stereoscopic three-dimensional (3D) technologies can engage students with complex disciplinary content as they are presented with informative representations of abstract concepts. In addition, preliminary evidence suggests that stereoscopy may enhance learning and retention in some educational settings. Biological concepts particularly benefit from this type of presentation since complex spatially oriented structures frequently define function within these systems. Viewing biological phenomena in 3D as they are in real life allows the user to relate these spatial relationships and easily grasp concepts making the key connection between structure and function. In addition, viewing these concepts interactively in 3D and in a manner that leads to increased engagement for young prospective scientists can further increase the impact. We conducted two studies evaluating the use of this technology as an instructional tool to teach high school students complex biological concepts. The first study tested the use of stereoscopic materials for teaching brain function and human anatomy to four classes. The second study evaluated stereoscopic images to support the learning of cell structure and DNA in four different high school classes. Most important, students who used stereoscopic 3D had significantly higher test scores than those who did not. In addition, students reported enjoying 3D presentations, and it was among their top choices for learning about these complex concepts. In summary, our evidence adds further support for the benefits of 3D images to students’ learning of science concepts 7).


The teaching of neuroanatomy in medical education has historically been based on didactic instruction, cadaveric dissections, and intra-operative experience for students. Multiple novel 3-Dimensional (3D) modalities have recently emerged. Among these, stereoscopic anaglyphic video is easily accessible and affordable, however, its effects have not yet formally been investigated.

This study aimed to investigate if 3D stereoscopic anaglyphic video instruction in neuroanatomy could improve learning for content-naive students, as compared to 2D video instruction.

A single-site controlled prospective case control study was conducted at the School of Education. Content knowledge was assessed at baseline, followed by the presentation of an instructional neuroanatomy video. Participants viewed the video in either 2D or 3D format, then completed a written test of skull base neuroanatomy. Pre-test and post-test performances were analyzed with independent t-tests and ANCOVA.

249 subjects completed the study. At baseline, the 2D (n=124, F=97) and 3D groups (n=125, F=96) were similar, although the 3D group was older by 1.7 years (p=.0355) and the curricula of participating classes differed (p<.0001). Average scores for the 3D group were higher for both pretest (2D, M=19.9%, SD=12.5% vs. 3D, M=23.9%, SD=14.9%, p=.0234) and posttest (2D, M=68.5%, SD=18.6% vs. 3D, M=77.3%, SD=18.8%, p=.003), but the magnitude of improvement across groups did not reach statistical significance (2D, M=48.7%, SD=21.3%, vs. 3D, M=53.5%, SD=22.7%, p=.0855).

Incorporation of 3D video instruction into curricula without careful integration is insufficient to promote learning over 2D video 8).


Preoperative 3D imaging provides reliable and detailed information about the intraoperative anatomical relationship between the trigeminal nerve and the SPV. This evaluation is useful for preoperative planning 9).


O arm 3D imaging with stereotactic navigation may be used to localize lesions intraoperatively with real-time dynamic feedback of tumor resection.

Stereotactic guidance may augment resection or biopsy of primary and metastatic spinal tumors. It offers reduced radiation exposure to OR personnel as well as the ability to use minimally invasive approaches that limit tissue injury. Further work may be done to assess the utility of stereotactic image guidance in oncological tumor resection, particularly with respect to outcomes for patients 10).


1)

Badani KK, Bhandari A, Tewari A, Menon M: Comparison of two- dimensional and three-dimensional suturing: Is there a difference in a robotic surgery setting? J Endourol 19:1212–1215, 2005.
2)

Taffinder N, Smith SG, Huber J, Russell RC, Darzi A: The effect of a second- generation 3D endoscope on the laparoscopic precision of novices and expe- rienced surgeons. Surg Endosc 13:1087–1092, 1999.
3)

Wu JZ, Tang CH. Correspondence: A combination of sectional micro-anatomy and micro-stereoscopic anatomy is an improved micro-dissection method. J Anat. 2022 Feb 6. doi: 10.1111/joa.13631. Epub ahead of print. PMID: 35128655.
4)

Ribas GC , Bento RF , Rodrigues AJ . Anaglyphic three-dimensional stereoscopic printing: revival of an old method for anatomical and surgical teaching and reporting . J Neurosurg 2001 ; 95 : 1057 – 66.
5)

Shimizu S , Tanaka R , Rhoton AL , Jr ., e t al . Anatomic dissection and classic three-dimensional documentation: a unit of education for neurosurgical anatomy revisited . Neurosurgery 2006 ; 58 : E1000. discussion E .
6)

Abarca-Olivas J, Monjas-Cánovas I, López-Álvarez B, Lloret-García J, Sanchez-del Campo J, Gras-Albert JR, Moreno-López P. [Three-dimensional endoscopic endonasal study of skull base anatomy]. Neurocirugia (Astur). 2014 Jan-Feb;25(1):1-7. doi: 10.1016/j.neucir.2013.02.009. Epub 2014 Jan 18. Spanish. PubMed PMID: 24447642.
7)

Ferdig R, Blank J, Kratcoski A, Clements R. Using stereoscopy to teach complex biological concepts. Adv Physiol Educ. 2015 Sep;39(3):205-8. doi: 10.1152/advan.00034.2014. PubMed PMID: 26330039.
8)

Goodarzi A, EdM SM, Lee D, Girgis F. The effect of stereoscopic anaglyphic 3-dimensional video didactics on learning neuroanatomy. World Neurosurg. 2017 Jul 29. pii: S1878-8750(17)31219-6. doi: 10.1016/j.wneu.2017.07.119. [Epub ahead of print] PubMed PMID: 28765017.
9)

Xiong NX, Zhou X, Yang B, Wang L, Fu P, Yu H, Wang Q, Abdelmaksoud A, Yuan Y, Liu W, Huang Y, Budrytė K, Huang T, Zheng X. Preoperative MRI Evaluation of Relationship between Trigeminal Nerve and Superior Petrosal Vein: Its Role in Treating Trigeminal Neuralgia. J Neurol Surg A Cent Eur Neurosurg. 2019 Mar 26. doi: 10.1055/s-0038-1669399. [Epub ahead of print] PubMed PMID: 30913572.
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