#habenula

[neurosciencenews]

Brain Circuits Controlling Social Behavior Identified

A new study by researchers at Roche in Basel, Switzerland has identified a key brain region of the neural circuit that controls social behavior. Increasing the activity of this region, called the habenula, led to social problems in rodents, whereas decreasing activity of the region prevented social problems.

The research is in Biological Psychiatry. (full access paywall)

[mavibirbahce]

'Beyin her aşamada bir hücre tipiyle gelişiyor' - Aynur Tekin

Norveç Teknik Üniversitesi’nden Prof. Dr. Emre Yakşi ve ekibi tarafından yapılan araştırma, beynin nasıl geliştiğine dair yeni bulgular ortaya çıkardı. Araştırmaya göre beyin gelişiminin her aşamasında yeni bir işe uzmanlaşmış bir hücre tipi devreye giriyor ve gelişim yeni modüllerin adım adım eklenmesiyle oluşuyor. Yakşi araştırmayla ilgili, "Bizim öğrenmeye çalıştığımız beyinde yeni eklenen sinir hücrelerinin yapmaları gereken görevi nasıl yaptıkları. Eğer bunu anlayabilirsek acaba Parkinson ya da Alzheimer'da olduğu gibi hücrelerin yeniden yapılanması gereken tedavilere bir katkı sağlayabilir miyiz diye düşünüyoruz" ifadelerini kullanıyor.

Araştırmada, gelişimlerini ana rahmi dışında ve tamamen şeffaf olarak devam ettiren zebra balığı yavruları mikroskopla gözlemlendi. Yakşi, bu teknikle zebra balığı yavrularında beyin hücrelerinin ne zaman bölündüğünü, ne zaman çalışmaya başladığını ve hangi tür bilgileri taşıdıklarını inceleyebildiklerini söylüyor. YAZIDAN ALINTI

[zebraphys]

Nicotine withdrawal, VTA and habenula-IPN interplay

The paired habenula nuclei are located bilaterally in the dorsal diencephalon surrounding the dorso-lateral walls of the third ventricle.

Fear / Anxiety related brain regions in Danio rerio:

Habenula (Medial and Lateral)

Interpeduncular Nucleus (IPN)

griseum centrale [homologous to periaqueductal gray (PAG) in mammals]

Nucleus Incertus 

Figure 1: Schematic showing asymmetric habenular circuitry in zebrafish. 

EmT neurons project bilaterally, innervating both left and right habenulae.

A subset of left- and right-sided neurons in the anterior pallium are a source of asymmetric innervation, selectively terminating in a small medial domain of the right habenula (indicated in purple). 

In addition, a small afferent input may derive from the posterior tuberculum ( Hendricks & Jesuthasan 2007). 

The parapineal exclusively innervates the left habenula (Concha et al. 2003).

Habenular neurons project efferent axons that course in the fasciculus retroflexus. 

A major target is the interpeduncular nucleus (IPN) : left and right- sided axons are segregated along the dorso-ventral (DV) axis of the IPN in a laterotopic manner (Aizawa et al. 2005). 

A symmetric contingent of habenular axons terminates caudal to the IPN in the serotonergic raphe.

(Schematic provided by Isaac Bianco taken from Bianco & Wilson, 2009)

 Stressors that mimics predator threat:

exposure to the alarm substance followed by an overhead shadow (predator threat)

Stress Responses  :

more time spent in the bottom quarter of the tank 

more episodes of slow swimming

more pauses / “freezing”

more darting episodes 

Notably, the habenula-damaged, transgenic TeTXlc fish display both active and passive responses, suggesting that :

there is an increase in the intensity of fear expression

rather than a bias toward a particular type of action.

Novel tank assay. 

Area in each color shows percentage time spent in either half of a novel tank in one minute 1min by five Control fish and five TeTXlc expressing fish. 

Arrows indicate median swim time in the bottom half for controls (20.4 ± 3.7%) and TeTXlc fish (48.6 ± 9%). \(C–F) 

Response to dilute alarm substance and an overhead shadow. 

(C) Time spent in the bottom quarter of a tank, and median number of 

(D) slow swimming, 

(E) pauses, and 

(F) darts

Non-parametric, Mann–Whitney U-test was used to compare behavior of control and TeTXlc fish following exposure to the stimuli. 

(Mann–Whitney U-test, *p < 0.05, **p < 0.01, ***p < 0.001).

For the novel tank assay:

Fish were transferred into a glass tank measuring 20 × 12 × 5 cm—L × H × W containing 1 L of water and observed for 1 min. 

Digital videos:

 were recorded as described before (Mathuru et al., 2012). Fish position in the tank was tracked and analyzed automatically using “track objects” algorithm in MetaMorph. 6.3 and custom written macros for Excel.

Alarm substance: was prepared as described before (Mathuru et al., 2012). This was introduced into the tank and a shadow, created by passing a hand under the overhead light, was presented after 2 min. 

Darting:

was defined as episodes during which the swimming speed exceeded baseline speed by more than 8 SD, 

Slow swim episodes:

were defined as episodes greater than one second in duration during which the swim speed never exceeded half the mean baseline speed,

Pause episodes:

while one second of immobility (speed less than 3 mm/s) was considered as a pause episode.

[sciencefriday]

This tiny, pea-sized part of the brain is why you worry all the time.

[booprenorphine]

Medical term of the day: habenula