Surgical Anatomy of the Rectovaginal Space: Does a Standalone Rectovaginal Septum or Denonvilliers Fascia Exist in Women?

BACKGROUND: Below the anterior peritoneal reflection, the anterior rectal wall and mesorectum are separated from the posterior vaginal wall by a virtual rectovaginal space. In this space, the description of a specific and independent rectovaginal septum as a female counterpart of Denonvilliers fascia has been the subject of debate over the years. OBJECTIVE: The aim of this study is to perform an accurate anatomical study of the rectovaginal area in a cadaveric simulation model of total mesorectal excision to evaluate the possible structures and the dissection planes contained within the rectovaginal space. DESIGN AND SETTING: This is a cadaveric study performed at the University of Valencia. PATIENTS: The pelvises of 25 formalin-preserved female cadavers were dissected. All the included specimens were sectioned in a midsagittal plane, at the level of the middle axis of the anal canal. MAIN OUTCOME MEASURES: Careful and detailed dissection was performed to visualize the anatomical structures and potential dissection planes during anterior mesorectal dissection in cadavers. Histological sections were made of the posterior vaginal wall. RESULTS: The rectovaginal space contains loose areolar tissue that allows an easy dissection plane distally. A distinct and independent rectovaginal fascia or septum is not present. The existence of 3 layers fused together in the posterior vaginal wall can be identified more or less precisely because of their different coloration. The histological study confirms this macroscopic arrangement of the posterior vaginal wall in 3 layers: the mucosa, the muscular, and the adventitia. An independent rectovaginal septum can be generated only with a splitting of the adventitia. LIMITATIONS: The cadaveric pelvic specimens of the oldest donors might have had age-related degeneration. CONCLUSIONS: The present anatomical study has shown only a plane of loose areolar tissue between the rectal and vaginal wall. We can conclude that there is no independent fascia or septum in the rectovaginal space. See Video Abstract at http://links.lww.com/DCR/B456. ANATOMÍA QUIRÚRGICA DEL ESPACIO RECTOVAGINAL: ¿EXISTE UN TABIQUE RECTOVAGINAL INDEPENDIENTE O UNA FASCIA DE DENONVILLIERS EN LAS MUJERES: Debajo del reflejo peritoneal anterior, la pared rectal anterior y el mesorrecto están separados de la pared vaginal posterior por un espacio rectovaginal virtual. En este espacio, la descripción de un tabique rectovaginal independiente específico como contraparte femenina de la fascia de Denonvilliers ha sido objeto de debate a lo largo de los años.Realizar un estudio anatómico preciso del área rectovaginal en un modelo de simulación cadavérica de escisión mesorrectal total, con el fin de evaluar las posibles estructuras y los planos de disección contenidos en el espacio rectovaginal.estudio cadavérico realizado en la Universidad de Valencia.Se disecaron las pelvis de 25 cadáveres femeninos conservados en formalina. Todas las muestras incluidas fueron seccionadas en un plano medio sagital, a la altura del eje medio del canal anal.Se llevó a cabo una disección cuidadosa y detallada para visualizar las estructuras anatómicas y los posibles planos de disección durante la disección mesorrectal anterior en cadáveres. Se realizaron cortes histológicos de la pared vaginal posterior.El espacio rectovaginal contiene tejido areolar laxo que permite un plano de disección fácil distalmente. No hay fascia o tabique rectovaginal distinto e independiente. La existencia de tres capas fusionadas en la pared vaginal posterior puede identificarse con mayor o menor precisión debido a su diferente coloración. El estudio histológico confirma esta disposición macroscópica de la pared vaginal posterior en tres capas: la mucosa, la muscular y la adventicia. Un tabique rectovaginal independiente solo se puede generar con una división de la adventicia.Las muestras pélvicas de cadáveres de los donantes más antiguos pueden haber tenido degeneración relacionada con la edad.El estudio anatómico actual solo ha mostrado un plano de tejido areolar laxo entre la pared rectal y vaginal. Podemos concluir que no hay fascia o tabique independiente en el espacio rectovaginal. Consulte Video Resumen en http://links.lww.com/DCR/B456. (Traducción-Dr. Adrian Ortega).

The fusion fascia of Fredet: an important embryological landmark for complete mesocolic excision and D3-lymphadenectomy in right colon cancer.

BACKGROUND: The fusion fascia of Toldt is a well-known landmark used by colorectal surgeons. On the contrary, the fusion fascia of Fredet (the plane between the ascending mesocolon and the visceral duodenal-pancreatic peritoneum) still remains a neglected embryological structure. Aim of this study was to provide an anatomic description of this fascia and its application to minimally invasive D3-lymphadenectomy (D3-L) and complete mesocolic excision (CME) for right colon cancer. METHODS: First phase: Cadaveric dissection and anatomic description of the fascia of Fredet. Second phase: prospective evaluation of its surgical application in a consecutive series of laparoscopic right hemicolectomies with CME and D3-L at a tertiary hospital. RESULTS: The fascia of Fredet was identified and dissected in one fresh and two formalin-fixed cadavers. The trunk of Henle and the medial border of the superior mesenteric vein defined the medial limit of this embryologic plane. Seventeen patients were operated on. Laparoscopic dissection of the fascia of Fredet was possible in every patient. Median operative time was 210 (120-380) min. There were no major postoperative complications. All cases were adenocarcinomas, except one adenomatous polyp. T stage was Tis in three, T2 in two, T3 in seven, and T4 in five patients. Median number of harvested lymph nodes was 24 (9-39). Lymphatic invasion was found in six patients. All resections were classified as satisfactory mesocolic excision and R0. Median postoperative length of stay was 6 (4-20) days. Median follow-up time was 28 (16-41) months. Local and distal recurrence rate was 0. CONCLUSION: The fusion fascia of Fredet is useful to achieve CME and D3-L in right colon cancers with reduced risk of intraoperative complications. This structure is particularly suitable for minimally invasive surgery; therefore, we encourage awareness of the fascia of Fredet by colorectal surgeons.

Simulation of Supralevator Abscesses and Complex Fistulas in Cadavers: Pelvic Dissemination and Drainage Routes.

BACKGROUND: Most perianal abscesses have a cryptoglandular origin, following the pathogenesis described by Parks in 1961. Supralevator abscesses have the most uncommon location. Nevertheless, such pathology results in a high morbidity because of their difficult diagnosis and treatment. OBJECTIVE: This study aimed to deepen the knowledge of the pathogenesis and management of supralevator abscesses, as well as the complications derived from incorrect treatment, by using simulation in cadavers. DESIGN: This study is an anatomosurgical description of pelvic and perianal zone and simulation of the different types of supralevator abscesses, their correct drainage routes, and secondary complex fistulas due to incorrect drainage. SETTINGS: This dynamic article is based on cadaveric simulation. PATIENTS: Three cadaveric pelvises (2 male and 1 female) were prepared in formalin and sagittally sectioned, and one perineal dissection was performed of a fresh male pelvis. This is an iconographic description of 3 patients treated for supralevator abscesses in our colorectal surgical unit. MAIN OUTCOME MEASURES: The virtual anatomical spaces map out a correct treatment. RESULTS: We reproduced the origin of the different types of supralevator abscesses, as well as their locations and possible drainage pathways, and we determined the definitive treatment of secondary fistulas and their morbidity due to their incorrect drainage. LIMITATIONS: The limitations of this study are inherent to anatomical studies without real case intervention. CONCLUSIONS: A proper anatomical knowledge of the supralevator abscesses and surgical training by using cadaveric simulations could improve the diagnostic criteria, facilitate the correct decision on surgical drainage pathways, and, thus, decrease postoperative morbidity in patients with this disease.

Atlases with Arcuate Foramen Present Cortical Bone Thickening That May Contribute to Lower Fracture Risk.

BACKGROUND: To date, no information about the cortical bone microstructural properties in atlas vertebrae with arcuate foramen has been reported. As a result, we aimed to test in an experimental model if there is a cortical bone thickening in an atlas vertebra which has an arcuate foramen that may play a protective role against bone fracture. METHODS: We analyzed by means of micro-computed tomography the cortical bone thickness, the cortical volume, and the medullary volume (SkyScan 1172 Bruker micro-CT NV, Kontich, Belgium) in cadaveric dry atlas vertebrae with arcuate foramen and without arcuate foramen. We also reviewed a case series of 31 posterior atlas arch fractures to correlate the possible presence in the same atlas of both fracture and arcuate foramen. RESULTS: The micro-computed tomography study revealed significant differences in cortical bone thickness (P < 0.001), cortical volume (P < 0.004), and medullary volume (P = 0.013) values between the arcuate foramen vertebrae and the nonarcuate foramen vertebrae. The clinical series found no coexistence in the same vertebra of a posterior atlas arch fractures and the arcuate foramen. CONCLUSIONS: An atlas with arcuate foramen presents cortical bone thickening. This advantage in bone microarchitecture seems to contribute to a lower fracture risk compared to subjects without arcuate foramen as no coexistence in the same vertebra of a posterior atlas arch fractures and arcuate foramen was found.

How to reduce the superior mesenteric vein bleeding risk during laparoscopic right hemicolectomy.

PURPOSE: The superior right colic vein (SRCV) has been proposed as the main cause of superior mesenteric vein bleeding by avulsion during laparoscopic right hemicolectomy. Our objective is to identify the main vessel causing transverse mesocolic tension during the extraction of the surgical specimen or extracorporeal anastomosis and to perform an anatomical description of the SRCV. METHODS: In this cadaveric study, we performed a simulation of right hemicolectomy and anatomical description of the surgical area of the gastrocolic trunk of Henle (SAGCTH), the gastrocolic trunk of Henle (GCTH), and SRCV. The length of the exteriorization of the anastomotic transverse colon (ATC) was measured before and after sectioning the vascular vessel causing the exteriorization tension. RESULTS: Five fresh cadavers and 12 formalin were dissected. In 100% of the specimens, the SRCV was present and drained in 95% into the GCTH and in 5% directly into the superior mesenteric vein (SMV). In 100% of the specimens, the SRCV caused the tension when extracting the ATC. The mean length of exteriorization of the ATC before and after SRCV section was 7.2 and 10.4 cm in formalin cadavers, meaning a 44% of increment in the length of exteriorization. In fresh cadavers, the mean length of exteriorization increased to 2.7 cm, meaning a 28% of the initial length of exteriorization. CONCLUSIONS: The SRCV is the main cause of tension in the extraction of the surgical specimen after right hemicolectomy. Its high tie increases the length of the ATC exteriorization, in about 3 cm, and could reduce the risk of SMV bleeding during laparoscopic right hemicolectomy and facilitate an extracorporeal anastomosis free of tension.

Cortical bone thickening in Type A posterior atlas arch defects: experimental report.

BACKGROUND CONTEXT: To date, no information about the cortical bone microstructural properties in atlas vertebrae with posterior arch defects has been reported. PURPOSE: To test if there is an increased cortical bone thickening in atlases with Type A posterior atlas arch defects in an experimental model. STUDY DESIGN: Micro-computed tomography (CT) study on cadaveric atlas vertebrae. METHODS: We analyzed the cortical bone thickness, the cortical volume, and the medullary volume (SkyScan 1172 Bruker micro-CT NV, Kontich, Belgium) in cadaveric dry vertebrae with a Type A atlas arch defect and normal control vertebrae. RESULTS: The micro-CT study revealed significant differences in cortical bone thickness (p=.005), cortical volume (p=.003), and medullary volume (p=.009) values between the normal and the Type A vertebrae. CONCLUSIONS: Type A congenital atlas arch defects present a cortical bone thickening that may play a protective role against atlas fractures.

Absence of circumflex artery with superdominant right coronary: a classic anatomical dissection study.

PURPOSE: We report a very unusual case of variant coronary artery anatomy, discovered during anatomical dissection in a medical school. METHODS: The heart from a very advanced age donor was dissected using classic anatomical techniques RESULTS: The right coronary artery showed a superdominant pattern, extending beyond the crux of the heart and circling the atrioventricular groove almost completely. It followed the usual path of the absent circumflex artery, and ended as a slender branch which almost reached the origin of the anterior interventricular artery. CONCLUSIONS: To our knowledge, these are the first reported dissection images of this kind of coronary artery variation. It may have clinical consequences, either leading to more accelerated atherosclerotic changes or causing technical difficulties during cardiac surgery.

Difficulties in distinguishing between an atlas fracture and a congenital posterior atlas arch defect in postmortem analysis.

We found one atlas from a sample of 148 skeletons (0.67%) that presented different anatomical variations which made it difficult to determine whether the vertebra had an atlas fracture, an unusual Type B posterior atlas arch defect, or a combination of both. We carried out a stereomicroscopy, radiographic, and computerized tomography scan study that revealed that the dry atlas we found presented a very uncommon congenital Type B posterior atlas arch defect, simulating a fracture. In short, the present paper has revealed that differentiating Type B posterior atlas arch defects from fractures in post-mortem dry vertebrae is more difficult than expected. Thus we believe that it can be easier than expected to mistake Type B posterior arch defects for fractures and vice versa in postmortem studies.

Anatomical basis for the low incidence of internal hernia after a laparoscopic Roux-en-Y gastric bypass without mesenteric closure.

BACKGROUND: Different techniques have been designed to reduce the rate of internal hernia (IH) after laparoscopic bariatric surgery, and mesenteric closure is possibly the most controversial. We propose a laparoscopic Roux-en-Y gastric bypass (LRYGB) procedure without mesenteric closure with several specific technical details to avoid IH. To support this view, we have reviewed the outcome of our LRYGB patients and have carried out an anatomical study on cadavers. METHODS: A retrospective observational study was carried out using the Unit's prospective database. The patients selected were those who were operated on for morbid obesity using LRYGB and who presented to the Emergency Unit with symptoms of intestinal obstruction (IO). Data concerning demographics, weight progress, technical details of the surgery, follow-up percentage, morbidity, and mortality were collected. Furthermore, an anatomical model was made in order to recreate the surgery on cadavers. RESULTS: Only 1.6 % of postoperative IO and very few (0.3 %) of IH cases were associated with our technique of LRYGB without mesenteric closure. The anatomical model showed two large potential hernia spaces, but their supramesocolic situation, the orientation of the bowel loops, leaving the mesentery and omentum undivided and the antecolic passage of the alimentary limb made intestinal herniation difficult even though the mesenteric spaces were not closed. CONCLUSIONS: With a proper technique, the closure of mesenteric spaces after a LRYGB is not essential to avoid postoperative IH in bariatric patients, as evidenced in an anatomical model.

White-to-white corneal diameter, pupil diameter, central corneal thickness and thinnest corneal thickness values of emmetropic subjects.

PURPOSE: This report assesses white-to-white corneal diameter, pupil diameter, central corneal thickness and thinnest corneal thickness values in a large sample of emmetropic subjects. METHODS: Three hundred and seventy-nine eyes of 379 young healthy emmetropic subjects were analyzed by means of scanning-slit corneal topography. The age of the subjects ranged from 18 to 53 years (mean ± SD = 29 ± 7). The mean of five consecutive measurements of the central corneal thickness, the thinnest corneal thickness, the white-to-white corneal diameter, and the photopic pupil diameter was recorded. RESULTS: The central corneal thickness ranged from 528 to 588 µm; the thinnest corneal thickness ranged from 504 to 574 µm; the white-to-white corneal diameter ranged from 11.5 to 12.3 mm; and the pupil diameter ranged from 3.0 to 4.7 mm. The central and the thinnest corneal thickness were positively correlated (r = 0.94, p < 0.001), and the pupil diameter was significantly higher in females (p < 0.001). CONCLUSIONS: This study shows that there are no differences in white-to-white corneal diameter, central corneal thickness, and thinnest corneal thickness between emmetropic females and males. However, pupil diameters are greater in emmetropic females.

An experimental comparative study of dexamethasone, melatonin and tacrolimus in noise-induced hearing loss.

CONCLUSION: The calcineurin inhibitor tacrolimus (TCR) and the pineal gland hormone and antioxidant melatonin (MLT) have been shown to possess otoprotective properties against noise-induced hearing loss (NIHL). In contrast, dexamethasone (DXM) was not effective as an otoprotective agent against NIHL. Further studies are needed to understand the exact molecular mechanisms involved. OBJECTIVE: Exposure to noise pollution and use of audio devices for long periods of time at high volume is known to cause hearing loss or NIHL. Our goal was to evaluate the effectiveness of various known compounds such as the anti-inflammatory DXM, the antioxidant MLT and the immunosuppressant TCR against NIHL. MATERIALS AND METHODS: Thirty-two Wistar rats were randomly divided into groups that were then exposed to intense white noise at 120 dB SPL for 4 h. The day before and for a period of 14 days, test groups were administered one of the three compounds. The efficacy of the compounds against NIHL was determined after examining the shifts in the levels of distortion product otoacoustic emissions (DPOAEs) and changes in the threshold of auditory brainstem responses (ABRs). Cytocochleograms and determination of gene expression in whole rat cochlea were carried out at day 21. RESULTS: Treatment with DXM had no otoprotective effect, while animals treated with MLT experienced an improvement in their hearing functionality. This effect, which is probably linked to MLT's ability to reduce c-fos and TNF-alpha gene expression thereby preventing outer hair cell (OHC) loss, was even more pronounced in week 3. For its part, TCR provided protection against injury to the cochlea from week 1, eventually leading to a full recovery in hearing. The compound reduced both c-fos and TNF-alpha expression, as well as OHC loss.

Differences in ocular dimensions between normal and dry eyes.

Assessment of ocular dimensions is essential for ophthalmic surgeons because these values must be determined before scheduling excimer laser refractive and cataract surgeries. Dry eye seems to affect central corneal thickness (CCT) values, but it is not clear if it affects anterior chamber depth (ACD), lens thickness (LT), vitreous chamber depth (VCD) and axial length values. Following on from this, we measured the CCT, ACD, LT, VCD and axial length of 64 healthy eyes (51.20%) and 61 dry eyes (48.80%). CCT was measured with scanning-slit corneal topography (Orbscan Topography System II, Orbscan, Inc., Salt Lake City, UT, USA) and ACD, LT, VCD and axial length with a 10-MHz A-mode ultrasound device (Compuscan; Storz, St. Louis, MO, USA). There were no significant differences in ACD (P=0.588), LT (P=0.739), VCD (P=0.568) and axial length (P=0.199) between normal and dry eyes. Nevertheless, the differences in CCT between normal (549+/-34 microm) and dry eyes (527+/-30 microm) were significant (P<0.001). In sum, it seems that only the CCT values are significantly lower in subjects with dry eye.

Quantitative anatomical differences in central corneal thickness values determined with scanning-slit corneal topography and noncontact specular microscopy.

PURPOSE: This study was designed to analyze the differences in central corneal thickness values determined with noncontact specular microscopy and scanning-slit corneal topography. The measurements were performed on the same eye. METHODS: We analyzed the central corneal thickness values of 93 patients (n = 93) by means of noncontact specular microscopy (Topcon SP-2000P noncontact specular microscope, Topcon Corp., Tokyo, Japan) and scanning-slit corneal topography (Orbscan Topography System II, Orbscan Inc., Salt Lake City, UT). One experienced physician performed 3 consecutive central corneal thickness measurements with both devices. RESULTS: The central corneal thickness values obtained by means of Orbscan pachymetry were 17 +/- 2.7 (range, 12-24) microm greater. A significant correlation was observed between scanning-slit corneal topography and noncontact specular microscopy (Pearson correlation coefficient, r = 0.976; P < 0.001). CONCLUSIONS: Researchers should know of the existence of this difference between noncontact specular microscopy and Orbscan pachymetry when interpreting central corneal thickness values.

Reduced corneal thickness values in postmenopausal women with dry eye.

PURPOSE: To study and compare the corneal thickness values of postmenopausal women with dry eye and postmenopausal women without dry eye. METHODS: The corneal thickness value of 30 postmenopausal women with dry eye (dry eye group; aged 52 to 55 years) and 32 postmenopausal women without dry eye (normal group; aged 51 to 55 years) was analyzed with the Orbscan Topography System II. Each woman underwent a tear breakup test, the Schirmer test, fluorescein staining of the cornea, and an analysis of the meibomian gland by slit lamp before corneal thickness measurement. The statistical analysis was performed by means of the unpaired Student t test. RESULTS: The mean corneal thickness value was significantly decreased in postmenopausal women with dry eye (P < 0.001 at each corneal location). The central cornea had the thinnest mean values in dry eyes and normal eyes (533.10 +/- 4.74 microm and 547.63 +/- 15.11 microm, respectively), whereas superonasal cornea had thicker mean values in both groups (632.43 +/- 6.11 microm and 648.78 +/- 14.98 microm in dry eye and normal eyes, respectively). CONCLUSIONS: Postmenopausal women with dry eye have lower corneal thickness values than postmenopausal women without dry eye. Special care must be taken with these reduced corneal thickness values when selecting postmenopausal women for surgery involving corneal photoablation.

Anatomic study of the corneal thickness of young emmetropic subjects.

PURPOSE: To study the corneal thickness of young emmetropic subjects. METHODS: One thousand eyes of 1000 young healthy emmetropic subjects were analyzed with the Orbscan Topography System II (Orbscan, Inc, Salt Lake City, UT) from January 2001 to May 2003. The age of the subjects ranged from 20 to 30 years old (mean +/- SD = 27.12 +/- 2.86). The mean of 5 consecutive measurements of the corneal thickness in the center of the cornea and at temporal, superotemporal, inferotemporal, nasal, inferonasal, and superonasal cornea were recorded. RESULTS: The corneal thickness at the following areas ranged as follows: 518 to 589 microm center; 603 to 678 microm nasal; 620 to 689 microm superonasal; 600 to 669 microm inferonasal; 571 to 639 microm temporal; 601 to 669 microm superotemporal; and 572 to 647 microm inferotemporal. In each individual the difference between the central thickness and the maximum paracentral thickness ranged from 85 to 107 microm (mean +/- SD, 99.21 +/- 3.80). The difference between the central thickness and the minimum paracentral thickness ranged from 36 to 59 microm (48.97 +/- 4.23 microm). The difference between the minimum paracentral corneal thickness and the maximum paracentral corneal thickness ranged from 37 to 58 microm (50.24 +/- 4.30). The tonometry was statistically correlated with the corneal thickness (P < 0.05 at each corneal location analyzed). CONCLUSIONS: In emmetropic corneas the difference between the minimum paracentral thickness and the maximum paracentral thickness was similar to the difference between the central thickness and the minimum paracentral thickness.

Segmental gracilis free flap based on secondary pedicles: anatomical study and clinical series.

The gracilis muscle has been used extensively in reconstructive surgery, based on the proximal dominant pedicle. In the literature, little attention has been paid to the secondary distal pedicles. The distribution of the secondary pedicles of the gracilis muscle was investigated in 20 cadaver thighs. The mean number of secondary pedicles was 2.2 (range, two to three). When two pedicles were present-the most common situation-they were located at a mean distance of 12.4 and 17.5 cm from the knee joint line. The most proximal secondary pedicle was injected with barium sulfate in five specimens, and constant and abundant connections with the main pedicle were noted. A series of seven clinical cases of segmental gracilis free muscle flaps based on a secondary pedicle is reported. The flaps were successfully transferred to reconstruct traumatic defects of limited size, with one case of partial necrosis caused by a technical error. The morbidity of this flap is minimal, the scar is well hidden, the muscle need not be sacrificed, elevation is fast and straightforward under tourniquet control, and the pedicle is sizable. This flap should be considered a viable option when a small, straightforward free flap is needed.

Cytoarchitecture and efferent projections of the nucleus incertus of the rat.

The nucleus incertus is located caudal to the dorsal raphe and medial to the dorsal tegmentum. It is composed of a pars compacta and a pars dissipata and contains acetylcholinesterase, glutamic acid decarboxylase, and cholecystokinin-positive somata. In the present study, anterograde tracer injections in the nucleus incertus resulted in terminal-like labeling in the perirhinal cortex and the dorsal endopyriform nucleus, the hippocampus, the medial septum diagonal band complex, lateral and triangular septum medial amygdala, the intralaminar thalamic nuclei, and the lateral habenula. The hypothalamus contained dense plexuses of fibers in the medial forebrain bundle that spread in nearly all nuclei. Labeling in the suprachiasmatic nucleus filled specifically the ventral half. In the midbrain, labeled fibers were observed in the interpeduncular nuclei, ventral tegmental area, periaqueductal gray, superior colliculus, pericentral inferior colliculus, pretectal area, the raphe nuclei, and the nucleus reticularis pontis oralis. Retrograde tracer injections were made in areas reached by anterogradely labeled fibers including the medial prefrontal cortex, hippocampus, amygdala, habenula, nucleus reuniens, superior colliculus, periaqueductal gray, and interpeduncular nuclei. All these injections gave rise to retrograde labeling in the nucleus incertus but not in the dorsal tegmental nucleus. These data led us to conclude that there is a system of ascending projections arising from the nucleus incertus to the median raphe, mammillary complex, hypothalamus, lateral habenula, nucleus reuniens, amygdala, entorhinal cortex, medial septum, and hippocampus. Many of the targets of the nucleus incertus were involved in arousal mechanisms including the synchronization and desynchronization of the theta rhythm.