Olfaction plays an important role to detect environmental risk, taste the food, and performs various additional roles crucial to the nutrition, mood and memory. But it has been overlooked compared with other sensory organs, such as vision or hearing function. Recently, a variety of studies associated with olfactory system are in progress from periphery to central area. This review shows the brief summary of the recent ongoing study on olfaction.
Hearing ; Memory ; Olfactory Bulb ; Olfactory Pathways ; Smell*

Olfactory processing involves a large number of central olfactory structures, interconnected with each other in complex fashion, and incorporating both feed forward and feed back interaction. Thus understanding how these structures in odor acquisition, perception, and memory perform functional roles is a central question in olfactory disorders that can only be addressed using a combination of approaches, including neuroimaging, neurophysiology and behavioral analyses. Recent whole-brain imaging studies have shown that multiple diverse neural structures become activated during tasks involving olfactory stimulation. This article reviews the current understanding of anatomy, sensory physiology of central olfactory structures. Especially the sensory physiology of main olfactory bulb, pyriform cortex, and orbitofrontal cortex will be emphasized here.
Memory ; Neuroimaging ; Neurophysiology ; Odors ; Olfactory Bulb ; Olfactory Pathways* ; Physiology ; Smell

External tufted (ET) cells are the major excitatory elements coordinating the activities of glomerulars and mediating the input from the olfactory neurons to mitral cells. The ET cells participate in inter-and intra-glomerular microcircuits in the olfactory bulb, link the isofunctional odor columns within the same olfactory bulb, and play an important role in olfactory information processing. This paper reviews the research progress of the anatomy and physiological properties and electrophysiological modeling of ET cells, elaborate the problems and defects in the field. And then it further gives some proposals for the future research of electrophysiological properties, development of olfactory information coding and performance of modeling of ET cells.
Electrophysiological Phenomena ; physiology ; Humans ; Olfactory Bulb ; cytology ; physiology ; Olfactory Pathways ; physiology ; Olfactory Receptor Neurons ; cytology

OBJECTIVETo study the olfactory function in rats by manganese-enhanced magnetic resonance imaging (MEMRI) and explore the regeneration of olfactory system from the imaging.

METHODSThirty-five adult male Sprague-Dawley (SD) rats were randomly divided into three groups. Twenty rats with bilateral nasal instillation of TritonX-100 were used as olfactory dysfunction model group (M group). The rats in this group received menthocamphorate stimulation. Ten rats with bilateral nasal instillation of sterile saline were used as olfactory normal group (N group), and were randomly divided into two groups:one group received menthocamphorate stimulation (N1 group), another group received odorless air (N2 group). The remaining five rats were used as the blank control (control group). All images were acquired with a 7.0 T micro-MR scanner. Signal-to-noise ratios (SNR) in the olfactory bulb (OB) were measured by Image J.

RESULTSMEMRI could clearly show the normal olfactory pathway in rats. MEMRI displayed a reversible change during the stages of olfactory recovery after injury. For the olfactory dysfunction model group (M group), the total volume of rat olfactory bulb at the initial, the 10th day, the 20th day, the 30th day and the 60th day were (49.44 ± 0.81), (32.85 ± 0.79), (27.78 ± 1.07), (35.89 ± 1.04), (43.63 ± 1.13) mm(3) respectively. At the 20th day after olfactory injury, the SNR in the OB was the lowest for 9.78 ± 0.07, when at the 60th day, the SNR recovered to 30.68 ± 1.01, which increased to near normal (N1group, 33.08 ± 0.15; N2 group, 31.31 ± 1.12), the SNR had no significant difference among the three groups (F = 3.04, P > 0.05).

CONCLUSIONThe MEMRI is an objective method to detect the olfactory function, and the olfactory system has the regenerative property after injury.

Animals ; Magnetic Resonance Imaging ; methods ; Male ; Manganese ; Olfactory Bulb ; Olfactory Pathways ; Rats ; Rats, Sprague-Dawley ; Smell

OBJECTIVES: Patients with smell loss after craniocerebral trauma are known to have some brain abnormalities, but there was no study to analyze the findings according to the time interval between injury and evaluation. We aimed to identify whether the time interval may influence on the findings in the brain. METHODS: Medical records of 19 patients with posttraumatic olfactory dysfunction were reviewed. All of them underwent a magnetic resonance imaging and olfactory function tests. The patients were divided into early (n=10) and delayed (n=9) groups according to the time interval. RESULTS: Magnetic resonance imaging was taken at a mean time of 2.2 and 59.6 months after trauma in the early and delayed groups, respectively. Abnormal findings in the brain were found in 6 and 8 patients in the early and delayed groups, respectively. The olfactory bulb and orbitofrontal cortex were commonly affected olfactory pathways in both groups. In the early group, the abnormalities were brain tissue defect, hemorrhage, and focal edema whereas tissue defect was the only finding in the delayed group. In the early group, 5 of 6 patients with severe olfactory dysfunction showed brain abnormality while 1 of 4 patients with mild dysfunction had abnormality. In the delayed group, all the patients had severe dysfunction and 8 of 9 patients showed brain abnormality. CONCLUSION: Most patients with traumatic olfactory dysfunction had abnormality in the brain, and brain abnormality might be different according to the timing of evaluation. Furthermore, there might be an association between the severity of olfactory dysfunction and radiological abnormalities.
Brain ; Craniocerebral Trauma ; Edema ; Hemorrhage ; Humans ; Magnetic Resonance Imaging* ; Medical Records ; Olfactory Bulb ; Olfactory Pathways ; Smell

MRI scanning is an important technique to evaluate the olfactory system, special scanning parameters could reveal the fine structures of the olfactory pathway. Olfactory cleft, olfactory bulb/tract, olfactory sulcus and olfactory center are the main targets of the scanning. Chronic rhino-sinusitis, head trauma, congenital dysplasia and neural degenerative diseases are the primary causes of the olfactory dysfunction and have particular imaging presentations respectively. Besides indicating the olfactory pathway lesions, MRI could also present the etiology and the prognosis of the olfactory disorder.
Humans ; Magnetic Resonance Imaging ; Olfaction Disorders ; diagnosis ; Olfactory Bulb ; Olfactory Pathways

BACKGROUND AND OBJECTIVES: The purpose of this study was to evaluate the time course of functional and anatomical recovery of the olfactory epithelium (OE) and olfactory bulb (OB) following intranasal instillation of 1% ZnSO4 in mice. MATERIALS AND METHOD: Two groups of mice, normal control group (intranasal instillation of normal saline, n=6) and experimental group (intranasal instillation of ZnSO4, n=18), were studied. Tissues of olfactory pathways were obtained at 1, 3 and 5 weeks after bilateral intranasal instillation of 1%, 100 microliter ZnSO4 solution, and processed for immunohistochemistry using antisera, olfactory marker protein (OMP), proliferating cell nuclear antigen (PCNA) and tyrosine hydroxylase (TH) to evaluate the olfactory regeneration. For histological study, OE thickness stained with hematoxylin-eosin was analyzed. RESULTS: At 1 week after ZnSO4 intranasal instillation, the lowest peak of OMP expression in OE appeared. Then the number of OMP-positive cells increased progressively at weeks. However, PCNA expression in OE showed quite the opposite. In the corresponding OB at 1 week, there was decrease of TH-positive cells and at 3 weeks, there was few TH-positive cells. At 5 weeks, there was increase in the number of TH-positive cells again. OE thickness was reduced to 20% of control OE at 1 week, and was significantly recovered to 80% of control OE at 5 weeks. CONCLUSION: Our results demonstrated that intranasal instillation of 1% ZnSO4 to mice produces a brief, reversible but essentially complete destruction of functional connection from the olfactory epithelium to the main olfactory bulb.
Animals ; Immune Sera ; Immunohistochemistry ; Mice* ; Olfactory Bulb* ; Olfactory Marker Protein ; Olfactory Mucosa* ; Olfactory Pathways ; Proliferating Cell Nuclear Antigen ; Regeneration ; Tyrosine 3-Monooxygenase

OBJECTIVETo explore the feasibility of functional magnetic resonance imaging (fMRI) in analysis of olfaction function with modified OEP-98C olfactometer and event-related design.

METHODSSix young right-handed men underwent olfactory fMRI with event-related design. OEP-98C olfactometer was modified to accommodate MR environment. There were 2 types of tasks in the experiment. In one task, only isoamyl acetate was used as odorant. In the other task, to avoid possible decreased olfactory attention, vanillin was given before each presentation of isoamyl acetate.

RESULTSIn both tasks, uniform activation in piriform cortex and secondary olfactory cortexes was determined. The activation of piriform cortex was not significantly different between the two tasks (P > 0.01).

CONCLUSIONSWith isoamyl acetate as odorant, modified OEP-98C olfactometer, and event-related design, olfaction fMRI can depict cortex activation at primary and secondary olfactory cortex. Applying other odorant with similar quality to avoid olfactory attention decrease can not promote depiction of activation in primary olfactory cortex.

Adult ; Evoked Potentials ; physiology ; Feasibility Studies ; Humans ; Magnetic Resonance Imaging ; methods ; Male ; Olfactory Pathways ; physiology ; Olfactory Perception ; physiology ; Pentanols

Compared with other sensory system, olfactory neural system may be the most unknown one. And it is reported that the research of the complicated olfactory system is beneficial to clarifying the whole mechanism of the sensory system. Focused on spatiotemporal coding and decoding mechanism, the studies on the olfactory neural system recognition models are especially introduced. Finally, this paper presents the research work carried out in our lab, and prospects the development of this field in the future.
Computer Simulation ; Humans ; Models, Neurological ; Neural Networks (Computer) ; Olfactory Pathways ; anatomy & histology ; physiology ; Olfactory Receptor Neurons ; cytology ; metabolism

OBJECTIVE: The purpose of this study is to compare the surgical outcomes of pterional-subolfactory approach for the high positioned anterior communicating artery (ACoA) aneurysm with the conventional pterional approach. METHODS: Between February 2005 and December 2012, 463 ACoA aneurysms were surgically treated in our institution. Forty eight high positioned ACoA aneurysms were treated with pterional-subolfactory or conventional pterional approach. High positioned ACoA aneurysms were defined as aneurysms located higher than 10 mm above the anterior clinoid process. Pterional-subolfactory approach is a procedure including dissection of olfactory tract and resection of the gyrus rectus inferior and medial to the olfactory tract. Thirty-four of the 48 cases were treated with pterional-subolfactory approach and 14 were treated conventionally. RESULTS: There were 2 postoperative cerebral infarction with the conventional pterional approach, but none with the pterional-subolfactory approach group (p = 0.026). Postoperative digital subtraction angiography revealed significant remnant aneurysm in the conventional pterional approach group. All patients with unruptured aneurysms had good clinical outcomes with Glasgow outcome score of 5. Among ruptured ACoA aneurysm patients, 2 patients with conventional pterional approach had postoperative cerebral infarctions but permanent neurologic deficit was found in only 1 patient. Three patients treated with the pterional-subolfactory approach, who had preoperative ruptured aneurysms had poor clinical outcomes. The mean operation time for the conventional pterional approach was 58 minutes longer than for the pterional-subolfactory approach (p = 0.001). CONCLUSION: We concluded that pterional-subolfactory approach is highly preferable for cases of high positioned ACoA aneurysm, giving a wide and effective operation view.
Aneurysm ; Aneurysm, Ruptured ; Angiography, Digital Subtraction ; Arteries ; Cerebral Infarction ; Humans ; Intracranial Aneurysm ; Neurologic Manifestations ; Olfactory Pathways