Multisensory interactions regulate feeding behavior in Drosophila.

The integration of two or more distinct sensory cues can help animals make more informed decisions about potential food sources, but little is known about how feeding-related multimodal sensory integration happens at the cellular and molecular levels. Here, we show that multimodal sensory integration contributes to a stereotyped feeding behavior in the model organism Drosophila melanogaster Simultaneous olfactory and mechanosensory inputs significantly influence a taste-evoked feeding behavior called the proboscis extension reflex (PER). Olfactory and mechanical information are mediated by antennal Or35a neurons and leg hair plate mechanosensory neurons, respectively. We show that the controlled delivery of three different sensory cues can produce a supra-additive PER via the concurrent stimulation of olfactory, taste, and mechanosensory inputs. We suggest that the fruit fly is a versatile model system to study multisensory integration related to feeding, which also likely exists in vertebrates.

Temporomandibular Joint Herniation Into the External Auditory Canal: Two Cases Involving a Persistent Foramen Tympanicum.

A congenital bony defect of the external auditory canal (EAC) may cause temporomandibular joint (TMJ) herniation into the EAC. This rare condition is known as persistent foramen tympanicum. We report 2 cases of symptomatic TMJ herniation through a patent foramen tympanicum. The patients complained of mastication-induced tinnitus. Otoscopic examination revealed that a whitish protruding mass at the anterior wall of the EAC bulged when the patients closed their mouths. After conservative managements such as avoidance of chewing foods on the affected side for 2 months, mastication-induced tinnitus disappeared and the size of protruding mass was decreased in one of the patients. Surgical repair of the bony defect has been the treatment of choice. In cases when symptoms are trivial and patients do not want surgical treatment, however, conservative management would be a sound alternative.

cAMP signalling in mushroom bodies modulates temperature preference behaviour in Drosophila.

Homoiotherms, for example mammals, regulate their body temperature with physiological responses such as a change of metabolic rate and sweating. In contrast, the body temperature of poikilotherms, for example Drosophila, is the result of heat exchange with the surrounding environment as a result of the large ratio of surface area to volume of their bodies. Accordingly, these animals must instinctively move to places with an environmental temperature as close as possible to their genetically determined desired temperature. The temperature that Drosophila instinctively prefers has a function equivalent to the 'set point' temperature in mammals. Although various temperature-gated TRP channels have been discovered, molecular and cellular components in Drosophila brain responsible for determining the desired temperature remain unknown. We identified these components by performing a large-scale genetic screen of temperature preference behaviour (TPB) in Drosophila. In parallel, we mapped areas of the Drosophila brain controlling TPB by targeted inactivation of neurons with tetanus toxin and a potassium channel (Kir2.1) driven with various brain-specific GAL4s. Here we show that mushroom bodies (MBs) and the cyclic AMP-cAMP-dependent protein kinase A (cAMP-PKA) pathway are essential for controlling TPB. Furthermore, targeted expression of cAMP-PKA pathway components in only the MB was sufficient to rescue abnormal TPB of the corresponding mutants. Preferred temperatures were affected by the level of cAMP and PKA activity in the MBs in various PKA pathway mutants.

Dopamine signalling in mushroom bodies regulates temperature-preference behaviour in Drosophila.

The ability to respond to environmental temperature variation is essential for survival in animals. Flies show robust temperature-preference behaviour (TPB) to find optimal temperatures. Recently, we have shown that Drosophila mushroom body (MB) functions as a center controlling TPB. However, neuromodulators that control the TPB in MB remain unknown. To identify the functions of dopamine in TPB, we have conducted various genetic studies in Drosophila. Inhibition of dopamine biosynthesis by genetic mutations or treatment with chemical inhibitors caused flies to prefer temperatures colder than normal. We also found that dopaminergic neurons are involved in TPB regulation, as the targeted inactivation of dopaminergic neurons by expression of a potassium channel (Kir2.1) induced flies with the loss of cold avoidance. Consistently, the mutant flies for dopamine receptor gene (DopR) also showed a cold temperature preference, which was rescued by MB-specific expression of DopR. Based on these results, we concluded that dopamine in MB is a key component in the homeostatic temperature control of Drosophila. The current findings will provide important bases to understand the logic of thermosensation and temperature preference decision in Drosophila.

Change of nystagmus direction during a head-roll test in lateral semicircular canal cupulolithiasis.

OBJECTIVE: To demonstrate positional nystagmus during a head-roll test in two patients with lateral semicircular canal (LSCC) cupulolithiasis who presented with spontaneous detachment of otoliths from the LSCC cupula, and to confirm that otoliths may adhere to both the utricle and canal sides of the cupula. PATIENTS AND METHODS: Using video nystagmography, positional nystagmus was evaluated in two patients with LSCC cupulolithiasis who showed the change of nystagmus direction during a head-roll test. RESULTS: Both patients presented with persistent left-beating and right-beating nystagmus when the head was bent forward and backward, respectively. This suggests the presence of either cupulolithiasis on the right side or light cupula on the left side of the LSCC. In Case 1, transformation from cupulolithiasis to canalolithiasis occurred, implicating the detachment of otoliths from the canal side of the right LSCC cupula. In Case 2, vigorous right-beating nystagmus was followed by persistent left-beating nystagmus when the head was rolled to the left. Following this, direction-fixed left-beating nystagmus was observed at all positions, which may indicate that otoliths attached on utricle side of the right LSCC cupula were detached and fell into the utricle under the influence of gravity. A conversion of nystagmus direction may be explained by an expression of short-term adaptation of vestibular tone. CONCLUSIONS: Otoliths can be attached to either side of the cupula in LSCC cupulolithiasis. Because it is difficult to determine the attached side at the time of diagnostic maneuver, the therapeutic approach should include maneuvers designed to detach otolith particles from both the utricle and canal side.

Abnormal Magnetic Resonance Imaging Findings in Patients With Sudden Sensorineural Hearing Loss: Vestibular Schwannoma as the Most Common Cause of MRI Abnormality.

The etiology of sudden sensorineural hearing loss (SSNHL) remains unclear in most cases. This study aimed to assess abnormal magnetic resonance imaging (MRI) findings in patients with SSNHL and evaluate the value of MRI in identifying the cause of SSNHL.A retrospective analysis of the charts and MRI findings of 291 patients with SSNHL was performed.In 291 patients, MRI abnormality, which was considered a cause of SSNHL, was detected in 13 patients. Vestibular schwannoma involving the internal auditory canal (IAC) and/or cerebellopontine angle was observed in 9 patients. All 9 patients had intrameatal tumors, and 6 of the 9 patients displayed extrameatal extension of their tumors. The tumor was small (<1 cm) or medium-sized (1.1-2.9 cm) in these 6 patients. Intralabyrinthine schwannoma, labyrinthine hemorrhage, IAC metastasis, and a ruptured dermoid cyst were each observed in 1 patient.The most commonly observed MRI abnormality in patients with SSNHL was vestibular schwannoma, and all of the lesions were small or medium-sized tumors involving the IAC.

Direction-reversing Nystagmus in Horizontal and Posterior Semicircular Canal Canalolithiasis.

OBJECTIVES: To investigate the incidence and characteristics of direction-reversing nystagmus in patients with horizontal (HSCC) and posterior semicircular canal (PSCC) canalolithiasis, and evaluate the effect of direction-reversing nystagmus on the treatment outcome. STUDY DESIGN: A retrospective study. METHODS: Between March 2014 and September 2015, 63 and 92 consecutive patients with HSCC and PSCC canalolithiasis, respectively, were enrolled. Positional nystagmus characteristics were examined using video-nystagmography. RESULTS: In HSCC canalolithiasis, direction-reversing nystagmus was observed in 73% of patients (46 of 63), of which 19 cases were bilateral and 27 unilateral. In patients with bilateral reversal, maximal slow-phase velocity (mSPV) was significantly greater when the head turned to the lesioned side than to the healthy side in both the first and second phase. In all patients with unilateral reversal, direction-reversing nystagmus always occurred in the side of stronger initial nystagmus in a supine roll test. The mean mSPV of first phase nystagmus was significantly greater on the side with reversal than without (p < 0.001). The duration of second-phase nystagmus exceeded 60 seconds in all patients with reversal. Although not statistically significant (p = 0.059), patients presenting with direction-reversing nystagmus required more repositioning maneuver sessions. In contrast to HSCC canalolithiasis, only 4% of patients (4 of 92) with PSCC canalolithiasis exhibited spontaneous reversal of initial nystagmus. CONCLUSION: The incidence of direction-reversing nystagmus was higher in HSCC canalolithiasis than in PSCC canalolithiasis, and second-phase (direction-reversing) nystagmus in HSCC canalolithiasis has a prolonged duration. Short-term adaptation of the vestibulo-ocular reflex may be responsible for the development of direction-reversing nystagmus.

Assessment of Change in Palatal Sensation in Obstructive Sleep Apnea Patients by Using Two-Point Palatal Discrimination.

OBJECTIVES: Patients with obstructive sleep apnea syndrome (OSAS) have impaired responses to inspiratory resistive loading during sleep. This may be due, in part, to a change in the upper airway sensation. Therefore, we hypothesized that patients with OSAS have diminished upper airway sensation due to snoring. METHODS: A total of 53 participants were selected based on clinical evaluation and polysomnography. Two-point discrimination was measured with modified calipers in the tongue and soft palate. RESULTS: A total of 10 participants were included in the control group, 12 participants in the simple snoring group, and 27 participants in the OSAS group. There were 12 patients in the impaired sensation group of the OSAS group. On comparing polysomnography, patients with impairment of their palatal sensory input in two-point discrimination (TPD) had a more protracted duration of the longest snoring episode than those with simple snoring and normal sensation. Patients with decreased sensory input in TPD had longer average duration of snoring episodes and relative snoring time than those with simple snoring and normal sensory input in cold uvular TPD. Comparison of the cold uvular TPD for normal sensation and impaired sensation in patients with OSAS after treatment showed a different trend. CONCLUSION: Impaired sensation of the soft palate was correlated with the longest snoring episode duration, average snoring episode duration, and relative snoring time. It is helpful in detecting the early stage of neural degradation in OSAS patients by assessing snoring components of polysomnography and TPD in the soft palate.

Conversion between geotropic and apogeotropic persistent direction-changing positional nystagmus.

CONCLUSION: Clinical features in the course of conversion differed between patients with SSNHL and cupulopathy, which indicates that the pathophysiology of persistent geotropic or apogeotropic DCPN and the mechanism of the change in nystagmus direction may differ between the two groups. OBJECTIVE: The aim of this study is to investigate clinical characteristics of 10 patients with persistent DCPN who exhibited a conversion of nystagmus direction between geotropic and apogeotropic, and discuss possible mechanisms. METHODS: Using video-oculography, serial examinations of nystagmus in a head-roll test were performed. RESULTS: Of these 10 patients, five had sudden sensorineural hearing loss (SSNHL) and the remaining five had cupulopathy. In SSNHL, direction of nystagmus changed from geotropic to apogeotropic in three patients and from apogeotropic to geotropic in two patients. In cupulopathy, persistent apogeotropic DCPN always preceded persistent geotropic DCPN. The change in nystagmus direction occurred earlier in patients with cupulopathy (1 or 2 days after vertigo onset) than in patients with SSNHL (4-23 days after vertigo onset). While the null plane was consistently identified on one side, regardless of the nystagmus direction in cupulopathy, it was not always identified on the side of hearing loss in SSNHL.

Ca-α1T, a fly T-type Ca2+ channel, negatively modulates sleep.

Mammalian T-type Ca(2+) channels are encoded by three separate genes (Cav3.1, 3.2, 3.3). These channels are reported to be sleep stabilizers important in the generation of the delta rhythms of deep sleep, but controversy remains. The identification of precise physiological functions for the T-type channels has been hindered, at least in part, by the potential for compensation between the products of these three genes and a lack of specific pharmacological inhibitors. Invertebrates have only one T-type channel gene, but its functions are even less well-studied. We cloned Ca-α1T, the only Cav3 channel gene in Drosophila melanogaster, expressed it in Xenopus oocytes and HEK-293 cells, and confirmed it passes typical T-type currents. Voltage-clamp analysis revealed the biophysical properties of Ca-α1T show mixed similarity, sometimes falling closer to Cav3.1, sometimes to Cav3.2, and sometimes to Cav3.3. We found Ca-α1T is broadly expressed across the adult fly brain in a pattern vaguely reminiscent of mammalian T-type channels. In addition, flies lacking Ca-α1T show an abnormal increase in sleep duration most pronounced during subjective day under continuous dark conditions despite normal oscillations of the circadian clock. Thus, our study suggests invertebrate T-type Ca(2+) channels promote wakefulness rather than stabilizing sleep.

Vibration- and hyperventilation-induced nystagmus in patients with Ramsay Hunt syndrome with vertigo.

OBJECTIVES: The aims of this study were to compare vibration-induced nystagmus (VIN) and hyperventilation-induced nystagmus (HVIN) findings in patients with Ramsay Hunt syndrome with vertigo (RHS-V), sudden sensorineural hearing loss with vertigo (SSNHL-V), and vestibular neuritis (VN) during the acute stage and to address the possible lesion sites of vestibular deficit in RHS-V. STUDY DESIGN: Case series with chart review. SETTING: Tertiary referral center. METHODS: We conducted a retrospective case series study in 27 patients with SSNHL-V, 104 patients with VN, and 17 patients with RHS-V and evaluated the findings of VIN and HVIN tests. RESULTS: An abnormal VIN was observed in 91% of the patients with VN, 89% of those with SSNHL-V, and 94% of those with RHS-V, and the prevalence of abnormal VIN was not significantly different (P = .436). An abnormal HVIN was observed in 51% of the patients with VN, 22% of those with SSNHL-V, and 59% of those with RHS-V. While the prevalence of an abnormal HVIN was significantly different between SSNHL-V and VN groups (P = .007) and between SSNHL-V and RHS-V groups (P = .014), that between VN and RHS-V groups did not show a significant difference (P = .547). CONCLUSION: Since the results of HVIN in RHS-V patients were more similar to those in VN patients than those in SSNHL-V patients, a lesioned site may be more likely within the vestibular nerve than the inner ear as a cause for vestibular deficit in patients with RHS-V who show caloric canal paresis of 25% or greater.