ABSTRACT
Detection of moving objects is an essential skill for animals to hunt prey, recognize conspecifics and avoid predators. The zebrafish, as a vertebrate model, primarily uses its elaborate visual system to distinguish moving objects against background scenes. The optic tectum (OT) receives and integrates inputs from various types of retinal ganglion cells (RGCs), including direction-selective (DS) RGCs and size-selective RGCs, and is required for both prey capture and predator avoidance. However, it remains largely unknown how motion information is processed within the OT. Here we performed in vivo whole-cell recording and calcium imaging to investigate the role of superficial interneurons (SINs), a specific type of optic tectal neurons, in motion detection of larval zebrafish. SINs mainly receive excitatory synaptic inputs, exhibit transient ON- or OFF-type of responses evoked by light flashes, and possess a large receptive field (RF). One fifth of SINs are DS and classified into two subsets with separate preferred directions. Furthermore, SINs show size-dependent responses to moving dots. They are efficiently activated by moving objects but not static ones, capable of showing sustained responses to moving objects and having less visual adaptation than periventricular neurons (PVNs), the principal tectal cells. Behaviorally, ablation of SINs impairs prey capture, which requires local motion detection, but not global looming-evoked escape. Finally, starvation enhances the gain of SINs' motion responses while maintaining their size tuning and DS. These results indicate that SINs serve as a motion detector for sensing and localizing sized moving objects in the visual field.
ABSTRACT
Important components of the Extracellular Field (EF) can be caused by a sequential or moving depolarization generated by some cell-groups at specific sub-regions. These depolarizations can be sensed not only by man-made techniques -as electroencephalography (EEG) and electrocardiography (ECG) - but also by some physiological processes associated to ephaptic interactions. METHODS: Based on principles of electromagnetism we implement two computer simulations where this can be studied: 1. Bilateral waves, where subregions can have up to 3 mesoscopic states: activated, resting or sleeping (hyperpolarized) and 2. Stochastic propagation without deactivation. RESULTS: Biphasic, Gaussian and Mexican hat functions can be generated by these models. CONCLUSIONS: (i) Mesoscopic minimalistic models can explain in a simple way some electrophysiological signals. (ii) We suggest an analogy between mechanisms used in animal and robots to detect visual motion and engineering techniques to detect moving depolarizations in the nervous system. Similarly, such mechanisms might exist in cell-groups. (iii) Distorted waves can cause pathologies and their modulation by electric or magnetic stimulation can be potentially beneficial.
Componentes importantes de los campos extracelulares (CE) pueden ser causados por despolarización secuencial o en movimiento, generadas por algunos grupos celulares en subregiones específicas. Estas despolarizaciones pueden ser detectadas no solo con técnicas hechas por el hombre -como la electroencefalografía (EEG) o la electrocardiografía (ECG)- sino también por algunos procesos fisiológicos asociados con interacciones por efectos directos de campo eléctrico local. MÉTODOS: Basados en principios del electromagnetismo nosotros implementamos dos simulaciones de computador donde esto puede ser estudiado: 1. Ondas bilaterales, donde las subregiones pueden tener hasta 3 estados mesoscópicos: activación, reposo o dormido (hiperpolarización) y 2. Propagación estocástica sin desactivación. RESULTADOS: Funciones bifásicas, Gaussianas y tipo sombrero mexicano pueden ser generadas por estos modelos. CONCLUSIONES: (i) Modelos mesoscópicos minimalísticos pueden explicar de una manera simple algunas señales electrofisiológicas. (ii) Sugerimos una analogía entre mecanismos usados en animales y robots para detectar movimiento visual y técnicas de ingeniería para detectar despolarizaciones en movimiento en el sistema nervioso. Asimismo, tales mecanismos pueden existir en grupos celulares. (iii) Ondas distorsionadas pueden causar patologías y su modulación con estimulación eléctrica y magnética puede ser beneficiosa.
Os principais componentes do campos extracelulares ( CE ) pode ser causada por movimentos despolarizações seqüenciais ou alguma célula adj Gerado em grupos sub-regiões específicas . Está despolarizações pode ser detectado não apenas as técnicas feita pelo homem , tais como a eletroencefalografia (EEG) e eletrocardiograma (ECG) - Sino também para algumas adj associados processos fisiológicos com interações epapticas . MÉTODOS : Com base em : princípios do eletromagnetismo Implementamos duas simulações de computador onde este pode ser estudada : 1. ondas bilaterais , onde as sub-regiões podem ter até 3 ESTADOS mesoscópicos : ativação, descanso ou hiperpolarização e 2. estocástico propagação pecado desativação. RESULTADOS: funções bifásicos , Gaussian e tipo chapéu mexicano pode ser gerada por esses modelos. CONCLUSÕES : (i) minimalisticos modelos mesoscópicos pode explicar de uma forma simples Alguns sinais eletrofisiológicos . (Ii) sugerir uma analogia entre -mecanismos de animais e robôs usados para detectar movimento visual e técnicas afins despolarizações Pará detectar movimento no sistema nervoso . Além disso, histórias de mecanismos podem existir em grupos de células . (Iii) as doenças podem causar ondas distorcidas e modulação estímulo elétrico e magnético pode ser benéfico.
ABSTRACT
PURPOSE: During brain MRI scanning, subject's head motion can adversely affect MRI images. To minimize MR image distortion by head movement, we developed an optical tracking system to detect the 3-D movement of subjects. MATERIALS AND METHODS: The system consisted of 2 CCD cameras, two infrared illuminators, reflective sphere-type markers, and frame grabber with desktop PC. Using calibration which is the procedure to calculate intrinsic/extrinsic parameters of each camera and triangulation, the system was desiged to detect 3-D coordinates of subject's head movement. We evaluated the accuracy of 3-D position of reflective markers on both test board and the real MRI scans. RESULTS: The stereo system computed the 3-D position of markers accurately for the test board and for the subject with glasses with attached optical reflective marker, required to make regular head motion during MRI scanning. This head motion tracking didn't affect the resulting MR images even in the environment varying magnetic gradient and several RF pulses. CONCLUSION: This system has an advantage to detect subject's head motion in real-time. Using the developed system, MRI operator is able to determine whether he/she should stop or intervene in MRI acquisition to prevent more image distortions.
Subject(s)
Brain , Calibration , Eyeglasses , Glass , Head , Head Movements , Imidazoles , Magnetic Resonance Imaging , Magnetics , Magnets , Nitro Compounds , Track and FieldABSTRACT
To understand the function of edges in perception of moving objects, we defined four questions to answer. Is the focus point in visual motion detection of a moving object: (1) the body or the edge of the object, (2) the leading edge or trailing edge of the object, (3) different in scotopic, mesopic and photopic luminance levels, or (4) different for colored objects? We measured the Optomotor Response (OMR) and Edge Triggering Response (ETR) of goldfish. We used a square and sine wave patterns with black and red stripes and a square wave pattern with black and grey stripes to generate OMR's and ETR's in the goldfish. When we used black and red stripes, the black leading edges stimulated an ETR under scotopic conditions, red leading edges stimulated an ETR under photopic conditions, and both black and red leading edges stimulated an ETR under mesopic luminance levels. For black and gray stripes, only black leading edges stimulated an ETR in all three light illumination levels. We observed less OMR and ETR results using the sine wave pattern compared to using the square wave pattern. From these results, we deduced that the goldfish tend to prefer tracking the leading edge of the pattern. The goldfish can also detect the color of the moving pattern under photopic luminance conditions. We decided that ETR is an intriguing factor in OMR, and is suitable as a method of behavioral measurement in visual system research.
Subject(s)
Goldfish , Light , Lighting , Track and FieldABSTRACT
The remote surveillance system based on the wireless home sensor network, wireless internet connection, and the portable, hand-held device has been designed for the patron to get the emergency alarm for immediate care for the Dementia aged, when the patron is not at home. It consists of transmitting server and the receiving terminal. The transmitting server gathers the information through bluetooth connection regarding to environment threatening the safety of the Dementia aged from five sensors, including fire, gas, conductivity, photo, and motion sensors, and cameras up to the number of 16, fixated within home. It also determines the emergency situation automatically from sensors' environmental condition and the motion detected from the camera output targeted to the aged people, and sends the alarm message with the picture taken from home to the patrol for comprehending the emergency situation remotely. Either the PDA or the cellular phone is used as the receiving terminal device through wireless connectivity without the location limitation for the patrol. The functional evaluation via the implemented prototype system has been performed to initially demonstrate the efficacy, the usefulness, and ease to operate for later use for either solitarily living old people or nursery schools and infantile shelters.