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The human visual system to process real‐time light signals and safeguard against excessive light exposure serves as a model for artificial vision systems. Despite the wide use of optoelectronic synaptic devices in such simulations, their complex circuitry and high energy consumption have impeded further development. Herein, a biomimetic ocular system utilizing organic all‐photonic synapses is constructed to realize sensation, memory, processing, and protective light reflex abilities. The synaptic performances are facially regulated by simple molecular engineering to afford a record PPF value of 430%. Impressively, a large area (400 cm2) synaptic device with a high uniformity (96%) exhibited four fundamental functions of an ocular system for the first time, which significantly simplified the circuit system and reduced energy consumption. This work provides a facial strategy to construct all‐photonic synapses, holding great potential in prosthetics and neurorobotics. [ABSTRACT FROM AUTHOR]

• Studies of ocular reflex adaptations support the cerebellar learning hypothesis. • Purkinje cell synapse plasticity driven by climbing fiber inputs induces adaptations. • The memory of adaptation is initially formed in cerebellar flocculus Purkinje cells. • Repetition of adaptations consolidate the memory of adaptations in vestibular nuclei. • The hypothesis includes integrative functions operated by the cerebrocerebellar loop. Masao Ito proposed a cerebellar learning hypothesis with Marr and Albus in the early 1970s. He suggested that cerebellar flocculus (FL) Purkinje cells (PCs), which directly inhibit the vestibular nuclear neurons driving extraocular muscle motor neurons, adaptively control the horizontal vestibulo-ocular reflex (HVOR) through the modification of mossy and parallel fiber-mediated vestibular responsiveness by visual climbing fiber (CF) inputs. Later, it was suggested that the same FL PCs adaptively control the horizontal optokinetic response (HOKR) in the same manner through the modification of optokinetic responsiveness in rodents and rabbits. In 1982, Ito and his colleagues discovered the plasticity of long-term depression (LTD) at parallel fiber (PF)–PC synapses after conjunctive stimulation of mossy or parallel fibers with CFs. Long-term potentiation (LTP) at PF–PC synapses by weak PF stimulation alone was found later. Many lines of experimental evidence have supported their hypothesis using various experimental methods and materials for the past 50 years by many research groups. Although several controversial findings were presented regarding their hypothesis, the reasons underlying many of them were clarified. Today, their hypothesis is considered as a fundamental mechanism of cerebellar learning. Furthermore, it was found that the memory of adaptation is transferred from the FL to vestibular nuclei for consolidation by repetition of adaptation through the plasticity of vestibular nuclear neurons. In this article, after overviewing their cerebellar learning hypothesis, I discuss possible roles of LTD and LTP in gain-up and gain-down HVOR/HOKR adaptations and refer to the expansion of their hypothesis to cognitive functions. [ABSTRACT FROM AUTHOR]

The effect of electrical parameters (intensity and voltage) to obtain an effective water-bath stunning in a commercial poultry slaughterhouse was studied. A total of 390 broilers were randomly divided into six experimental groups according to the intensity (150 and 200 mA) and voltage (51-60, 61-80 and 81-100 V). Statistical analysis showed a significant (p

Abstract: Adaptation of mouse horizontal optokinetic response (HOKR) eye movement provides an experimental model for cerebellum-dependent motor learning. Our previous study revealed that the memory trace of HOKR adaptation is initially encoded in the cerebellar flocculus after hours of optokinetic training, and transferred to the vestibular nuclei to be consolidated to long-term motor memory after days of training . To reveal how the cerebellar cortex operates in the transfer of the memory trace of adaptation, we examined the effects of shutdown of the cerebellar cortex after daily training. Three groups of mice received 1h of optokinetic training daily for 4 days, and showed similar amounts of adaptation after the end of 1h of training throughout 4 days. However, in the mice which daily received bilateral floccular muscimol infusion under gas anesthesia in the post-training period, consolidation of memory of the adaptation was markedly impaired, compared with the control mice which daily received bilateral floccular Ringer''s solution infusions under gas anesthesia or those which daily received only gas anesthesia. These results are consistent with the studies of the effects of inactivation of cerebellar cortex on the consolidation of motor memory of rabbit eyeblink conditioning , and suggest that the post-training cerebellar cortex activity play an important for the consolidation of motor memory of HOKR adaptation. [Copyright &y& Elsevier]

Cerebellar long-term depression (LTD) at parallel fibre–Purkinje cell (P-cell) synapses is thought to embody neuronal information storage for motor learning. Transgenic L7-protein kinase C inhibitor (PKCI) mice in which cerebellar LTD is selectively blocked do indeed exhibit impaired adaptation in the vestibulo-ocular reflex (VOR) while their default oculomotor performance is unaffected. Although supportive, these data do not definitively establish a causal link between memory storage required for motor learning and cerebellar LTD. As the L7-PKCI transgene is probably activated from the early stages of P-cell development, an alternative could be that P-cells develop abnormal signals in L7-PKCI mutants, disturbing mechanisms of motor learning that rely on proper P-cell outputs. To test this alternative hypothesis, we studied simple spike (SS) and complex spike (CS) activity of vertical axis P-cells in the flocculus of L7-PKCI mice and their wild-type littermates during sinusoidal optokinetic stimulation. Both SS and CS discharge dynamics appeared to be very similar in wild-type and transgenic P-cells at all stimulus frequencies (0.05–0.8 Hz). The CS activity of all vertical axis cells increased with contralateral stimulus rotation and lagged ipsiversive eye velocity by 165–180°. The SS modulation was roughly reciprocal to the CS modulation and lagged ipsiversive eye velocity by ∼ 15°. The baseline SS and CS discharge characteristics were indistinguishable between the two genotypes. We conclude that the impaired VOR learning in L7-PKCI mutants does not reflect fundamental aberrations of the cerebellar circuitry. The data thus strengthen the evidence that cerebellar LTD is implicated in rapid VOR learning but not in the development of normal default response patterns. [ABSTRACT FROM AUTHOR]

The vestibulo-ocular reflex (VOR) was studied in adult squirrel monkeys before and after adaptation to magnifying and minifying viewing conditions. Monkeys were subjected to broadband (0.05-0.71 Hz) conditioning rotation for six hours in head yaw, pitch, and roll on separate occasions, and the VORs in these three planes were studied in darkness to assess adaptive plasticity in the reflexes. The gain of the horizontal VOR (H-VOR) averaged 0.8 across the frequency bandwidth studied (0.025-4 Hz). Phase was near 0° from 4 to around 0.1 Hz, but developed a progressive lead as frequency declined further. Normal vertical VOR (V-VOR) gain climbed from 0.6 at 0.025 Hz to near 1 as frequency increased to 4 Hz. Phase lead was more pronounced at low frequencies than in the H-VOR. The normal torsional VOR (T-VOR) qualitatively resembled the V-VOR, showing similar phase but lower gains (0.3-0.7) across the frequency bandwidth. These findings suggest that the dynamics of the V-VOR and T-VOR resemble canal characteristics more closely than does the H-VOR. After adaptation to visual minification and conditioning rotation (0.5X for yaw and pitch, 0X for roll), gain decreased in each of the planes of conditioning. Similarly, gain increased in the plane of conditioning after adaptation to visual magnification (2X). The adaptive changes were greater at low (0.025-1 Hz) than at high (2.5-4 Hz) frequencies, and were more robust when gain was driven downward than upward. However, control (sham) adaptation experiments showed that VOR gain tended to drop slightly over 6 h in the absence of adaptive drive to do so, suggesting that the gain modifications may be more symmetric when referenced to the control. Adaptive VOR gain enhancement or decrement in the plane of conditioning did not result in systematic and parallel changes in orthogonal VOR planes. [ABSTRACT FROM AUTHOR]

(1) Vestibulo-ocular reflex excitation of the six extraocular muscles was studied by recording their electromyographic activity in decerebrate cats during oscillations about horizontal and vertical axes, at frequencies from 0.07 to 4 Hz. Animals were oriented in many different positions and rotated about axes that lay in the horizontal, frontal, or sagittal planes defined by our coordinate system. (2) The strengths of modulation (gains) of the responses of all extraocular muscles were a sinusoidal function of the orientation of the rotation axis within a coordinate plane, and this function was nearly independent of rotation frequency. (3) The responses were used to determine an axis of maximal excitation for each of the extraocular muscles by the vestibulo-ocular reflex. Antagonistic muscle pairs were found to have best axes in nearly opposite directions, confirming their operation as pairs. (4) Excitation of the medial and lateral rectus could be explained by input from the paired horizontal semicircular canals, with essentially no convergent input from vertical canals. (5) Excitation of the vertical rectus and oblique muscles could be explained by convergent inputs from the vertical canals with little or no horizontal canal input. [ABSTRACT FROM AUTHOR]

The vestibulo-ocular reflex (VOR) is under adaptive control which corrects VOR performance when visual-vestibular mismatch arises during head movements. However, the dynamic characteristics of VOR adaptive plasticity remain controversial. In this study, eye movements (coil technique) were recorded from normal human subjects during sinusoidal rotations in darkness before and after 8 h. of adaptation to 2X binocular lenses. The VOR was studied at 7 frequencies between 0.025 and 4.0 Hz at 50°/s peak head velocity (less for 2.5-4 Hz). For 0.025 and 0.25 Hz, the VOR was tested at 4 peak head velocities between 50 and 300° /s. Before 2X lens adaptation, VOR gain was around 0.9 at 2.5-4.0 Hz and dropped gradually with decreasing frequency to under 0.6 at 0.025 Hz. Phase showed a small lead at the highest frequencies which declined to 0° as frequency decreased to 0.5-0.25 Hz, but then rose to 14° by 0.025 Hz. VOR gain was independent of head velocity in the range 50-300°/s at both 0.025 and 0.25 Hz. However, Phase lead rose with increasing head velocity, more so at 0.025 than at 0.25 Hz. After 2X lens adaptation, gain rose across the frequency bandwidth. However, the proportional gain enhancement was frequency dependent; it was greatest at 0.025 Hz (44%), and declined with increasing frequency to reach a minimum at 4 Hz (19%). Phase lead increased after 2X lens adaptation at lower frequencies, but decreased at higher frequencies. New velocity-dependent gain nonlinearities also developed which were not present prior to adaptation; gain declined as peak head velocity increased from 50 to 300°/s at both 0.025 (23% drop) and 0.25 Hz (15% drop). This may suggest an amplitude-dependent limitation in VOR adaptive plasticity. Results indicate both frequency and amplitude dependent nonlinearities in human VOR response dynamics before and after adaptive gain recalibration. [ABSTRACT FROM AUTHOR]

When a normal human subject is briefly turned in total darkness while trying to 'look' at a spatially fixed target, the vestibulo-ocular reflex (VOR) produces slow-phase compensatory eye movements tending to hold the eyes on target. However, slow-phase compensation per se is generally inadequate in these circumstances. Nevertheless it has recently been found, that even in the dark, this inadequacy tends to be corrected by supplementary saccades usually acting in the compensatory direction. The present study further investigates this phenomenon by measuring the respective contributions of saccadic, slow-phase and overall net compensation in 9 subjects tested before and after 30% adaptive attenuation of VOR slow-phase gain. In each test series, subjects attempted to stabilize their gaze on a previously seen target during each of 40 brief (≈0.5 s) whole body rotations (40°/s, 20° amp) conducted in complete darkness. The adaptive experience comprised 2 h of full-field visual suppression of the VOR during sinusoidal rotation of subject and surround at 1/6 Hz and 40°/s velocity amplitude. Before adaptation, the cumulative slow-phase and cumulative saccadic components produced on average 78% and 14% respectively of the ideal (100%) compensation, thus yielding an overall net compensation which was 92% of the desired value. After adaptation, the corresponding values in the same population were 53%, 18% and 71% respectively. Thus after adaptation, the combined saccadic-slow-phase response brought the final gaze position to a point in space that was systematically shifted in the direction of head rotation (i.e. undercompensation). Subjects re-exposed to 30 min of normal visual-vestibular interaction displayed a variety of recovery patterns using different combinations of slow and saccadic eye movements. However, there was a consistent 'synergistic' tendency for saccadic eye movements to improve slow-phase performance, regardless of the subject's adaptive state. In one subject, compensatory saccadic eye movements corrected a consistent directional asymmetry in the slow-phase response. It is suggested that a conscious vestibular percept of self-rotation might underlie the combined saccadic-slow-phase response, and that the net under performance after adaptation might reflect attenuation of this percept relative to the actual rotational stimulus. [ABSTRACT FROM AUTHOR]

The video head impulse test (vHIT) is a diagnostic tool to examine patients experiencing dizziness by assessing the function of the semicircular canals. vHIT has been widely studied in adults but relatively less so in children. The aim of this study was to evaluate the causes of dizziness and the results of vHIT in children. We also identified factors that affect the vHIT results such as artifacts and technical errors. Retrospective review; Tertiary care center. A total of 39 patients who visited our clinic for dizziness from 2014 to 2017. The gain of vestibulo-ocular reflex, refixation saccades, and artifacts were analyzed using vHIT. We analyzed 691 individual vHIT traces and categorized the artifacts into 8 categories. Twenty-three males and 16 females were included. The mean age was 13.84 ± 2.60 years (range, 7–18). Common causes of dizziness were benign paroxysmal vertigo of childhood (25.6%), vestibular neuritis (20.5%), and vestibular migraine (17.9%). The sensitivity and specificity of vHIT based on the bithermal caloric test results were 40% and 94%, respectively. The analysis of vHIT traces revealed that the children had higher artifact ratios of vHIT than the adults. The main artifacts were high gain and blinking eyes. The vHIT results showed a higher percentage of artifacts in children than in the adults. More careful efforts are required to obtain more accurate results during the test, and it is necessary to check for technical errors while interpreting the results. [ABSTRACT FROM AUTHOR]

Evidence is presented for a preliminary and speculative classification of central vestibular disorders of the brain stem according to the three major planes of action of the vestibuloocular reflex (VOR), 1. Disorders of the VOR in horizontal (yaw) plane: horizontal nystagmus-vertigo; 2. Disorders of the VOR in sagittal (pitch) plane: downbeat or upbeat nystagmus-vertigo; 3. Disorders of the VOR in frontal (roll) plane: ocular tilt reaction and lateropulsion. [ABSTRACT FROM AUTHOR]