Synchrony of Spontaneous Burst Firing between Retinal Ganglion Cells Across Species

Neurons communicate with other neurons in response to environmental changes. Their goal is to transmit information to their targets reliably. A burst, which consists of multiple spikes within a short time interval, plays an essential role in enhancing the reliability of information transmission through synapses. In the visual system, retinal ganglion cells (RGCs), the output neurons of the retina, show bursting activity and transmit retinal information to the lateral geniculate neuron of the thalamus. In this study, to extend our interest to the population level, the burstings of multiple RGCs were simultaneously recorded using a multi-channel recording system. As the first step in network analysis, we focused on investigating the pairwise burst correlation between two RGCs. Furthermore, to assess if the population bursting is preserved across species, we compared the synchronized bursting of RGCs between marmoset monkey (callithrix jacchus), one species of the new world monkeys and mouse (C57BL/6J strain). First, monkey RGCs showed a larger number of spikes within a burst, while the inter-spike interval, burst duration, and inter-burst interval were smaller compared with mouse RGCs. Monkey RGCs showed a strong burst synchronization between RGCs, whereas mouse RGCs showed no correlated burst firing. Monkey RGC pairs showed significantly higher burst synchrony and mutual information than mouse RGC pairs did.Comprehensively, through this study, we emphasize that two species have a different bursting activity of RGCs and different burst synchronization suggesting two species have distinctive retinal processing.

The advantage of topographic prominence-adopted filter for the detection of short-latency spikes of retinal ganglion cells

Electrical stimulation through retinal prosthesis elicits both short and long-latency retinal ganglion cell (RGC) spikes. Because the short-latency RGC spike is usually obscured by electrical stimulus artifact, it is very important to isolate spike from stimulus artifact. Previously, we showed that topographic prominence (TP) discriminator based algorithm is valid and useful for artifact subtraction. In this study, we compared the performance of forward backward (FB) filter only vs. TP-adopted FB filter for artifact subtraction. From the extracted retinae of rd1 mice, we recorded RGC spikes with 8×8 multielectrode array (MEA). The recorded signals were classified into four groups by distances between the stimulation and recording electrodes on MEA (200-400, 400-600, 600-800, 800-1000 µm). Fifty cathodic phase-1(st) biphasic current pulses (duration 500 µs, intensity 5, 10, 20, 30, 40, 50, 60 µA) were applied at every 1 sec. We compared false positive error and false negative error in FB filter and TP-adopted FB filter. By implementing TP-adopted FB filter, short-latency spike can be detected better regarding sensitivity and specificity for detecting spikes regardless of the strength of stimulus and the distance between stimulus and recording electrodes.

Intermittent Oroesophageal Tube Feeding via the Airway in Patients With Dysphagia

OBJECTIVE: To investigate the feasibility of the use of the oropharyngeal airway (OPA) during intermittent oroesophageal tube (IOET) feeding. METHODS: Ten patients, who were evaluated using the videofluoroscopic swallowing study (VFSS), were enrolled. One patient withdrew from the study during the study period. Tube insertion time with and without OPA use was recorded in the same patients in a random order during the VFSS. Patients who could safely undergo IOET feeding were then randomly allocated to 2 groups (OPA and non-OPA). Satisfaction Questionnaire with Gastrostomy Feeding (SAGA-8) scores and pneumonia incidence were assessed on the 3rd and 10th day after the VFSS. Non-parametric analysis was used for statistical analyses. RESULTS: The IOET insertion time was significantly shorter in the OPA group than in the non-OPA group (17.72±5.79 vs. 25.41±10.41 seconds; p=0.017). Complications were not significantly different between the 2 groups (p=0.054). Furthermore, although there were no significant differences in the SAGA-8 scores (25.50±2.38 vs. 21.40±3.13; p=0.066), which reflect the patient/caregiver satisfaction and the ease of tube insertion, patients in the OPA group tended to be more satisfied with the feeding procedure. CONCLUSION: Although the small size of the study cohort is a limitation of our study, the use of the OPA appears to be beneficial during IOET feeding in patients with dysphagia.

Mirror Therapy Using Virtual Reality on the Wrsit of Rheumatoid Arthritis; Pilot Trial

OBJECTIVE: Authors conducted the pilot trial to evaluate whether the virtual reality using mirror therapy induces analgesia and functional improvement to the patients of rheumatoid wrist arthritis. METHOD: Three patients with no symptom or sign of active phase at both wrists were recruited. Voluntary range of motion (ROM) of each wrist over as far as possible was recorded and then the same movement was recorded only over 60% of the previous one after break of 5 minutes. For the virtual reality treatment, the second recorded motion was reconstructed into the another one of as same ROM and spent time as the first one, providing confusing visual information to the patients while patients were instructed to reach only the red flags (60% ROM of 1st one). This exercise was repeated for 5 days. Numerous scales such as VAS, ROM, Michigan Hand Outcomes Questionaire (MHQ), Performance and Satisfaction in Activities of Daily Living (PS-ADL), patient-rated wrist evaluation (PRWE) were evaluated before and after repetition. RESULTS: The increased satisfaction with their hands (satisfaction score of MHQ; 5.8 ± 2.3, [6-30]), improved ADL performances (PS-ADL score: 5.0 ± 3.5, [0-117]), and no side effect were noticed. CONCLUSION: The virtual reality using mirror therapy may be safe and has some analgesic effect, which warrants a clinical trial in the future for the patients of rheumatoid wrist arthritis.

Effect of Stimulus Waveform of Biphasic Current Pulse on Retinal Ganglion Cell Responses in Retinal Degeneration (rd1) mice

A retinal prosthesis is being developed for the restoration of vision in patients with retinitis pigmentosa (RP) and age-related macular degeneration (AMD). Determining optimal electrical stimulation parameters for the prosthesis is one of the most important elements for the development of a viable retinal prosthesis. Here, we investigated the effects of different charge-balanced biphasic pulses with regard to their effectiveness in evoking retinal ganglion cell (RGC) responses. Retinal degeneration (rd1) mice were used (n=17). From the ex-vivo retinal preparation, retinal patches were placed ganglion cell layer down onto an 8x8 multielectrode array (MEA) and RGC responses were recorded while applying electrical stimuli. For asymmetric pulses, 1st phase of the pulse is the same with symmetric pulse but the amplitude of 2nd phase of the pulse is less than 10 microA and charge balanced condition is satisfied by lengthening the duration of the pulse. For intensities (or duration) modulation, duration (or amplitude) of the pulse was fixed to 500 micros (30 microA), changing the intensities (or duration) from 2 to 60 microA (60 to 1000 micros). RGCs were classified as response-positive when PSTH showed multiple (3~4) peaks within 400 ms post stimulus and the number of spikes was at least 30% more than that for the immediate pre-stimulus 400 ms period. RGC responses were well modulated both with anodic and cathodic phase-1st biphasic pulses. Cathodic phase-1st pulses produced significantly better modulation of RGC activity than anodic phase-1st pulses regardless of symmetry of the pulse.