Origins of direction selectivity in the primate retina

From mouse to primate, there is a striking discontinuity in our current understanding of the neural coding of motion direction. In non-primate mammals, directionally selective cell types and circuits are a signature feature of the retina, situated at the earliest stage of the visual process1,2. In primates, by contrast, direction selectivity is a hallmark of motion processing areas in visual cortex3,4, but has not been found in the retina, despite significant effort5,6. Here we combined functional recordings of light-evoked responses and connectomic reconstruction to identify diverse direction-selective cell types in the macaque monkey retina with distinctive physiological properties and synaptic motifs. This circuitry includes an ON-OFF ganglion cell type, a spiking, ON-OFF poly-axonal amacrine cell and the starburst amacrine cell, all of which show direction selectivity. Moreover, we found unexpectedly that macaque starburst cells possess a strong, non-GABAergic, antagonistic surround mediated by input from excitatory bipolar cells that is critical for the generation of radial motion sensitivity in these cells. Our findings open a new door to investigation of a novel circuitry that computes motion direction in the primate visual system.

Dorsal and Ventral Stream Function in Children With Developmental Coordination Disorder

Dorsal stream cortical networks underpin a cluster of visuomotor, visuospatial, and visual attention functions. Sensitivity to global coherence of motion and static form is considered a signature of visual cortical processing in the dorsal stream (motion) relative to the ventral stream (form). Poorer sensitivity to global motion compared to global static form has been found across a diverse range of neurodevelopmental disorders, suggesting a “dorsal stream vulnerability.” However, previous studies of global coherence sensitivity in Developmental Coordination Disorder (DCD) have shown conflicting findings. We examined two groups totalling 102 children with DCD (age 5–12 years), using the “Ball in the Grass” psychophysical test to compare sensitivity to global motion and global static form. Motor impairment was measured using the Movement-ABC (M-ABC). Global coherence sensitivity was compared with a typically developing control group (N = 69) in the same age range. Children with DCD showed impaired sensitivity to global motion (p = 0.002), but not global form (p = 0.695), compared to controls. Within the DCD group, motor impairment showed a significant linear relationship with global form sensitivity (p < 0.001). There was also a significant quadratic relationship between motor impairment and global motion sensitivity (p = 0.046), where poorer global motion sensitivity was only apparent with greater motor impairment. We suggest that two distinct visually related components, associated with global form and global motion sensitivity, contribute to DCD differentially over the range of severity of the disorder. Possible neural circuitry underlying these relationships is discussed.

Dark blood cardiovascular magnetic resonance of the heart, great vessels, and lungs using electrocardiographic-gated three-dimensional unbalanced steady-state free precession

Background Recently, we reported a novel neuroimaging technique, unbalanced T1 Relaxation-Enhanced Steady-State (uT1RESS), which uses a tailored 3D unbalanced steady-state free precession (3D uSSFP) acquisition to suppress the blood pool signal while minimizing bulk motion sensitivity. In the present work, we hypothesized that 3D uSSFP might also be useful for dark blood imaging of the chest. To test the feasibility of this approach, we performed a pilot study in healthy subjects and patients undergoing cardiovascular magnetic resonance (CMR). Main body The study was approved by the hospital institutional review board. Thirty-one adult subjects were imaged at 1.5 T, including 5 healthy adult subjects and 26 patients (44 to 86 years, 10 female) undergoing a clinically indicated CMR. Breath-holding was used in 29 subjects and navigator gating in 2 subjects. For breath-hold acquisitions, the 3D uSSFP pulse sequence used a high sampling bandwidth, asymmetric readout, and single-shot along the phase-encoding direction, while 3 shots were acquired for navigator-gated scans. To minimize signal dephasing from bulk motion, electrocardiographic (ECG) gating was used to synchronize the data acquisition to the diastolic phase of the cardiac cycle. To further reduce motion sensitivity, the moment of the dephasing gradient was set to one-fifth of the moment of the readout gradient. Image quality using 3D uSSFP was good-to-excellent in all subjects. The blood pool signal in the thoracic aorta was uniformly suppressed with sharp delineation of the aortic wall including two cases of ascending aortic aneurysm and two cases of aortic dissection. Compared with variable flip angle 3D turbo spin-echo, 3D uSSFP showed improved aortic wall sharpness. It was also more efficient, permitting the acquisition of 24 slices in each breath-hold versus 16 slices with 3D turbo spin-echo and a single slice with dual inversion 2D turbo spin-echo. In addition, lung and mediastinal lesions appeared highly conspicuous compared with the low blood pool signals within the heart and blood vessels. In two subjects, navigator-gated 3D uSSFP provided excellent delineation of cardiac morphology in double oblique multiplanar reformations. Conclusion In this pilot study, we have demonstrated the feasibility of using ECG-gated 3D uSSFP for dark blood imaging of the heart, great vessels, and lungs. Further study will be required to fully optimize the technique and to assess clinical utility.

Reduced vestibular perception thresholds in persistent postural-perceptual dizziness- a cross-sectional study

Background Persistent postural-perceptual dizziness (PPPD) is the most common functional vestibular disorder. A multisensory mismatch altered by psychological influences is considered to be an important pathophysiological mechanism. Increased cortical and subcortical excitability may play a role in the pathophysiology of PPPD. We hypothesized that decreased motion perception thresholds reflect one mechanism of the abnormal vestibular responsiveness in this disorder. We investigated the vestibular perception thresholds and the vestibular ocular reflex with a rotatory chair experiment to gain insights in the processing and adaption to vestibular provocation. Methods In this cross-sectional study 26 female PPPD patients and 33 healthy female age matched controls (HC) were investigated sitting in a motorized rotary chair shielded regarding visual and acoustic stimuli. The chair was rotated for 20 minutes with slowly increasing velocity to a maximum of 72°/s. We functionally tested motion perception thresholds and vegetative responses to rotation as well as vestibular-ocular reflex thresholds. We additionally investigated several psychological comorbidities (i.e. depression, anxiety, somatosensory amplification) using validated scores. Conventional dizziness scores were obtained to quantify the experienced dizziness and impact on daily life. Results PPPD patients showed a significant reduced vestibulo-perceptual threshold (PPPD: 10.9°/s vs. HC: 29.5°/s; p<0.001) with increased motion sensitivity and concomitant vegetative response during and after the chair rotation compared to healthy controls. The extent of increased vestibular sensitivity was in correlation with the duration of the disease (p=0.043). No significant difference was measured regarding nystagmus parameters between both groups. Conclusion PPPD patients showed increased vegetative response as well as decreased vestibulo-perceptual thresholds which are related to disease duration. This is of interest as PPPD might be sustained by increased vestibular excitability leading to motion intolerance and induction of dizziness when exposed to movement.

Perspective Cues Make Eye-specific Contributions to 3-D Motion Perception

Robust 3-D visual perception is achieved by integrating stereoscopic and perspective cues. The canonical model describing the integration of these cues assumes that perspective signals sensed by the left and right eyes are indiscriminately pooled into a single representation that contributes to perception. Here, we show that this model fails to account for 3-D motion perception. We measured the sensitivity of male macaque monkeys to 3-D motion signaled by left-eye perspective cues, right-eye perspective cues, stereoscopic cues, and all three cues combined. The monkeys exhibited idiosyncratic differences in their biases and sensitivities for each cue, including left- and right-eye perspective cues, suggesting that the signals undergo at least partially separate neural processing. Importantly, sensitivity to combined cue stimuli was greater than predicted by the canonical model, which previous studies found to account for the perception of 3-D orientation in both humans and monkeys. Instead, 3-D motion sensitivity was best explained by a model in which stereoscopic cues were integrated with left- and right-eye perspective cues whose representations were at least partially independent. These results indicate that the integration of perspective and stereoscopic cues is a shared computational strategy across 3-D processing domains. However, they also reveal a fundamental difference in how left- and right-eye perspective signals are represented for 3-D orientation versus motion perception. This difference results in more effective use of available sensory information in the processing of 3-D motion than orientation and may reflect the temporal urgency of avoiding and intercepting moving objects.

Correlation between anxiety and chronic motion sensitivity

BACKGROUND: Chronic motion sensitivity (CMS) is a combination of autonomic symptoms provoked by exposure to motion. The correlation between anxiety and CMS is not yet well understood. OBJECTIVES: 1) To compare median anxiety levels between young adults with and without CMS. 2) To examine the effect of anxiety on postural stability with immersion virtual reality. 3) To compare anxiety levels between sexes. METHODS: Participants included 60 adults (20–40 years), with and without CMS. After determining their current and general anxiety levels, postural stability was measured. RESULTS: There were significant differences in median (minimum, maximum) state- and trait-anxiety scores between participants with and without CMS, but no significant differences in median state- and trait-anxiety scores between males and females with CMS. There was a significant inverse relationship between state- and trait-anxiety scores and postural stability (ρ= –0.28, p = 0.03, and ρ= –0.32, p = 0.01, respectively). The stepwise regression analysis showed the Motion Sickness Susceptibility Questionnaire-Short Form score to be the only variable contributing significantly to postural stability (R2 = 26.2%; t = –4.5, p < 0.001). CONCLUSIONS: Young adults with CMS are more anxious, although anxiety does not contribute to postural stability in this group. Anxiety levels do not appear to differ between young adult males and females with CMS.

A-95 The Relationship between Attention Deficit Hyperactivity Disorder (ADHD) and Vestibular Impairments Following Adolescent Sports-Related Concussion (SRC)

Objective Athletes with ADHD may experience longer and/or more complicated recoveries following SRC; however, previous research has focused on neurocognitive outcomes. The objective of this study was to investigate the relationship between a history of ADHD among adolescent athletes and vestibular impairments following SRC. Method Participants included 166 athletes aged 15.9 +/− 1.5 who sustained an SRC, including 25 with a documented history of ADHD. Appropriate summary statistics were used to describe the data. ADHD and non-ADHD groups were compared using t-tests and Mann–Whitney U tests for continuous variables and Chi-square tests for categorical variables. A linear regression model analyzed the relationship between a history of ADHD and vestibular outcomes including horizontal and vertical vestibulo-ocular reflex (hVOR; vVOR), visual motion sensitivity (VMS), and Dizziness Handicap Index (DHI), while referral to vestibular therapy (VT) was analyzed using logistic regression. Results Athletes with ADHD experienced significantly higher rates of on-field dizziness, (p = 0.039) and dizziness following vVOR testing on the Vestibular/Ocular Motor Screening (VOMS; p = 0.041). Athletes with ADHD were more likely to be referred to vestibular therapy (VT) (p = 0.033) and displayed abnormal vVOR test during the initial VT visit (p = 0.040). Conclusions Adolescent athletes with a history of ADHD are more likely to report on-field dizziness following SRC and increased dizziness with vVOR testing on VOMS, thus resulting in more frequent referrals to VT, where they also display abnormal vVOR results. Additional research is needed to improve treatment strategies and recovery outcomes in athletes after SRC.

Center-surround interactions underlie bipolar cell motion sensing in the mouse retina

Motion is a critical aspect of vision. We studied the representation of motion in mouse retinal bipolar cells and found, surprisingly, that some bipolar cells possess motion-sensing capabilities that rely on their center-surround receptive fields. Using a glutamate sensor, we directly observed motion-sensitive bipolar cell synaptic output, which was strongest for local motion and dependent on the motion's origin. We characterized bipolar cell receptive fields and found that there are motion and non-motion sensitive bipolar cell types, the majority being motion sensitive. Next, we used these bipolar cell receptive fields along with connectomics to design biophysical models of downstream cells. The models and experiments demonstrated that bipolar cells pass motion-sensitive excitation to starburst amacrine cells through direction-specific signals mediated by bipolar cells' center-surround receptive field structure. As bipolar cells provide excitation to most amacrine and ganglion cells, their motion sensitivity may contribute to motion processing throughout the visual system.

Age-Related Vestibular and Ocular Motor Outcomes Following a Sport-Related Concussion

Context: Vestibular and ocular motor assessment is an emerging clinical assessment for sport-related concussion (SRC). The increased use of these assessments by clinicians calls for examination of outcomes in populations that may impact clinical practice. Objective: Compare vestibular and ocular motor impairments in high school and collegiate athletes within 72 hours of SRC. Second, examine the distribution of impairments in these populations based upon pre-established clinical cut-off scores. Design: Cross-sectional study. Setting: High school (HS) and collegiate athletics (COL). Patient or Other Participants: Data were collected from 110 athletes (HS: n=47, age=15.40±1.35 years; COL: n=63, age=19.46±1.28 years) within 72 hours of sustained SRC. Main Outcome Measure(s): Total and change scores were calculated for the Vestibular/Ocular Motor Screening (VOMS) assessment, along with average near point of convergence (NPC) distance. Separate Mann Whitney U tests were used to compare group differences and Chi-square analyses were used to examine athlete distribution above clinical cutoff scores for all VOMS outputs (a priori Alpha level&lt;0.5). Results: No significant differences were found between high school and collegiate athletes for VOMS total scores, change scores, and NPC distance. A significantly larger proportion of the sample reported scores above the cutoff for all total scores (p&lt;0.001) and change scores in horizontal vestibulo-ocular reflex (VOR; 59.01%, p&lt;0.001), vertical VOR (60.91%, p&lt;0.001), and visual motion sensitivity (60.91%, p&lt;0.001). However, a significantly larger proportion reported smooth pursuit change scores (85.45%, p&lt;0.001) and NPC distance (73.64%, p=0.01) below the cutoff scores. Conclusions: During the acute phase of SRC, high school and collegiate athletes present with similar vestibular and ocular motor impairments as measured by the VOMS, but vestibular tasks appear to cause greater symptom provocation in concussed athletes. Lastly, VOMS change scores may offer more clinical utility in assessing specific impairments following SRC compared to total scores.