Perceptual learning with dichoptic attention tasks improves attentional modulation in V1 and IPS and reduces interocular suppression in human amblyopia.

Long-term and chronic visual suppression to the non-preferred eye in early childhood is a key factor in developing amblyopia, as well as a critical barrier to treat amblyopia. To explore the relationship between selective visual attention and amblyopic suppression and its role in the success of amblyopic training, we used EEG source-imaging to show that training human adults with strabismic and anisometropic amblyopia with dichoptic attention tasks improved attentional modulation of neural populations in the primary visual cortex (V1) and intraparietal sulcus (IPS). We also used psychophysics to show that training reduced interocular suppression along with visual acuity and stereoacuity improvements. Importantly, our results revealed that the reduction of interocular suppression by training was significantly correlated with the improvement of selective visual attention in both training-related and -unrelated tasks in the amblyopic eye, relative to the fellow eye. These findings suggest a relation between interocular suppression and selective visual attention bias between eyes in amblyopic vision, and that dichoptic training with high-attention demand tasks in the amblyopic eye might be an effective way to treat amblyopia.

Mental Visualization in the Cerebellum: Rapid Non-motor Learning at Sub-Lobular and Causal Network Levels.

It is generally understood that the main role of the cerebellum is in movement planning and coordination, but neuroimaging has led to striking findings of its involvement in many aspects of cognitive processing. Mental visualization is such a cognitive process, extensively involved in learning and memory, artistic and inventive creativity, etc. Here, our aim was to conduct a multidimensional study of cerebellar involvement in the non-motor cognitive tasks. First, we used fMRI to investigate whether the cognitive task of visualization from an immediate memory of complex spatial structures (line drawings) engages the cerebellum, and identified a cerebellar network of both strongly activated and suppressed regions. Second, the task-specificity of these regions was examined by comparative analysis with the task of perceptual exploration and memorization of the drawings to be later visualized from memory. BOLD response patterns over the iterations of each task differed significantly; unexpectedly, the suppression grew markedly stronger in visualization. Third, to gain insights in the organization of these regions into cerebellar networks, we determined the directed inter-regional causal influences using Granger Causal Connectivity analysis. Additionally, the causal interactions of the cerebellar networks with a large-scale cortical network, the Default Mode Network (DMN), were studied. Fourth, we investigated rapid cognitive learning in the cerebellum at the level of short-term BOLD response evolution within each region of interest, and at the higher level of network reorganization. Our paradigm of interleaved sequences of iteration between two tasks combined with some innovative analyses were instrumental in addressing these questions. In particular, rapid forms of non-motor learning that strongly drive cerebellar plasticity through mental visualization were uncovered and characterized at both sub-lobular and network levels. Collectively, these findings provide novel and expansive insights into high-order cognitive functions in the cerebellum, and its macroscale functional neuroanatomy. They represent a basis for a framework of rapid cerebellar reorganization driven by non-motor learning, with implications for the enhancement of cognitive abilities such as learning and memory.

Excitatory Contribution to Binocular Interactions in Human Visual Cortex Is Reduced in Strabismic Amblyopia.

Binocular summation in strabismic amblyopia is typically reported as being absent or greatly reduced in behavioral studies and is thought to be because of a preferential loss of excitatory interactions between the eyes. Here, we studied how excitatory and suppressive interactions contribute to binocular contrast interactions along the visual cortical hierarchy of humans with strabismic and anisometropic amblyopia in both sexes, using source-imaged steady-state visual evoked potentials (SSVEP) over a wide range of relative contrast between the two eyes. Dichoptic parallel grating stimuli modulated at unique temporal frequencies in each eye allowed us to quantify spectral response components associated with monocular inputs (self-terms) and the response components because of interaction of the inputs of the two eyes [intermodulation (IM) terms]. Although anisometropic amblyopes revealed a similar pattern of responses to normal-vision observers, strabismic amblyopes exhibited substantially reduced IM responses across cortical regions of interest (V1, V3a, hV4, hMT+ and lateral occipital cortex), indicating reduced interocular interactions in visual cortex. A contrast gain control model that simultaneously fits self- and IM-term responses within each cortical area revealed different patterns of binocular interactions between individuals with normal and disrupted binocularity. Our model fits show that in strabismic amblyopia, the excitatory contribution to binocular interactions is significantly reduced in both V1 and extra-striate cortex, whereas suppressive contributions remain intact. Our results provide robust electrophysiological evidence supporting the view that disruption of binocular interactions in strabismus or amblyopia is because of preferential loss of excitatory interactions between the eyes.SIGNIFICANCE STATEMENT We studied how excitatory and suppressive interactions contribute to binocular contrast interactions along the visual cortical hierarchy of humans with normal and amblyopic vision, using source-imaged SSVEP and frequency-domain analysis of dichoptic stimuli over a wide range of relative contrast between the two eyes. A dichoptic contrast gain control model was used to characterize these interactions in amblyopia and provided a quantitative comparison to normal vision. Our model fits revealed different patterns of binocular interactions between normal and amblyopic vision. Strabismic amblyopia significantly reduced excitatory contributions to binocular interactions, whereas suppressive contributions remained intact. Our results provide robust evidence supporting the view that the preferential loss of excitatory interactions disrupts binocular interactions in strabismic amblyopia.

Contrast Normalization Accounts for Binocular Interactions in Human Striate and Extra-striate Visual Cortex.

During binocular viewing, visual inputs from the two eyes interact at the level of visual cortex. Here we studied binocular interactions in human visual cortex, including both sexes, using source-imaged steady-state visual evoked potentials over a wide range of relative contrast between two eyes. The ROIs included areas V1, V3a, hV4, hMT+, and lateral occipital cortex. Dichoptic parallel grating stimuli in each eye modulated at distinct temporal frequencies allowed us to quantify spectral components associated with the individual stimuli from monocular inputs (self-terms) and responses due to interaction between the inputs from the two eyes (intermodulation [IM] terms). Data with self-terms revealed an interocular suppression effect, in which the responses to the stimulus in one eye were reduced when a stimulus was presented simultaneously to the other eye. The suppression magnitude varied depending on visual area, and the relative contrast between the two eyes. Suppression was strongest in V1 and V3a (50% reduction) and was least in lateral occipital cortex (20% reduction). Data with IM terms revealed another form of binocular interaction, compared with self-terms. IM response was strongest at V1 and was least in hV4. Fits of a family of divisive gain control models to both self- and IM-term responses within each cortical area indicated that both forms of binocular interaction shared a common gain control nonlinearity. However, our model fits revealed different patterns of binocular interaction along the cortical hierarchy, particularly in terms of excitatory and suppressive contributions.SIGNIFICANCE STATEMENT Using source-imaged steady-state visual evoked potentials and frequency-domain analysis of dichoptic stimuli, we measured two forms of binocular interactions: one is associated with the individual stimuli that represent interocular suppression from each eye, and the other is a direct measure of interocular interaction between inputs from the two eyes. We demonstrated that both forms of binocular interactions share a common gain control mechanism in striate and extra-striate cortex. Furthermore, our model fits revealed different patterns of binocular interaction along the visual cortical hierarchy, particularly in terms of excitatory and suppressive contributions.

Learning face perception without vision: Rebound learning effect and hemispheric differences in congenital vs late-onset blindness.

To address the longstanding questions of whether the blind-from-birth have an innate face-schema, what plasticity mechanisms underlie non-visual face learning, and whether there are interhemispheric face processing differences in face processing in the blind, we used a unique non-visual drawing-based training in congenitally blind (CB), late-blind (LB) and blindfolded-sighted (BF) groups of adults. This Cognitive-Kinesthetic Drawing approach previously developed by Likova (e.g., 2010, 2012, 2013) enabled us to rapidly train and study training-driven neuroplasticity in both the blind and sighted groups. The five-day two-hour training taught participants to haptically explore, recognize, memorize raised-line images, and draw them free-hand from memory, in detail, including the fine facial characteristics of the face stimuli. Such drawings represent an externalization of the formed memory. Functional MRI was run before and after the training. Tactile-face perception activated the occipito-temporal cortex in all groups. However, the training led to a strong, predominantly left-hemispheric reorganization in the two blind groups, in contrast to right-hemispheric in blindfolded-sighted, i.e., the post-training response-change was stronger in the left hemisphere in the blind, but in the right in the blindfolded. This is the first study to discover interhemispheric differences in non-visual face processing. Remarkably, for face perception this learning-based change was positive in the CB and BF groups, but negative in the LB-group. Both the lateralization and inversed-sign learning effects were specific to face perception, but absent for the control nonface categories of small objects and houses. The unexpected inversed-sign training effect in CB vs LB suggests different stages of brain plasticity in the ventral pathway specific to the face category. Importantly, the fact that only after a very few days of our training, the totally-blind-from-birth CB manifested a very good (haptic) face perception, and even developed strong empathy to the explored faces, implies a preexisting face schema that can be "unmasked" and "tuned up" by a proper learning procedure. The Likova Cognitive-Kinesthetic Training is a powerful tool for driving brain plasticity, and providing deeper insights into non-visual learning, including emergence of perceptual categories. A rebound learning model and a neuro-Bayesian economy principle are proposed to explain the multidimensional learning effects. The results provide new insights into the Nature-vs-Nurture interplay in rapid brain plasticity and neurorehabilitation.

Analysis of Neural-BOLD Coupling Through Four Models of the Neural Metabolic Demand.

The coupling of the neuronal energetics to the blood-oxygen-level-dependent (BOLD) response is still incompletely understood. To address this issue, we compared the fits of four plausible models of neurometabolic coupling dynamics to available data for simultaneous recordings of the local field potential and the local BOLD response recorded from monkey primary visual cortex over a wide range of stimulus durations. The four models of the metabolic demand driving the BOLD response were: direct coupling with the overall LFP; rectified coupling to the LFP; coupling with a slow adaptive component of the implied neural population response; and coupling with the non-adaptive intracellular input signal defined by the stimulus time course. Taking all stimulus durations into account, the results imply that the BOLD response is most closely coupled with metabolic demand derived from the intracellular input waveform, without significant influence from the adaptive transients and nonlinearities exhibited by the LFP waveform.

Deficits in the Activation of Human Oculomotor Nuclei in Chronic Traumatic Brain Injury.

Binocular eye movements form a finely tuned system that requires accurate coordination of the oculomotor dynamics of the brainstem control nuclei when tracking the fine binocular disparities required for 3D vision. They are particularly susceptible to disruption by brain injury and other neural dysfunctions. Here, we report functional magnetic resonance imaging activation of the brainstem oculomotor control nuclei by binocular saccadic and vergence eye movements, and significant reductions in their response amplitudes in mild or diffuse traumatic brain injury (dTBI). Bilateral signals were recorded from a non-TBI control group (n = 11) in the oculomotor control system of the superior colliculi, the oculomotor nuclei, the abducens nuclei, and in the supra-oculomotor area (SOA), which mediate vergence eye movements. Signals from these nuclei were significantly reduced overall in a dTBI group (n = 12) and in particular for the SOA for vergence movements, which also showed significant decreases in velocity for both the convergence and divergence directions.

Consequences of traumatic brain injury for human vergence dynamics.

PURPOSE: Traumatic brain injury involving loss of consciousness has focal effects in the human brainstem, suggesting that it may have particular consequences for eye movement control. This hypothesis was investigated by measurements of vergence eye movement parameters. METHODS: Disparity vergence eye movements were measured for a population of 123 normally sighted individuals, 26 of whom had suffered diffuse traumatic brain injury (dTBI) in the past, while the remainder served as controls. Vergence tracking responses were measured to sinusoidal disparity modulation of a random-dot field. Disparity vergence step responses were characterized in terms of their dynamic parameters separately for the convergence and divergence directions. RESULTS: The control group showed notable differences between convergence and divergence dynamics. The dTBI group showed significantly abnormal vergence behavior on many of the dynamic parameters. CONCLUSION: The results support the hypothesis that occult injury to the oculomotor control system is a common residual outcome of dTBI.

Analysis of human vergence dynamics.

Disparity vergence is commonly viewed as being controlled by at least two mechanisms, an open-loop vergence-specific burst mechanism analogous to the ballistic drive of saccades, and a closed-loop feedback mechanism controlled by the disparity error. We show that human vergence dynamics for disparity jumps of a large textured field have a typical time course consistent with predominant control by the open-loop vergence-specific burst mechanism, although various subgroups of the population show radically different vergence behaviors. Some individuals show markedly slow divergence responses, others slow convergence responses, others slow responses in both vergence directions, implying that the two vergence directions have separate control mechanisms. The faster time courses usually had time-symmetric velocity waveforms implying open-loop burst control, while the slow response waveforms were usually time-asymmetric implying closed-loop feedback control. A further type of behavior seen in a distinct subpopulation was a compound anomalous divergence response consisting of an initial convergence movement followed by a large corrective divergence movement with time courses implying closed-loop feedback control. This analysis of the variety of human vergence responses thus contributes substantially to the understanding of the oculomotor control mechanisms underlying the generation of vergence movements [corrected].

Crossed pin fixation of displaced supracondylar humerus fractures in children.

The results of 42 children with displaced supracondylar fractures of the humerus (six Gartland Type II and 36 Gartland Type III) treated with crossed pin fixation are reported. In 37 fractures (88%) the teardrop configuration was restored successfully. All fractures healed without loss of reduction. No patients had iatrogenic ulnar nerve injury. Crossed-pin fixation of supracondylar humeral fractures is a safe and effective way of maintaining skeletal stability in children. Careful technique safeguards against ulnar nerve injury.

Ender rod fixation of femoral shaft fractures in children.

Ender rod fixation for femoral shaft fractures in children was evaluated in a prospective study at two Level 1 trauma centers. Fifty-seven fractures in 52 patients were evaluated. Criteria for inclusion in the study included age younger than 14 years, femoral shaft fractures occurring in the middle 3/5, canal size greater than 7 mm, and parental consent. Hip and knee motion, gait, leg length discrepancy, and rotational asymmetry were evaluated by clinical examination. Standard radiographs were used to measure any residual angulation. A subset of patients whose injuries occurred more than 12 months previously was evaluated using scanograms. Followup averaged 20 months. There were no delayed unions and all fractures healed within 12 weeks. Clinically significant leg length discrepancy, malunion, or loss of motion did not occur. Functional results were excellent and complications were minor. Ender rod fixation of femur fractures in children allows the advantages of surgical fixation with minimal risk of complications.

Sensitivity of objective parameters in the diagnosis of pediatric septic hips.

This study examines the sensitivity of temperature, leukocyte count, and erythrocyte sedimentation rate in the diagnosis of pediatric septic arthritis of the hip by retrospective case analysis of 26 children, aged 0 to 6 years, in hospitals of central Brooklyn. The average presenting temperature was 38.4 degrees C, with 65% of the patients having had a temperature higher than 38 degrees C. The average leukocyte count was 13,500 per mL, with 73% of patients having a leukocyte count greater than 9000 per ml. The average erythrocyte sedimentation rate (21 cases) was 51 mm per hour, with 95% of the patients presenting with an erythrocyte sedimentation rate greater than 20 mm per hour. Of these children with septic hips, only 5% had a normal erythrocyte sedimentation rate, although 35% had a normal temperature and 27% had a normal leukocyte count. Neonates (age younger than 1 month) were not febrile (average temperature, 36.7 degrees C) and did not have an elevated leukocyte count (average leukocyte count, 9300 per mL) but did have an elevated erythrocyte sedimentation rate (average erythrocyte sedimentation rate, 45 mm per hour). Of these 3 values, erythrocyte sedimentation rate is the most sensitive indicator of septic arthritis of the hip in children 0 to 6 years of age.

Clubfeet and tarsal coalition.

Tarsal coalition was noted in 18 cases of rigid equinovarus deformity. Sixteen cases were encountered at surgery and two at morbid dissection. There were 14 patients in the series; six had associated pathologic conditions that might have caused their clubfeet to be deemed "teratologic," whereas eight did not and were considered to have congenital clubfeet. Four patients in the series had bilateral coalitions. Preoperative radiographs demonstrated the coalition in only one case. A presurgical magnetic resonance image (MRI) clearly showed the coalition in another case. Nonoperative treatment was unsuccessful. Two patients with tibial dysplasia had ankle disarticulations. The remaining 16 feet required extensive soft-tissue releases, internal fixation, and coalition excision. The vast majority of cases showed cartilaginous subtalar coalition at the medial facet. The patients were followed for an average of 6 years, and two recurrences were noted. Remaining feet were painless and plantargrade, but were rather stiff. This anomaly may be more common than previously described. It is usually not suspected preoperatively and may likewise be difficult to recognize at surgery. A preoperative MRI scan may also be helpful.

Slipped capital femoral epiphysis in black children: incidence of chondrolysis.

The risk of chondrolysis and avascular necrosis (AVN) in black children treated for slipped capital femoral epiphysis (SCFE) is controversial. A retrospective study was conducted of 29 black patients (44 hips) treated for SCFE at Kings County Hospital, Brooklyn, New York, to evaluate our own experience. All patients were treated with in situ pinning. The overall rates of chondrolysis and AVN were 6.8 and 4.5%, respectively. Fifty-two percent of patients had bilateral SCFE. Obesity was extremely common and correlated significantly with bilateral disease. Obesity did not correlate directly with a higher incidence of chondrolysis or AVN. Adherence to technical details described should reduce complications further.

Closed flexible intramedullary nailing of adolescent femoral shaft fractures.

Twenty-five femoral shaft fractures in twenty-three patients aged 10-16 years with open epiphyses and treated with flexible intramedullary nailing were studied retrospectively. Clinical and roentgenographic follow-up averaged 28 months. Hospitalization, which included patients with multiple injuries, averaged 11.7 days. Patients ambulated without assist devices as early as 2 weeks postoperatively (average of 7.7 weeks). All fractures healed with no leg length inequality--21 with anatomic alignment and full range of motion of the hip and knee. Three patients sustained intraoperative extension of the fracture resulting in healing with angular or rotatory malalignment. One patient with associated knee ligamentous injury had less than full knee flexion at follow-up. All patients had normal gait (except one patient with residual hemiplegia) and were able to participate in full activities including athletics. Early ambulation and functional recovery with low morbidity and cost suggest that this procedure should be considered for the treatment of femoral shaft fractures in this age group.

Hemipelvectomy, a lifesaving operation in severe open pelvic injury in childhood.

Near-complete traumatic hemipelvectomy probably carries an extremely high mortality rate. The usual techniques which have been used to control major hemorrhage associated with pelvic fractures such as transperitoneal vascular ligation, intra-arterial embolization, and packing are not applicable (14). Successful management requires prompt recognition of the nature of this injury so that surgical efforts may be directed at resuscitation and expeditious operative completion of the traumatic amputation. When this decision is made appropriately, the dual goals of control of hemorrhage and prevention of sepsis can be achieved. We report the management of a 7-year-old boy who sustained this injury after being struck by a tractor-trailer. In spite of massive resuscitation, hemorrhage could not be controlled and the child remained in shock. When it was recognized that he had sustained an incomplete traumatic left hemipelvectomy, it was surgically completed, permitting prompt control of the hemorrhage and restoration of hemodynamic stability. Intestinal and urinary diversion allowed an uneventful postoperative recovery without significant infection. Although hemipelvectomy appears to be a radical procedure in children with major pelvic injuries, it may be lifesaving and should therefore be considered in those with severe unilateral pelvic injury and uncontrollable hemorrhage. The potential for physical rehabilitation in the group of young, mostly male patients who have survived this injury appears to be unexpectedly good.

Hip adductor transfer compared with adductor tenotomy in cerebral palsy.

In a ten-year study in patients with cerebral palsy, fifty patients had ninety-eight adductor transfers and fifty-two patients had 102 adductor tenotomies with or without obturator neurectomy. The groups were similar with regard to severity of their disease, age, and associated concomitant surgery. Results were evaluated in three ways: functional change, change in passive motion of the hip, and change in stability of the hip. Our data support the view that although the adductor transfer operation takes longer and is associated with a higher incidence of postoperative drainage, the over-all improvement is greater and is maintained better than that after adductor tenotomy with or without neurectomy. The transferred muscle provides greater pelvic stability, decreases hip-flexion contractures, and reduces instability of the hip.

A method of repair of late quadriceps rupture.

Delayed treatment of a quadriceps rupture is an infrequent but difficult situation. The fibrous degeneration and muscle retraction and subsequent hiatus present a challenging technical problem. A 54-year-old laborer with a 7-week quadriceps rupture was treated by a method that seems not to have been previously reported. At surgery there was a 9-cm gap that could not be approximated by either a Bunnell suture, or Codvilla lengthening of Scuderi inverted triangle. Repair was successfully accomplished by transposing the inner one-third of the patellar tendon. The tendon was split longitudinally and separated from the medial and lateral aspects in a distal to proximal direction with an osteoperiosteal flap. This was proximally sutured across the gap in the quadriceps mechanism. Eighteen months postoperatively there was no extension lag with knee range of motion of 0 degrees-125 degrees and good power.