Reversibility of visual field defects through induction of brain plasticity: vision restoration, recovery and rehabilitation using alternating current stimulation

For decades visual field defects were considered irreversible because it was thought that in the visual system the regeneration potential of the neuronal tissues is low.Nevertheless,there is always some potential for partial recovery of the visual field defect that can be achieved through induction of neuroplasticity.Neuroplasticity refers to the ability of the brain to change its own functional architecture by modulating synaptic efficacy.It is maintained throughout life and just as neurological rehabilitation can improve motor coordination,visual field defects in glaucoma,diabetic retinopathy or optic neuropathy can be improved by inducing neuroplasticity.In ophthalmology many new treatment paradigms have been tested that can induce neuroplastic changes,including non-invasive alternating current stimulation.Treatment with alternating current stimulation(e.g.,30 minutes,daily for 10 days using transorbital electrodes and^10 Hz)activates the entire retina and parts of the brain.Electroencephalography and functional magnetic resonance imaging studies revealed local activation of the visual cortex,global reorganization of functional brain networks,and enhanced blood flow,which together activate neurons and their networks.The future of low vision is optimistic because vision loss is indeed,partially reversible.

Predictive visual field outcomes after optic chiasm decompressive surgery by retinal vessels parameters using optical coherence tomography angiography

AIM:To evaluate the predictive value of superficial retinal capillary plexus(SRCP)and radial peripapillary capillary(RPC)for visual field recovery after optic cross decompression and compare them with peripapillary nerve fiber layer(pRNFL)and ganglion cell complex(GCC).METHODS:This prospective longitudinal observational study included patients with chiasmal compression due to sellar region mass scheduled for decompressive surgery.Generalized estimating equations were used to compare retinal vessel density and retinal layer thickness preand post-operatively and with healthy controls.Logistic regression models were used to assess the relationship between preoperative GCC,pRNFL,SRCP,and RPC parameters and visual field recovery after surgery.RESULTS:The study included 43 eyes of 24 patients and 48 eyes of 24 healthy controls.Preoperative RPC and SRCP vessel density and pRNFL and GCC thickness were lower than healthy controls and higher than postoperative values.The best predictive GCC and pRNFL models were based on the superior GCC[area under the curve(AUC)=0.866]and the tempo-inferior pRNFL(AUC=0.824),and the best predictive SRCP and RPC models were based on the nasal SRCP(AUC=0.718)and tempo-inferior RPC(AUC=0.825).There was no statistical difference in the predictive value of the superior GCC,tempo-inferior pRNFL,and tempo-inferior RPC(all P>0.05).CONCLUSION:Compression of the optic chiasm by tumors in the saddle area can reduce retinal thickness and blood perfusion.This reduction persists despite the recovery of the visual field after decompression surgery.GCC,pRNFL,and RPC can be used as sensitive predictors of visual field recovery after decompression surgery.

Values of macular ganglion cell-inner plexiform layer and 10-2 visual field measurements in detecting and evaluating glaucoma

AIM:To assess the performance of macular ganglion cell-inner plexiform layer thickness(mGCIPLT)and 10-2 visual field(VF)parameters in detecting early glaucoma and evaluating the severity of advanced glaucoma.METHODS:Totally 127 eyes from 89 participants(36 eyes of 19 healthy participants,45 eyes of 31 early glaucoma patients and 46 eyes of 39 advanced glaucoma patients)were included.The relationships between the optical coherence tomography(OCT)-derived parameters and VF sensitivity were determined.Patients with early glaucoma were divided into eyes with or without central 10°of the VF damages(CVFDs),and the diagnostic performances of OCT-derived parameters were assessed.RESULTS:In early glaucoma,the mGCIPLT was significantly correlated with 10-2 VF pattern standard deviation(PSD;with average mGCIPLT:β=-0.046,95%CI,-0.067 to-0.024,P<0.001).In advanced glaucoma,the mGCIPLT was related to the 24-2 VF mean deviation(MD;with average mGCIPLT:β=0.397,95%CI,0.199 to 0.595,P<0.001),10-2 VF MD(with average mGCIPLT:β=0.762,95%CI,0.485 to 1.038,P<0.001)and 24-2 VF PSD(with average mGCIPLT:β=0.244,95%CI,0.124 to 0.364,P<0.001).Except for the minimum and superotemporal mGCIPLT,the decrease of mGCIPLT in early glaucomatous eyes with CVFDs was more severe than that of early glaucomatous eyes without CVFDs.The area under the curve(AUC)of the average mGCIPLT(AUC=0.949,95%CI,0.868 to 0.982)was greater than that of the average circumpapillary retinal nerve fiber layer thickness(cpRNFLT;AUC=0.827,95%CI,0.674 to 0.918)and rim area(AUC=0.799,95%CI,0.610 to 0.907)in early glaucomatous eyes with CVFDs versus normal eyes.CONCLUSION:The 10-2 VF and mGCIPLT parameters are complementary to 24-2 VF,cpRNFLT and ONH parameters,especially in detecting early glaucoma with CVFDs and evaluating the severity of advanced glaucoma in group level.

Characteristics of central visual field defect after macular hole surgery

AIM: To investigate the characteristics of postoperative central visual field defect(cVFD) in patients with macular hole(MH).METHODS: Eighteen eyes from 18 MH patients were involved in this retrospective study which reviewed square root of loss variance(sLV) and mean defect(MD) of the visual field test in all subjects. The relationship between cVFD and MH stage, as well as the postoperative ellipsoid zone disruption were evaluated using Spearman's correlation test. RESULTS: Our analysis determined Spearman coefficient is 0.705 for the correlation between sLV and MH stage(P<0.01), 0.877 for the correlation between sLV and postoperative ellipsoid zone disruption(P<0.01) and 0.721 for the correlation between MD and postoperative ellipsoid zone disruption(P<0.01). A significant relationship was also detected between postoperative ellipsoid zone disruption and MH stage(r=0.470, P<0.05). Univariate regression analysis indicated that sLV and MD were associated with postoperative ellipsoid zone disruption(P<0.01, P<0.01, respectively). CONCLUSION: Postoperative cVFD is highly correlated with MH stage and postoperative ellipsoid zone disruption in patients with MH.

Validation and reproducibility of the Heidelberg Edge Perimeter in the detection of glaucomatous visual field defects

AIM: To validate the ability of the Heidelberg Edge Perimeter(HEP) in detecting glaucomatous visual field(VF) defects compared to the Octopus Visual Field(OVF) Analyzer and to determine the test-retest repeatability of both modalities.METHODS: This prospective, cross-sectional study was conducted at Wills Eye Hospital, Philadelphia, PA. Glaucoma subjects and unaffected controls underwent VF testing using HEP standard automated perimetry(SAP) Ⅲ 30-2 Adaptive Staircase Thresholding Algorithm(ASTA) FAST protocol and OVF G-TOP white-on-white strategy. Testing order was randomized. Pearson's correlation coefficient was calculated for both mean deviation(MD) and pattern standard deviation/square root of loss of variance(PSD/s LV). Receiver operating characteristic(ROC) curves were used to determine the diagnostic abilities of both modalities. Glaucoma subjects returned for repeat testing and intraclass correlation coefficients(ICCs) were calculated to assess test-retest repeatability. RESULTS: Seventy-nine subjects with glaucoma and 36 unaffected controls were enrolled. HEP and OVF were significantly correlated for both MD(r=-0.84; P<0.01) and PSD/s LV(r=0.79; P<0.01). Areas under the ROC curves(AUCs) were also comparable between HEP and OVF for both MD(0.74 and 0.79, respectively; P=0.26) and PSD/sL V(0.74 and 0.82; P=0.08). ICC was high for both HEP (0.96 for MD, 0.95 for PSD/s LV) and OVF(0.82 and 0.88, respectively). Mean test duration(min) was significantly shorter for OVF(2.63) compared to HEP(5.15; P<0.01). CONCLUSION: HEP and OVF show strong correlation for both MD and PSD/s LV, and have similar validity for detecting glaucoma. The test-retest repeatability is high for both HEP and OVF, however the average testing duration of HEP is significantly longer than that of OVF.

Visual field defects and retinal nerve fiber layer damage in buried optic disc drusen: a new insight

AIM: To assess the association between buried optic disc drusen(BODD) location using spectral-domain optical coherence tomography(SD-OCT) and the location of associated visual field defects(VFD) using the Garway-Heath mapping.METHODS: This monocentric retrospective crosssectional study was led at the authors’ institution. Adult patients diagnosed with BODD who had complete records with a reliable Humphrey? 24-2 visual field, macular, and papillary OCT were enrolled. Fisher’s exact test was used to measure the association between BODD location and VFD distribution according to Garway-Heath’s mapping.RESULTS: Totally 20 eyes of 15 patients were included(60% females). The median age(interquartile range) was 63(43)y and the median best corrected visual acuity(BCVA) was-0.08(0.08) log MAR. BODD were mostly located in zones A, E, and F. The minimal rim width(MRW) was globally preserved. The retinal nerve fiber layer(RNFL) was predominantly altered in zones D, E, and F. There was a significant correlation between BODD location and that of RNFL alterations in zones D(P=0.03) and E(P=0.025);Moreover, the presence of BODD in the E zone was significantly related to damaged RNFL in the neighbouring sectors D and F(P=0.012;P=0.02 respectively). Sixty-three percent(12/19) of visual fields were abnormal and there was a significant match(Phi=0.7, P=0.009) between drusen location and VFD only in zone D.CONCLUSION: BODD do not only affect young patients and can be more harmful than usually expected, as we found VFD in 63% of cases. There is a correspondence between BODD location, RNFL damage, and VFD distributions. The presence of BODD induces the overestimation of MRW,thereby disrupting its sensitivity as an early indicator of ganglion fibers damage.

Factors influencing improvement of visual field after trans-sphenoidal resection of pituitary macroadenomas:a retrospective cohort study

AIM: To investigate the influencing factors of visual field improvement after trans-sphenoidal resection of pituitary macroadenomas. METHODS: This retrospective cohort study included 201 patients (366 eyes) with visual field defect induced by pituitary macroadenomas. All of them were treated with trans-sphenoidal surgery. Ophthalmologic evaluation, best -corrected visual acuity (BCVA), and visual field examination were performed before and 3mo after surgery. BCVA, visual field defect index mean deviation (MD), duration of symptoms, age, sex, and volume of tumors were compared. Expression of vascular endothelial growth factor (VEGF) and Ki-67 of tumor tissue were detected by immunohistochemical technique. RESULTS: The mean age of patients was 44.23 +/- 1.29y. Ninety -three patients were female and 108 were male. The mean tumor volume was 14.36 +/- 6.23 cm(3). The mean duration of preoperative symptoms was 11.50 +/- 0.88mo. Mean preoperative MD was -17.50 +/- 0.82 dB. Mean Preoperative visual acuity was 0.64 +/- 0.04. Postoperative visual field improved in 270 (73.77%) eyes, unchanged in 96 (26.23%) eyes. Multivariate logistic regression displayed that the factors independently influencing visual field improvement were young age (OR=1.71, 95%CI: 1.325-2.387, P=0.013), low preoperative MD absolute value (OR=1.277, 95%CI: 1.205-1.355, P<0.001), small volume of tumor (OR=1.458, 95%CI: 1.060-4.289, P<0.001), low expression of VEGF in tumor tissue (OR=1.554, 95%CI: 1.089-2.457, P=0.022), and low expression of Ki-67 in tumor tissue (OR=1.552, 95%CI: 1.161-2.847, P=0.026). CONCLUSION: After pituitary macroadenomas trans sphenoidal resection, the independent influencing factors of the visual fields recovery were low preoperative MD absolute value, young age, small volume of tumor, and expression levels of VEGF/Ki-67.

Visual field mean deviation and relevant factors in 928 Chinese retinitis pigmentosa patients

AIM: To investigate the associations between demographic and clinical factors with the rate of visual field mean derivation(MD) decline in retinitis pigmentosa(RP) patients.METHODS: Correlations of MDs with the visual acuity and retinal pigmentation were analyzed in 928 RP patients. MD decreasing rate in 10 y and potential influences of gender, age, family history and retinal pigmentation on the rate were explored in 201 RP patients. RESULTS: In the 928 patients, average MD and visual acuity were-14.44±8.61 dB and 0.79±0.35 respectively and when MD was lower than-9.18 dB the visual acuity would be below 1.0(20/20). The average MD medium between eyes with or without retinal pigmentation was-14.82 dB. In 123 non-pigmented eyes, the average MD were lower than the medium but in 153 pigmented eyes it was higher than that. In the 201 patients, the average decreasing value of MD in 10 years’ period was-8.01±3.66 dB and the value were correlated to retinal pigmentation but not to gender, age or RP family history. CONCLUSION: The rate of MD decline in RP eyes is significantly related to retinal pigmentation. Our study demonstrates the quantitative rate of MD decline in RP patients and the value of MD could well reflect the severity of RP.

Comparison of corneal biomechanical properties in normal tension glaucoma patients with different visual field progression speed

AIM：To compare the corneal biomechanical properties difference by ocular response analyzer（ORA） in normal tension glaucoma（NTG） patients with different visual field（VF） progression speed. METHODS：NTG patients with well-controlled Goldmann applanation tonometer（GAT） who routinely consulted Kitasato University Hospital Glaucoma Department between January 2010 and February 2014 were enrolled.GAT and ORA parameters including corneal compensated intraocular pressure（lOPcc）,Goldmann estimated intraocular pressure（lOPg）,corneal hysteresis（CH）,corneal resistance factor（CRF） were recorded.VF was tested by Swedish interactive threshold algorithm（SITA）-standard 30-2 fields.All patients underwent VF measurement regularly and GAT did not exceed 15 mm Hg at any time during the 3y follow up.Patients were divided into four groups according to VF change over 3y,and ORA findings were compared between the upper 25th percentile group（slow progression group） and the lower 25th percentile group（rapid progression group）.RESULTS：Eighty-two eyes of 56 patients were studied.There were 21 eyes（21 patients） each in rapid and slow progression groups respectively.GAT,lOPcc,lOPg,CH,CRF were 12.1＋1.4 mm Hg,15.8±1.8 mm Hg,12.8±2.0 mm Hg,8.4±1.1 mm Hg,7.9±1.3 mm Hg respectively in rapid progression group and 11.5±1.3 mm Hg,13.5±2.1 mm Hg,11.2±1.6 mm Hg,9.3±1.1 mm Hg,8.2±0.9 mm Hg respectively in slow progression group（P=0.214,〈0.001,0.007,0.017,0.413,respectively）.In bivariate correlation analysis,lOPcc,lOPcc-GAT and CH were significant correlated with m△MD（r =-0.292,-0.312,0.228 respectively,P =0.008,0.004,0.039 respectively）.CONCLUSION：Relatively rapid VF progression occurred in NTG patients whose lOPcc are rather high,CH are rather low and the difference between lOPcc and GAT are relatively large.Higher lOPcc and lower CH are associated with VF progression in NTG patients.This study suggests that GAT measures might underestimate the IOP in such patients.

Bruch's membrane opening-minimum rim width and visual field loss in glaucoma:a broken stick analysis

AIM：To determine the Bruch＇s membrane opening-minimum rim width（BMO-MRW） tipping point where corresponding visual field（VF） damages become detectable.METHODS：A total of 85 normal subjects and 83 glaucoma patients（one eye per participant） were recruited for the study.All of the patients had VF examinations and spectral-domain optical coherence tomography to measure the BMO-MRW.Total deviation values for 52 VF points were allocated to the corresponding sector according to the Garway-Heath distribution map.To evaluate the relationship between VF loss and BMOMRW measurements,a ＂broken-stick＂ statistical model was used.The tipping point where the VF values started to sharply decrease as a function of BMO-MRW measurements was estimated and the slopes above and below this tipping point were compared.RESULTS：A 25.9% global BMO-MRW loss from normative value was required for the VF loss to be detectable.Sectorally,substantial BMO-MRW thinning in inferotemporal sector（33.1%） and relatively less BMO-MRW thinning in the superotemporal sector（8.9%） were necessary for the detection of the VF loss.Beyond the tipping point,the slopes were close to zero throughout all of the sectors and the VF loss was unrelated to the BMO-MRW loss.The VF loss was related to the BMO-MRW loss below the tipping point.The difference between the two slopes was statistically significant（P≤0.002）.CONCLUSION：Substantial BMO-MRW loss appears to be necessary for VF loss to be detectable in patients with open angle glaucoma with standard achromatic perimetry.

Impact of binocular visual field loss on driving performance in glaucoma patients

AIM:To evaluate the driving performance in young and middle-aged Chinese glaucoma patients with mild to severe visual field loss compared to those without glaucoma by using a driving simulation test.METHODS:Twenty-nine participants were included in this study:nine patients with glaucoma but pass the binocular Esterman visual field test,ten patients with glaucoma and fail the binocular Esterman visual field test,and ten age-matched healthy controls.A driving simulation test was designed as a frequency-based analysis of a lanekeeping task.The total performance error,the controlresponse amplitude and delay were calculated.RESULTS:Esterman visual field test fail group showed the longest delay of control-response among three groups(P=0.02).And the delay in lane-keeping task was significantly associated with inferior field of better-eye(r=0.51,P=0.004)and integrated visual field(r=0.55,P=0.002).CONCLUSION:Young and middle-aged glaucoma patients with binocular visual field loss suffered from a longer delay of response in driving simulation test,while inferior visual field having more impact than superior visual field.

Comparison of the SITA Faster–a new visual field strategy with SITA Fast strategy

AIM:To compare visual field defects using the Swedish Interactive Thresholding Algorithm(SITA)Fast strategy with SITA Faster strategy,a newly developed time-saving threshold visual field strategy.METHODS:Ninety-three participants(60 glaucoma patients and 33 normal controls)were enrolled.One eye from each participant was selected randomly for the study.SITA Fast and SITA Faster were performed using the 24-2 default mode for each test.The differences of visual field defects between the two strategies were compared using the test duration,false-positive response errors,mean deviation(MD),visual field index(VFI)and the numbers of depressed test points at the significant levels of P<5%,<2%,<1%,and<0.5%in probability plots.The correlation between strategies was analyzed.The agreement between strategies was acquired by Bland-Altman analysis.RESULTS:Mean test durations were 246.0±60.9 s for SITA Fast,and 156.3±46.3 s for SITA Faster(P<0.001).The test duration of SITA Faster was 36.5%shorter than SITA Fast.The MD,VFI and numbers of depressed points at P<5%,<2%,<1%,and<0.5%in probability plots showed no statistically significant difference between two strategies(P>0.05).Correlation analysis showed a high correlation for MD(r=0.986,P<0.001)and VFI(r=0.986,P<0.001)between the two strategies.Bland-Altman analysis showed great agreement between the two strategies.CONCLUSION:SITA Faster,which saves considerable test time,has a great test quality comparing to SITA Fast,but may be not directly interchangeable.

A virtual model of the retina based on histological data as a tool for evaluation of the visual fields

Background:To settle the fundamentals of a numerical procedure that relates retinal ganglion-cell density and threshold sensitivity in the visual field.The sensitivity of a generated retina and visual pathways to virtual stimuli are simulated,and the conditions required to reproduce glaucoma-type defects both in the optic-nerve head(ONH)and visual fields are explored.Methods:A definition of selected structural elements of the optic pathways is a requisite to a translation of clinical knowledge to computer programs for visual field exploration.The program is able to generate a database of normalized visual fields.The relationship between the number of extant receptive fields and threshold sensitivity is plotted for background sensitivity and corresponding automated perimetry.A solution in two planes to the 3D distribution of axons in the ONH is proposed.Visual fields with induced damage in the optic disc are comparable in pattern and quantity to glaucomatous records.Results:The two-level simulation of the ONH facilitates the analysis of optic-cup/retinal defects.We can generate the virtual optic pathways tailored to the age and morphology of the patient’s eye,and it is possible to reproduce glaucomatous damage by“reverse engineering”engineering.The virtual cortical model renders a quantitative relationship between visual defect and neural damage.Conclusions:A two-level computing of the retina/optic nerve facilitates the analysis of neuroretinal defects and can be incorporated to automatic perimeters to facilitate visual field analysis.

Effect of intraocular lens implantation on visual field in glaucoma and comorbid cataracts

AIM: To investigate the effects of intraocular lens(IOL) implantation on visual field(VF) in patients with glaucoma and comorbid cataracts(G&C) with different disease severities.METHODS: Totally 56 eyes of 50 patients with primary G&C were included. All patients were divided into three groups based on the severity of the VF defect: the mild, moderate, and severe stage. Phacoemulsification was performed for cataract removal combined with IOL implantation. Visual acuity(VA) and VF tests were performed for all enrolled patients, up to 3 mo after surgery. Changes in VF threshold and global VF index in various groups were also recorded before and after surgery. The mean light sensitivity(MS) values and the changes following surgery(DMS) were compared between the three groups. Advanced Glaucoma Intervention Study(AGIS) scoring was analyzed on all VF results for analysis of changes in VF before and after surgery.RESULTS: Following surgery, the MS values of the three groups of G&C increased significantly, while the AGIS scores decreased statistically in all groups. The DMS values for the three zones in moderate and severe stage but not mild stage were statistically different between zones. The DMS value was significantly higher in zone I than those in zone II and III(zone I>zone II>zone III;P<0.05). The DMS was significantly higher in zone I than that in zone III in moderate stage patients(zone I>zone II>zone III;P<0.01), while the DMS values in the severe stage patients was significantly higher in zone I than those in zone II and III(zone I>zone II>zone III;P<0.01). CONCLUSION: The mean VF sensitivity of glaucoma patients increased significantly after cataract removal and IOL implantation. Variations in the severity and distribution of characteristics of VF defects result in differences in postoperative VF improvements after cataract surgery. The magnitude of increase in VF sensitivity is associated with VF defect characteristic in glaucoma.

The Effect of Monocular Blur on the Binocular Visual Field

Purpose/Aim: We aimed to investigate the effect of monocular blur on the binocular visual field. Materials and Methods: A total of 13 healthy young volunteers participated in this study. The mean subjective refractive error of the dominant eye (DE) was -3.33 ± 1.65D, and the non-dominant eye (NDE) was -3.15 ± 2.84D. The DE was determined by using the hole-in-the-card test. The visual field was examined by the Humphrey Visual Field Analyzer using the 30-2 SITA Standard program. The visual field was measured while wearing soft contact lens under three conditions;① both eyes: near vision correction;② DE: near vision correction +3.00D added, NDE: near vision correction;and ③ DE: near vision correction, NDE: near vision correction +3.00D added. The foveal threshold, mean deviation (MD), and pattern standard deviation (PSD) values were investigated. Results: The foveal threshold value (dB) at ①, ②, and ③ was 41.2, 37.8, and 38.1, respectively. The values at ② and ③ were both significantly lower than that at ① (p Conclusion: These results suggest that monocular blur reduced the sensitivity within the binocular visual field.

Evening exercise is associated with lower odds of visual field progression in Chinese patients with primary open angle glaucoma

Background:Exercise is widely known to lower intraocular pressure and increase ocular blood flow,which may be beneficial for glaucoma management.However,there are few studies that have reported on the relationship between exercise and glaucoma progression.The aim of our study was to investigate the exercise habits of those with primary open angle glaucoma(POAG)and its association with the progression of visual field(VF)loss.Methods:Daily physical activity(PA)was monitored by an accelerometer(ActiGraph wGT3x-BT)which patients wore for more than 10 h of being awake on their right wrists for 1 week.Results:Seventy-one non-progressive and 27 progressive patients were enrolled in the study.24-h moderate to vigorous physical activity(MVPA)exercise showed that POAG patients had similar variation trends consisting of 3 wave peaks and 2 wave hollows.Minutes spent in MVPA was 19.89±15.81 and 21.62±15.10 during 07:00–09:00 h(p=0.204),15.40±14.49 and 15.67±12.43 during 15:00–17:00 h(p=0.822)and 17.26±21.11 and 11.42±11.58 during 18:00–20:00 h(p=0.001)in the non-progressive and progressive group,respectively.Univariate analysis indicated that 10 min of MVPA(18:00–20:00 h)[odds ratio,OR(95%CI)=0.82(0.73,0.92)],average mean arterial pressure[OR(95%CI)=0.96(0.94,0.98)],age[OR(95%CI)=1.06(1.03,1.08)],male[OR(95%CI)=0.67(0.48,0.96)],spherical equivalent[OR(95%CI)=1.14(1.07,1.22)]and IOP-lowering medications[OR(95%CI)=1.54(1.16,2.05)]were significantly correlated with having progressive VF damage.Multivariable analysis showed that 10 min of MVPA(18:00–20:00 h)[OR(95%CI)=0.85(0.75,0.97)]was associated with progressive VF loss even after adjusting for other risk factors.Conclusions:Evening exercise may lower the odds of VF progression,suggesting that exercise habits possibly play an important role in glaucoma progression.

VISUAL FIELD TOPOGRAPHY AND BINOCULAR RESPONSES IN FROG’S NUCLEUS ISTHMI

Visual responses of 125 units have been extracellularly recorded with glass micropipettesfrom the left nucleus isthmi in the frog Rana nigromaculata, and 101 electrode tip positionsmarked with cobalt staining to reconstruct a visual field map in the nucleus. 80% of the unitsrecorded show ON-OFF responses to a stationary spot of light and many are directionally selec-tive in response to black or white targets moving through their receptive fields. All the cobalt-marked ssots are within the nucleus, indicating that the nucleus isthmus proper is a restrictedpart of the frog visual system. There is a visual field map in the nucleus. The entire contra-lateral hemifield and the nasal 40°of the ipsilateral hemifield project on the nucleus topog-raphically. A cell-free band inside the nucleus is a boundary line separating the contralat-eral hemifield from the ipsilateral one. Dorsal to it is the contralateral field representation.The upper visual field projects on the rostral half of the nucleus and the central and medio-ventral portion of its caudal half. The lower field is represented on the dorsal and lateralpart of the caudal half. Fifteen binocular units have been found from the nucleus, 13 ofwhich arc dominantly activated by the contralateral eye, the other two are almost equallyexcited by either eye. These binocular units are mainly situated in the medulla of the rostralhalf of the nucleus isthmus.

Dynamic visual simulation of marine vector field based on LIC——a case study of surface wave field in typhoon condition

Line integral convolution(LIC)is a useful visualization technique for a vector field.However,the output image produced by LIC has many problems in a marine vector field.We focus on the visual quality improvement when LIC is applied in the ocean steady and unsteady flow field in the following aspects.When a white noise is used as the input in a steady flow field,interpolation is used to turn the discrete white noise into continuous white noise to solve the problem of discontinuity.The"cross"high-pass filtering is used to enhance the textures of streamlines to be more concentrated and continuity strengthened for each streamline.When a sparse noise is used as the input in a steady flow field,we change the directions of background sparse noise according to the directions of vector field to make the streamlines clearer and brighter.In addition,we provide a random initial phase for every streamline to avoid the pulsation effect during animation.The velocities of vector field are encoded in the speed of the same length streamlines so that the running speed of streamlines can express flow rate.Meanwhile,to solve the problem of obvious boundaries when stitching image,we change the streamline tracking constraints.When a white noise is used as an input in an unsteady flow field,double value scattering is used to enhance the contrast of streamlines;moreover,the"cross"high-pass filtering is also adopt instead of two-dimensional high-pass filtering.Finally,we apply the above methods to a case of the surface wave field in typhoon condition.Our experimental results show that applying the methods can generate high-quality wave images and animations.Therefore,it is helpful to understand and study waves in typhoon condition to avoid the potential harm of the waves to people's lives and property.

Synchronization between frontal eye field and area V4 during free-gaze visual search

Information flow between the prefrontal and visual cortices is critical for visual behaviors such as visual search. To investigate its mechanisms, we simultaneously recorded spike and local field potential (LFP) signals in the frontal eye field (FEF) and area V4 while monkeys performed a free-gaze visual search task. During free-gaze search, spike-LFP coherence between FEF and V4 was enhanced in the theta rhythm (4–8 Hz) but suppressed in the alpha rhythm (8–13 Hz). Cross-frequency couplings during the Cue period before the search phase were related to monkey performance, with higher FEF theta-V4 gamma coupling and lower FEF alpha-V4 gamma coupling associated with faster search. Finally, feature-based attention during search enhanced spike-LFP coherence between FEF and V4 in the gamma and beta rhythms, whereas overt spatial attention reduced coherence at frequencies up to 30 Hz. These results suggest that oscillatory coupling may play an important role in mediating interactions between the prefrontal and visual cortices during visual search.

Visualizing diffusion tensor fields on streamsurfaces with merging ellipsoids

Streamsurfaces in diffusion tensor fields are used to represent structures with pri- marily planar diffusion. So far, however, no effort has been made on the visualization of the anisotropy of diffusion on them, although this information is very important to identify the problematic regions of these structures. We propose two methods to display this anisotropy information. The first one employs a set of merging ellipsoids, which simultaneously character- ize the local tensor details - anisotropy - on them and portray the shape of the streamsurfaces. The weight between the streamsurfaces continuity and the discrete local tensors can be inter- actively adjusted by changing some given parameters. The second one generates a dense LIC （line integral convolution） texture of the two tangent eigenvector fields along the streamsurfaces firstly, and then blends in some color mapping indicating the anisotropy information. For high speed and high quality of texture images, we confine both the generation and the advection of the LIC texture in the image space. Merging ellipsoids method reveals the entire anisotropy information at discrete points by exploiting the geometric attribute of ellipsoids, and thus suits for local and detailed examination of the anisotropy; the texture-based method gives a global representation of the anisotropy on the whole streamsurfaces with texture and color attributes. To reveal the anisotropy information more efficiently, we integrate the two methods and use them at two different levels of details.