Friday, 8 May 2015

Surgical sight restoration: A sticking point and treatment with alternating current.

I decided to write this article after reading quite sad notification dedicated to a patient whose cornea was restored after longstanding blindness. In spite of operation successfulness, researchers observing the patient during 7 months after the operation, concluded that due to long-term visual deprivation the vision restoration may never be complete.

Being flurried with this unpromising news I decided to investigate whether any solutions may exist. Now I would like to share my findings with you.

Finding No.1: the issue does really exist.

One would think that the newly developed surgical techniques, such as corneal and limbal stem-cell transplantation, intraocular lens and artificial cornea implantation would have to solve the issue of complete visual perception restoration for the targeted patients. However what have turned out in fact? Studies of patients who underwent the restorative eyesight surgery after years of blindness do not give encouraging results. For example, Dr. Fine et al. studied the patient MM, who lost one eye at the age of 3,5 and was blinded in the other one after chemical and thermal damage to cornea [1]. This patient underwent the corneal and limbal stem-cell transplantation surgery when he was 43 years old. The surgery was successful and the patient gained acuity of 0,02 [2]. He could easily recognize simple shapes, identify colors and discriminate the direction of both simple and complex plaid motion [1].  In spite the patient regained the important vision functions; he still had low acuity performance even upon 2 years after surgery as well as difficulties with three-dimensional form, face, and gender recognition and interpretation [1].  Even 7 years after the operation, he still had poor spatial resolution and limited visual abilities [3].

With this regard it is worth to mention about the “critical period theory”. The critical period is a period of visual development when the visual stimuli are necessary for the visual function development. This theory was extended by researchers Dr. Lewis and Dr. Maurer, who noted that different visual functions have different sensitive periods of development [4]. Thus, in case the visual deprivation starts at 6 months of age, it prevents the development of normal acuity, but does not affect the sensitivity to the global direction of motion, which develops during the period near birth. 

Accordingly, Dr. Fine et al. supposed that MM had dissimilarities in visual function restoration because the ability to  interpret three-dimensional forms and faces develops after early development, while the ability to interpret motions is formed earlier in childhood [1]. Regarding the acuity it was concluded that long standing visual loss deteriorated the spatial resolution of the patient’s relevant visual cortex area. 

Another observation Dr. Ostrovsky et al. did while studying two congenitally blind children suffering from dense bilateral cataract [5]. The children gained partial vision restoration at the age of 7 and 13 due to intraocular lens implantation. As the result, after operation children had acuity of 0,2 and 0,25 and both could perform simple shape recognition. Nevertheless they still had poor but improved with time (during 10-18 months) recognition of overlapping simple shapes, i.e.  perceptual organization of the visual scene.

Thus, the theory about critical / sensitive periods may explain the partial visual function recovery after restorative eyesight surgery in patients who lost sight in the childhood. Nevertheless, how the similar issue may be explained when the vision loss happens in the adulthood?

Dr. Sikl et al. studied the subject who lost his vision at the age of 17 because of the explosion [6]. The patient’s cornea was damaged in both eyes. At the age of 71 he underwent an artificial cornea implantation. As the result, the patient gained acuity of 0,33. Upon 6 and 8 months post surgery he performed a good object recognition: 92% recognition of canonical form objects versus 20-30% demonstrated by early-blindness patients postoperatively. Also the patient differentiated face from non-face stimuli and successfully fulfilled simple tasks of visual space perception.  At the same time he still had difficulties with complex 3-dimentional visual scenes recognition, gender and two faces shown simultaneously differentiation, as well as limited ability to integrate partial information. A neuropsychological examination did not reveal any cognitive deficits and the patient’s performance matched his age.

As far as is known, the sensory substitution (e.g. spatial detection of sound, Braille reading) helps greatly to sightless individuals in their daily life. However, does this result of cross modal plasticity always have an advantageous impact?

Unfortunately, it does not. Dr. Dormal et al. investigated a patient whose vision severely deteriorated in childhood (during the age of 2,5-13 years) because of dense bilateral cataracts [7]. After artificial cornea implantation at the age of 47, the subject’s acuity improved from 0,04 up to 0,2 (1,5 months post surgery) and up to 0,7 (7 months post surgery). The researchers noted the contrast sensitivity and face individuation improvements (which though were still below the normal range). The activity of the visual cortex before and after the restorative eyesight surgery was monitored via functional magnetic resonance imaging (fMRI). The researchers noted that before the surgery visual cortex of the patient actively responded to audio stimuli. After the surgery the visual cortex still responded to audio input which overlapped with visual responses. Though the activation of visual cortex with sound was decreased post surgery, it still was recorded even 7 months after the surgery. In other words, the audio signals still competed with visual ones for being analyzed by visual cortex. In the researcher’s opinion it may explain why the patient’s visual performance still was below the normal level after the sight-restorative surgery.

According to all above mentioned, 

it seems that if the longstanding eyesight loss happens due to damage of anterior eye tissues, surgical restoration of the tissues is not enough to regain the visual functions to the full extent. Sounds quite pessimistic, isn’t it? 

It may well be not so sad if to come to understanding that the visual function loss is not restricted solely to the local tissue damage [8].

Finding No.2: applying of alternating current may partially return visual perception to sightless. 

After alpha band oscillations monitoring in both visually impaired and sighted subjects, Michal Bola et al. noted that visual function loss is accompanied with disturbance of brain networks synchronization (BNS). Moreover, the researchers came further and demonstrated that BNS may be adjusted with alternating current application. The method which was used by the researchers is called “noninvasive repetitive transorbital alternating current stimulation” (rtACS) wherein the stimulating electrodes are applied to the skin at the ocular region [8]. 

Formerly I have already written about this therapeutic approach. Treatment with rtACS leads to improvement of patients’ visual tasks performance. The success of rtACS was ascertained, particularly, by clinical observational study, where patients with optic nerve damage exhibited significant improvements in both visual field (by 9,3%) and acuity (by 0.02) after the treatment [9]. An explanation of such phenomenon was proposed by Dr. Sabel et al. within “residual vision activation theory” [10]. 

According to the theory, the visual system pathway usually is not damaged totally. There still exist some survived residual structures. Nevertheless they can’t provide proper transfer of visual information because the neuronal cell loss leads to neuronal network disorganization, i.e. to loss of network synchrony. Stimulation with rtACS forces the disorganized neuronal network to fire simultaneously. That restores the network synchrony of both survived cells within damaged region and cells of upstream visual pathway. Repetition of rtACS stimulation stabilizes the network firing synchrony. The mechanism involved is similar to one underlying the process of normal learning.

Notably that even patients considered to be “legally blind,” almost always have some degree of residual vision and therefore some restoration potential [10]. 

According to Dr. Sabel, the subject’s age, as well as age, type and location of the damage throughout visual system pathway do not influence the degree of visual restoration (it refers to injuries of nerve tissues, that is retina, optic nerve, brain regions). The only known parameter that matters for restoration, though, is the size and topography of areas of residual vision (ARVs). Vision restoration may be induced in most visual field impairments (scotoma, tunnel vision, hemianopia, acuity loss), irrespective of their etiology (e.g. stroke, neurotrauma, glaucoma, amblyopia, age-related macular degeneration). However, vision restoration is rarely complete and does not take place in all patients.

Sum of Findings No.1 and No.2: should we expect a light at the end of the tunnel?

Comparing of all abovementioned facts brought me to one presumption. Whereas noninvasive stimulation of visual system tissues with alternating current may improve visual perception even in patients whose blindness is caused by damage to the nervous tissues of the visual pathway. Probably, such approach could also help to the patients whose nerve tissues are not affected but because of the long term visual input absence the visual function restoration doesn’t happen completely. Definitely this is what should be investigated, but what if rtACS is what could help in rehabilitation of the patients after surgical vision restoration and allow them to regain the visual function to the full extent?


1. Fine I, Wade AR, Brewer AA, May MG, Goodman DF, Boynton GM, Wandell BA, MacLeod DIA (2003). Long-term deprivation affects visual perception and cortex. Nat Neurosci 6: 915–916. DOI:10.1038/nn1102

2. Saenz M., Lewis L. B., Huth A.G., Fine I., Koch C.(2008). Visual motion area MT+/V5 responds to auditory motion in human sight-recovery subjects. J Neurosci. 28(20): 5141–5148. doi:10.1523/JNEUROSCI.0803-08.2008.

3. Heimler B et al. Revisiting the adaptive and maladaptive effects of crossmodal plasticity. Neuroscience (2014), http://

4. Lewis T. L., Maurer D. (2005). Multiple Sensitive Periods in Human Visual Development: Evidence from Visually Deprived Children.  2005 Wiley Periodicals, Inc., DOI: 10.1002/dev.20055.

5. Ostrovsky, Y., Meyers, E., Ganesh, S., Mathur, U., and Sinha, P. (2009). Visual parsing after recovery from blindness. Psychol. Sci. 20, 1484–1491. doi: 10.1111/j.1467-9280.2009.02471.x

6. Šikl R, Šimeček M, Porubanová-Norquist M, Bezdíček O, Kremláček J, Stodůlka P, Fine I, Ostrovsky Y  (2013). Vision after 53 years of blindness. i-Perception 4(8) 498–507; doi:10.1068/i0611

7. Dormal G, Lepore F, Harissi-Dagher M, Albouy G, Bertone A, Rossion B, Collignon O (2014). Tracking the evolution of crossmodal plasticity and visual functions before and after sight-restoration. Journal of Neurophysiology, 113, 1727-1742. doi: 10.1152/jn.00420.2014

8. Bola M., Gall C., Moewes C., Fedorov A., Hinrichs H., Sabel B.A.(2014).Brain functional connectivity network breakdown and restoration in blindness. Neurology 6, 542–551.doi:10.1212/ WNL.0000000000000672

9. Fedorov A, Jobke S, Bersnev V, Chibisova  A., Chibisova Y., Gall C., Sabel B. A. (2011). Restoration of vision after optic nerve lesions with noninvasive transorbital alternating current stimulation: a clinical observational study. Brain Stimul.4:189-201. DOI:10.1016/j.brs.2011.07.007

10. Sabel B.A, Henrich-Noack P., Fedorov A., Gall C. (2011). Vision restoration after brain and retina damage: The “Residual Vision Activation Theory”. Prog Brain Res, 192, 199-262. DOI: 10.1016/B978-0-444-53355-5.00013-0


Monday, 4 May 2015

The Second Workshop and Lecture Series on “Cognitive neuroscience of auditory and cross-modal perception” took place in Košice, Slovakia on 20 – 24 April 2015

I was happy to participate in The Workshop dedicated to neural processes of auditory, visual and cross-modal perception. The talks were related to cognitive neuroscience research, covering behavioral, neuroimaging, and modeling approaches, as well as applications of the research in auditory prosthetic devices (cochlear implants, hearing aids).
Topics and presenters (detailed abstracts please find here):

Monday, 20 April 2015

Learning From Nature’s Experiments: What Clinical Research Can Mean for Sensory Scientists, Frederick (Erick) Gallun, US Dept. of Veterans Affairs and Oregon Health & Science University

Pursuit eye movements and perceived object velocity, potential clinical applications
Arash Yazdanbakhsh, Boston University

Active listening: Speech intelligibility in cocktail party listening.
Simon Carlile, Auditory Neuroscience Laboratory, School of Medical Science and Bosch Institute, University of Sydney, Australia 2006

Perceptual Learning; specificity, transfer and how learning is a distributed process
Aaron Seitz, Department of Psychology, University of California, Riverside, USA

Spatial hearing: Effect of hearing loss and hearing aids
Virginia Best, Boston University

Toward an evolutionary theory of speech: how and why did it develop the way it did
Pierre Divenyi, Center for Computer Research for Music and Acoustics, Stanford UniversityU.S.A.

On the single neuron computation 
Petr Marsalek, Charles University in Prague

How spectral information triggers sound localization in sagittal planes
Robert Baumgartner, Piotr Majdak, and Bernhard Laback, Acoustics Research Institute, Austrian Academy of Sciences, Vienna, Austria

Cognitively Inspired Speech Processing For Multimodal Hearing Technology
Dr Andrew Abel, Prof. Amir Hussain, Computing Science and Mathematics, University of Stirling, Scotland

Auditory Distance Perception and DRR-ILD Cues Weighting
Jana Eštočinová, Jyrki Ahveninen, Samantha Huang, Stephanie Rossi, and Norbert Kopčo, Institute of Computer Science, P. J. Šafárik University, Košice, Slovakia; Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Harvard Medical School/Massachusetts General Hospital; Center for Computational Neuroscience and Neural Technology, Boston University

Tuesday, 21 April 2015

RESTART theory: discrete sampling of binaural information during envelope fluctuations is a fundamental constraint on binaural processing.
G. Christopher Stecker, Vanderbilt University School of Medicine, Nashville TN USA

Sound Localization Cues and Perceptual Grouping in Electric Hearing
Bernhard Laback, Austrian Academy of Sciences

Brain Training; How to train cognition to yield transfer to real world contexts
Aaron Seitz, Department of Psychology, University of California, Riverside, USA

Coincidence detection in the MSO - computational approaches
Petr Marsalek, Charles University in Prague

Auditory Processing After mild Traumatic Brain Injury: New Findings and Next Steps
Frederick (Erick) Gallun, US Dept. of Veterans Affairs and Oregon Health & Science University

Hearing motion in motion
Carlile, S, Leung J, Locke, S, and Burgess, M., Auditory Neuroscience Laboratory, School of Medical Science and Bosch Institute, University of Sydney, Australia 2006

Auditory processing capabilities supporting communication in preverbal infants
István Winkler, Research Centre for Natural Sciences, Hungarian Academy of Sciences

Chirp stimuli for entrainment: chirp up, chirp down and task effects
Aleksandras Voicikas, Ieva Niciute, Osvaldas Ruksenas, Inga Griskova-Bulanova, Vilnius University, Department of Neurobiology and Biophysics.

Cross-modal interaction in spatial attention
Marián Špajdel, Zdenko Kohút, Barbora Cimrová, Stanislav Budáč, Igor Riečanský
Laboratory of Cognitive Neuroscience, Institute of Normal and Pathological Physiology,
Slovak Academy of Sciences; Department of Psychology, Faculty of Philosophy and Arts, University of Trnava, Slovakia; Centre for Cognitive Science, Department of Applied Informatics, Faculty of Mathematics, Physics and Informatics, Comenius University in Bratislava, Slovakia; SCAN Unit, Institute of Clinical, Biological and Differential Psychology, Faculty of Psychology, University of Vienna, Austria

Prediction processes in the visual modality – an EEG study
Gábor Csifcsák, Viktória Balla, Szilvia Szalóki, Tünde Kilencz, Vera Dalos

Early electophysiological correlates of susceptibility to the double-flash illusion
Simon Júlia, Csifcsák Gábor, Institute of Psychology University of Szeged

Suggestion of rehabilitative treatment for patients subjected to sight restorative surgeryOlena Markaryan, Independent researcher

Learning of auditory distance with intensity and reverberation cues
Hladek Lubos1, Seitz Aaron, Kopco Norbert, Institute of Computer Science, P. J. Safarik University in Kosice, Slovakia, Department of Psychology, University of California Riverside, USA

Streaming and sound localization with a preceding distractor
Gabriela Andrejková1, Virginia Best3, Barbara G. Shinn-Cunningham3, and Norbert Kopčo
Institute of Computer Science, P. J. Šafárik University, Košice, Slovakia; Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Harvard Medical School/ Massachusetts General Hospital, Charlestown MA; Center for Computational Neuroscience and Neural Technology, Boston University, Boston MA

Exposure to Consistent Room Reverberation Facilitates Consonant Perception
Norbert Kopčo, Eleni Vlahou, Kanako Ueno3 & Barbara Shinn-Cunningham
Institute of Computer Science, P. J. Šafárik University; Department of Psychology, University of California, Riverside; School of Science and Technology, Meiji University Center for Computational Neuroscience and Neural Technology, Boston University

Contextual plasticity in sound localization: characterization of spatial properties and neural locus, Beáta Tomoriová, Ľuboš Marcinek, Ľuboš Hládek, Norbert Kopčo
Pavol Jozef Šafárik University in Košice, Slovakia; Technical University of Košice, Slovakia.

Visual Adaptation And Spatial Auditory Processing
Peter Lokša, Norbert Kopčo, Institute of Computer Science, P. J. Šafárik University in Košice, Slovakia

Speech Localization in a Multitalker Reverberant Environment
Peter Toth, Norbert Kopco, Charles University in Prague

Wednesday, 22 April 2015

Visuospatial memory and where eyes look when the percept changes
Arash Yazdanbakhsh, Boston University

Modeling Auditory Scene Analysis by multidimensional statistical filtering
Volker Hohmann, Medical Physics, University of Oldenburg, Germany

Modeling auditory stream segregation by predictive processes
István Winkler, Research Centre for Natural Sciences, Hungarian Academy of Sciences

What is the cost of simultaneously listening to the "what" and the "when" in speech?
Pierre Divenyi, Center for Computer Research for Music and Acoustics, Stanford UniversityU.S.A.

Neuroimaging of task-dependent spatial processing in human auditory cortex.
G. Christopher Stecker, Vanderbilt University School of Medicine, Nashville TN USA

Temporal Effects in the Perception of Interaural Level Differences: Data and Model Predictions, Bernhard Laback, Austrian Academy of Sciences

Modeling Cocktail Party Processing in a Multitalker Mixture using Harmonicity and Binaural FeaturesVolker Hohmann, Medical Physics, University of Oldenburg, Germany

Audibility and spatial release from maskingVirginia Best, Frederick Gallun, Norbert Kopčo