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Contact

Amalia Papanikolaou

Address: Spemannstr. 38
72076 Tübingen
Phone: +49 7071 601 1662
Fax: +49 7071 601 652
E-Mail: amalia.papanikolaou

 

Picture of Papanikolaou, Amalia

Amalia Papanikolaou

Position: PhD Student  Unit: Logothetis

My PhD research has mainly focused on the ability of the visual cortex to reorganize following injury of the visual pathways. Damage to the primary visual cortex (V1) or its postchiasmatic inputs as a result of stroke or other brain diseases can lead to a loss of conscious vision in the contralateral visual hemifield. There are currently no widely accepted treatment options available for people with visual cortical damage. Understanding brain repair processes is an important step in the effort to design treatments aimed at enhancing the ability of the nervous system to recover after injury. In attempting to achieve this, it is important to study in detail how the adult human brain reorganizes after injury.

 

We propose to perform a systematic study of visual cortical plasticity in a cohort of adult human patients with carefully selected cortical pathology like stroke,

 

This will be done by: 1) Mapping changes in human visual cortex organization using functional magnetic imaging (fMRI) and comparing both with the intact hemispheres in the same patients and with control subjects without lesion and 2) Determine whether rehabilitative training increases the degree of cortical reorganization.

 

Personal website: apapanikolaou.com

Population receptive field mapping in human subjects with visual cortical lesions.

 

Introduction

Damage to the primary visual cortex (V1) as a result of stroke typically leads to the inability to perceive visual stimuli in the affected region of the contralateral visual hemifield (scotoma). However, in spite of this, several higher visual areas have been shown to be modulated by visual stimuli presented inside the scotoma. A much debated issue is whether adult visual cortex is able to reorganize after injury, and if so, what is the extent and the mechanism of the observed reorganization.

 

Goals

We propose to perform a systematic study of visual cortical plasticity in a cohort of adult human patients with carefully selected cortical pathology like stroke. This will be done by: 1) Mapping changes in human visual cortex organization and comparing both with the intact hemispheres in the same patients and with control subjects without lesion. 2) Determine whether rehabilitative training increases the degree of cortical reorganization.

 

Methods

We have used functional magnetic resonance imaging (fMRI) methods to study visual cortex reorganization after injury in adult human subjects. To this end we applied a method introduced by Dumoulin and Wandell [1],  which uses functional magnetic resonance imaging (fMRI) to measure the aggregate receptive field properties of neuronal populations voxel by voxel in the visual cortex. FMRI measurements were obtained during the presentation of a moving bar stimulus which traversed the visual field while the subjects were fixating and these measurements were used to derive an estimate of the voxel based population receptive field center and radius. We studied several subjects with quadrandanopsia and hemianopsia resulting from  cortical lesions and compared them to the range of measurements obtained from a group of  normal controls.

 

Initial results and conclusions

There appear to be no significant retinotopic map alteration in the early visual areas of patients suffering from V1 lesions. However, there is a change in the distribution of receptive field centers in higher visual areas like hV5/MT+. This may in part reflect the fact that some of the input to hV5/MT+ receptive fields has been lost with the V1+ lesion, but is also suggesting that they receive contributions from a V1 bypassing pathway which could be enhanced after training. Gathering information about the role that specific networks of brain areas play in cortical reorganization and recovery following injury will allow us to generate concrete hypotheses about how modulating the activity of these networks may enhance recovery.

 

References

1.      Dumoulin, S.O., Wandell, B.A. (2008). Population receptive field estimates in human visual cortex, Neuroimage 39.

 

Supervisor

Prof. Stelios Smirnakis

Collaborators

Dr. Georgios Keliris

Yibin Shao


EDUCATION:

2009-

Phd student at the Max-Planck Institute for Biological Cybernetics.
Project: Functional neuroimaging of cortical plasticity in the human visual system

2008 – 2009

Msc in Artificial Intelligence at the University of Edinburgh
Specializations: Learning from Data, Neuroinformatics
Master thesis: Reinforcement learning in spiking neurons
Supervisor: Dr Peggy Series (http://homepages.inf.ed.ac.uk/pseries/people.htm)


2004 – 2008

BSc of honors in Biomedical Informatics at the University of Central Greece.

2001 – 2004

3rd General High School of Euosmos, Thessaloniki

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Articles (4):

Lee S , Papanikolaou A Person, Keliris GA Person and Smirnakis SM (June-2014) Topographical estimation of visual population receptive fields by fMRI Journal of Visualized Experiments . in press
Papanikolaou A Person, Keliris GA Person, Papageorgiou TD , Shao Y Person, Krapp E , Papageorgiou E , Stingl K , Bruckmann A , Schiefer U , Logothetis NK Person and Smirnakis SM (April-2014) Population receptive field analysis of the primary visual cortex complements perimetry in patients with homonymous visual field defects Proceedings of the National Academy of Sciences of the United States of America 111(16) E1656–E1665.
Lee S Person, Papanikolaou A Person, Logothetis NK Person, Smirnakis SM and Keliris GA Person (November-2013) A new method for estimating population receptive field topography in visual cortex NeuroImage 81 144–157.
Shao Y Person, Keliris GA Person, Papanikolaou A Person, Fischer MD , Zobor D , Jägle H , Logothetis NK Person and Smirnakis SM (November-2013) Visual cortex organisation in a macaque monkey with macular degeneration European Journal of Neuroscience 38(10) 3456–3464.

Contributions to books (1):

Papageorgiou D , Papanikolaou A Person and Smirnakis SM : A Systematic Approach to Visual System Rehabilitation: Population Receptive Field Analysis and Real-time Functional Magnetic Resonance Imaging Neurofeedback Methods, 359-390. In: Advanced Topics in Brain Neuroimaging: Methods and Applications in Health and Disease, (Ed) T.D. Papageorgiou, InTech, Rijeka, Croatia, (May-2014).

Posters (11):

Keliris GA Person, Shao Y Person, Papanikolaou A Person, Logothetis NK Person and Smirnakis M (November-13-2013): Estimation of average single-unit receptive field size by fMRI, 43rd Annual Meeting of the Society for Neuroscience (Neuroscience 2013), San Diego, CA, USA.
Shao Y Person, Keliris GA Person, Schmid MC , Papanikolaou A Person, Logothetis NK Person and Smirnakis SM (November-9-2013): Population receptive field measurements in the visual cortex of macaque monkeys with and without retinal lesions, 43rd Annual Meeting of the Society for Neuroscience (Neuroscience 2013), San Diego, CA, USA.
Smirnakis SM , Keliris GA Person, Shao Y Person, Papanikolaou A Person and Logothetis NK Person (August-2012): Population receptive field measurements in macaque visual cortex, 12th Annual Meeting of the Vision Sciences Society (VSS 2012), Naples, FL, USA, Journal of Vision, 12(9) 1397.
Papanikolaou A Person, Keliris GA Person, Papageorgiou DT , Shao Y Person, Krapp E , Schiefer U , Logothetis N Person and Smirnakis SM (June-2012): Population Receptive Field Mapping in Human Subjects after Lesions of the Visual Pathway, AREADNE 2012: Research in Encoding and Decoding of Neural Ensembles, Santorini, Greece.
Shao Y Person, Keliris GA Person, Papanikolaou A Person, Fischer DM , Nagy D , Jaegle H , Augath M Person, Logothetis NK Person and Smirnakis SM (June-2012): Population receptive field measurements in the visual cortex of macaque monkeys with and without retinal lesions, AREADNE 2012: Research in Encoding and Decoding of Neural Ensembles, Santorini, Greece.
Papanikolaou A Person, Keliris GA Person, Shao Y Person, Krapp E , Papageorgiou E , Schiefer U , Logothetis NK Person and Smirnakis SM (November-2011): Population receptive field mapping in human subjects with lesions of the visual cortex, 41st Annual Meeting of the Society for Neuroscience (Neuroscience 2011), Washington, DC, USA.
Shao Y Person, Keliris GA Person, Papanikolaou A Person, Augath M Person, Logothetis NK Person and Smirnakis SM (November-2011): Population receptive field measurements in visual cortex of macaque monkeys, 41st Annual Meeting of the Society for Neuroscience (Neuroscience 2011), Washington, DC, USA.
Papanikolaou A Person, Keliris G Person, Shao Y Person, Krapp E , Schiefer U , Logothetis NK Person and Smirnakis S (October-2011): Population receptive field mapping in human subjects with visual cortical lesions, 12th Conference of Junior Neuroscientists of Tübingen (NeNA 2011), Heiligkreuztal, Germany.
Keliris GA Person, Shao Y Person, Papanikolaou A Person, Peng X , Logothetis NK Person and Smirnakis SM Person (November-2010): Assessing the spatio-temporal dynamics of visual receptive fields by fMRI, 40th Annual Meeting of the Society for Neuroscience (Neuroscience 2010), San Diego, CA, USA.
Shao Y Person, Keliris GA Person, Papanikolaou A Person, Fischer DM , Nagy D , Jägle H , Seeliger MW , Augath M Person, Logothetis NK Person and Smirnakis SM Person (November-2010): Population receptive field mapping in a macaque monkey with macular degeneration, 40th Annual Meeting of the Society for Neuroscience (Neuroscience 2010), San Diego, CA, USA.
Papanikolaou A Person, Keliris GA Person, Peng X , Shao Y Person, Krapp E , Papageorgiou E , Schiefer U , Logothetis NK Person and Smirnakis SM Person (November-2010): Population receptive field mapping in human subjects with visual cortical lesions, 40th Annual Meeting of the Society for Neuroscience (Neuroscience 2010), San Diego, CA, USA.

Talks (2):

Papanikolaou A Person, Keliris GA Person, Papageorgiou GT , Shao Y Person, Krapp E , Papageorgiou E , Schiefer U , Logothetis NK Person and Smirnakis SM (November-12-2013) Abstract Talk: Human area V5/MT+ organization changes following lesions of the primary visual cortex, 43rd Annual Meeting of the Society for Neuroscience (Neuroscience 2013), San Diego, CA, USA(602.07).
Lee S Person, Keliris GA Person, Papanikolaou A Person, Smirnakis SM and Logothetis NK Person (October-2012) Abstract Talk: Visualization of the population receptive field structures in human visual cortex, 42nd Annual Meeting of the Society for Neuroscience (Neuroscience 2012), New Orleans, LA, USA(723.08).

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Last updated: Friday, 17.01.2014