Dr. Kristina Nielsen is an associate professor of neuroscience at the John Hopkins University School of Medicine and a researcher at the Zanvyl Krieger Mind/Brain Institute. Her research focuses on the function and development of higher level visual cortex.
Dr. Nielsen earned her PhD from the Max Planck Institute for Biological Cybernetics in Tübingen, Germany. There, she conducted research in the lab of Nikos Logothetis, investigating the encoding of objects and object parts in the inferotemporal cortex. In 2006, she joined the labs of Ed Callaway and Rich Krauzlis at the Salk Institute in La Jolla, California, as a post-doctoral fellow. Her post-doctoral work focused on two techniques that allow the study of the function of neural circuits in vivo with a high degree of specificity: viral vector-based approaches and two-photon microscopy.
Dr. Nielsen joined the Johns Hopkins faculty in 2012. Ongoing research in her lab focuses on the structure and function of circuits in higher visual cortex, as well as their development and plasticity.
Function and development of higher level visual cortex
We are interested in understanding how visual information is transformed between processing stages in visual cortex. Early stages of our visual system represent visual stimuli in a pixel-like fashion, akin to the picture format used by a digital camera. This is a complete, general representation of visual information. However, further processing is required to efficiently store complex visual information, and to carry out the complicated functions accomplished by our visual system. Consider object recognition, for example. Changes in position, color or lighting conditions lead to large changes in the physical appearance of an object, and thereby its pixel-level description. Nonetheless, object recognition is largely invariant to these changes. This is achieved by transforming the initial pixel-level representation into a more invariant and efficient object-level representation. These transformations are implemented in a hierarchy of visual areas.
In general, each processing stage in the visual system transforms its input into a more abstract representation to aid visual perception and cognition. My lab is interested in the structure and function of these circuits, both between primary and higher order visual areas, as well as within individual visual areas. We study how visual information is represented at different processing stages to investigate the nature of the transformations occurring in visual cortex. In addition, we are interested in the development of these circuits and their plasticity. Techniques employed in the lab include two-photon calcium imaging, extracellular recordings, psychophysics, and immunohistochemistry.
Nauhaus, I*., Nielsen, K.J.*, Callaway, E.M., Efficient receptive field tiling in primate V1. Neuron 91(4): 893-904, 2016. *, equal contributions.
Nauhaus , I., Nielsen, K.J., Building maps from maps in primary visual cortex. Current Opinion in Neurobiology 24: 1-6, 2014.
Nauhaus, I.*, Nielsen, K.J.*, Disney, A.A., Callaway, E.M., Orthogonal micro-organization of orientation and spatial frequency in primate primary visual cortex. Nature Neuroscience 15(12): 1683-1690, 2012. *, equal contributions.
Nielsen, K.J., Callaway, E.M., Krauzlis, R.J., Viral vector-based reversible neuronal inactivation and behavioral manipulation in the macaque monkey, Frontiers in Systems Neuroscience 6:48. DOI: 10.3389/fnsys.2012.00048, 2012.
Nauhaus, I., Nielsen, K.J., Callaway, E.M., Nonlinearity of two-photon Ca2+ imaging yields distorted measurements of tuning for V1 neuronal populations. Journal of Neurophysiology 107(3): 923-936, 2012.
Marshel, J.H., Mori, T., Nielsen, K.J., Callaway, E.M., Targeting single neuronal networks for gene expression and cell labeling in vivo. Neuron 67(4): 562-574, 2010.
Nielsen, K.J., Logothetis, N.K., Rainer, G., Object features used by humans and monkeys to identify rotated shapes. Journal of Vision 8(2): Article 9, 1-15, 2008.
Nielsen K.J. and Callaway, E.M., More than a feeling: sensation from cortical stimulation. Nature Neuroscience 11(1): 10-11, 2008.
Nielsen, K.J. and Rainer, G., Object recognition: Similar visual strategies of birds and mammals. Current Biology 17(5): R174-R176, 2007.
Nielsen, K.J., Logothetis, N.K., Rainer, G., Dissociation between LFP and spiking activity in macaque inferior temporal cortex reveals diagnosticity-based encoding of complex objects. Journal of Neuroscience 26(38), 9639-9645, 2006.
Nielsen, K.J., Logothetis, N.K., Rainer, G., Discrimination strategies of human and rhesus monkeys for complex visual displays. Current Biology 16, 814-820, 2006.
Kayser, C., Nielsen, K.J., Logothetis, N.K., Fixations in natural scenes: an interaction of image saliency and content. Vision Research 46(16), 2535-2545, 2006.
Ghazanfar, A.A., Nielsen, K., Logothetis, N.K., Eye movements of monkey observers viewing vocalizing conspecifics. Cognition 101(3): 515-529, 2006.
Nielsen, K.J., Two-photon calcium imaging in the macaque monkey. In: Advances in multineuronal monitoring of brain activity, P. Kara, ed., Washington, DC: Society for Neuroscience (2014).
Nielsen, K.J. and Rainer, G., Using spikes and local field potentials to unravel computational mechanisms in monkey cortex. In: Information processing by neuronal populations, C. Hölscher and M. Munk, ed., Oxford University Press, Oxford, UK, pp. 350-362, 2007.