Understanding how the circuits of the cortex are organized and how they function is a central goal of neuroscience. We have been studying the primary visual cortex, V1, in order to understand its role in vision and also because V1 is one of the best understood regions of the cerebral cortex. On one hand we often have detailed knowledge of the receptive field properties of neurons determined from neuronal firing in V1, to an array of visual stimuli, obtained from extracellular recording. On the other hand from anatomical studies we know about the intricate neuronal architecture and patterns of synaptic connections both within V1 and between V1 and extrastriate cortex. Our proposal aims to bridge the gap between the structure of neurons in circuits in monkey primary visual cortex and their receptive field properties. We use a method called loose-patch juxtacellular recording to monitor extracellular action potentials, that enables us to functionally characterize the RF of the neurons, and then we label same neuron with a tracer molecule and subsequently recover and reconstruct the three dimensional dendritic and axonal arbors of the labeled neurons. Layer 4a, the main target of the magnocellular afferents from the lateral geniculate nucleus, provides input to layer 4b. Both layers have a variety of neurons with distinct morphologies. There is also a range of receptive field properties in the two layers.
Our first aim i s to characterize the excitatory neurons in layers 4ca and 4b. We will test the hypothesis that there are distinct functional characteristics that associate with distinct morphological types. Among the pyramidal neurons of layer 6 there are distinct classes of neurons based on their pattern of intra-cortical axonal arborization. The axonal patterns are linked to the (vi- and P-cell divisions of layer 4. We will use functional tests that allow us to determine whether labeled neurons are dominated by magnocellular or parvocellular input in addition to tuning for orientation, spatial frequency, temporal frequency and size.
Our second aim i s to test to what degree morphological classes have specific functional labels, how pathway specific information such as motion and color are retained within different cortical circuits and the extent to which summation and surround suppression are represented within the population of identified neurons. Inhibitory neurons are thought to play specific roles in determining the emergent properties of V1 receptive fields such as orientation, direction and size selectivity. The extent or degree of tuning among the excitatory and inhibitory populations is unknown.
Our third aim i s to characterize inhibitory neurons in the input and infragranular layers of cortex. There are numerous disorders that are a result of structure-function abnormalities in cortical circuits including, amblyopia, epilepsy and schizophrenia. Understanding how the normal circuits operate provides opportunities for understanding neuronal abnormalities.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY017945-03
Application #
7659546
Study Section
Central Visual Processing Study Section (CVP)
Program Officer
Steinmetz, Michael A
Project Start
2007-08-01
Project End
2012-07-31
Budget Start
2009-08-01
Budget End
2010-07-31
Support Year
3
Fiscal Year
2009
Total Cost
$369,600
Indirect Cost
Name
New York University
Department
Neurology
Type
Schools of Arts and Sciences
DUNS #
041968306
City
New York
State
NY
Country
United States
Zip Code
10012
Kelly, Jenna G; Hawken, Michael J (2017) Quantification of neuronal density across cortical depth using automated 3D analysis of confocal image stacks. Brain Struct Funct 222:3333-3353
Garcia-Marin, Virginia; Sundiang, Marina; Hawken, Michael J (2015) Reduced density of geniculocortical terminals in foveal layer 4A in the macaque primary visual cortex: relationship to S-cone density. Brain Struct Funct 220:2783-96
Garcia-Marin, Virginia; Ahmed, Tunazzina H; Afzal, Yasmeen C et al. (2013) Distribution of vesicular glutamate transporter 2 (VGluT2) in the primary visual cortex of the macaque and human. J Comp Neurol 521:130-51
Henry, Christopher A; Hawken, Michael J (2013) Stability of simple/complex classification with contrast and extraclassical receptive field modulation in macaque V1. J Neurophysiol 109:1793-803
Shapley, Robert; Hawken, Michael J (2011) Color in the cortex: single- and double-opponent cells. Vision Res 51:701-17
Constantinople, Christine M; Disney, Anita A; Maffie, Jonathan et al. (2009) Quantitative analysis of neurons with Kv3 potassium channel subunits, Kv3.1b and Kv3.2, in macaque primary visual cortex. J Comp Neurol 516:291-311