Assistant Professor

Dr. Philip O'Herron


phone-office icon - (706) 721-9103
fax icon - (706) 721-7299
envelope icon - 
building icon - CA-2094
microscope icon - CA-2064

Dr. O'Herron's Faculty Profile

Lab Personnel


Kun Xie
Research Associate



Open Positions

Our lab is looking to hire. Interested post-docs and graduate students can contact Post-doctoral applicants can apply here. (Job ID: 258134)

Education and Training

Johns Hopkins University, Neuroscience, PhD, 2009
George Mason University, Chemistry, BA, 2002
Christendom College, Philosophy, BA, 2000

Academic Appointments

2023 | Assistant Professor, Augusta University
2018 | Research Assistant Professor, Augusta University
2017-2018 | Research Assistant Professor, Medical University of South Carolina




Research Interests

My lab’s research focuses on questions of neurovascular coupling and visual processing. Our neurovascular coupling work seeks to determine how neural activity in the cortex drives hemodynamic responses (functional hyperemia) and, in turn, how important this increased blood flow is to healthy neuronal function.

Recent Research

We recently developed a mouse model to block functional hyperemia using optogenetics. This mouse expresses the red-shifted cation channel opsin ReaChR in vascular mural cells, allowing the vessels to be constricted with light. Using two-photon activation we are able to constrict individual vessels, and using widefield single-photon activation all the vessels in the cranial window can be constricted. We also established that sensory-stimulus-evoked vasodilation can be offset by optogenetic activation of the vessels.

Optogenetic vasoconstriction

O'herron science image

Check out the gif here!

All of the arteries constrict to a 100 ms flash of the LED light (seen as a brief dimming of the image) over the cranial window. Vessels in mouse visual cortex labeled with FITC dextranand simultaneously imaged with two photon microscopy during activation.

O'herron science image

     Check out the gif here!

Only a single vessel segment (red arrow) constricts to targeted two-photon optogenetic activation using a Spatial Light Modulator. 

visual stimuli

Visual stimuli activate neurons leading to dilation of vessels in the visual cortex (blue trace). When the visual stimuli are paired with pulses of light, the optogenetic evoked constriction blocks the usual functional hyperemia response (red trace).


  • 3D optogenetic control of arteriole diameter in vivo
    O'Herron, P. J., Hartmann, D. A., Xie, K., Kara, P. & Shih, A. Y., Sep 2022, eLife. 11, e72802.



Ongoing Research

Two-photon imaging of GCaMP in neurons, Texas Red Dextran in vessels, and Methoxy-X04 labelling amyloid-β plaques in mouse visual cortex.
Two-photon imaging of GCaMP in neurons, Texas Red Dextran in vessels,
and Methoxy-X04 labelling amyloid-β plaques in mouse visual cortex.

We are currently investigating the role functional hyperemia plays in healthy neural function. It has been known for more than a century than brain activity causes increases in local blood flow, and the widely held assumption is that this is necessary for providing increases in oxygen and glucose to support the increase in neural activity. However, this hypothesis has never been directly tested and there are reasons to believe that this may not be the full explanation.

Therefore, we are using the recently developed model (see above) to block functional hyperemia while monitoring neuronal and astrocytic responses to sensory stimuli.

  • We use two-photon imaging to determine if response strength and selectivity are altered by the loss of functional hyperemia. Electrophysiological recordings are used to determine if action potential timing and network synchrony are also affected.
  • Another component of our project - which is a collaboration with Dr. Felipe
    Barros from the CECS in Valdivia Chile - is to determine if metabolic processing
    in neurons and astrocytes adapts to the reduction in functional hyperemia to
    enable sustained neural activity in the face of reduced blood flow. We use
    fluorescent imaging and other measures of metabolic substrates to address this
  • We are also examining if functional hyperemia is more critical in aging and
    disease. We use a mouse model of Alzheimer’s disease to study the interaction
    of neural and vascular dysfunction with disease pathology to understand the
    role blood flow plays in the development of the disease.

Another ongoing project in the lab involves a collaboration with Dr. Jessica Filosa here at Augusta University. We use this same optogenetic model to constrict vessels during spontaneous states (absence of visual stimulation) to study vasculo-glia-neuronal coupling - signalling from vessels back to astrocytes and neurons. This coupling was established previously in Dr. Filosa’s lab in brain slices (Kim et al. J Neuroscience 2016). We are now seeking to determine if vasoconstriction in vivo can directly alter astrocytic and neural activity patterns.


Past Research

My introduction to neurovascular coupling came during my post-doctoral fellowship. There I studied the correspondence between regions of active neural tissue and regions of increased blood flow. We found that both neuronal spiking and synaptic activity were more anatomically localized than the regional increase in blood flow. This work will help to interpret hemodynamic imaging studies which use vascular signals as surrogates for neural activity.

  • Neural correlates of single-vessel haemodynamic responses in vivo. O'Herron P, Chhatbar PY, Levy M, Shen Z, Schramm AE, Lu Z, Kara P (2016) Nature 534:378-382
    • Spotlighted in Neuron: Denfield George H, Fahey Paul G, Reimer J, Tolias Andreas S (2016) Investigating the Limits of Neurovascular Coupling. Neuron 91:954-956
  • Targeted Labeling of Neurons in a Specific Functional Micro-domain of the Neocortex by Combining Intrinsic Signal and Two-photon Imaging. O’Herron P., Shen Z., Lu, Z., Schramm A., Levy M., & Kara P. (2012). Journal of Visualized Experiments (70): e50025
  • An artery-specific fluorescent dye for studying neurovascular coupling in vivo. Shen, Z.M., Lu, Z.Y., Chhatbar, P.Y., O’Herron, P., Kara, P. (2012). Nature Methods 9, 273-276.

Visual Processing Research

My PhD work was on visual processing in primate visual cortex. I studied figure-ground signals using electrophysiological recordings.

  • Short-term memory for figure-ground organization in the visual cortex. O'Herron, P., and von der Heydt, R. (2009). Neuron 61, 801-809.
  • Representation of object continuity in the visual cortex. O'Herron, P., and von der Heydt, R. (2011). Journal of Vision 11(2): 12.
  • Remapping of border ownership in the visual cortex. O'Herron, P., and von der Heydt, R. (2013). Journal of
    Neuroscience 33(5): 1964-1974

More recently, I have also studied how neuronal response properties vary with depth in the upper layers of mouse primary visual cortex

  • An Unexpected Dependence of Cortical Depth in Shaping Neural Responsiveness and Selectivity in Mouse Visual Cortex. O’Herron P., Levy M., Woodward J. J. & Kara P. (2020) eNeuro, ENEURO.0497-0419.2020



Related Links

Link to Dr. O'Herron on PubMed