Our research is focused on electrical synapses. Formed by pores that connect the cytoplasm of coupled cells, these synapses allow ions and information to flow directly between neurons.
We are interested in determining the relationships between electrical synaptic strength, synchrony in circuits of coupled neurons, and the more abstract process of attention. These ideas coalesce within the thalamus, in a specific nucleus where electrical synapses are particularly dense; it is this nucleus that is thought to gate cortical attention to the sensory surround. I hypothesize that the strength of electrical synapses within this nucleus is a crucial component for the control of human attention.
To study electrical synapses, our main tool is dual whole-cell patch clamping. In the image, two electrode tips are shown in preparation for patching the two cell bodies, which are connected by an electrical synapse (also known as a gap junction) where the ‘arms’ of the two neurons cross.
Electrical synapses can share and cause spiking activity between coupled neurons. In the example to the left, the spikes in one cell (grey) of a coupled pair caused spikes in its coupled neighbor (black). With these methods, we measure strength of electrical synapses before and after the cells are active together.
We also stimulate activity in electrically coupled neurons with optogenetics, the newest coolest tool in neuroscience. Light-sensitive channelrhodopsin channels are delivered to neuronal membranes through either viral injection or breeding transgenetic animals. Shown below is a slice of mouse tissue under brightfield illumination (left) and fluorescent reporting of ChR2 expression (right). In vitro, we provide 490 nm light to neurons, and they respond by spiking. With this tool, we explore the impact of electrical synapses and plasticity on the dynamics of electrically coupled networks in this brain area.
Sevetson J, Fittro S, Heckman E and Haas JS (2017). A calcium-dependent pathway underlies activity-dependent plasticity of electrical synapses J. Physiology (in press).
How do electrical synapses regulate their strength? Debanne D and Russier M., J. Physiology (2017)
Haas JS, Greenwald C, and Pereda A (2016). Activity-dependent plasticity of electrical synapses: increasing evidence for its presence and functional roles in the mammalian brain. BMC Cell Biology. DOI: 10.1186/s12860-016-0090-z
Haas JS (2015). A new measure for the strength of electrical synapses. Front. Cell. Neurosci. 9:378. doi: 10.3389/fncel.2015.00378.
Sevetson J and Haas JS (2014). Asymmetry and modulation of spike timing in electrically coupled neurons. J. Neurophysiol. doi: 10.1152/jn.00843.2014.
Vogels TP, Froemke R, Doyon N, Gilson M, Haas JS, Liu R, Maffei A, Miller P, Wierenga P, Woodin M, Zenke F and Sprekeler H (2013). Inhibitory synaptic plasticity: Spike-timing dependence and putative network function. Frontiers in Neural Circuits 7:119.
Haas JS and Landisman CE (2012) Bursts modify electrical synaptic strength. Brain Research, special issue on Electrical Synapses, in press.
Haas JS, Zavala B and Landisman CE (2011) Activity-dependent long-term depression of electrical synapses. Science 334(6054):389-393.
Haas JS and Landisman CE (2011) State-dependent modulation of gap junction signaling by the persistent sodium current. Frontiers in Cellular Neuroscience 5:31.
Haas JS, Kreuz T, Torcini A, Politi A, Abarbanel HDI (2010) Rate maintenance in spiking neurons driving with strong inputs of varying speeds. European Journal of Neuroscience 32(11):1930-9.
Kreuz T, Chicharro D, Andrzejak RG, Haas JS, Abarbanel HDI, Politi A (2009). Measuring multiple spike train synchrony. J. Neurosci. Methods 182(2):287-299.
Kreuz T, Haas JS, Morelli A, Abarbanel HDI, Politi A (2007). Measuring spike train synchrony. J. Neurosci. Methods 165(1):151-61.
Haas JS, Dorval AD, White JA (2007). Contributions of Ih to feature selectivity in layer II stellate cells of the entorhinal cortex. J. Computational Neuroscience 22(2):161-71.
Haas JS, Nowotny TN, Abarbanel HDI (2006). Spike-timing-dependent plasticity at inhibitory synapses in the entorhinal cortex. J. Neurophysiol 96: 3305-3313.
Netoff TI, Banks MI, Dorval AD, Acker CD, Haas JS, Kopell N, White JA (2004). Synchronization in hybrid neuronal networks of the hippocampal formation. J. Neurophysiol. 93(3):1197-1208.
Haas JS and White JA (2002). Frequency selectivity of layer II stellate cells in the medial entorhinal cortex.
J. Neurophysiol. 88(5): 2422-2429.
Abarbanel HDI, Haas JS, Talathi SS (2007) Synapses and neurons: Basic properties and their use in the recognition of environmental signals. In Lecture Notes in Supercomputational Neuroscience, Springer-Verlag.
White JA and Haas JS (2001) Noise from voltage-gated ion channels: effects on dynamics and reliability in intrinsically oscillatory neurons. In Handbook of Biological Physics, Vol. 4, F Moss and S Gielen (eds.), Elsevier Press, Amsterdam.
Current Lab Personnel
The Haas Lab - 2015
Undergraduate Researchers: Sarah Fittro, Emily Heckman, Bijal Desai;
Julie Haas, Ph.D. Principal Investigator
Julie Haas, Ph.D.
- currently a graduate student at Brown University