Profile: Farzan Nadim

Professor

Faculty
Department of Biological Sciences

 

My lab studies the cellular and synaptic mechanisms that give rise to oscillatory activity in networks of neurons. Our research focuses on the interaction between short-term mechanisms of synaptic plasticity and the nonlinear properties of membrane ion channels in neurons of pattern-generating networks.

Synaptic interactions are key components in the generation of temporal dynamics and are present in all synapses, but only recently have been studied in the context of generation and patterning of oscillations. In an oscillatory network, such short-term dynamics provide a mechanism that allows synapses to adjust their strength as a function of frequency; the synapses, in turn, shape the output of the network. This recursive relationship underlies the formidable complexity of these networks.

Small neuronal networks are amenable to studying such complexities. We investigate the cellular and synaptic mechanisms underlying oscillations in the crustacean pyloric network, a model system for studying rhythmic motor pattern generation. Using a combination of electrophysiology and computational modeling techniques, we examine how distinct mechanisms of synaptic release interact to produce synaptic output. Our aim is to understand how the effects of frequency on synaptic strength give rise to new emergent network properties. There is overwhelming evidence that network activity is shaped not only by synaptic dynamics, but also by extrinsic neuromodulation, enabling networks to produce multiple functional outputs. Furthermore, synaptic dynamics are also altered by neuromodulators, thus leading to new patterns of network activity. We explore how neuromodulation affects short-term synaptic dynamics and how these effects reshape the network output. Characterizing the effects of neuromodulatory substances on synaptic dynamics may elucidate the actions of these substances in generating network oscillations such as during transitions between sleep and arousal states.

Model networks in invertebrates have been used for decades to extract principles that were later shown to apply in mammalian networks. General principles obtained from studying the functions of synaptic dynamics in the generation and coordination of pyloric oscillations may potentially apply to other oscillatory networks that show activity-dependent changes in synaptic efficacy. Understanding these cellular and synaptic mechanisms provides important insight into the generation of self-organized oscillations of the brain, such as the multiple rhythms observed during sleep cycles or in structures involved in learning and memory formation and often affected in pathological conditions including epilepsy, depression and schizophrenia.
 

  • Education

    M.S., Boston University, 1989.
    Ph.D. in Mathematics, Boston University, 1994.

  • Publications

    Oh M, Zhao S, Matveev V, and Nadim F.  Neuromodulatory changes in short-term synaptic dynamics may be mediated by two distinct mechanisms of presynaptic calcium entry.  J Comput Neurosci 33: 573-585, 2012.

    Ballo AW, Nadim F, and Bucher D.  Dopamine modulation of Ih improves temporal fidelity of spike propagation in an unmyelinated axon.  J Neurosci 32: 5106-5119, 2012.

    Nadim F, Zhao S, Zhou L, and Bose A.  Inhibitory feedback promotes stability in an oscillatory network.  J Neural Eng 8:065001, 2011.

    Zhao S, Sheibanie AF, Oh M, Rabbah P, and Nadim F.  Peptide neuromodulation of synaptic dynamics in an oscillatory network.  J Neurosci. 31:13991-4004, 2011.

    Johnson BR, Brown JM, Kvarta MD, Lu JY, Schneider LR, Nadim F, and Harris-Warrick RM.  Differential modulation of synaptic strength and timing regulate synaptic efficacy in a motor network.  J Neurophysiol. 105:293-304, 2011.

    Tseng HA, and Nadim F.  The membrane potential waveform of bursting pacemaker neurons is a predictor of their preferred frequency and the network cycle frequency.  J Neurosci. 30:10809-19, 2010.

    Ballo AW, Keene JC, Troy PJ, Goeritz ML, Nadim F, and Bucher D.  Dopamine modulates Ih in a motor axon.  J Neurosci. 30:8425-34, 2010.

    Zhao S, Golowasch J, and Nadim F.  Pacemaker neuron and network oscillations depend on a neuromodulator-regulated linear current.  Front Behav Neurosci. 4:21, 2010.

     

    Daur N, Nadim F, and Stein W.  Regulation of motor patterns by the central spike-initiation zone of a sensory neuron.  Eur J Neurosci. 30:808-22, 2009.

    Golowasch J, Thomas G, Taylor AL, Patel A, Pineda A, Khalil C, and Nadim F.  Membrane capacitance measurements revisited: dependence of capacitance value on measurement method in nonisopotential neurons.  J Neurophysiol. 102:2161-75, 2009.

    Tohidi V, and Nadim F.  Membrane resonance in bursting pacemaker neurons of an oscillatory network is correlated with network frequency.  J Neurosci. 29:6427-35, 2009.

    Zhang Y, Bose A, Nadim F.  The influence of the A-current on the dynamics of an oscillator-follower inhibitory network.  SIAM J Appl Dyn Syst. 8:1564-1590, 2009.

    Nadim F, Brezina V, Destexhe A, Linster C.  State dependence of network output: modeling and experiments.  J Neurosci. 28:11806-13. 2008.

    Clewley R, Soto-Treviño C, and Nadim F.  Dominant ionic mechanisms explored in spiking and bursting using local low-dimensional reductions of a biophysically realistic model neuron.  J Comput Neurosci. 26:75-90, 2009.

    Zhang Y, Bose A, and Nadim F.  Predicting the activity phase of a follower neuron with A-current in an inhibitory network.  Biol Cybern. 99:171-84, 2008.

    Zhou L, Zhao S, and Nadim F.  Neuromodulation of short-term synaptic dynamics examined in a mechanistic model based on kinetics of calcium currents.  Neurocomputing. 2007 Jun;70(10-12):2050-2054.

    Blitz, D, White RS, Saideman SR, Cook A, Christie A, Nadim F and Nusbaum MP: A newly identified extrinsic input triggers a distinct gastric mill rhythm via activation of modulatory projection neurons, J Exp Biol, 211: 1000-1011, 2008.

    Kintos N, Nusbaum MP and Nadim F: Comparing projection neuron and neuromodulator-elicited oscillations in a motor network, J Comput Neurosci, 24: 374-397, 2008.

    Gansert J, Golowasch J and Nadim F: Sustained rhythmic activity in gap-junctionally coupled neurons depends on the diameter of coupled dendrites, 98:3450-3460, 2007.

    Matveev V, Bose A and Nadim F: Describing the bursting dynamics of a two-cell inhibitory network using a one-dimensional map, J Computational Neuroscience, 23: 169-187, 2007.

    Rabbah P and Nadim F: Distinct synaptic dynamics of heterogeneous pacemaker neurons in an oscillatory network, J Neurophysiology, 97: 2239-2253, 2007.

    Zhou L, Zhao S and Nadim F: Neuromodulation of short-term synaptic dynamics examined in a mechanistic model based on kinetics of calcium currents, Neurocomputing, 70: 2050-2054, 2007.

    Drover J, Tohidi V, Bose A and Nadim F: Combining synaptic and cellular resonance in a feed-forward neuronal network, Neurocomputing, 70: 2041-2045, 2007.

    Nadim F and Golowasch J: Signal transmission between gap-junctionally coupled passive cables occurs at an optimal cable diameter, J Neurophysiology, 95: 3831-3843, 2006.

    Rabbah P and Nadim F: Synaptic dynamics do not determine proper phase of activity in a central pattern generator, J. Neuroscience, 25: 11269-11278, 2005.

    Johnson BR, Schneider LR, Nadim F, Harris-Warrick RM: Dopamine modulation of phasing of activity in a rhythmic motor network: contribution of synaptic and intrinsic modulatory actions. J. Neurophysiology, 94: 3101-3111, 2005.

    Mamiya A and Nadim F: Target-specific regulation of short-term synaptic depression is important for the function of the synapses in an oscillatory neural network, J. Neurophysiology, 94: 2590 - 2602, 2005.

    Beenhakker MP, DeLong ND, Saideman SR, Nadim F and Nusbaum MP, Proprioceptor Regulation of Motor Circuit Activity by Presynaptic Inhibition of a Modulatory Projection Neuron. J. Neuroscience, 25: 8794-8806, 2005.

    Soto-Treviño C, Rabbah P, Marder E and Nadim F: A computational model of electrically coupled, intrinsically distinct pacemaker neurons, J. Neurophysiology, 94: 590-604 , 2005.

    Rabbah P, Golowasch J and Nadim F: Effect of electrical coupling on ionic current and synaptic potential measurements, J. Neurophysiology, 94: 519-530, 2005.