Farzan Nadim, Ph.D. Professor

The research in our laboratory is supported by

the National Institute of Mental Health

 and the National Science Foundation

RESEARCH

Oscillations are ubiquitous in the central nervous system. Our research focuses on the cellular and synaptic mechanisms that underlie the generation and modification of oscillations in neural networks.

Network oscillations arise as coordinated activity among populations of neurons and their abnormalities are implicated in various cognitive impairments. The role of neuronal circuits in the generation of oscillations is perhaps best studied in central pattern generators (CPGs), networks responsible for rhythmic motor activity.  Given the significant role of oscillations in a multitude of behaviors and pathological conditions, it is necessary to understand how oscillations are generated in the nervous system, what controls their frequency and how oscillatory components are coordinated to produce synchronous activity. 

The pyloric central pattern generator (CPG) in the crustacean stomatogastric nervous system (STNS) is an excellent system to address these issues. The STNS is an extension of the crustacean central nervous system and consists of four connected ganglia including the stomatogastric ganglion (STG; ~30 neurons). The pyloric network produces rhythms in a range of frequencies (0.5-2 Hz), controlling rhythmic contractions of striated muscles in the pylorus, a section of the foregut responsible for the filtering of masticated food. The anatomical connections in the pyloric network are well known, but the network is subject to such a diverse modulatory environment that individual synapses can be rendered functional or inactive in the presence of known neuromodulators. There are 11 to14 pyloric neurons located in the STG.

The STNS is affected by multiple neuromodulators and neurohormones that produce a large degree of plasticity in the rhythmic patterns produced by these networks. The amplitude and dynamics of synaptic currents is greatly affected by neuromodulation. Moreover, the effect of these modulators is dependent on the previous history of activity, or the state of the system. Such state-dependence produces an extra degree of plasticity that is another research focus in our laboratory.

Our laboratory uses experiments to measure the dynamic activity of the neurons and synapses in control conditions and in the presence of neuromodulators or while activating modulatory projection pathways. The experiments performed are primarily electrophysiology, including current- and voltage-clamp measurements and dynamic clamp manipulations of network activity. We also perform cell ablations and have pioneered the use of realistic voltage waveforms in the measurement of ion channel and synaptic currents.

In addition to our experimental work, we use mathematical and computer models to explore the generation, dynamics and stability of oscillations in the nervous system.

A list of publications from our laboratory can be found here: PUBLICATIONS

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.

Our laboratory develops and maintains several software Virtual Instruments in LabWindows/CVI (National Instruments, TX). These software instruments include a Windows version of dynamic clamp, an arbitrary waveform generator and even a software chart-recorder, oscilloscope and digitizer. These software applications are available at SOFTWARE

Federated Dept. of Biological Sciences and

Dept. of Mathematical Sciences,

Copyright: STG Lab 2012
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Last Modified:May 31, 2012