[WhatsUpUoH] Talk at CNCS Feb 7th

Talk by

Dr. Sridhar Devarajan

Postdoctoral fellow
Department of Neurobiology
Stanford University

http://www.stanford.edu/group/brainsinsilicon/Sridhar_bio.html

Venue: Lecture hall, CNCS, Science Complex

Time: 4:30-5:30pm

Date: 7 Feb 2014

An avian midbrain model for the role of gamma oscillations in sensory coding and selective attention

 

Oscillatory activity in the gamma frequency range (25-140 Hz) has been reported extensively in the mammalian forebrain. Gamma oscillations of the local field potential (LFP) are evoked by sensory stimuli, and spike discharges and LFPs synchronize in the gamma-frequency range across forebrain regions during selective attention. However, a mechanistic understanding of how synchronized gamma oscillations contribute to attention has thus far proven elusive. Oscillations in the gamma-band have also been observed in a midbrain structure: the avian optic tectum (OT, also known as the superior colliculus in mammals). The OT and the adjoining isthmic nuclei (NI), form the core components of a midbrain network that has been shown to play an important role in the selection of stimuli for gaze and attention [1].

 

The avian optic tectum provides an attractive model for investigating the mechanistic basis and functional role of gamma oscillations in spatial attention, for several reasons. First, we have shown that sensory stimuli of multiple modalities (visual, auditory) evoke high amplitude, spatially localized gamma oscillations in the OT in passive birds [2]. Second, we have discovered that these oscillations can be evoked reliably and robustly even in slices of the midbrain with the OT-NI network intact [3]. This preparation has permitted us to demonstrate that inhibitory circuitry in the OT, and cholinergic input from the NI regulate the periodicity and power, respectively, of OT gamma oscillations. Third, the well-characterized anatomy and physiology of the midbrain network permits developing biologically realistic computational models that provide mechanistic insight into the role of these oscillations in sensory coding and selective attention. Ongoing work involves characterizing the role of the gamma-generating midbrain network in behaving birds performing spatial detection and attention tasks [4].

 

References:

1. Knudsen, E.I. Control from below: the role of a midbrain network in spatial attention. Eur J Neurosci, 2011, 33: p. 1961-1972. 

2. Sridharan, D., Boahen, K. and Knudsen, E.I. Space coding by gamma oscillations in the barn owl optic tectum. J Neurophysiol. 2011, 105(5): p. 2005-17. 

3. Goddard, C.A.*, Sridharan, D.*, Huguenard, J. and Knudsen, E.I. Gamma oscillations are generated locally in an attention-related midbrain network. Neuron, 2012, 73(3): p. 567-80. 

4. Sridharan, D., Ramamurthy, D.L. and Knudsen, E.I. Spatial probability dynamically modulates visual target detection in chickens. PLoS One, 2013, 8(5):e64136.

Joby Joseph Reader Center for Neural and Cognitive Sciences University of Hyderabad, India Ph: +918008531777 Fax: +914023134493 Web:Neuronal Systems Lab Alt email: jjcncs@uohyd.ernet.in

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