Our senses convey rich and detailed information about the external world, but we can selectively attend to some details while ignoring others. This capacity for selective attention is critical for survival and essential for complex tasks. Our lab studies the mechanisms of selective attention in two species (humans and non-human primates) and at four “levels” of recordings: spikes, local field potential (LFP), electrocorticogram (ECoG) and electroencephalogram (EEG) (see Figure below).

In particular, we focus on a brain rhythm called gamma (30-80 Hz), which is modulated by attentional load and is also highly dependent on the properties of visual stimuli, and can provide useful clues about the network architecture. This cross-scale, cross-species recording setup is also used for brain-computer interfacing applications and for diagnosis of mental disorders.

Different recording scales in humans and non-human primates

  1. Microelectrode recordings from monkeys: This allows us to record activity of single neurons using microelectrode arrays. We also get a second “level” called local field potential (LFP), which represents the local activity of a few thousand neurons, by low-pass filtering the signal.
  2. EEG from humans: Complex behaviours such as attention are studied at a coarse “network” level using EEG, in which electrodes are placed on the scalp.
  3. EEG from monkeys: We have modified our recording system that is used for microelectrode recordings to simultaneously record EEG from monkeys as well.
  4. Electrocorticogram (ECoG) from monkeys: ECoG is obtained from macro-electrodes placed directly on the brain, and is typically recorded from humans undergoing epilepsy treatment. We have collaborated with companies that make microelectrodes (Blackrock Microsystems) and ECoG arrays (Ad-Tech Medical Instrumentation) to design a hybrid electrode grid that includes both. We are therefore able to simultaneously record from four scales in monkeys (spikes, LFP, ECoG and EEG).


Neural basis of LFP, ECoG and EEG

Our setup allows a thorough investigation of the properties of macro-signals such as LFP, ECoG and EEG, since we have...
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Neural mechanisms of selective attention

We study the relationship between selective attention, gamma rhythm and a neural mechanism called normalization, which has been recently associated...
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Signal Processing Techniques

Bridging brain signals across scales requires mathematical and signal processing tools (such as power spectral density and coherence), which are...
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Stimulus dependence of gamma oscillations

Gamma oscillations induced in the visual cortex are highly dependent on the properties of the visual stimulus, such as its...
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In addition, we are also expanding our research to the following areas: (1) building detailed biophysical models to better understand brain signals at various scales, (2) clinical applications using gamma rhythm as a diagnostic tool and (3) brain-machine interfacing applications.

See our poster for the Wellcome-DBT India Alliance end report that has a summary of completed and ongoing projects here.