Supratim Ray


Office : Ground floor of PRL at Central Animal Facility
Phone : 080-22933437
E-Mail : sray[at]iisc.ac.in
web : https://cns.iisc.ac.in/sray/

Research Areas

Neural Oscillations and high-level Cognition.

Research Details

Our lab studies the neural basis of high-level cognition such as selective attention and meditation, with a focus on a brain rhythm called “gamma” (30-80 Hz), which is thought to be associated with high-level cognitive processes. We record from both humans and non-human primates using a variety of neurophysiological techniques while they are engaged in cognitive tasks. In humans, we record brain signals using electroencephalogram (EEG) from healthy people of different age groups, people with mild-cognitive impairment (MCI) or early Alzheimer’s Disease (AD), as well as long term meditators, to study how neural oscillations are modulated with healthy aging, mental disorders and with meditative practices. In non-human primates, we record using microelectrode chips implanted in the brain and study how vision, cognition and brain stimulation affects brain oscillations, allowing us to understand the mechanisms underlying these processes. Establishment of this cross-species, cross-modality link between brain signals has applications in Brain-computer Interfacing (BCI) and clinical diagnosis of brain disorders.


Das A, Nandi N and Ray S, (2023), Alpha and SSVEP power outperforms Gamma power in capturing Attentional Modulation in Human EEG, Cerebral Cortex

Aggarwal S and Ray S, (2023), Slope of the power spectral density flattens at low frequencies (<150 Hz) with healthy aging but also steepens at higher frequency (>200 Hz) in human electroencephalogram, Cerebral Cortex Communications, Vol 4(2), tgad011

Krishnakumaran R and Ray S, (2023), Temporal characteristics of gamma rhythm constrain properties of noise in an inhibition-stabilized network model, Cerebral Cortex, 33, 10108-10121

Kumar WS and Ray S, (2023), Healthy aging and cognitive impairment alter EEG functional connectivity in distinct frequency bands, European Journal of Neuroscience, 58, 3432-49

Pattisapu S and Ray S, (2023), Stimulus-induced narrow-band gamma oscillations in humans can be recorded using open-hardware low-cost EEG amplifier, PLoS One, 18(1), e0279881

Shirhatti V, Ravishankar P and Ray S, (2022), Gamma oscillations in primate primary visual cortex are severely attenuated by small stimulus discontinuities, PLoS Biology, 20(6), e3001666

Prakash SS, Mayo JP and Ray S, (2022), Decoding of attentional state using local field potentials, Current Opinion in Neurobiology, 76, 102589

Liza K and Ray S, (2022), Local interactions between steady-state visually evoked potentials at nearby flickering frequencies, Journal of Neuroscience, 42(19), 3965-74

Ray S, (2022), Spike-Gamma phase relationship in visual cortex, Annual Review of Vision Sciences, 8:1

Murty DVPS and Ray S, (2022), Stimulus-induced robust narrow-band gamma oscillations in human EEG using cartesian gratings, Bio-protocol, 12(7), e4379

Krishnakumaran R, Raees M, Ray S, (2022), Shape analysis of gamma rhythm supports a superlinear inhibitory regime in an inhibition-stabilized network, PLoS Computational Biology, 18, e1009886

Kumar WS, Manikandan K, Murty DVPS, Ramesh RG, Purokayastha S, Javali M, Rao NP and Ray S, (2022), Stimulus-induced narrowband gamma oscillations are test-retest reliable in healthy elderly in human EEG, Cerebral Cortex Communications, 3(1), tgab066

Murty DVPS, Manikandan K, Kumar WS, Ramesh RG, Purokayastha S, Nagendra B, Abhishek ML, Balakrishnan A, Javali M, Rao NP and Ray S, (2021), Stimulus-induced Gamma rhythms are weaker in human elderly with Mild Cognitive Impairment and Alzheimer’s Disease, Elife, 10, e61666.

Prakash SS, Das A, Kanth ST, Mayo JP, Ray S, (2021), Decoding of attentional state using high-frequency local field potential is as accurate as using spikes, Cerebral Cortex, 31(9), 4314-4328

Das A and Ray S, (2021), Effect of cross-orientation normalization on different neural measures in macaque primary visual cortex, Cerebral Cortex Communications, 2(1), tgab009.

Dinavahi MVPS, Manikandan K, Kumar WS, Ramesh RG, Purokayastha S, Javali M, Rao NP, Ray S, (2020), Gamma oscillations weaken with age in healthy elderly in human EEG, Neuroimage, 215, 116826

Salelkar S and Ray S, (2020), Interaction between steady-state visually evoked potentials at nearby flicker frequencies, Scientific Reports, 10, 5344

Kanth ST and Ray S, (2020), Electrocorticogram (ECoG) is highly informative in primate visual cortex, Journal of Neuroscience, 40(12), 2430-2444

Dubey A and Ray S, (2019), Cortical electrocorticogram (ECoG) is a local signal, Journal of Neuroscience, 39(22), 4299-4311

Salelkar S, Somasekhar GM, and Ray S, (2018), Distinct frequency bands in the local field potential are differently tuned to stimulus drift rate, Journal of Neurophysiology, 120:, 681-692

Dinavahi MVPS*, Shirhatti V*, Ravishankar P* and Ray S, (2018), Large visual stimuli induce two distinct gamma oscillations in primate visual cortex, Journal of Neuroscience, 38, 2730-44

Subhash Chandran KS, Seelamantula CS, and Ray S, (2018), Duration Analysis Using Matching Pursuit Algorithm Reveals Longer Bouts of Gamma Rhythm, Journal of Neurophysiology, 119(3), 808-821

Biswas A and Ray S, (2017), Control of alpha rhythm (8-13 Hz) using neurofeedback, Journal of the Indian Institute of Science, 97:4, 527-531

Subhash Chandran K S, Mishra A, Shirhatti V and Ray S., (2016), Comparison of Matching Pursuit algorithm with other signal processing techniques for computation of the time-frequency power spectrum of brain signals, Journal of Neuroscience, 36(12): 3399-3408

Shirhatti V, Borthakur A, and Ray S, (2016), Effect of Reference Scheme on Power and Phase of the Local Field Potential, Neural Computation, 28(5), 882-913.

Dubey A and Ray S, (2016), Spatial Spread of local field potential is band-pass in the primate visual cortex, Journal of Neurophysiology, 116(4):1986-99

Ray S and Maunsell, JHR, (2015), Do gamma oscillations play a role in cerebral cortex?, Trends in Cognitive Sciences, 19(2), 78-85.

Ray S, (2015), Challenges in the quantification and interpretation of spike-LFP relationships, Current Opinion in Neurobiology, 31, 111-118.

Srinath R and Ray S., (2014), Effect of Amplitude Correlations on Coherence in the Local Field Potential, Journal of Neurophysiology, 112(4), 741-751

Ray S, Ni AM and Maunsell JHR., (2013), Strength of Gamma Rhythm depends on Normalization, PLoS Biology, 11(2), e1001477.

Ni AM, Ray S and Maunsell JHR, (2012), Tuned Normalization Explains the Size of Attention Modulations, Neuron, 73(4), 803-813.

Ray S and Maunsell JHR, (2011), Different origins of gamma rhythm and high-gamma activity in macaque visual cortex, PLoS Biology, 9(4), e1000610.

Ray S and Maunsell JHR, (2011), Network rhythms influence the relationship between spike-triggered local field potential and functional connectivity, Journal of Neuroscience, 31(35), 12674-12682.

Ray S, Niebur E, Hsiao SS, Sinai A and Crone NE†, (2008), High-frequency gamma activity (80-150 Hz) is increased in human cortex during selective attention, Clinical Neurophysiology, 119(1), 116-133.

Ray S†, Hsiao SS, Crone NE, Franaszczuk PJ and Niebur E, (2008), Effect of stimulus intensity on the spike-local field potential relationship in the secondary somatosensory cortex, Journal of Neuroscience, 28(29), 7334-7343.

Ray S†, Crone NE, Niebur E, Franaszczuk PJ and Hsiao SS, (2008), Neural correlates of high-gamma oscillations (60-200 Hz) in macaque local field potentials and their potential implications in electrocorticography, Journal of Neuroscience, 28(45), 11526-11536.

Muniak MA, Ray S, Hsiao SS, Dammann JF, Bensmaia SJ†, (2007), The neural coding of stimulus intensity: linking the population response of mechanoreceptive afferents with psychophysical behavior, Journal of Neuroscience, 27(43), 11687-11699.

Ray S†, Jouny CC, Crone NE, Boatman D, Thakor NV, Franaszczuk PJ, (2003), Human ECoG analysis during speech perception using matching pursuit: a comparison between stochastic and dyadic dictionaries, IEEE Transactions in Biomedical Engineering, 50(12), 1371-1373