Poster No:
2530
Submission Type:
Abstract Submission
Authors:
Seokyun Ryun1, Chun Kee Chung1
Institutions:
1Seoul National University, Seoul, Seoul
First Author:
Co-Author:
Introduction:
High-gamma (HG) activity is a well-known and robust neurophysiological activity observed in various cortical regions, including the primary somatosensory cortex (S1) and hippocampus. However, its functional roles and mechanisms remain unclear. Specifically, although the relationship between theta-gamma activity is relatively well-established in the hippocampus, it is unclear whether this relationship can also be applied to other cortical regions, such as the S1 and the primary visual cortex (V1). Here, we investigate this issue using phase-amplitude coupling and effective connectivity analysis. In this study, we first confirm the coupling between theta-HG activities and then evaluate the information flow between them.
Methods:
Twelve patients with drug-resistant epilepsy were included in this study. Patients underwent electrocorticography (ECoG) grid or depth electrode insertion surgery. Eight patients with electrodes located on the S1 participated in the texture stimulation task, and four patients with electrodes located in the hippocampus performed a memory encoding task. We calculated theta-HG phase amplitude comodulation (PAC) using ECoG signals from the S1 and hippocampus during texture stimulation and encoding periods, respectively. To evaluate information flow between theta activity and HG envelope, we calculated partial directed coherence (PDC) between them. For significance testing, we created surrogate datasets using the multiple partitioning method for PAC and the fast Fourier transform (FFT)-surrogate method (phase randomization) for PDC. We then performed the simulation 1000 times and extracted the z-scores or p-values of each condition.
Results:
We found that HG activities are phase-locked to the theta oscillations both in the S1 and hippocampus during tasks. However, the information flow between theta-HG activities showed distinct differences in S1 and hippocampus. That is, in the hippocampus, the theta oscillation drove the hippocampal HG activity. On the other hand, in the S1, the fluctuation of the HG envelope drove the theta oscillatory activity. These results were consistent across patients. Additionally, we found that HG activity in S1 modulates theta activity in surrounding cortical areas.
Conclusions:
In this study, we showed that the relationship between theta and HG activities varies across cortical regions. Expressly, results from the S1 area indicated that S1 HG activity during stimulation is not induced by slow oscillatory activity such as theta oscillation but may be driven directly by external inputs. Therefore, we suggest that HG activities in the S1 and hippocampus have distinctly different generation mechanism.
Perception, Attention and Motor Behavior:
Perception: Tactile/Somatosensory 1
Perception and Attention Other 2
Keywords:
Cortex
ELECTROCORTICOGRAPHY
Memory
Somatosensory
Other - High-gamma
1|2Indicates the priority used for review
Provide references using author date format
Baccalá, L.A., Sameshima, K., (2001), 'Partial directed coherence: a new concept in neural structure determination', vol. 84, no. 6, pp. 463-474
Canolty, R.T. et al., (2006), 'High gamma power is phase-locked to theta oscillations in human neocortex', Science, vol. 313, no. 5793, pp. 1626-1628
Tort, A.B. et al., (2008), 'Dynamic cross-frequency couplings of local field potential oscillations in rat striatum and hippocampus during performance of a T-maze task', Proceedings of the National Academy of Sciences, vol. 105, no. 51, pp. 20517-20522