The dynamic beamformer

Contains fulltext : 100980.pdf (author's version ) (Closed access)As the number of possible neural sources is much higher than the number of MEG or EEG sensor readings, the inverse problem of estimating source amplitudes from sensor readings has many solutions. A common approach to tackle this problem is to assume that all sources are independent from each other. This approach is widely used in the neuroscience community and is known as beamforming. Since the source amplitude is likely to change smoothly over time, we expect to improve the source localization by taking the temporal dynamics into account. In this paper, we incorporate the independence assumption of the standard beamformer in a linear dynamic system, and we show that by using the leadfield matrix as the observation model and setting the covariance of the observation noise to be proportional to the covariance of the observation, we arrive at the dynamic beamformerInternational Workshop on Machine Learning and Interpretation in Neuroimaging (MLINI 2011) (Sierra Nevada, Spain, December 16-17, 2011

Propagating neocortical gamma bursts are coordinated by traveling alpha waves

Contains fulltext : 122913.pdf (publisher's version ) (Open Access)Neocortical neuronal activity is characterized by complex spatiotemporal dynamics. Although slow oscillations have been shown to travel over space in terms of consistent phase advances, it is unknown how this phenomenon relates to neuronal activity in other frequency bands. We here present electrocorticographic data from three male and one female human subject and demonstrate that gamma power is phase locked to traveling alpha waves. Given that alpha activity has been proposed to coordinate neuronal processing reflected in the gamma band, we suggest that alpha waves are involved in coordinating neuronal processing in both space and time.6 p

Looking around with your brain in a virtual world

Contains fulltext : 83539.pdf (publisher's version ) (Open Access)eNTERFACE'1

Suppression of Pythium and Phytophthora damping-off of rooibos by compost and a combination of compost and nonpathogenic <I>Pythium </I>taxa

Please help populate SUNScholar with the full text of SU research output. Also - should you need this item urgently, please send us the details and we will try to get hold of the full text as quick possible. E-mail to [email protected]. Thank you.Journal Articles (subsidised)AgriwetenskappePlantpatologi

Exploring the impact of alternative feature representations on BCI classification

Contains fulltext : 75525.pdf (publisher's version ) (Closed access)ESANN'2009, 17 th European Symposium on Artificial Neural Networks Computational Intelligence and Machine Learning, Bruges (Belgium), 22 april 200

Modulations in alpha activity by covert attention: a new 2D control signal for BCI

Item does not contain fulltexthttp://www.enpmeeting.org/2009/ShowAbstractOnline.php?uai=8b77e5910329215929ENP 2009, 3 juni 200

<I>Pythium cederbergense </I>sp. nov. and related taxa from <I>Pythium </I>clade G associated with the South African indigenous plant <I>Aspalathus linearis </I>(rooibos)

Please help populate SUNScholar with the full text of SU research output. Also - should you need this item urgently, please send us the details and we will try to get hold of the full text as quick possible. E-mail to [email protected]. Thank you.Journal Articles (subsidised)AgriwetenskappePlantpatologi

Distinct directional couplings between slow and fast gamma power to the phase of theta oscillations in the rat hippocampus

Contains fulltext : 218743.pdf (Publisher’s version ) (Closed access)It is well-established that theta (~4-10 Hz) and gamma (~25-100 Hz) oscillations interact in the rat hippocampus. This cross-frequency coupling might facilitate neuronal coordination both within and between brain areas. However, it remains unclear whether the phase of theta oscillations controls the power of slow and fast gamma activity or vice versa. We here applied spectral Granger causality, phase slope index and a newly developed cross-frequency directionality (CFD) measure to investigate directional interactions between local field potentials recorded within and across hippocampal subregions of CA1 and CA3 of freely exploring rats. Given the well-known CA3 to CA1 anatomical connection, we hypothesized that interregional directional interactions were constrained by anatomical connection, and within-frequency and cross-frequency directional interactions were always from CA3 to CA1. As expected, we found that CA3 drove CA1 in the theta band, and theta phase-to-gamma power coupling was prominent both within and between CA3 and CA1 regions. The CFD measure further demonstrated that distinct directional couplings with respect to theta phase was different between slow and fast gamma activity. Importantly, CA3 slow gamma power phase-adjusted CA1 theta oscillations, suggesting that slow gamma activity in CA3 entrains theta oscillations in CA1. In contrast, CA3 theta phase controls CA1 fast gamma activity, indicating that communication at CA1 fast gamma is coordinated by CA3 theta phase. Overall, these findings demonstrate dynamic directional interactions between theta and slow/fast gamma oscillations in the hippocampal network, suggesting that anatomical connections constrain the directional interactions.12 p