Synchronous chaos and broad band gamma rhythm in a minimal multi-layer model of primary visual cortex

Visually induced neuronal activity in V1 displays a marked gamma-band component which is modulated by stimulus properties. It has been argued that synchronized oscillations contribute to these gamma-band activity [... however,] even when oscillations are observed, they undergo temporal decorrelation over very few cycles. This is not easily accounted for in previous network modeling of gamma oscillations. We argue here that interactions between cortical layers can be responsible for this fast decorrelation. We study a model of a V1 hypercolumn, embedding a simplified description of the multi-layered structure of the cortex. When the stimulus contrast is low, the induced activity is only weakly synchronous and the network resonates transiently without developing collective oscillations. When the contrast is high, on the other hand, the induced activity undergoes synchronous oscillations with an irregular spatiotemporal structure expressing a synchronous chaotic state. As a consequence the population activity undergoes fast temporal decorrelation, with concomitant rapid damping of the oscillations in LFPs autocorrelograms and peak broadening in LFPs power spectra. [...] Finally, we argue that the mechanism underlying the emergence of synchronous chaos in our model is in fact very general. It stems from the fact that gamma oscillations induced by local delayed inhibition tend to develop chaos when coupled by sufficiently strong excitation.Comment: 49 pages, 11 figures, 7 table

The Evolving Role of Consumers

The culmination of the changes in healthcare, motivated in many ways by the rapid evolution of information and communication technologies in parallel with the shift toward increased patient decision-making and empowerment, has critical implications for clinical research, from recruitment and participation to, ultimately, successful outcomes. This chapter explores the developments impacting health consumers from various perspectives, with some focus on foundational issues in health communication and information behaviors as related to health consumerism. An overarching concern is the information environment within which health consumers are immersed, which is increasingly social, and underlying communication issues and emerging technologies contributing to the changing nature of patients’ information world. Not surprisingly, we will see that core findings from communication and information behavior research have relevance for our current understanding and future models of the evolving role of the health consumer