Abstract
Even in the absence of external stimulation, the visual system shows ongoing fluctuations of neural activity. While some early theoretical analyses suggest that the impact of such fluctuations in activity on visual perception may be minimal, recent empirical results have given new insights on this issue. We will review this evidence and the new theoretical perspectives in this symposium. Below are a few key themes:
- Coverage of multiple experimental methods and fluctuations in activity at different time scales:
The 5 speakers will discuss experiments that employ different methods to measure ongoing fluctuations in neural activity, such as human fMRI (functional magnetic resonance imaging) in patients and healthy subjects, intracranial cortical EEG (electroencephalography) in presurgical epileptics, combined use of TMS (transcranial magnetic stimulation) and optical imaging, and electrophysiological studies in non-human primates. These methods investigate fluctuations in neural activity at different time scales, from 10–20 seconds per cycle to the sub-second oscillatory range. The relationship between these different activities will be discussed.
- What ongoing activities tell us about the mechanisms of attention?
In addition to discussing the nature of ongoing activity and its impact on perception, several speakers will also use ongoing activity as a tool to understand the basic mechanisms of attention and awareness.
- Implication for clinical studies of perception:
Several speakers will discuss data collected from presurgical epileptics, where intracranial cortical EEG data were recorded. The nature of ongoing fMRI activity in patients suffering from strokes will also be discussed.
- Debate of theoretical perspectives and interpretations of data:
The different speakers will present competing theoretical perspectives on the nature of ongoing activity, as well as alternative interpretations of the same results. This will promote an exchange of ideas and hopefully lead to consensus on and illumination of the issues.
The nature of ongoing neural activity and its relationship to perception should be relevant to all attendants of VSS. We aim to have a broad audience, as we will be covering different experimental paradigms with different empirical methods. We expect the symposium to be especially interesting for researchers specializing in attention and awareness. Also, although the topic is primarily on neural activity, one focus of the symposium is its relationship to behavior. Hence some speakers will also present behavioral studies inspired by the investigation of ongoing neural activity, which will be of interests to many. Specifically, in some talks the implications of our understanding of ongoing neural activity and issues of experimental design will be discussed.