Symposia abstracts > Tuesday 24th October 2.30pm-3.45pm

Timing, Neural Dynamics, and Temporal Scaling (Dean Buonomano)

Speakers: Hugo Merchant (Mexico), Mehrdad Jazayeri (USA), Dean Buonomano (USA)

There is increasing experimental and theoretical support for the notion that timing on the scale of hundreds of milliseconds to second relies on neural dynamicsi.e. changing populations of neural activity, in which time is encoded in the population of neurons active at any given movement (population clocks). Electrophysiological recordings in a large number of brain areas, including the motor cortex, premotor cortex, prefrontal cortex, hippocampus, and striatum have reported that it is possible to decode elapsed time from reproducible patterns of neural activity in these areas. A number of questions, however, remain unclear, including the neural mechanisms underlying temporal scaling, that is, the ability to produce the same motor patterns at different speeds. This symposium will explore behavioral and neurophysiological data, and neurocomputational models, underlying timing and temporal scaling in the range of hundreds of milliseconds to seconds. 




Perception: Continuous or Discrete? (Michael Herzog & Adrien Doerig)

Speakers: Rufin VanRullen (France), Michael Herzog (Switzerland), Tomer Fekete (Belgium) 

Intuitively, consciousness seems to be a continuous stream of percepts. A diver is jumping off a cliff. We see her trajectory against the blue sky at each single moment in time. Many models in vision rely explicitly and implicitly on continuous perception.. For example, in visual backward masking, continuous perception is assumed to explain how a trailing mask can render a preceding target unconscious. However, continuous accounts are in fact challenged by demonstrations where, as in masking, a trailing element determines perception. Another classic example is the color phi paradigm. When a green disk is presented for a short time, it is perceived as such. When a second red disk is presented a bit later and at a different location, motion is perceived during which the color changes midway. Perception has changed qualitatively. Whereas discrete models have been proposed for centuries, continuous perception seems to be so intuitive that there are only a few explicit proponents. In this symposium Cees van Leeuwen and Tomer Fekete (Leuven) will propose and defend the continuous account against discrete proposals. Rufin VanRullen (Toulouse) will show how brain rhythms produce discrete perception, which can be envisioned as a one-stage model of discrete perception. Michael Herzog and Adrien Doerig (Lausanne) will propose a two stage model of discrete perception, in which the temporal resolution of unconscious processing is independent of the duration of percepts, which can last up to 400ms. Clearly, the temporal nature of perception is one of the fundamental questions in perception research and, as mentioned, the answer to this question has important ramifications for most fields of perception science. For this reason, it is surprising to see this topic remain largely unexplored. This controversial symposium is the first step in understanding the temporal nature of perception in a systematic fashion. 


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