J. A. Scott Kelso | PubMed Health

PubMed1995

Self-organizing dynamics of the human brain: Critical instabilities and Sil'nikov chaos.

Using a sensorimotor coordination task in conjunction with an array of SQUIDs (Superconducting QUantum Interference Devices) we demonstrate critical instabilities in human brain activity patterns. Analysis of the dominant spatial pattern of the brain and its time-varying amplitude displays a task-dependent geometry characteristic of Sil'nikov-like chaos, which changes qualitatively at the transition. (c) 1995 American Institute of Physics.

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PubMed1995

Characterizing the dynamics of auditory perception.

After listening to a sound that is presented repeatedly, subjects report hearing different transforms of the original sound. The frequency of reported transforms is a sensitive index of some speech disorders as well as cognitive flexibility in aging. In this paper, we propose and investigate quantitative measures that characterize the dynamics of this phenomenon, known as the verbal transformation effect. In particular, we show that the distribution of the dwell time, the time spent perceiving a string of a given phonemic form before switching to another form, obeys a power law for normal subjects with an exponent valued between 1 and 2. This result suggests that within this paradigm there is no characteristic time scale for the perceptual process. Additionally, we analyze the correlation properties of the transforms. We suggest that the complexity measures and techniques introduced here might be useful diagnostic tools for a number of speech and cognitive disorders. (c) 1995 American Institute of Physics.

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