John Case — Publication

ABSTRACT

How do humans flexibly respond to changing environmental demands on a subsecond temporal scale? Extensive research has highlighted the key role of the prefrontal cortex in flexible decision-making and adaptive behaviour, yet the core mechanisms that translate sensory information into behaviour remain undefined. Using direct human cortical recordings, we investigated the temporal and spatial evolution of neuronal activity (indexed by the broadband gamma signal) in 16 participants while they performed a broad range of self-paced cognitive tasks. Here we describe a robust domain- and modality-independent pattern of persistent stimulus-to-response neural activation that encodes stimulus features and predicts motor output on a trial-by-trial basis with near-perfect accuracy. Observed across a distributed network of brain areas, this persistent neural activation is centred in the prefrontal cortex and is required for successful response implementation, providing a functional substrate for domain-general transformation of perception into action, critical for flexible behaviour.

ABSTRACT

Aging is associated with performance decrements across multiple cognitive domains. The neural noise hypothesis, a dominant view of the basis of this decline, posits that aging is accompanied by an increase in spontaneous, noisy baseline neural activity. Here we analyze data from two different groups of human subjects: intracranial electrocorticography from 15 participants over a 38 year age range (15–53 years) and scalp EEG data from healthy younger (20 –30 years) and older (60 –70 years) adults to test the neural noise hypothesis from a 1/f noise perspective. Many natural phenomena, including electrophysiology, are characterized by 1/f noise. The defining characteristic of 1/f is that the power of the signal frequency content decreases rapidly as a function of the frequency ( f ) itself. The slope of this decay, the noise exponent (), is often1 for electrophysiological data and has been shown to approach white noise (defined as 0) with increasing task difficulty.Weobserved, in both electrophysiological datasets, that aging is associated with a flatter (more noisy) 1/f power spectral density, even at rest, and that visual cortical 1/f noise statistically mediates age-related impairments in visual working memory. These results provide electrophysiological support for the neural noise hypothesis of aging.

AUTHORS

Bradley Voytek
Mark A. Kramer
John Case
Kyle Q. Lepage
Zachary Tempesta
Robert T. Knight
Adam Gazzaley

Date: 2015

DOI: 10.1523/JNEUROSCI.2332-14.2015

View PDF

Persistent neuronal activity in human prefrontal cortex links perception and action

ABSTRACT

AUTHORS

Age-Related Changes in 1/f Neural Electrophysiological Noise

ABSTRACT

AUTHORS