Abstract
Strategically adopting decision biases allows organisms to tailor their choices to environmental demands. For example, a liberal response strategy pays off when target detection is crucial, whereas a conservative strategy is optimal for avoiding false alarms. Implementing strategic bias shifts is presumed to rely on prefrontal cortex, but human evidence for this is scarce. We hypothesized that strategic liberal bias shifts during a continuous target detection task arise through a more unconstrained neural regime (higher entropy) suited to the detection of unpredictable events. Upregulation of entropy in frontal brain regions indeed strongly characterized the degree to which individuals shifted from a conservative to a liberal bias. EEG standard deviation and spectral power could not account for this relationship, highlighting the unique contribution of moment-to-moment neural variability to bias shifts. Modulation of neural variability through prefrontal cortex appears instrumental for permitting an organism to tailor its decision bias to environmental demands.
Impact statement Moment-to-moment variability is a prominent feature of neural activity. Rather than representing mere noise, this variability might enable us to flexibly adapt our decision biases to the environment.