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The hues or the colorimetric purities of a pair of colored targets can be compared with similar precision whether the targets are juxtaposed or fall at well-separated positions in the visual field. This is the case even if the stimuli are 10° apart and fall in opposite hemifields. What could be the neural processes that underlie such comparisons? We are led to ask whether the long-range, white-matter tracts of the brain constitute a neural net (where representations are embodied in the weightings and signs of connections between the nodes of the net) or a communication network (where the same physical substrate carries different information from moment to moment).

BackgroundPain is modulated by expectation. Event-related potential (ERP) studies of the influence of expectation on pain typically utilise laser heat stimulation to provide a controllable nociceptive-specific stimulus. Short painful electric stimulation has a number of practical advantages, but is less nociceptive-specific. We compared the modulation of electric versus laser-evoked pain by expectation, and their corresponding pain-evoked and anticipatory ERPs.New MethodWe developed understanding of recognised methods of laser and electric stimulation. We tested whether pain perception and neural activity induced by electric stimulation was modulated by expectation, whether this expectation elicited anticipatory neural correlates, and how these measures compared to those associated with laser stimulation. We elicited cue-evoked expectations of high and low pain and compared subjective ratings and corresponding ERPs in response to the delivery of laser and electric stimulation in a within-participant design.ResultsDespite sensory and affective differences between laser and electric pain, intensity ratings and pain-evoked potentials were modulated equivalently by expectation, though ERPs only correlated with pain ratings in the laser pain condition. Anticipatory correlates significantly differentiated pain intensity expectation to laser but not electric pain.Comparison with Existing MethodPrevious studies have consistently shown that laser-evoked potentials are modulated by expectation. We extend this by showing electric pain-evoked potentials are equally modulated by expectation, within the same participants. We also show a difference between the pain types in anticipation.ConclusionsThough laser-evoked potentials express a stronger relationship with pain perception, both laser and electric stimulation may be used to study the modulation of pain-evoked potentials by expectation. Anticipatory-evoked potentials are elicited by both pain types, but they may reflect different processes and did not correlate with pain perception.

Academic research on whether social networks influence financial outcomes is still undeveloped. The literature has typically focused on three major questions — whether social networks affect investor behavior, firm behavior, or intermediary behavior. Because the theoretical framework in finance is organized around an accepted set of paradigms, and because data on intermediaries and firms have been publicly available for a long time, the financial economics area has just started using big data in its analysis. This note describes the extant research in this area and outlines how the field is likely to evolve.