Brain-state based triggering of target sounds as a novel paradigm in selective attention research
The neural basis selective attention (i.e., how one can select, out of the massive amount of stimuli that constantly bombard one’s senses, the concurrently relevant ones for further processing) is one of the most interesting research questions in cognitive neuroscience. The importance of research on selective attention is further enhanced by the central role that selective attention deficits play in a number of neurological and psychiatric disorders. Dichotic listening is one of the most often-used task paradigms in selective attention research, where subjects are instructed to attend sounds presented to one ear and to ignore sounds presented to the opposite ear. Average neural responses to attended vs. ignored sounds are then compared to disclose neural correlates of selective attention. Fluctuation of the focus of attention over the course of the experiment has been one potential shortcoming of this otherwise excellent paradigm.
In their recent study, Andermann et al. (2012) detected online the attentional states of experimental subjects and triggered presentation of near-threshold target stimuli based on the presence of correct vs. incorrect attentional state. Specifically, electroencephalogram epochs time-locked to onset of stimuli were first recorded to attended vs. ignored sound streams during a dichotic listening task. These data were then utilized to teach a brain computer interface algorithm to detect high vs. low selective attention states that triggered presentation of the near-threshold targets in the experiment proper. Notably, when the near-threshold target stimuli were presented during estimated correct (i.e., towards the designated ear) vs. incorrect (i.e., fluctuation of attention away from the designated ear) attentional state, the target sounds were detected at a higher rate. Curiously, in the near-threshold target detection task, correct attentional state also resulted in higher number of “illusory percepts” (i.e., a target was detected when none was present). It was also observed that there was considerable fluctuation in the attentional states of the subjects over the course of the experiment.
The strength of this study is that it provides a new type of research paradigm for the investigation of the neural basis of selective attention. More generally, the authors suggest that the brain state-triggered stimulus delivery will enable efficient, statistically tractable studies of rare patterns of ongoing activity in single neurons and distributed neural circuits, and their influence on subsequent behavioral and neural responses.
Reference: Andermann ML, Kauramaki J, Palomaki T, Moore CI, Hari R, Jaaskelainen IP, Sams M. Brain state-triggered stimulus delivery: An efficient tool for probing ongoing brain activity. Open Journal of Neuroscience (2012) 2-5.