Task difficulty,probability, and inter-stimulus interval as determinants of P300 from auditory stimuli |
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| Institution: | 1. Department of Psychology, University of Utah, 380 S. 1530 E. BEHS 502, Salt Lake City, UT 84112, USA;2. Department of Psychology, University of New Mexico, MSC03 2220, Albuquerque, NM 87131, USA;3. The Mind Research Network, 1101 Yale Blvd. NE, Albuquerque, NM 87106, USA;4. Department of Neurosurgery, University of New Mexico, MSC10 5615, Albuquerque, NM 87131, USA;5. Department of Psychiatry, University of New Mexico, MSC 09 5030, Albuquerque, NM 87131, USA |
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| Abstract: | The P300 event-related potential was elicited with auditory stimuli in 4 experiments which manipulated combinations of stimulus target probability (10% vs. 30%), task difficulty (easy vs. hard), and inter-stimulus interval (5 sec vs. 2 sec). P300 amplitude was smaller and peak latency longer for the more difficult relative to the easier tasks across experiments. Increases in stimulus target probability generally diminished P300 amplitude and shortened peak latency more for the easy relative to difficult task conditions. Increasing the number of non-target stimulus tones decreased P300 amplitude reliably, but increased latency only slightly. Task difficulty did not interact with variations in inter-stimulus interval which produced generally weak effects for both amplitude and latency. These findings suggests that P300 amplitude and latency obtained from auditory discrimination paradigms reflect processing difficulty independently of stimulus target probability unless differences in task requirements affect stimulus encoding. |
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