Improvement in visual search with practice: mapping learning-related changes in neurocognitive stages of processing.

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Practice can improve performance on visual search tasks; the neural mechanisms underlying such improvements, however, are not clear. Response time typically shortens with practice, but which components of the stimulus-response processing chain facilitate this behavioral change? Improved search performance could result from enhancements in various cognitive processing stages, including (1) sensory processing, (2) attentional allocation, (3) target discrimination, (4) motor-response preparation, and/or (5) response execution. We measured event-related potentials (ERPs) as human participants completed a five-day visual-search protocol in which they reported the orientation of a color popout target within an array of ellipses. We assessed changes in behavioral performance and in ERP components associated with various stages of processing. After practice, response time decreased in all participants (while accuracy remained consistent), and electrophysiological measures revealed modulation of several ERP components. First, amplitudes of the early sensory-evoked N1 component at 150 ms increased bilaterally, indicating enhanced visual sensory processing of the array. Second, the negative-polarity posterior-contralateral component (N2pc, 170-250 ms) was earlier and larger, demonstrating enhanced attentional orienting. Third, the amplitude of the sustained posterior contralateral negativity component (SPCN, 300-400 ms) decreased, indicating facilitated target discrimination. Finally, faster motor-response preparation and execution were observed after practice, as indicated by latency changes in both the stimulus-locked and response-locked lateralized readiness potentials (LRPs). These electrophysiological results delineate the functional plasticity in key mechanisms underlying visual search with high temporal resolution and illustrate how practice influences various cognitive and neural processing stages leading to enhanced behavioral performance.





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Clark, Kait, L Gregory Appelbaum, Berry van den Berg, Stephen R Mitroff and Marty G Woldorff (2015). Improvement in visual search with practice: mapping learning-related changes in neurocognitive stages of processing. J Neurosci, 35(13). pp. 5351–5359. 10.1523/JNEUROSCI.1152-14.2015 Retrieved from

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Marty G. Woldorff

Professor in Psychiatry and Behavioral Sciences

Dr. Woldorff's main research interest is in the cognitive neuroscience of attention. At each and every moment of our lives, we are bombarded by a welter of sensory information coming at us from a myriad of directions and through our various sensory modalities -- much more than we can fully process. We must continuously select and extract the most important information from this welter of sensory inputs. How the human brain accomplishes this is one of the core challenges of modern cognitive neuroscience. Dr. Woldorff uses a combination of electrophysiological (ERP, MEG) and functional neuroimaging (fMRI) methods to study the time course, functional neuroanatomy, and mechanisms of attentional processes. This multimethodological approach is directed along several main lines of research: (1) The influence of attention on sensory and perceptual processing; (2) Cognitive and attentional control mechanisms; (3) The role of attention in multisensory environments; (4) The interactive relationship between attention and reward; and (5) The role of attention in perceptual awareness.

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