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INTRODUCTIONIn the stop-task, a fast choice response to a visual stimulus must be withheld when an auditory signal is unpredictably presented after a short delay. Successful stops are associated with a larger frontocentral negative event-related potential (ERP) in the N1 latency range than failed stops, here referred to as the ‘switch-ERP’.
ACUE - PASSIVE
In adult patients with attention deficit hyperactivitydisorder (ADHD), this effect is absent,suggesting a disturbed link between the ability to switch attention from visual to auditory stimuli and subsequent inhibitory control (Bekker et al., 2005a,b).
VCUE - PASSIVE
*Same pattern of effects for n=8
We investigate the mechanisms of this hypothesized switch-ERP and ask whether it involves a modality-specific or supra-modal process.
Valid - Invalid
Neural Correlates of Cross-Modality Attentional Switching
Evelijne M. Bekker, Santani Teng, David M. Horton, George R. Mangun
Center for Mind and Brain, University of California, Davis
Invalidly cued targets evoked longer reaction times, especially in the auditory modality (F(1,13)=13.5,p<.01; F(1,7)=5.6,p<.05), and smaller variability of responding (F(1,13)=4.5,p<.05; F(1,7)=9.9, p<.02).
Scalp distributions and fMRI indicated similar fronto-parietal activation when preparing for upcoming target in either modality.
Difference waves reveals specific biasing in sensory areas.
Invalid trials elicited more negativity than valid trials from 100-160 msec. This effect was largest at Cz (F(4,10)=3.7,p<.05), and did not interact with modality.
VCUE - ACUE
ERP: 14 right-handed, healthy subjects participated (age=23.3 (3.6), 7 males). fMRI: 8 of those tested with ERPs (age=24.3(4.3), 5 males).
Invalidly cued targets elicited a larger N1 than validly cued targets (replication of switch-ERP effect). Scalp distributions suggest similar although not identical generators across modalities. fMRI data shows activity in posterior parietal and superior prefrontal areas, in line with previous cross-modality switching studies (Shomstein and Yantis, 2004). In addition, TPJ activity previously reported for invalid trials in visuo-spatial studies was found (not shown here) (Corbetta et al., 2000).
Symbolic cues activated fronto-parietal attentional control regions. In contrast to Foxe et al. (2005), no modality differences were found for control. However, difference waves did reveal sensory specific biasing in line with both Shomstein and Yantis (2004) and Foxe et al. (2005).
Symbolic visual cues validly or invalidly signaled the modality of an upcoming target. Passive cues did not require preparation.Subjects pressed a button with the index/middle finger of the right hand upon presentation of a grating (visual) or a tone (auditory) with a high/low frequency.
Symbolic cues elicited more positivity from – ms, and more negativity from – ms. Auditory cues elicited more positivity/less negativity at posterior sites.
EEG: 128 leads, 0.05-30Hz, A/D=250Hz, re-reference left mastoid
fMRI: 3T, EPI w/ TR=2000, TE=25, 34 axial slices, 4mm, interleaved
FUNDING AND CONTACT
This study was supported by NIMH grant MH55741, and by NWO (Netherlands Organization of Scientific Research) Talent Fund.
Correspondence: [email protected]