Is the potential evoked by visual stimulus dependent on verbal instruction, which determined the stimulus significance?

0205629 - UPT-D 20030011 RIV CZ eng J - Journal Article
Roman, R. - Brázdil, M. - Jurák, Pavel - Kukletal, M. - Rektor, I.
Is the potential evoked by visual stimulus dependent on verbal instruction, which determined the stimulus significance?
Homeostasis. Roč. 41, č. 5 (2001), s. 224 - 226. ISSN 0960-7560
R&D Projects: GA ČR GA102/02/1339
Institutional research plan: CEZ:AV0Z2065902
Keywords : visual stimulus * intracerebrally recorded EEG * epileptogenic zone
Subject RIV: FA - Cardiovascular Diseases incl. Cardiotharic Surgery

Letters X and O commonly represent stimuli possessing no specific information. In an experimental design the meaning of such neutral stimuli can be changed by instruction. For example, in visual oddball paradigm letter X can become the target stimulus and letter O non-target (frequent) stimulus. In active form of this paradigm, a subject is instructed to act in respon se to target stimuli as quickly as possible, for instance, to count them mentally and/or mark them by some instructed movement, and not to do anything on non-target stimuli. Scalp or intracerebrally recorded EEG correlates of target responses are constituted by waveforms, from which P3 component is one of the most studied. This waveform with typical latency range of 250-600 ms with positive or negative polarity on intracerebral electrodes is usually being described as reflecting decision or cognitive closure of the recognition processing (Brázdil et al., 1999). Our previous analysis of the EEG data recorded intracerebrally in epileptic patients during visual oddball paradigm demonstrated two new findings: (1) when analyzing the relationship between stimulus-response interval and the latency of P3 peak, three different types of P3 were observed - P3 time-locked to the motor response (movement), P3 time-locked to the stimulus and P3 with ambiguous time relationship to stimulus and motor response (Roman et al., 2001). (2) when investigating the shapes of ERPs evoked by target and non-target stimuli, the identical or almost identical responses to these two types of stimuli were observed in approximately 13% of explored contacts (Kukleta et al., 2001).
Permanent Link: http://hdl.handle.net/11104/0101242