The effects of varying task difficulty on event related potential components in visual three stimulus paradigm

Recording of the electrical activity in the brain on the scalp is called electroencephalogram (EEG). In EEG, potential changes occur in response to cognitive, sensory or motor stimuli along with the spontaneous activity of the brain, and these potential changes are called Evoked Potentials (EP). Early latency and late latency responses are observed in evoked potentials. Late latency responses are associated with cognitive processes and are called "Event-related potentials" (ERP). Attention can be viewed in terms of top-down and bottom-up mechanisms. When focusing on a task, the top-down mechanism operates in line with the objectives, while the bottom-up mechanism operates when a stimulus unrelated to the task is perceived. ERPs that occur against novel stimuli can be studied with the three stimulus paradigm. In this paradigm, there are standard stimuli, target stimuli and novel distracter stimuli. In this study, we aimed to investigate the relationship between the difficulty of the focused task and the involuntary attention response to novel stimuli using the three stimulus paradigm. The novel stimuli included two subgroups of abstract pictures and familiar pictures. In addition, we divided the novel stimuli into three groups according to their distance from the target stimuli. Thus, we aimed to examine more than one parameter together in a single experimental setup. In the study, ERP records were obtained from 21 healthy young adults. In the applied visual three stimulus paradigm, they were asked to respond to target stimuli of different difficulty, and the components of ERP against novel stimuli in the paradigm were examined. TAMEEG/ERP program was used for recording and analysis of EEG-ERP data. The amplitude and latency values of the ERP components were analyzed with repeated measures ANOVA test. In our study, there was no significant relationship between the difficulty level of target stimuli and P3a responses to novel stimuli. Higher P3a responses occurred to novel stimuli with abstract content than those with familiar content. In addition, P3a potential amplitudes increased when novel stimuli moved away from the target stimuli according to the order of arrival in the paradigm. Our findings support the view that resources are shared among cognitive processes.