**5. Complementary issues**

We have described several ERP components involved in studies of social and cognitive neuroscience. Now, in this section we review some methodological approaches of ERP research that complement and improve the advances in traditional ERP assessment: sleep research, intracranial recordings, source location analysis and co-recordings with fMRI.

#### **5.1 Sleep research**

406 Neuroimaging – Cognitive and Clinical Neuroscience

decision-making tasks would be not so sensitive as to assess subtle deficits in decision making in disorders such as adult attention deficit hyperactivity disorder and bipolar disorders. Conversely, ERP abnormal neural processing of valence and magnitude of rewards in a gambling task in those disorders may help to integrate reward, action-selection and monitoring systems, providing an excellent shortcut to goal-directed action (Ibanez et al., Submitted a). ERP research on gambling tasks provides both a clinical and a theoretical branch of research linking decision making, soft frontal diseases, monitoring-reward

Fig. 4. A neuroanatomical model of decision making. Three main systems are thought to be involved in decision making: a stimulus-encoding system (orbitofrontal cortex shown in red), an action-selection system (anterior cingulate cortex shown in green) and an expected-reward system (basal ganglia and amygdala shown in blue). The anterior, medial and posterior cingulate cortex, together with basal ganglia (ellipse), seem to modulate the ERN and fERN in gambling and error-monitoring tasks. Modified from

We have described several ERP components involved in studies of social and cognitive neuroscience. Now, in this section we review some methodological approaches of ERP research that complement and improve the advances in traditional ERP assessment: sleep research, intracranial recordings, source location analysis and co-recordings with fMRI.

systems and psychiatry.

Gleichgerrcht et al., 2010.

**5. Complementary issues** 

The study of cognitive processing during sleep is a topic of great interest because ERPs allow the study of stimulation with passive paradigms (without conscious or behavioral response), opening multiple research possibilities during different sleep phases (Ibanez et al., 2008a). Different cognitive discriminations during sleep related to the learning, frequency, intensity, duration, saliency, novelty, proportion of appearance, meaning and even sentential integration of stimuli are topics of intense research (e.g., Ibanez et al., 2006). Methodological control of ERP sleep research, such the use of qualitative and quantitative measures of sleep stages (see Figure 5), the control of the so-called first night effect and the assessment of sleep disturbances are important factors for improving this research area (Ibanez et al., 2008b). Better control of experimental paradigms is relevant for the growth of the neuroscience of sleep.

Fig. 5. Quantitative assessment of sleep stages during ERP recordings. A) The voltage maps and N400 waveform modulation of contextual semantic discrimination during REM sleep. B).Comparison of frequency bands between sleep stages (time-frequency charts for stage II sleep, REM sleep and stage II-minus-REM subtraction). Microvolt differences (mean and standard deviations) of delta band activity during stage II and REM (right bottom). Modified from Ibanez et al., 2006, 2008b.
