Robert Roman

Error processing – evidence from intracerebral ERP recordings

Over the last decade, several authors have described an early negative (Ne) and a later positive (Pe) potential in scalp event-related potentials (ERPs) of incorrect choice reactions. The aim of the present study was to investigate the intracerebral origin and distribution of these potentials. Seven intractable epileptic patients participated in the study. A total of 231 sites in the frontal, temporal, and parietal lobes were investigated by means of depth electrodes. A standard visual oddball paradigm was performed, and electroencephalogram (EEG) epochs with correct and incorrect motor reactions were averaged independently. Prominent, mostly biphasic, ERP complexes resembling scalp Ne/Pe potentials were consistently observed in several cortical locations after incorrect trials. The most consistent findings were obtained from mesiotemporal structures; in addition to P3-like activity found after correct responses, an Ne/Pe complex was generally detected after incorrect trials. The Pe had a longer latency than the P3. Other generators of Ne/Pe-like potentials were located in different regions of the frontal lobe. The latency of the Ne was shortest in parietal, longer in temporal, and longest in frontal regions. Our findings firstly show that multiple cortical structures generate Ne and Pe. In addition to the rostral anterior cingulate cortex, the mesiotemporal and some prefrontal cortical sites seem to represent integral components of the brain’s errorchecking system. Secondly, the coupling of Ne and Pe to a complex suggests a common origin of Ne and Pe. Thirdly, the latency differences of the Ne across lobes suggest that the Ne is primarily elicited in posterior and temporal, and only later in frontal regions.

Intracerebral Error-Related Negativity in a Simple Go/NoGo Task

Abstract: Performance monitoring represents a critical executive function of the human brain. In an effort to identify its anatomical and physiological aspects, a negative component of event-related potentials (ERPs), which occurs only on incorrect trials, has been used in the extensive investigation of error processing. This component has been termed “error-negativity” (Ne) or error-related negativity (ERN) and has been interpreted as a correlate of error detection. The aim of the present intracerebral ERP study was to contribute knowledge of the sources of the Ne/ERN, with a particular focus on the involvement of a frontomedian wall (FMW) in the genesis of this negativity. Seven patients with intractable epilepsy participated in the study. Depth electrodes were implanted to localize the seizure origin prior to surgical treatment. A total of 574 sites in the frontal, temporal, and parietal lobes were investigated. A simple Go/NoGo task was performed and EEG epochs with correct and erroneous motor respons...

Intracerebral somatosensory event-related potentials: effect of response type (button pressing versus mental counting) on P3-like potentials within the human brain

OBJECTIVE To assess the contribution of different anatomical brain sites to the genesis of P3 phenomena with respect to button pressing versus mental counting tasks. METHODS Eight intractable epileptic patients undergoing depth electrode recordings prior to their surgery participated in the study. A total of 546 cerebral sites were recorded. A standard somatosensory oddball paradigm was used. The experiment was carried out in two sessions, differing in the requested responses to targets. The averaged responses in both tasks were compared. RESULTS After targets, two kinds of P3-like potentials were observed within different cortical sites. Task-non-specific P3 potentials were seen for both types of responses to targets. The mean amplitude of these task-non-specific P3 potentials was significantly higher in the button pressing task. The intracerebral generators of this somatosensory P3 did not differ from the known generators of auditory and visual P3s. Task-specific P3-like potentials were found much less frequently. Button pressing unequivocally generated additional P3-like potentials in the premotor cortical sites. Mental counting repeatedly evoked additional P3-like waveforms in the left-side middle and inferior temporal gyri. CONCLUSIONS In addition to multiple intracerebral P3 generators that reflect target detection processing, other task-specific P3-like potential generators can be found in the human brain. Their activity may affect the topography and precise parameters of scalp P3 potential.

Directional functional coupling of cerebral rhythms between anterior cingulate and dorsolateral prefrontal areas during rare stimuli: A directed transfer function analysis of human depth EEG signal

What is the neural substrate of our capability to properly react to changes in the environment? It can be hypothesized that the anterior cingulate cortex (ACC) manages repetitive stimuli in routine conditions and alerts the dorsolateral prefrontal cortex (PFC) when stimulation unexpectedly changes. To provide evidence in favor of this hypothesis, intracerebral stereoelectroencephalographic (SEEG) data were recorded from the anterior cingulate and dorsolateral PFC of eight epileptic patients in a standard visual oddball task during presurgical monitoring. Two types of stimuli (200 ms duration) such as the letters O (frequent stimuli; 80% of probability) and X (rare stimuli) were presented in random order, with an interstimulus interval between 2 and 5 s. Subjects had to mentally count the rare (target) stimuli and to press a button with their dominant hand as quickly and accurately as possible. EEG frequency bands of interest were θ (4–8 Hz), α (8–12 Hz), β (14–30 Hz), and γ (30–45 Hz). The directionality of the information flux within the EEG rhythms was indexed by a directed transfer function (DTF). The results showed that compared with the frequent stimuli, the target stimuli induced a statistically significant increase of DTF values from the anterior cingulate to the dorsolateral PFC at the θ rhythms (P < 0.01). These results provide support to the hypothesis that ACC directly or indirectly affects the oscillatory activity of dorsolateral PFC by a selective frequency code under typical oddball conditions. Hum Brain Mapp 2009.

Neural correlates of affective picture processing — A depth ERP study

Using functional neuroimaging techniques (PET and fMRI), various cortical, limbic, and paralimbic structures have been identified in the last decade as neural substrates of human emotion. In this study we used a novel approach (intracerebral recordings of event-related potentials) to add to our knowledge of specific brain regions involved in affective picture processing. Ten intractable epileptic patients undergoing pre-surgical depth electrode recording viewed pleasant, neutral, and unpleasant pictures and intracerebral event-related potentials (ERPs) were recorded. A total of 752 cortical and subcortical sites were investigated. Significant differences in ERPs to unpleasant as compared to neutral or pleasant pictures were frequently and consistently observed in recordings from various brain areas--the mesial temporal cortex (the amygdala, the hippocampus, the temporal pole), the lateral temporal cortex, the mesial prefrontal cortex (ACC and the medial frontal gyrus), and the lateral prefrontal cortex. Interestingly, the mean latencies of responses to emotional stimuli were somewhat shorter in the frontal lobe structures (with evidently earlier activation within lateral prefrontal areas when compared to mesial prefrontal cortex) and longer in the temporal lobe regions. These differences, however, were not significant. Additional clearly positive findings were observed in some rarely investigated regions--in the posterior parietal cortex, the precuneus, and the insula. An approximately equivalent number of positive findings was revealed in the left and right hemisphere structures. These results are in agreement with a multisystem model of human emotion, distributed far beyond the typical limbic system and substantially comprising lateral aspects of both frontal lobes as well.

Intracerebral P3-like waveforms and the length of the stimulus–response interval in a visual oddball paradigm

OBJECTIVE This study investigated the possible linkage of intracerebrally recorded P3-like waveforms to the processes induced by stimulus perception or motor response formation. METHODS Event-related potentials were recorded from 560 cerebral sites in 17 patients suffering from intractable epilepsy during visual oddball task. Potentials evoked by the target stimuli were sorted according to button-pressing response times, and the P3 waveform was analyzed both in stimulus-locked and response-locked averages, which were separately averaged for fast and slow responses. RESULTS P3-like waveforms were identified in 180 sites in 17 patients. Three different types of P3-like waveforms, diffusely distributed within the brain, were found: (1) time-locked to the stimulus (30 sites in 11 patients); (2) time-locked to the motor response (52 sites in 13 patients); and (3) with ambiguous time relationship to stimulus and motor response (98 sites in 16 patients). CONCLUSIONS The intracerebral P3-like waveform could represent different processes involved in performing active oddball tasks. Therefore, our results support the hypothesis that the P3 waveform registered by surface electrodes could be a heterogeneous phenomenon. SIGNIFICANCE These results provide evidence that the P3 waveform is not only related to stimulus processing, which differs from what has been generally claimed in the literature.

On the Time Course of Synchronization Patterns of Neuronal Discharges in the Human Brain during Cognitive Tasks

Using intracerebral EEG recordings in a large cohort of human subjects, we investigate the time course of neural cross-talk during a simple cognitive task. Our results show that human brain dynamics undergo a characteristic sequence of synchronization patterns across different frequency bands following a visual oddball stimulus. In particular, an initial global reorganization in the delta and theta bands (2–8 Hz) is followed by gamma (20–95 Hz) and then beta band (12–20 Hz) synchrony.

Identical event-related potentials to target and frequent stimuli of visual oddball task recorded by intracerebral electrodes

OBJECTIVE The shape of visually elicited event-related potentials (ERP) of epileptic patients during their presurgical evaluation with intracerebral electrodes was investigated in the study. METHODS Twenty intractable epileptic patients with depth electrodes at several intracranial locations in the frontal, temporal, parietal lobes, and in the amygdalo-hippocampal complex participated in the study. To evoke the ERP, a standard visual oddball task was used with target stimuli, and frequent non-habituated and habituated stimuli. The averaged responses of the 3 groups were superimposed and visually analyzed whether the shape appeared identical or non-identical. RESULTS The EEG response to target and frequent stimuli was recorded in 660 intra-cerebral sites. In 88 sites (14 different patients) localized in the amygdala, parahippocampal gyrus, superior, middle, and inferior temporal gyri, fusiform and lingual gyri, sensorimotor cortex, prefrontal cortex, hippocampus, and cingulated gyrus, the identical ERPs to target and both groups of frequent stimuli were observed. In 442 sites located in the above listed structures, and in the basal ganglia and parietal cortex, the shape of the ERP differed from 0.3 to 0.47 s on after the stimulus. The remaining 130 sites did not yield the task-specific potential change. CONCLUSIONS The existence of identical ERPs to target and frequent stimuli in the oddball task suggests that a part of mental operations underlying the brain engagement in this task is not dependent on the way of responding.

Very High-Frequency Oscillations: Novel Biomarkers of the Epileptogenic Zone

In the present study, we aimed to investigate depth electroencephalographic (EEG) recordings in a large cohort of patients with drug‐resistant epilepsy and to focus on interictal very high‐frequency oscillations (VHFOs) between 500Hz and 2kHz. We hypothesized that interictal VHFOs are more specific biomarkers for epileptogenic zone compared to traditional HFOs.

Hippocampal negative event‐related potential recorded in humans during a simple sensorimotor task occurs independently of motor execution

A hippocampal‐prominent event‐related potential (ERP) with a peak latency at around 450 ms is consistently observed as a correlate of hippocampal activity during various cognitive tasks. Some intracranial EEG studies demonstrated that the amplitude of this hippocampal potential was greater in response to stimuli requiring an overt motor response, in comparison with stimuli for which no motor response is required. These findings could indicate that hippocampal‐evoked activity is related to movement execution as well as stimulus evaluation and associated memory processes. The aim of the present study was to investigate the temporal relationship between the hippocampal negative potential latency and motor responses. We analyzed ERPs recorded with 22 depth electrodes implanted into the hippocampi of 11 epileptic patients. Subjects were instructed to press a button after the presentation of a tone. All investigated hippocampi generated a prominent negative ERP peaking at ∼420 ms. In 16 from 22 cases, we found that the ERP latency did not correlate with the reaction time; in different subjects, this potential could either precede or follow the motor response. Our results indicate that the hippocampal negative ERP occurs independently of motor execution. We suggest that hippocampal‐evoked activity, recorded in a simple sensorimotor task, is related to the evaluation of stimulus meaning within the context of situation.