Intracranial ERPs in humans during a lateralized visual oddball task: I. Occipital and peri-Rolandic recordings

Suggested visual blockade during hypnosis: Top-down modulation of stimulus processing in a visual oddball task

Several theories of hypnosis assume that responses to hypnotic suggestions are implemented through top-down modulations via a frontoparietal network that is involved in monitoring and cognitive control. The current study addressed this issue re-analyzing previously published event-related-potentials (ERP) (N1, P2, and P3b amplitudes) and combined it with source reconstruction and connectivity analysis methods. ERP data were obtained from participants engaged in a visual oddball paradigm composed of target, standard, and distractor stimuli during a hypnosis (HYP) and a control (CON) condition. In both conditions, participants were asked to count the rare targets presented on a video screen. During HYP participants received suggestions that a wooden board in front of their eyes would obstruct their view of the screen. The results showed that participants’ counting accuracy was significantly impaired during HYP compared to CON. ERP components in the N1 and P2 window revealed no amplitude differences between CON and HYP at sensor-level. In contrast, P3b amplitudes in response to target stimuli were significantly reduced during HYP compared to CON. Source analysis of the P3b amplitudes in response to targets indicated that HYP was associated with reduced source activities in occipital and parietal brain areas related to stimulus categorization and attention. We further explored how these brain sources interacted by computing time-frequency effective connectivity between electrodes that best represented frontal, parietal, and occipital sources. This analysis revealed reduced directed information flow from parietal attentional to frontal executive sources during processing of target stimuli. These results provide preliminary evidence that hypnotic suggestions of a visual blockade are associated with a disruption of the coupling within the frontoparietal network implicated in top-down control.

Dose-related modulation of event-related potentials to novel and target stimuli by intravenous Δ⁹-THC in humans

Cannabinoids induce a host of perceptual alterations and cognitive deficits in humans. However, the neural correlates of these deficits have remained elusive. The current study examined the acute, dose-related effects of delta-9-tetrahydrocannabinol (Δ⁹-THC) on psychophysiological indices of information processing in humans. Healthy subjects (n=26) completed three test days during which they received intravenous Δ⁹-THC (placebo, 0.015 and 0.03 mg/kg) in a within-subject, double-blind, randomized, cross-over, and counterbalanced design. Psychophysiological data (electroencephalography) were collected before and after drug administration while subjects engaged in an event-related potential (ERP) task known to be a valid index of attention and cognition (a three-stimulus auditory 'oddball' P300 task). Δ⁹-THC dose-dependently reduced the amplitude of both the target P300b and the novelty P300a. Δ⁹-THC did not have any effect on the latency of either the P300a or P300b, or on early sensory-evoked ERP components preceding the P300 (the N100). Concomitantly, Δ⁹-THC induced psychotomimetic effects, perceptual alterations, and subjective 'high' in a dose-dependent manner. Δ⁹-THC -induced reductions in P3b amplitude correlated with Δ⁹-THC-induced perceptual alterations. Lastly, exploratory analyses examining cannabis use status showed that whereas recent cannabis users had blunted behavioral effects to Δ(9)-THC, there were no dose-related effects of Δ⁹-THC on P300a/b amplitude between cannabis-free and recent cannabis users. Overall, these data suggest that at doses that produce behavioral and subjective effects consistent with the known properties of cannabis, Δ⁹-THC reduced P300a and P300b amplitudes without altering the latency of these ERPs. Cannabinoid agonists may therefore disrupt cortical processes responsible for context updating and the automatic orientation of attention, while leaving processing speed and earlier sensory ERP components intact. Collectively, the findings suggest that CB1R systems modulate top-down and bottom-up processing.

Late divergence of target and nontarget ERPs in a visual oddball task

Different mental operations were expected in the late phase of intracerebral ERPs obtained in the visual oddball task with mental counting. Therefore we searched for late divergences of target and nontarget ERPs followed by components exceeding the temporal window of the P300 wave. Electrical activity from 152 brain regions of 14 epileptic patients was recorded by means of depth electrodes. Average target and nontarget records from 1800 ms long EEG periods free of epileptic activity were compared. Late divergence preceded by almost identical course of the target and nontarget ERPs was found in 16 brain regions of 6 patients. The mean latency of the divergence point was 570+/-93 ms after the stimulus onset. The target post-divergence section of the ERP differed from the nontarget one by opposite polarity, different latency of the components, or even different number of the components. Generators of post-divergence ERP components were found in the parahippocampal gyrus, superior, middle and inferior temporal gyri, amygdala, and fronto-orbital cortex. Finding of late divergence indicates that functional differences exist even not sooner than during the final phase of the task.

Modifications of cognitive and motor tasks affect the occurrence of event-related potentials in the human cortex

This study concerns the question of how task modification affects the frequency occurrence of event-related potentials (ERP) inside the active cortical areas. In 13 candidates for epilepsy surgery, 156 sites in the temporal (74), frontal (73), and parietal (9) cortices were recorded by means of depth and subdural electrodes. Four modifications of the somatosensory evoked P3-like potentials were performed; (i) an oddball paradigm with silent counting of target stimuli (P3c); (ii) an oddball paradigm with a hand movement in response to target stimuli (P3m); (iii) an S1-S2 paradigm, ERP in the P300 time window after the S2 stimulus, with silent counting of target stimuli (S2c), and (iv) an S1-S2 paradigm with a hand movement in response to target stimuli (S2m). In comparing the oddball paradigms with the S1-S2 (contingent negative variation, CNV) paradigms, four regions emerge that are significantly linked with the oddball P3; the prefrontal cortex, the cingulate, the amygdalo-hippocampal complex, and the lateral temporal cortex. A prominent role of the cingulate and the fronto-orbital cortex in the cognitive processing of movement was supported when tasks with identical cognitive loads but different required responses were compared. Even relatively simple cognitive tasks activate many cortical regions. The investigated areas were activated in all tests; however, small regions in each field were active or inactive in relation to the nature of the task. The study indicates a variable and task-dependent internal organization of a highly complex and widely distributed system of active cortical areas.

Event Related Potentials (Erp) and Behavioral Measurements to Verbal Stimulation of Visual Fields

Event related potentials (ERP) to visually presented linguistic stimuli were examined using a lexical-decision task and an oddball paradigm. Stimuli were presented to the central, right or left visual fields (CVF, RVF and LVF) and generated ERP with very clear N100-P300 components. The question addressed was whether there is ERP evidence for left hemisphere (LH) superiority in linguistic discrimination as reported behaviorally. Nineteen young, right-handed male subjects participated. The main factor influencing the latency and amplitude of N100 was that of contralateral versus ipsilateral stimulation. Shorter N100 latency and larger amplitude were recorded over the hemisphere contralateral to the visual field stimulated. In contrast, the factors influencing the P300 parameters were the visual field stimulated and the hemisphere over which the ERP was recorded. P300 amplitude was significantly larger and P300 latency significantly shorter over the LH than over the RH. Significantly shorter P300 latency and larger peak amplitude were found for RVF than for LVF stimulation.

Brain potentials implicate temporal lobe abnormalities in criminal psychopaths

Psychopathy is associated with abnormalities in attention and orienting. However, few studies have examined the neural systems underlying these processes. To address this issue, the authors recorded event-related potentials (ERPs) while 80 incarcerated men, classified as psychopathic or nonpsychopathic via the Hare Psychopathy Checklist--Revised (R. D. Hare, 1991, 2003), completed an auditory oddball task. Consistent with hypotheses, processing of targets elicited larger frontocentral negativities (N550) in psychopaths than in nonpsychopaths. Psychopaths also showed an enlarged N2 and reduced P3 during target detection. Similar ERP modulations have been reported in patients with amygdala and temporal lobe damage. The data are interpreted as supporting the hypothesis that psychopathy may be related to dysfunction of the paralimbic system--a system that includes parts of the temporal and frontal lobes.

On the relation of movement-related potentials to the go/no-go effect on P3

According to Simson et al. [Simson, R., Vaughan, H.G., Jr., Ritter, W., 1977. The scalp topography of potentials in auditory and visual go/nogo tasks. Electroencephalography and Clinical Neurophysiology 43, 864-875], the difference between no-go P3 and go-P3 (the go/no-go effect) is due to overlap of P3 onto the return of the preceding contingent negative variation (CNV) in no-go trials and onto the continuing CNV in go trials. Similarly, according to Kok [Kok, A., 1986. Effects of degradation of visual stimuli on components of the event-related potential (ERP) in go/nogo reaction tasks. Biological Psychology 23, 21-38], the go/no-go effect is due to movement-related negative potentials, in particular contralateral negativity, adding with P3 in go trials. To investigate these notions, we studied how CNV, go-P3 and no-go P3 are lateralized at fronto-central sites when the side of the response varies across trials, comparing these effects between hand movements and eye movements and delineating them more precisely for hand movements with multichannel recordings. The go/no-go effect was larger and contralaterally lateralized with hand movements than with eye movements. Dipole analysis dissected its components into a large contribution of the medial cingulate gyrus, into activity of motor areas contralateral to the cued hand and a left-frontal source. Motor-related portions of the effect seemed to build upon and extend motor-related components included in CNV. Results provide support for the notion that the go/no-go effect is related to movement-related potentials. We suggest that go-P3 and no-go P3 are characterized by addition and reduction of motor-related activation to the core P3.

The p300: where in the brain is it produced and what does it tell us?

Intracranial recordings, lesion studies, and the combination of functional imaging with source analysis have produced a solid body of evidence about the generators of the P300 event-related potential. Although it is impossible to square all findings obtained across and within methodologies, a consistent pattern of generators has emerged, with target-related responses in the parietal cortex and the cingulate and novelty-related activations mainly in the inferior parietal and prefrontal regions. Stimulus modality-specific contributions come from the inferior temporal and superior parietal cortex for the visual and from the superior temporal cortex for the auditory modality. The P300 continues to be an important signature of cognitive processes such as attention and working memory and of its dysfunction in neurologic and mental disorders. It is increasingly being investigated as a potential genetic marker of mental disorders. Knowledge about the generators of the P300 will be crucial for a better understanding of its cognitive significance and its continuing clinical application.

An adaptive reflexive processing model of neurocognitive function: supporting evidence from a large scale (n = 100) fMRI study of an auditory oddball task

Recent hemodynamic imaging studies have shown that processing of low probability task-relevant target stimuli (i.e., oddballs) and low probability task-irrelevant novel stimuli elicit widespread activity in diverse, spatially distributed cortical and subcortical systems. The nature of this distributed response supports the model that processing of salient and novel stimuli engages many brain regions regardless of whether said regions were necessary for task performance. However, these latter neuroimaging studies largely employed small sample sizes and fixed-effect analyses, limiting the characterization and inference of the results. The present study addressed these issues by collecting a large sample size (n = 100) and employed random effects statistical models. Analyses were also conducted to determine the inter-subject reliability of the hemodynamic response and the effects of gender and age on target detection and novelty processing. Group data demonstrated highly significant activation in all 34 specified regions of interest for target detection and all 24 specified regions of interest for processing of novel stimuli. Neither age nor gender systematically influenced the results. These data are discussed within the context of a model that proposes that the mammalian brain has evolved to adopt a strategy of engaging distributed neuronal systems when processing salient stimuli despite the low probability that many of these brain regions are required for successful task performance. This process may be termed 'adaptive reflexive processing.' The implications of these results for interpreting functional MRI studies are discussed.

Abnormal hemodynamics in schizophrenia during an auditory oddball task

BACKGROUND

Schizophrenia is a heterogeneous disorder characterized by diffuse brain abnormalities that affect many facets of cognitive function. One replicated finding in schizophrenia is abnormalities in the neural systems associated with processing salient stimuli in the context of oddball tasks. This deficit in the processing of salience stimuli might be related to abnormalities in orienting, attention, and memory processes.

METHODS

Behavioral responses and functional magnetic resonance imaging data were collected while 18 patients with schizophrenia and 18 matched healthy control subjects performed a three-stimulus auditory oddball task.

RESULTS

Target detection by healthy participants was associated with significant activation in all 38 regions of interest embracing distributed cortical and subcortical systems. Similar reproducibility was observed in healthy participants for processing novel stimuli. Schizophrenia patients, relative to control subjects, showed diffuse cortical and subcortical hypofunctioning during target detection and novelty processing, including bilateral frontal, temporal, and parietal cortices and amygdala, thalamus, and cerebellum.

CONCLUSIONS

These data replicate and extend imaging studies of target detection in schizophrenia and present new insights regarding novelty processing in the disorder. The results are consistent with the hypothesis that schizophrenia is characterized by a widespread pathologic process affecting many cerebral areas, including cortical, subcortical, and cerebellar circuits.

Qualitative differences between conscious and nonconscious processing? On inverse priming induced by masked arrows

In general, both consciously and unconsciously perceived stimuli facilitate responses to following similar stimuli. However, masked arrows delay responses to following arrows. This inverse priming has been ascribed to inhibition of premature motor activation, more recently even to special processing of nonconsciously perceived material. Here, inverse priming depended on particular masks, was insensitive to contextual requirements for increased inhibition, and was constant across response speeds. Putative signs of motor inhibition in the electroencephalogram may as well reflect activation of the opposite response. Consequently, rather than profiting from inhibition of primed responses, the alternative response is directly primed by perceptual interactions of primes and masks. Thus there is no need to assume separate pathways for nonconscious and conscious processing.

Cortical and subcortical distribution of middle and long latency auditory and visual evoked potentials in a cognitive (CNV) paradigm

OBJECTIVE

This study concerned sensory processing (post-stimulus late evoked potential components) in different parts of the human brain as related to a motor task (hand movement) in a cognitive paradigm (Contingent Negative Variation). The focus of the study was on the time and space distribution of middle and late post-stimulus evoked potential (EP) components, and on the processing of sensory information in the subcortical-cortical networks.

METHODS

Stereoelectroencephalography (SEEG) recordings of the contingent negative variation (CNV) in an audio-visual paradigm with a motor task were taken from 30 patients (27 patients with drug-resistant epilepsy; 3 patients with chronic thalamic pain). The intracerebral recordings were taken from 337 cortical sites (primary sensorimotor area (SM1); supplementary motor area (SMA); the cingulate gyrus; the orbitofrontal, premotor and dorsolateral prefrontal cortices; the temporal cortex, including the amygdalohippocampal complex; the parietooccipital lobes; and the insula) and from subcortical structures (the basal ganglia and the posterior thalamus). The concurrent scalp recordings were obtained from 3 patients in the thalamic group. In 4 patients in the epilepsy group, scalp recordings were taken separately from the SEEG procedure. The middle and long latency evoked potentials following an auditory warning (S1) and a visual imperative (S2) stimuli were analyzed. The occurrences of EPs were studied in two time windows (200-300 ms; and over 300 ms) following S1 and S2.

RESULTS

Following S1, a high frequency of EP with latencies over 200 ms was observed in the primary sensorimotor area, the supplementary motor area, the premotor cortex, the orbitofrontal cortex, the cingulate gyrus, some parts of the temporal lobe, the basal ganglia, the insula, and the posterior thalamus. Following S2, a high frequency of EP in both of the time windows over 200 ms was observed in the SM1, the SMA, the premotor and dorsolateral prefrontal cortex, the orbitofrontal cortex, the cingulate gyrus, the basal ganglia, the posterior thalamus, and in some parts of the temporal cortex. The concurrent scalp recordings in the thalamic group of patients twice revealed potentials peaking approximately at 215 ms following S1. Following S2, EP occurred with latencies of 215 and 310 ms, respectively. Following S1, separate scalp recordings in 4 patients in the epilepsy group displayed EP 3 times in the 'over 300 ms' time window. Following S2, EP were presented once in the '200-300 ms' time window and 3 times in the 'over 300 ms' time window.

CONCLUSIONS

The SM1, the SMA, multiple sites of the frontal lobe, some parts of the temporal lobe, the cingulate gyrus, the basal ganglia, the insula, and the posterior thalamus all participate in a cortico-subcortical network that is important for the parallel cognitive processing of sensory information in a movement related task.

Neural mechanisms for detecting and remembering novel events

The ability to detect and respond to novel events is crucial for survival in a rapidly changing environment. Four decades of neuroscientific research has begun to delineate the neural mechanisms by which the brain detects and responds to novelty. Here, we review this research and suggest how changes in neural processing at the cellular, synaptic and network levels allow us to detect, attend to and subsequently remember the occurrence of a novel event.

Basal ganglia involvement in sensory and cognitive processing. A depth electrode CNV study in human subjects

OBJECTIVE

Intracranial recordings were taken from the basal ganglia (BG) in order to explore the possible role of the BG in the cognitive processing of sensory information.

METHODS

Ten patients with intractable temporal lobe epilepsy, who were candidates for epilepsy surgery, underwent intracranial recordings with depth electrodes. A frontal approach was used for the insertion of diagonal depth electrodes into the amygdalo-hippocampal complex (AH complex). These electrodes passed through the BG. The putamen was explored in 8 patients; the nucleus caudatus and pallidum were explored in two patients. The contingent negative variation (CNV) paradigm was tested using auditory warning stimuli and visual imperative stimuli followed by a hand flexion. The auditory and visual middle and late latency potentials evoked by the warning and imperative stimuli were analyzed.

RESULTS

(1) Auditory evoked potentials (EPs): the amplitude potential gradient was observed with latencies of (a) 150-195ms (9 patients); (b) 215-290ms (9 patients); and (c) 350-600ms (10 patients). Negative potentials, with latencies of 100 and 110ms were observed in two patients. (2) Visual EPs: (a) 160-195ms (9 patients); (b) 210-295ms (9 patients); and (c) 330-550ms (7 patients). Negative potentials with latencies between 100 and 120ms were observed in 4 patients. CNV was obtained from the BG in 8 patients; a phase reversal was observed twice.

CONCLUSIONS

(1) The BG generate middle and late latency EPs in a cognitive paradigm linked to the motor task. (2) The BG generate CNV. (3) The BG could play an integrative role in the processing of sensory, cognitive, and motor information.

Influence of Time Pressure in a Simple Response Task, a Choice-by-Location Task, and the Simon Task

Abstract The influence of strategy was examined for a simple response task, a choice-by-location task, and the Simon task by varying time pressure. Besides reaction time (RT) and accuracy, we measured response force and derived two measures from the event-related EEG potential to form an index for attentional orienting (posterior contralateral negativity: PCN) and the start of motor activation (the lateralized readiness potential: LRP). For the choice-by-location task and the Simon task, effects of time pressure were found on the response-locked LRP, but not on the onset of the PCN and the stimulus-locked LRP. Thus, strategy influences processing after the start of motor activation in choice tasks. A small effect of time pressure was found on the peak latency of the PCN in the Simon task, which suggests that time pressure may affect attentional orienting. In the simple response task, time pressure reduced the amplitude of the PCN. This finding suggests that strategy affects attentional orienting to stimuli when these stimuli are not highly relevant. Finally, the effect of time pressure on RT was much larger in the simple response task than in the other tasks, which may be ascribed to the possibility of preparing the required response in the simple response task.

Timing and localization of movement-related spectral changes in the human peri-Rolandic cortex: intracranial recordings

Event-related spectral power (ERSP) was measured from intracranial EEG and used to characterize the time-course and localization of the Rolandic mu rhythms in 12 patients during the delayed recognition of words or faces (DR) and the discrimination of simple lateralized visual targets (LVD). On each trial, the subject decided whether to make manual response (Go) or not (NoGo). ERSP increased on both Go and NoGo trials in peri-Rolandic regions of all subjects with a peak latency of approximately 330-ms poststimulus and duration of 260 ms during the DR task. The peak of this ERSP increase preceded movement by approximately 300 ms. All subjects produced a subsequent movement specific ERSP decrease of peri-Rolandic mu rhythms (starting approximately 90 ms before the average reaction time) with an peak latency of approximately 800 ms and duration of approximately 520 ms. The LVD task produced bilateral movement-selective readiness potentials and reproduced the movement-specific late ERSP decreases seen in the DR task (strongest from 7-24 Hz). Furthermore, the LVD task demonstrated that the late movement-related ERSP decrease is larger for the contralateral hand. However, the LVD task did not consistently reproduce the early ERSP increase seen in the DR task. Movement-related ERSP decreases were widespread, occurring in pre- and post-Rolandic as well as primary-motor, supplemental motor, and cingulate cortical regions. Other cortical areas including frontal, temporal, and occipital regions did not show movement-related ERSP changes. Peri-Rolandic ERSP decreases in mu rhythms correlate with the generation of a motor command. The early increases in mu may reflect a transient state of motor inhibition just prior to motor execution.

Electrophysiological measures and dual-task performance in Tourette syndrome indicate deficient divided attention mechanisms

Tourette syndrome has been associated with impairments of attentional functions such as distractability, even in subjects without co-morbid attention deficit hyperactivity disorder. Based on the results of earlier research we hypothesized that Tourette syndrome patients might employ altered control mechanisms of attentional processes and have concurrent difficulties in allocating their attentional resources among competing tasks. Event-related brain potentials (ERPs) were recorded in a group of Tourette syndrome patients and in a matched control group during a dual task experiment. This experiment required the simultaneous detection of visual and auditory target stimuli which were manipulated to yield two different difficulty levels each of which were varied orthogonally. The behavioural parameters confirmed the intended performance differences between difficult-to-detect targets and easy-to-detect targets. This was paralleled by lower amplitudes and longer latencies of the corresponding P3b-ERP subcomponents. Although Tourette syndrome patients were unimpaired in overall performance they showed an increased interference of visual task demands with auditory target perception. In parallel they also exhibited a reduced amplitude of the P3b component to auditory targets. The findings show that Tourette syndrome patients are not generally impaired in their dual task performance. The allocation of attentional resources to competing tasks however, is altered. We speculate that this may be related to deficient inhibitory functions.

Dimensional overlap between arrows as cueing stimuli and responses? Evidence from contra-ipsilateral differences in EEG potentials

In the S1-S2 interval, 400 ms after an arrow as S1, an EEG-potential difference occurs between scalp sites contralateral and ipsilateral to arrow direction. Eimer [J. Exp. Psychol. Hum. Percept. Perform. 21 (1995) 837-854] interpreted this difference as a sign of automatic activation of the manual response, due to dimensional overlap of arrows and responses. However, according to Kornblum et al.'s [Psychol. Rev. 97 (1990) 253-270] notion of dimensional overlap, responses can only be automatically primed if they are included in the response set. Therefore, participants of the present study had to respond to S2 in separate blocks either by key-press, as in Eimer [J. Exp. Psychol. Hum. Percept. Perform. 21 (1995) 837-854], or by making saccades. In addition, contra-ipsilateral differences were recorded not only from central positions, overlying the hand-motor area, but across the whole scalp. Contralateral negativity at 400 ms after S1 was indeed found over the hand-motor area in the 'hand blocks'. However, this 'L-400' (=lateralization at 400 ms) was generally as large in the 'eye' blocks as in the 'hand' blocks. Therefore, L-400 does not reflect automatic activation of manual responses in the sense of Kornblum et al. [Psychol. Rev. 97 (1990) 253-270]. Further, its topographical maximum was more anterior than the hand-motor-related negativity that preceded the manual response ('LRP') with its maximum at central sites. Therefore, L-400 probably does not originate in the hand-motor cortex. Rather, it may be related to activity of the lateral premotor cortex found in fMRI studies of spatial orienting. The present EEG study extends these studies by delimiting the time period of this activity, suggesting that it reflects encoding of the spatial properties of the arrow for action.

Intracranial ERPs in humans during a lateralized visual oddball task: II. Temporal, parietal, and frontal recordings

OBJECTIVE

We investigated the relative participation of each cerebral hemisphere during a lateralized task that can be performed by a single hemisphere. While our companion article ( Clarke et al. 1999) focused on visual and motor event-related potentials (ERPs) recorded from occipital and peri-Rolandic sites, the present article is concerned with ERP correlates of intermediate stages of information processing from remaining cerebral regions.

METHODS

Intracranial ERPs were recorded from temporal, parietal and frontal lobe sites in 13 patients with intractable epilepsy while they performed a lateralized visual oddball task.

RESULTS

Visually-responsive N2 and/or P3 effects were recorded from medial temporal and supramarginal sites that appear to reflect activity along ventral and dorsal visual streams, respectively. Likewise, certain prefrontal sites, that are probably involved in working memory, were also visually-responsive. The majority of sites exhibiting N2, P3 and/or slow wave components, however, were unaffected by lateralized visual field or response hand effects. Target-evoked P3-like components were most frequently recorded from medial temporal and prefrontal sites. Post-response slow wave components were pervasive, and polarity reversals were present in the insula/operculum region, apparently reflecting somatosensory activity from SII.

CONCLUSIONS

The general absence of lateralized ERP effects despite lateralized stimulus input and response output suggests the importance of interhemispheric integration over hemispheric independence in the processing of this type of task.