Impact of orbitofrontal lesions on electrophysiological signals in a stop signal task

Authors:

• Anne-Kristin Solbakk

• Ingrid Funderud

• Tor Endestad

• Torstein Meling

• Magnus Lindgren

• Robert T. Knight

• Ulrike M. Krämer

Date: 2014

DOI: 10.1162/jocn_a_00561

PubMed: 24392904

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Abstract:

Behavioral inhibition and performance monitoring are critical cognitive functions supported by distributed neural networks including the pFC. We examined neurophysiological correlates of motor response inhibition and action monitoring in patients with focal orbitofrontal (OFC) lesions (n = 12) after resection of a primary intracranial tumor or contusion because of traumatic brain injury. Healthy participants served as controls (n = 14). Participants performed a visual stop signal task. We analyzed behavioral performance as well as event-related brain potentials and oscillations. Inhibition difficulty was adjusted individually to yield an equal amount of successful inhibitions across participants. RTs of patients and controls did not differ significantly in go trials or in failed stop trials, and no differences were observed in estimated stop signal RT. However, electrophysiological response patterns during task performance distinguished the groups. Patients with OFC lesions had enhanced P3 amplitudes to congruent condition go signals and to stop signals. In stop trials, patients had attenuated N2 and error-related negativity, but enhanced error positivity. Patients also showed enhanced and prolonged post-error beta band increases for stop errors. This effect was particularly evident in patients whose lesion extended to the subgenual cingulate cortex. In summary, although response inhibition was not impaired, the diminished stop N2 and ERN support a critical role of the OFC in action monitoring. Moreover, the increased stop P3, error positivity, and post-error beta response indicate that OFC injury affected action outcome evaluation and support the notion that the OFC is relevant for the processing of abstract reinforcers such as performing correctly in the task.

Preparatory attention after lesions to the lateral or orbital prefrontal cortex: an event-related potential study

Authors:

• Ingrid Funderud

• Marianne Lovstad

• Magnus Lindgren

• Tor Endestad

• Paulina Due-Tønnesse

• Torstein Meling

• Robert T. Knight

• Anne-Kristin Solbakk

Date: 2013

PubMed: 23831520

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Abstract:

The prefrontal cortex (PFC) plays a central role in preparatory and anticipatory attentional processes. To investigate whether subregions of the PFC play differential roles in these processes we investigated the effect of focal lesions to either lateral prefrontal (lateral PFC; n=11) or orbitofrontal cortex (OFC; n=13) on the contingent negative variation (CNV), an electrophysiological index of preparatory brain processes. The CNV was studied using a Go/NoGo delayed response task where an auditory S1 signaled whether or not an upcoming visual S2 was a Go or a NoGo stimulus. Neither early (500–1000 ms) nor late (3200–3700 ms) phase Go trial CNV amplitude was reduced for any of the patient groups in comparison to controls. However, the lateral PFC group showed enhanced Go trial early CNV and reduced late CNV Go/NoGo differentiation. These data suggests that normal orienting and evaluation as reflected by the CNV is intact after OFC lesions. The enhanced early CNV after lateral PFC damage may be due to failure in inhibition and the reduced late CNV difference wave confirms a deficit in preparatory attention after damage to this frontal subregion.

Differential Go/NoGo activity in both contingent negative variation and spectral power

Authors:

• Ingrid Funderud

• Magnus Lindgren

• Marianne Lovstad

• Tor Endestad

• Bradley Voytek

• Robert T. Knight

• Anne-Kristin Solbakk

Date: 2012

DOI: 10.1371/journal.pone.0048504

PubMed: 23119040

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Abstract:

We investigated whether both the contingent negative variation (CNV), an event-related potential index of preparatory brain activity, and event-related oscillatory EEG activity differentiated Go and NoGo trials in a delayed response task. CNV and spectral power (4-100 Hz) were calculated from EEG activity in the preparatory interval in 16 healthy adult participants. As previously reported, CNV amplitudes were higher in Go compared to NoGo trials. In addition, event-related spectral power of the Go condition was reduced in the theta to low gamma range compared to the NoGo condition, confirming that preparing to respond is associated with modulation of event-related spectral activity as well as the CNV. Altogether, the impact of the experimental manipulation on both slow event-related potentials and oscillatory EEG activity may reflect coordinated dynamic changes in the excitability of distributed neural networks involved in preparation.

Anterior Cingulate Cortex and Cognitive Control: Neuropsychological and Electrophysiological Findings in Two Patients with Lesions to Dorsomedial Prefrontal Cortex

Authors:

• Marianne Lovstad

• Ingrid Funderud

• Torstein Meling

• Ulrike M. Krämer

• Bradley Voytek

• Paulina Due-Tønnesse

• Tor Endestad

• Magnus Lindgren

• Robert T. Knight

• Anne-Kristin Solbakk

Date: 2012

DOI: 10.1016/j.bandc.2012.07.008

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Abstract:

Whereas neuroimaging studies of healthy subjects have demonstrated an association between the anterior cingulate cortex (ACC) and cognitive control functions, including response monitoring and error detection, lesion studies are sparse and have produced mixed results. Due to largely normal behavioral test results in two patients with medial prefrontal lesions, a hypothesis has been advanced claiming that the ACC is not involved in cognitive operations. In the current study, two comparably rare patients with unilateral lesions to dorsal medial prefrontal cortex (MPFC) encompassing the ACC were assessed with neuropsychological tests as well as Event-Related Potentials in two experimental paradigms known to engage prefrontal cortex (PFC). These included an auditory Novelty Oddball task and a visual Stop-signal task. Both patients performed normally on the Stroop test but showed reduced performance on tests of learning and memory. Moreover, altered attentional control was reflected in a diminished Novelty P3, whereas the posterior P3b to target stimuli was present in both patients. The error-related negativity, which has been hypothesized to be generated in the ACC, was present in both patients, but alterations of inhibitory behavior were observed. Although interpretative caution is generally called for in single case studies, and the fact that the lesions extended outside the ACC, the findings nevertheless suggest a role for MPFC in cognitive control that is not restricted to error monitoring.

Contribution of Subregions of Human Frontal Cortex to Novelty Processing

Authors:

• Marianne Lovstad

• Ingrid Funderud

• Magnus Lindgren

• Tor Endestad

• Paulina Due-Tønnesse

• Torstein Meling

• Bradley Voytek

• Robert T. Knight

• Anne-Kristin Solbakk

Date: 2012

DOI: 10.1162/jocn_a_00099

PubMed: 21812562

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Abstract:

Novelty processing was studied in patients with lesions centered in either OFC or lateral pFC (LPFC). An auditory novelty oddball ERP paradigm was applied with environmental sounds serving as task irrelevant novel stimuli. Lesions to the LPFC as well as the OFC resulted in a reduction of the frontal Novelty P3 response, supporting a key role of both frontal subdivisions in novelty processing. The posterior P3b to target sounds was unaffected in patients with frontal lobe lesions in either location, indicating intact posterior cortical target detection mechanisms. LPFC patients displayed an enhanced sustained negative slow wave (NSW) to novel sounds not observed in OFC patients, indicating prolonged resource allocation to task-irrelevant stimuli after LPFC damage. Both patient groups displayed an enhanced NSW to targets relative to controls. However, there was no difference in behavior between patients and controls suggesting that the enhanced NSW to targets may index an increased resource allocation to response requirements enabling comparable performance in the frontal lesioned patients. The current findings indicate that the LPFC and OFC have partly shared and partly differential contributions to the cognitive subcomponents of novelty processing.

Executive functions after orbital or lateral prefrontal lesions: neuropsychological profiles and self-reported executive functions in everyday living

Authors:

• Marianne Lovstad

• Ingrid Funderud

• Tor Endestad

• Paulina Due-Tønnesse

• Torstein Meling

• Magnus Lindgren

• Robert T. Knight

• Anne-Kristin Solbakk

Date: 2012

DOI: 10.3109/02699052.2012.698787

PubMed: 22731818

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Abstract:

OBJECTIVE: This study examined the effects of chronic focal lesions to the lateral prefrontal cortex (LPFC) or orbitofrontal cortex (OFC) on neuropsychological test performance and self-reported executive functioning in everyday living. METHODS: Fourteen adults with OFC lesions were compared to 10 patients with LPFC injuries and 21 healthy controls. Neuropsychological tests with emphasis on measures of cognitive executive function were administered along with the Behavior Rating Inventory of Executive Functions (BRIEF-A) and a psychiatric screening instrument. RESULTS: The LPFC group differed from healthy controls on neuropsychological tests of sustained mental effort, response inhibition, working memory and mental switching, while the BRIEF-A provided more clinically important information on deficits in everyday life in the OFC group compared to the LPFC group. Correlations between neuropsychological test results and BRIEF-A were weak, while the BRIEF-A correlated strongly with emotional distress. CONCLUSIONS: It was demonstrated that LPFC damage is particularly prone to cause cognitive executive deficit, while OFC injury is more strongly associated with self-reported dysexecutive symptoms in everyday living. The study illustrates the challenge of identifying executive deficit in individual patients and the lack of strong anatomical specificity of the currently employed methods. There is a need for an integrative methodological approach where standard testing batteries are supplemented with neuropsychiatric and frontal-specific rating scales.

Detecting violations of sensory expectancies following cerebellar degeneration: a mismatch negativity study

Authors:

• Torgeir Moberget

• Christina M. Karns

• Leon Y. Deouell

• Magnus Lindgren

• Robert T. Knight

• Richard B. Ivry

Date: 2008

DOI: 10.1016/j.neuropsychologia.2008.03.016

PubMed: 18486157

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Abstract:

Two hypotheses concerning cerebellar function and predictive behavior are the sensory prediction hypothesis and the timing hypothesis. The former postulates that the cerebellum is critical in generating expectancies regarding forthcoming sensory information. The latter postulates that this structure is critical in generating expectancies that are precisely timed; for example, the expected duration of an event or the time between events. As such, the timing hypothesis constitutes a more specific form of prediction. The present experiment contrasted these two hypotheses by examining the mismatch negativity (MMN) response in patients with cerebellar cortical atrophy and matched controls. While watching a silent movie, a stream of task-irrelevant sounds was presented. A standard sound was presented 60% of the time, whereas the remaining sounds deviated from the standard on one of four dimensions: duration, intensity, pitch, or location. The timing between stimuli was either periodic or aperiodic. Based on the sensory prediction hypothesis, the MMN for the patients should be abnormal across all four dimensions. In contrast, the timing hypothesis would predict a selective impairment of the duration MMN. Moreover, the timing hypothesis would also predict that the enhancement of the MMN observed in controls when the stimuli are presented periodically should be attenuated in the patients. Compared to controls, the patients exhibited a delayed latency in the MMN to duration deviants and a similar trend for the intensity deviants, while pitch and location MMNs did not differ between groups. Periodicity had limited and somewhat inconsistent effects. The present results are at odds with a general role for the cerebellum in sensory prediction and provide partial support for the timing hypothesis.