, ,

Affective and cognitive modulation of performance monitoring: behavioral and ERP evidence

, ,

Authors:

  • Emiliana R. Simon-Thomas

  • Robert T. Knight

Date: 2005

PubMed: 16396095

View PDF

Abstract:

This study investigates the effects of negative affect on performance monitoring. EEG was acquired during a lateralized, numeric Stroop working memory task that featured task-irrelevant aversive and neutral pictures between stimuli. Performance accuracy showed a right-hemisphere advantage for stimuli that followed aversive pictures. Response-locked event-related potentials (ERPs) from accurate trials showed an early negative component (CRN; correct response/conflict-related negativity) followed by a positive wave comparable to the Pe (error positivity). The CRN was bi-peaked with an earlier peak that was sensitive to aversive pictures during early portions of the experiment and a later peak that increased with error likelihood later in the experiment. Pe amplitude was increased with aversive pictures early in the experiment and was sensitive to picture type, Stroop interference, and hemisphere of stimulus delivery during later trials. This suggests that ERP indices of performance monitoring, the CRN and Pe, are dynamically modulated by both affective and cognitive demands.

, , , , ,

Temporal kinetics of prefrontal modulation of the extrastriate cortex during visual attention

, , , , ,


Authors:

  • Elena Yago

  • Audrey Duarte

  • Ting Wong

  • Francisco Barceló

  • Robert T. Knight

Date: 2004

PubMed: 15849901

View PDF


Abstract:

Single-unit, event-related potential (ERP), and neuroimaging studies have implicated the prefrontal cortex (PFC) in top-down control of attention and working memory. We conducted an experiment in patients with unilateral PFC damage (n = 8) to assess the temporal kinetics of PFC-extrastriate interactions during visual attention. Subjects alternated attention between the left and the right hemifields in successive runs while they detected target stimuli embedded in streams of repetitive task-irrelevant stimuli (standards). The design enabled us to examine tonic (spatial selection) and phasic (feature selection) PFC-extrastriate interactions. PFC damage impaired performance in the visual field contralateral to lesions, as manifested by both larger reaction times and error rates. Assessment of the extrastriate P1 ERP revealed that the PFC exerts a tonic (spatial selection) excitatory input to the ipsilateral extrastriate cortex as early as 100 msec post stimulus delivery. The PFC exerts a second phasic (feature selection) excitatory extrastriate modulation from 180 to 300 msec, as evidenced by reductions in selection negativity after damage. Finally, reductions of the N2 ERP to target stimuli supports the notion that the PFC exerts a third phasic (target selection) signal necessary for successful template matching during postselection analysis of target features. The results provide electrophysiological evidence of three distinct tonic and phasic PFC inputs to the extrastriate cortex in the initial few hundred milliseconds of stimulus processing. Damage to this network appears to underlie the pervasive deficits in attention observed in patients with prefrontal lesions.

, , , ,

High-field, T2 reversed MRI imaging of the hippocampus in transient global amnesia

, , , ,

Authors:

  • Tsutomu Nakada

  • Ingrid L. Kwee

  • Yukihiko Fujii

  • Robert T. Knight

Date: 2005

PubMed: 15824342

View PDF

Abstract:

OBJECTIVE: To investigate the fine structural integrity of the hippocampus in patients with transient global amnesia (TGA) using high-resolution T2 reversed (T2R) MRI. METHODS: The authors performed detailed structural analysis of the hippocampus in 15 patients who had recovered from an episode of TGA and 150 randomly recruited normal volunteers across the adult age spectrum using high-resolution T2R MRI obtained on a 3.0-T system. An additional 100 subjects, with stroke or tumor, were similarly studied and served as disease controls. RESULTS: The overall incidence of hippocampal cavities detected in normal volunteers increased with age but never exceeded 40%, whereas the incidence in disease control group was 31%. They were always unilateral. In contrast, cavities were found in all 15 patients with TGA (100%), an incidence higher than in normal or disease controls (p < 0.05; Ryan's multiple comparison test), and were bilateral in eight patients (53%). The cavities in all but one of the normal volunteers (99%) and all disease controls (100%) were crescent shaped and < or =2 mm in width. The cavities in 14 of 15 patients with TGA (93%) were considerably larger (>3 mm in width), and five of the patients had giant cavities (>5 mm in width). Most of the cavities in patients with TGA had a rounded shape and resembled pathologic cavities described in specimens of hypoxia-related CA1 necrosis. CONCLUSION: The data indicate that transient global amnesia may not be a benign entity. Delayed neuronal loss within CA1 area of Lorente de No may represent its important sequel.

, , , , , ,

Mild hypoxia disrupts recollection, not familiarity

, , , , , ,

Authors:

  • Andrew P. Yonelinas

  • Joel R. Quamme

  • Keith F. Widaman

  • Neal E. A. Kroll

  • Mary Jane Sauve

  • Robert T. Knight

Date: 2004

PubMed: 15535174

View PDF

Abstract:

Yonelinas et al. (2002) found that hypoxic patients exhibited deficits in recollection that left familiarity relatively unaffected. In contrast, Manns, Hopkins, Reed, Kitchener, and Squire (2003) studied a group of hypoxic patients who suffered severe and equivalent deficits in recollection and familiarity. We reexamine those studies and argue that the discrepancy in results is likely due to differences in the hypoxic groups that were tested (i.e., differences in amnestic severity, subject sampling methods, and patient etiology). Yonelinas et al. examined memory in 56 cardiac arrest patients who suffered a brief hypoxic event, whereas Manns et al. examined a group of severely amnesic patients that consisted of 2 cardiac arrest patients, 2 heroin overdose patients, 1 carbon monoxide poisoning patient, and 2 patients with unknown etiologies. We also consider an alternative explanation proposed by Wixted and Squire (2004), who argued that the two patient groups suffered similar deficits, but that statistical or methodological artifacts distorted the results of each of Yonelinas et al.'s experiments. A consideration of those results, however, indicates that such an explanation does not account for the existing data. All of the existing evidence indicates that recollection, but not familiarity, is disrupted in mild hypoxic patients. In more severe cases of hypoxia, or those with more complex etiologies such as heroin overdose, more profound deficits may be observed.

, , , ,

Rapid Prefrontal-Hippocampal Habituation to Novel Events

, , , ,

Authors:

  • Shuhei Yamaguchi

  • Laura A. Hale

  • Mark D'Esposito

  • Robert T. Knight

Date: 2004

PubMed: 15190108

View PDF

Abstract:

Unexpected novel events generate an orienting response that plays an important role in some forms of learning and memory. The orienting response involuntarily captures attention and rapidly habituates as events become familiarized. Although evidence from patients with focal lesions and scalp and intracranial event-related brain potential recordings supports the involvement of a distributed neural network involving association cortex and the limbic system in novelty detection, the key neural substrates and temporal dynamics have not been defined. While subjects performed a bi-field visual-selective attention task with random novel stimuli embedded in either attended or unattended visual fields, we measured rapid changes of regional blood oxygenation level-dependent (BOLD) signal to target and novel stimuli using single-trial analysis of event-related functional magnetic resonance imaging with a 4T scanner. Habituation was quantified by serial BOLD signal changes during the first 10 novel stimuli for each subject. Novel stimuli activated the bilateral superior/middle frontal gyrus, temporal-parietal junction, superior parietal lobe, cingulate gyrus, hippocampus, and fusiform gyrus. The superior/middle frontal gyrus and hippocampus showed significant reduction of BOLD signal during the first few novel stimuli, whereas the signals in the fusiform and cingulate gyrus were constant. Prefrontal and hippocampal responses to attended and unattended novel stimuli were comparably habituated. These results, and previous data from lesion studies, support the view that prefrontal and hippocampal regions are involved in rapid automatic detection and habituation to unexpected environmental events and are key elements of the orienting response in humans.

, , , , , ,

The impact of orbital prefrontal cortex damage on emotional activation to unanticipated and anticipated acoustic startle stimuli

, , , , , ,

Authors:

  • Nicole A. Roberts

  • Jennifer S. Beer

  • Kelly H. Werner

  • Sara M. Levens

  • Robert T. Knight

  • Robert W. Levenson

Date: 2004

PubMed: 15535166

View PDF

Abstract:

Damage to the orbital prefrontal cortex has been implicated in selectively diminishing electrodermal autonomic nervous system responses to anticipated punishing stimuli (e.g., losing money; Bechara, Damasio, & Damasio, 2000), but not to unanticipated punishing stimuli (e.g., loud noises; Damasio, Tranel, & Damasio, 1990). We extended this research by examining the effects of orbitofrontal damage on emotional responses to unanticipated and anticipated acoustic startles and collecting a more extensive set of physiological measures, emotional facial behavior, and self-reported emotional experience. Consistent with previous research, patients showed intact physiology to an unanticipated startle but failed to show appropriate anticipatory cardiovascular responses (patients' heart rates decreased, controls' increased). In addition, patients displayed more surprise facial behavior and reported marginally more fear than did controls in response to the unanticipated startle. Thus, orbitofrontal damage may compromise the ability to anticipate physiologically the onset of aversive stimuli, despite intact or enhanced emotional responses when such stimuli occur unexpectedly.

, , ,

Subcortical discrimination of unperceived objects during binocular rivalry

, , ,

Authors:

  • Brian Pasley

  • L. C. Mayes

  • R. T. Schultz

Date: 2004

DOI: dx.doi.org/10.1016/S0896-6273(04)00155-2

PubMed: 15066273

View PDF

Abstract:

Rapid identification of behaviorally relevant objects is important for survival. In humans, the neural computations for visually discriminating complex objects involve inferior temporal cortex (IT). However, less detailed but faster form processing may also occur in a phylogenetically older subcortical visual system that terminates in the amygdala. We used binocular rivalry to present stimuli without conscious awareness, thereby eliminating the IT object representation and isolating subcortical visual input to the amygdala. Functional magnetic resonance imaging revealed significant brain activation in the left amygdala but not in object-selective IT in response to unperceived fearful faces compared to unperceived nonface objects. These findings indicate that, for certain behaviorally relevant stimuli, a high-level cortical representation in IT is not required for object discrimination in the amygdala.

, , , ,

Hemispheric asymmetries for kinematic and positional aspects of reaching

, , , ,

Authors:

  • Kathleen Y. Haaland

  • Jillian L. Prestopnik

  • Robert T. Knight

  • Roland R. Lee

Date: 2004

PubMed: 15033898

View PDF

Abstract:

Kinematic analyses of reaching have suggested that the left hemisphere is dominant for controlling the open loop component of the movement, which is more dependent on motor programmes; and the right hemisphere is dominant for controlling the closed loop component, which is more dependent on sensory feedback. This open and closed loop hypothesis of hemispheric asymmetry would also predict that advance planning should be dependent on the left hemisphere, and on-line response modification, which defines closed loop processes, should be dependent on the right hemisphere. Using kinematic analyses of reaching in patients with left or right hemisphere damage (LHD or RHD), we examined the ability: (i) to plan reaching movements in advance by examining changes in reaction time (RT) when response amplitude and visual feedback were cued prior to the response; and (ii) to modify the response during implementation when target location changed at the RT. Performance was compared between the stroke groups, using the ipsilesional arm, and age-matched control groups using their right (RNC) or left (LNC) arm. Aiming movements to a target that moved once or twice, with the second step occurring at the RT, were performed with or without visual feedback of hand position. There were no deficits in advance planning in either stroke group, as evidenced by comparable group changes in RT with changes in amplitude and visual feedback. Response modification deficits were seen for the LHD group in secondary velocity only. In addition, LHD produced slower initial peak velocity with prolongation of the deceleration phase and faster secondary peak velocities, and the RHD group produced deficits in final error only. These differences are more consistent with the dynamic dominance hypothesis, which links left hemisphere specialization to movement trajectory control and right hemisphere specialization to position control, rather than to global deficits in open and closed loop processing.

, , , , ,

Synchronization measures of bursting data: Application to the electrocoricogram of an auditory event-related experiment

, , , , ,

Authors:

  • Mark A. Kramer

  • Erik Edwards

  • Maryam Soltani

  • Mitchel S. Berger

  • Robert T. Knight

  • Andrew J. Szeri

Date: 2004

PubMed: 15324095

View PDF

Abstract:

Synchronization measures have become an important tool for exploring the relationships between time series. We review three recently proposed nonlinear synchronization measures and expand their definitions in a straightforward way to apply to an ensemble of measurements. We also develop a synchronization measure in which nearest neighbors are determined across the ensemble. We compare these four nonlinear synchronization measures and show that our measure succeeds in physically motivated examples where the other methods fail. We apply the synchronization measure to human electrocorticogram data collected during an auditory event-related potential experiment. The results suggest a crude model of cortical connectivity.

, , , , ,

Distributed neural activity during object, spatial and integrated processing in humans

, , , , ,

Authors:

  • Emiliana R. Simon-Thomas

  • Kim Brodsky

  • Cammy Willing

  • Rashmi Sinha

  • Robert T. Knight

Date: 2003

PubMed: 12706225

View PDF

Abstract:

Information about the form and the spatial location of objects is seamlessly integrated during visual perception. We used event-related potentials (ERPs) to explore neural activity related to processing form, location or the combination of both kinds of features. Healthy subjects performed three versions of a 'match-to-sample' task: a two-object task, a two-location task and an integrated object-location task. Responses were quickest and most accurate during the integrated task, slower and less accurate in the two-location task and slowest and least accurate in the two-object task. ERPs locked to the 'sample' stimulus at encoding, and to the 'target' stimulus during feature comparison differentiated between tasks. 'Sample' stimulus ERPs exhibited task-specific posterior cortical involvement in processing distinct visual features. 'Target' stimulus ERPs revealed task-related differences in features associated with frontal lobe mediated attentional processes: an early latency P300 showed increased amplitude during the integrated task. Results from this experiment support the view that distinct neural circuits mediate form vs. location processing and that form-location integration engages both pathways and upregulates frontal-parietal association networks.

, , , ,

Does the representation of time depend on the cerebellum? Effect of cerebellar stroke

, , , ,

Authors:

  • Deborah L. Harrington

  • Roland R. Lee

  • Lara A. Boyd

  • Steven Z. Rapcsak

  • Robert T. Knight

Date: 2004

PubMed: 14711883

View PDF

Abstract:

Behaviours that appear to depend on processing temporal information are frequently disrupted after cerebellar damage. The present study examined the role of the cerebellum in explicit timing and its relationship to other psychological processes. We hypothesized that if the cerebellum regulates timekeeping operations then cerebellar damage should disrupt the perception and the reproduction of intervals, since both are thought to be supported by a common timekeeper mechanism. Twenty-one patients with cerebellar damage from stroke and 30 normal controls performed time perception and time reproduction tasks. In the time reproduction task, timing variability was decomposed into a central timing component (clock variability) and a motor component (motor implementation variability). We found impairments only in time reproduction (increased clock variability) in patients with medial and lateral damage involving the middle- to superior-cerebellar lobules. To explore potential reasons for the temporal processing deficits, time reproduction and perception performance were correlated with independent measures of attention, working memory, sensory discrimination and processing speed. Poorer working memory correlated with increased variability in the 'clock' component of time reproduction. In contrast, processing speed correlated best with time perception. The results did not support a role for the cerebellum in timekeeping operations. Rather, deficits in timing movements may be related to a disruption in acquiring sensory and cognitive information relevant to the task, coupled with an additional impairment in the motor-output system.

, , , , ,

Dissociable neural correlates for familiarity and recollection during the encoding and retrieval of pictures

, , , , ,

Authors:

  • Audrey Duarte

  • Charan Ranganath

  • Laurel Winward

  • Dustin Hayward

  • Robert T. Knight

Date: 2004

PubMed: 14741312

View PDF

Abstract:

Results from behavioral studies have supported the idea that recognition memory can be supported by at least two different processes, recollection and familiarity. However, it remains unclear whether these two forms of memory reflect neurally distinct processes. Furthermore, it is unclear whether recollection and familiarity can be best conceived as differing primarily in terms of retrieval processing, or whether they additionally differ at encoding. To address these issues, we used event-related brain potentials (ERPs) to monitor neural correlates of familiarity and recollection at both encoding and retrieval. Participants studied pictures of objects in two types of study blocks and subsequently made remember-know and source memory judgments during retrieval. Results showed that, during encoding, neural correlates of subsequent familiarity and recollection onsetted in parallel, but exhibited differences in scalp topography and time course. Subsequent familiarity-based recognition was associated with a left-lateralized enhanced positivity and observed at anterior scalp sites from 300 to 450 ms, whereas subsequent recollection was associated with a topographically distinct right-lateralized positivity at anterior scalp sites from 300 to 450 ms and bilateral activity from 450 to 600 ms. During retrieval, neural correlates of familiarity emerged earlier than correlates of recollection. Familiarity was associated with an enhanced positivity at frontopolar scalp sites from 150 to 450 ms, whereas recollection was associated with positive ERP modulations over bilateral frontal (300-600 ms) and parietal (450-800 ms) sites. These results demonstrate that familiarity and recollection reflect the outcome of neurally distinct memory processes at both encoding and retrieval.

, , ,

The regulatory function of self-conscious emotion: insights from patients with orbitofrontal damage

, , ,

Authors:

  • Jennifer S. Beer

  • Erin A. Heerey

  • Dacher Keltner

  • Robert T. Knight

Date: 2003

PubMed: 14561114

View PDF

Abstract:

Although once considered disruptive, self-conscious emotions are now theorized to be fundamentally involved in the regulation of social behavior. The present study examined the social regulation function of self-conscious emotions by comparing healthy participants with a neuropsychological population--patients with orbitofrontal lesions--characterized by selective regulatory deficits. Orbitofrontal patients and healthy controls participated in a series of tasks designed to assess their social regulation and self-conscious emotions. Another task assessed the ability to infer others' emotional states, an appraisal process involved in self-conscious emotion. Consistent with the theory that self-conscious emotions are important for regulating social behavior, the findings show that deficient behavioral regulation is associated with inappropriate self-conscious emotions that reinforce maladaptive behavior. Additionally, deficient behavioral regulation is associated with impairments in interpreting the self-conscious emotions of others.

, , , , , ,

The neural substrates of visual implicit memory: do the two hemispheres play different roles?

, , , , , ,

Authors:

  • Neal E. A. Kroll

  • Andrew P. Yonelinas

  • Mark M. Kishiyama

  • Kathleen Baynes

  • Robert T. Knight

  • Michael S. Gazzaniga

Date: 2003

PubMed: 14511536

View PDF

Abstract:

Identification of visually presented words is facilitated by implicit memory, or visual priming, for past visual experiences with those words. There is disagreement over the neuro-anatomical substrates of this form of implicit memory. Several studies have suggested that this form of priming relies on a visual word-form system localized in the right occipital lobe, whereas other studies have indicated that both hemispheres are equally involved. The discrepancies may be related to the types of priming tasks that have been used because the former studies have relied primarily on word-stem completion tasks and the latter on tasks like word-fragment completion. The present experiments compared word-fragment and word-stem measurements of visual implicit memory in patients with right occipital lobe lesions and patients with complete callosotomies. The patients showed normal visual implicit memory on fragment completion tests, but essentially no visual priming on standard stem completion tests. However, when we used a set of word stems that had only one correct solution for each test item, as was true of the items in the fragment completion tests, the patients showed normal priming effects. The results indicate that visual implicit memory for words is not solely dependent upon the right hemisphere, rather it reflects changes in processing efficiency in bilateral visual regions involved in the initial processing of the items. However, under conditions of high lexical competition (i.e., multiple completion word stems), the lexical processes, which are dominant in the left hemisphere, overshadow the visual priming supported by the left hemisphere.

, , , , ,

Prefrontal cortex and episodic memory: integrating findings from neuropsychology and event-related neuroimaging.

, , , , ,

ABSTRACT

Although it has been speculated for many years that the prefrontal cortex plays a role in long-term memory for events, or episodic memory, only recently have researchers made a concerted attempt to define this role. Most theories of prefrontal function suggest that this region implements “topdown” or “executive” processes that influence a variety of domains, including memory. For example, Luria (1966) postulated a role for the frontal lobes in the regulation of voluntary attention and the organisation of goal-directed behavior. Building on the work of Luria, Shallice (1982) argued that the frontal lobes are required for the attentional selection of schemes of action in novel situations. A complementary role suggested for the prefrontal cortex is the suppression of irrelevant or interfering stimuli (Brutkowski, 1965; Fuster, 1997; Knight, Staines, Swick, & Chao, 1999; Pribram, Ahumada, Hartog, & Roos, 1964; Shimamura, 1995). Teuber (1964) additionally proposed that the frontal lobes prepare sensory areas for environmental changes that will be induced by motor actions. This concept was later extended to include the generation of anticipatory behavioural sets (Fuster, 1997; Nauta, 1971). Several researchers have also postulated a central role for the prefrontal cortex in active, or working memory (Fuster, 1997; Goldman-Rakic, 1987).





AUTHORS

  • Charan Ranganath

  • Robert T. Knight

Date: 2003

ISBN-13: 978-1841692463

ISBN-10: 9781841692463


, , ,

A new ERP paradigm for studying individual differences in the executive control of attention

, , ,

Authors:

  • Francisco Barceló

  • Jose A. Perianìez

  • Robert T. Knight

Date: 2003

View PDF

Abstract:

Event-related potentials (ERPs) provide valuable information about the fast brain dynamics subserving cognitive functions such as atten- tion and working memory. Most ERP studies employ cognitive para- digms with a fixed task-set (i.e., press a button to named targets), but few have measured ERPs time-locked to shifts in set using a task- switching paradigm. The Madrid Card Sorting Test (MCST) is a dual task protocol in which feedback cues signal unpredictable shifts in set (i.e., from “sort cards by colour” to “sort cards by shape”). This pro- tocol offers an integrated analysis of ERPs to both feedback cues and target card events, providing separate ERP indexes for the shifting, updating and rehearsal of attention sets in working memory. Two of these ERP indices are the frontal and posterior aspects of the P300 response. Feedback cues that direct a shift in set also elicit both a frontally distributed P3a potential (300 to 400 ms) and a posteriorly distributed P3b potential (350 to 600 ms). In turn, target card events evoke posterior P3b responses whose amplitude increases as the new task set is gradually rehearsed. In line with current models about the role of prefrontal cortex in the executive control of attention, this P3a/P3b response system appears to reflect the coordinated action of prefrontal and posterior association cortices during the switching and updating of task sets in working memory.

, , , ,

Spatial asymmetries of auditory event-synthesis in humans

, , , ,

Authors:

  • Leon Y. Deouell

  • Christina M. Karns

  • Tamara B. Harrison

  • Robert T. Knight

Date: 2003

PubMed: 12531460

View PDF

Abstract:

We used the mismatch negativity event-related potential to examine how spatial location and feature variation affect the capacity of the auditory system to automatically respond to pairs of rapid (180 ms apart) acoustic changes within a single tone. When a tone first deviated from a standard tone in source location and then in its duration, we found independent responses to both deviations for right but not left field stimuli. In contrast, when the first deviation was in pitch and the second in duration, only the first deviation elicited a response, regardless of presentation side. These results suggest that information from either side of space is asymmetrically processed even in a free-field, and that the extent of the temporal window of integration is not a fixed property of the auditory system.