David Friedman | Columbia University (original) (raw)

Papers by David Friedman

Neuropsychiatry, neuropsychology, and behavioral neurology, 1997

The hallmark symptom in probable Alzheimer's disease (PAD) is dramatic difficulty in storing ... more The hallmark symptom in probable Alzheimer's disease (PAD) is dramatic difficulty in storing and/or retrieving new information on tests of explicit or direct memory. However, in many studies of implicit or indirect memory, these same patients show repetition-priming magnitudes (i.e., facilitation of performance on the basis of previous experience) similar to that of normal controls. Recent studies of repetition priming have shown that PAD subjects have an intact event-related potential (ERP) repetition effect, which is thought to index indirect memory functioning. The present study was designed to test the effect of multiple repetitions of verbal stimuli on the ERPs of PAD patients. ERPs were recorded from 8 subjects with PAD, 8 age-matched elderly and 16 young healthy controls. Subjects were asked to make speeded but accurate choice responses to infrequently occurring animal words and frequently occurring nonanimal words, some of which repeated across three blocks of trials. Al...

Psychophysiology, 1994

A hypothesis of overfocused attention in obsessive‐compulsive disorder was investigated by measur... more A hypothesis of overfocused attention in obsessive‐compulsive disorder was investigated by measuring auditory event‐related potentials (ERPs) during a selective attention task. Unmedicated patients (n= 18) with this disorder showed significantly larger attention‐related processing negativity (PN), with earlier onset and longer duration, than did normal controls (n= 15). In the N200 region (160–250 ms), PN was larger in patients with fewer nonspecific neurological soft signs. This task, however, did not yield any group differences in mismatch negativity (N2a) or classical N200 (N2b). P300 amplitudes for attended targets were smaller for patient than normal groups, but the reverse was true for P300 and positive slow wave amplitudes for unattended nontargets. Collectively, these ERP abnormalities suggest a misallocation of cognitive resources. Because of the importance of the frontal lobe in the control of selective attention, PN enhancement in patients with obsessive‐compulsive disord...

Psychophysiology, 2003

The novelty P3 is an event-related potential component that is most often elicited by environment... more The novelty P3 is an event-related potential component that is most often elicited by environmental sounds within the "novelty oddball" paradigm. Within the context of this paradigm, it is not clear if the novelty P3 can be elicited by deviant stimuli regardless of whether they serve as target or nontarget deviants, or to what extent the physical characteristics of the stimulus contributes to the amplitude of the novelty P3. The current study examines this issue by systematically switching target and nontarget deviants between environmental sounds and tonal stimuli. Participants were 36 young adults. Auditory stimuli were 48 unique tones and 48 unique environmental sounds presented under three experimental conditions. The results showed that target and nontarget deviants elicited novelty P3s with anterior and posterior aspects. The major determinant of the extent of the anterior aspect was the degree of difference between the physical characteristics of the deviant stimuli and the standards. By contrast, the major determinant of the posterior aspect was the task relevance of the deviant stimuli.

Psychophysiology, 2010

According to the dual-mechanisms of cognitive control framework (DMC), older adults rely predomin... more According to the dual-mechanisms of cognitive control framework (DMC), older adults rely predominantly on reactive as opposed to proactive control. As a result, we expected elevated response conflict for older relative to younger adults with increasing task difficulty. Response-locked ERP activity was examined separately for fast and slow responses (representing proactive and reactive control, respectively) at low, medium, and high levels of difficulty. Older adults recruited reactive control more often than the young, as reflected by increased behavioral costs and enhanced pre-response negativity (PRN). No age differences in conflict detection (medial frontal negativity, MFN) were evident at low levels of difficulty, but response conflict increased along with difficulty for older adults. These data provide empirical support for the DMC suggesting that aging is associated with a less efficient reactive-control mode of processing.

NeuroImage, 2009

The auditory oddball task is a well-studied stimulus paradigm used to investigate the neural corr... more The auditory oddball task is a well-studied stimulus paradigm used to investigate the neural correlates of simple target detection. It elicits several classic event-related potentials (ERPs), the most prominent being the P300 which is seen as a neural correlate of subjects' detection of rare (target) stimuli. Though trial-averaging is typically used to identify and characterize such ERPs, their latency and amplitude can vary on a trial-to-trial basis reflecting variability in the underlying neural information processing. Here we simultaneously recorded EEG and fMRI during an auditory oddball task and identified cortical areas correlated with the trial-to-trial variability of task-discriminating EEG components. Unique to our approach is a linear multivariate method for identifying taskdiscriminating components within specific stimulus-or response-locked time windows. We find fMRI activations indicative of distinct processes that contribute to the single-trial variability during target detection. These regions are different from those found using standard, including trialaveraged, regressors. Of particular note is strong activation of the lateral occipital complex (LOC). The LOC was not seen when using traditional event-related regressors. Though LOC is typically associated with visual/spatial attention, its activation in an auditory oddball task, where attention can wax and wane from trial-to-trial, indicates it may be part of a more general attention network involved in allocating resources for target detection and decision making. Our results show that trial-to-trial variability in EEG components, acquired simultaneously with fMRI, can yield task-relevant BOLD activations that are otherwise unobservable using traditional fMRI analysis.

Neurobiology of Aging, 2002

Young (M ϭ 22) and elderly volunteers (M ϭ 74) participated in an ERP study that examined rule-ba... more Young (M ϭ 22) and elderly volunteers (M ϭ 74) participated in an ERP study that examined rule-based feature abstraction in the auditory modality. Stimuli were either a frequent ascending tone pair or an infrequent descending tone pair. Tone-pairs were presented under three conditions. Physical feature monaural (1 tone pair), abstract feature monaural (10 tone pairs), and abstract feature binaural (10 tone pairs). Volunteers watched a silent movie during ERP recordings. After completion of the ERP session all volunteers participated in a behavioral discrimination task. MMNs were elicited under all three conditions for the young. For the elderly, MMNs were elicited under both monaural conditions but not under binaural conditions. Behavioral discrimination was high under the physical feature condition but fell to near chance under the two rule-based feature conditions for both age groups. Thus rule-based neural representations were generated for both age groups under monaural conditions, but only for the young under binaural conditions, suggesting that there is an age-related decline in the efficacy of integrating multiple sources into a single auditory stream.

Human Brain Mapping, 2009

An important function of the brain's orienting response is to enable the evaluation of novel, env... more An important function of the brain's orienting response is to enable the evaluation of novel, environmental events in order to prepare for potential behavioral action. Here, we assessed the eventrelated hemodynamic (erfMRI) correlates of this phenomenon using unexpected (i.e., novel) environmental sounds presented within the context of an auditory novelty oddball paradigm. In ERP investigations of the novelty oddball, repetition of the identical novel sound leads to habituation of the novelty P3, an ERP sign of the orienting response. Repetition also leads to an enhancement of a subsequent positivity that appears to reflect semantic analysis of the environmental sounds. In this adaptation for erfMRI recording, frequent tones were intermixed randomly with infrequent target tones and equally infrequent novel, environmental sounds. Subjects responded via speeded button press to targets. To assess habituation, some of the environmental sounds were repeated two blocks after their initial presentation. As expected, novel sounds and target tones led to activation of widespread, but somewhat different, neural networks. Contrary to expectation, however, there were no significant areas in which activation was reduced in response to second compared to first presentations of the novel sounds. Conversely, novel sounds relative to target tones engendered activity in the inferior frontal gyrus (BA 45) consistent with semantic analysis of these events. We conclude that a key concomitant of the orienting response is the extraction of meaning, thereby enabling one to determine the significance of the environmental perturbation and take appropriate goal-directed action.

Brain Research, 2011

Behavioral studies show that no-longer-relevant information, although presumably removed from wor... more Behavioral studies show that no-longer-relevant information, although presumably removed from working memory (WM), still engenders proactive interference (PI). However, the timing of selecting items within WM and resolving PI is relatively unknown. To assess this, we recorded ERPs during WM from 20 young adults. In all conditions, a 4-digit display was followed by a cue indicating which digits to remember. In the selection condition, 2 digits were cued. The reaction time difference between the intrusion probe, a match of a to-be-rejected digit, and the non-intrusion probe, which did not match any of the 4 digits, was reliable, indicating a robust effect of PI. In the neutral-2 (remember 2 digits) and −4 (remember all 4) conditions, participants maintained the digits following the cue. Relative to neutral-4, selection elicited larger positivity at parietal sites (approximately 260 ms) and negativity at frontal sites (approximately 420 ms). Relative to the non-intrusion probe ERP, that to the intrusion probe was more negative over frontal scalp (approximately 500 ms). We conclude that initial selection occurs over parietal cortex and reflects top-down attention to task relevant items, whereas the subsequent negativity may reflect inhibition of no-longer-relevant items over frontal cortex. The probe-locked ERPs suggest that the frontal negativity (approximately 500 ms) reflects the final resolution of PI.

Brain Research, 2008

A critical function of the brain's orienting response is to evaluate novel environmental events i... more A critical function of the brain's orienting response is to evaluate novel environmental events in order to prepare for potential behavioral action. Here, measures of synchronization (power, coherence) and nonlinear cross-frequency phase coupling (m:n phase locking measured with bicoherence and crossbicoherence) were computed on 62-channel electroencephalographic (EEG) data during a paradigm in which unexpected, highly-deviant, novel sounds were randomly intermixed with frequent standard and infrequent target tones. Low frequency resolution analyses showed no significant changes in phase coupling for any stimulus type, though significant changes in power and synchrony did occur. High frequency resolution analyses, on the other hand, showed significant differences in phase coupling, but only for novel sounds compared to standard tones. Novel sounds elicited increased power and coherence in the delta band together with m:n phase locking (bicoherence) of delta:theta (1:3) and delta:alpha (1:4) rhythms in widespread fronto-central, right parietal, temporal, and occipital regions. Cross-bicoherence revealed that globally synchronized delta oscillations were phase coupled to theta oscillations in central regions and to alpha oscillations in right parietal and posterior regions. These results suggest that globally synchronized low frequency oscillations with phase coupling to more localized higher frequency oscillations provide a neural mechanism for the orienting response.

Biological Psychology, 1990

Event-related brain potentials (ERPs) were recorded from 10 young adults during a version of the ... more Event-related brain potentials (ERPs) were recorded from 10 young adults during a version of the continuous recognition memory paradigm. Words were presented after lags of either 2, 8 or 32 intervening items (equiprobable) following their first presentation, and subjects were required on each trial to make a choice: new (never presented previously) or old (previously presented) response. To assess the effect of probability of new to old items, words were presented in separate blocks with ratios of new to old of 2:1 and 1:1. Reaction time increased and successful recognition decreased systematically as the lag between first and second presentations of an item increased, supporting the distinction between primary (immediate memory) and secondary memory for verbal material. However, there were no systematic effects of item lag on the ERP components. ERPs to new items were characterized by larger N300 and smaller P300 amplitudes (from about 250 to 700 ms) than those to old items. These amplitude differences between old and new ERPs were interpreted as primarily reflecting repetition as opposed to semantic priming effects. These old/new effects did not interact with probability, suggesting that frequency of occurrence is not a major determinant the ERP old/new difference. Old items elicited a late negativity following the behavioral response that was interpreted as due to the presence of a "positive slow wave," with a frontally oriented distribution to new words that was absent in the ERPs to old words. Similarly, subtraction of ERPs elicited by new items that were subsequently unrecognized from those subsequently recognized, showed that underlying the ERP subsequent "memory effect" was a "frontal positive slow wave," dissociable from P300 on the basis of differences in scalp distribution. Since positive slow wave has been interpreted as reflecting "further processing," the data suggest that such processing, possibly similar to elaboration (Graf & Mandler, 1984), enhanced the probability of subsequent recognition.

Biological Psychiatry, 1992

Cerebral laterality in bipolar and unipolar major depression was compared using visual half-field... more Cerebral laterality in bipolar and unipolar major depression was compared using visual half-field and dichotic listening measures of perceptual asymmetry. The results replicate our prior finding of abnormal laterality in bipolar depressed patients on a visuospatial test. Bipolar patients (n-11) failed to show the left visual field (right hemisphere) advantage for dot enumeration seen for both unipolar patients (n-43) and normal controls (n = 24). Bipolar patients performed signi~cantly poorer than unipolar patients on normal controls for left visual field, but not right visual field stimuli. An electrophysiological correlate of abnormal visual field asymmetry in bipolar depression was found in brain event-related potentials recorded during audiospatial and temporal discrimination tasks. Bipolar patients had smaller NIO0 amplitudes for test stimuli in the left than right hemifieid, whereas unipolar patients and normals did not. The origins of left hemifield deficits in bipolar depression are discussed in terms of right-sided dysfunction of an arousal/attentional system involving temporoparietal and possibly frontal regions.

International Journal of Psychophysiology, 1999

Impairments of recognition memory for words and attenuation of the ERP 'old᎐new' effect have been... more Impairments of recognition memory for words and attenuation of the ERP 'old᎐new' effect have been found in patients with left medial temporal lobe damage. If left temporal lobe dysfunction in schizophrenia involves medial Ž. structures e.g. hippocampus , then schizophrenic patients might show similar abnormalities of verbal recognition memory. This study recorded ERPs from 30 electrode sites while subjects were engaged in a continuous word Ž. recognition memory task. Results are reported for 24 patients having a diagnosis of schizophrenia n 16 or Ž. schizoaffective disorder n 8 and 19 age-matched healthy controls. Both patients and controls showed the expected 'old᎐new' effect, with greater late positivity to correctly recognized old words at posterior sites, and there was also no significant difference between groups in P3 amplitude. However, accuracy of word recognition memory was poorer in patients than controls, and patients showed markedly smaller N2 amplitude. Reduced amplitudes of N2 Ž. and N2᎐P3 were associated with poorer performance, with highest correlations over the left inferior parietal N2 Ž. and left medial parietal N2᎐P3 region. Moreover, patients failed to show significantly greater left than right

NeuroImage, 2009

The auditory oddball task is a well-studied stimulus paradigm used to investigate the neural corr... more The auditory oddball task is a well-studied stimulus paradigm used to investigate the neural correlates of simple target detection. It elicits several classic event-related potentials (ERPs), the most prominent being the P300 which is seen as a neural correlate of subjects' detection of rare (target) stimuli. Though trial-averaging is typically used to identify and characterize such ERPs, their latency and amplitude can vary on a trial-to-trial basis reflecting variability in the underlying neural information processing. Here we simultaneously recorded EEG and fMRI during an auditory oddball task and identified cortical areas correlated with the trial-to-trial variability of task-discriminating EEG components. Unique to our approach is a linear multivariate method for identifying taskdiscriminating components within specific stimulus-or response-locked time windows. We find fMRI activations indicative of distinct processes that contribute to the single-trial variability during target detection. These regions are different from those found using standard, including trialaveraged, regressors. Of particular note is strong activation of the lateral occipital complex (LOC). The LOC was not seen when using traditional event-related regressors. Though LOC is typically associated with visual/spatial attention, its activation in an auditory oddball task, where attention can wax and wane from trial-to-trial, indicates it may be part of a more general attention network involved in allocating resources for target detection and decision making. Our results show that trial-to-trial variability in EEG components, acquired simultaneously with fMRI, can yield task-relevant BOLD activations that are otherwise unobservable using traditional fMRI analysis.

Biological Psychiatry, 1992

Cerebral laterality in bipolar and unipolar major depression was compared using visual half-field... more Cerebral laterality in bipolar and unipolar major depression was compared using visual half-field and dichotic listening measures of perceptual asymmetry. The results replicate our prior finding of abnormal laterality in bipolar depressed patients on a visuospatial test. Bipolar patients (n -11) failed to show the left visual field (right hemisphere) advantage for dot enumeration seen for both unipolar patients (n -43) and normal controls ( n = 24). Bipolar patients performed signi~cantly poorer than unipolar patients on normal controls for left visual field, but not right visual field stimuli. An electrophysiological correlate of abnormal visual field asymmetry in bipolar depression was found in brain event-related potentials recorded during audiospatial and temporal discrimination tasks. Bipolar patients had smaller NIO0 amplitudes for test stimuli in the left than right hemifieid, whereas unipolar patients and normals did not. The origins of left hemifield deficits in bipolar depression are discussed in terms of right-sided dysfunction of an arousal/attentional system involving temporoparietal and possibly frontal regions.

Biological Psychiatry, 1991

P3 latency, a brain event-related potential CERP~ correlate of stimulus evak~ation time, was meas... more P3 latency, a brain event-related potential CERP~ correlate of stimulus evak~ation time, was measured in 25 unmedk-ated depressed patients and 27 normal con-~ ='~.s d:~,';,,8 auditor 3, temporal and spatial discrimination tasks. Patients were divided into two subgroups, one having a a.,pical major depression (melancholia or simple mood reactive ~epressiom and one having an aO,pical depression. Typical depressives had abnorma~b¢ long P3 latency for the spatial task but not the temporal task. The)" also showed an abnormal lateral ao, mmeto', with longer P3 latency for stimuli in the right hemifieM than the left. In contrast, atypical depressives did not differ from normals in either respect. Longer P3 latency correlated with ratings of insomnia, while abnormal lateral ao'mmetr3' correlated with reduced right visual field advantage for ~qlables. The P3 latenc3' findings point to a task-related slowing of perceptual decisions in a subgroup of depression.

… and Clinical Neurophysiology/ …

In this overview of 7 studies, the scalp distribution of the P3b component (i.e. the P3 or P300) ... more In this overview of 7 studies, the scalp distribution of the P3b component (i.e. the P3 or P300) of the event-related potential elicited by target events in young and older adults was assessed. The target P3b data were recorded in either auditory oddball paradigms or in visual study tasks in which orienting activity was manipulated (as a within-subjects variable) in investigations of indirect memory. Some of the studies required choice reaction time responses, whereas others required responses only to the target stimuli. Motor response requirements had a profound effect on the P3b scalp distribution of older but not of younger subjects. The presence of a frontally oriented scalp focus in the topographies of the older adults in most of the tasks described here is consistent with older adults continuing to use prefrontal processes for stimuli that should have already been well encoded and/or categorized. However, although older subjects generally had different P3b scalp distributions than younger subjects, their scalp distributions were modulated similarly by task requirements. These data suggest that similar mechanisms modulate the scalp distribution of P3b in older compared to younger adults. However, in the older adult, these scalp distribution changes in response to task demands are superimposed on a frontally oriented scalp focus due to a putative frontal lobe contribution to target P3b topography.

Journal of Cognitive …, 1995

Behavior Research …, 1998

Surface maps of brain activity can be obtained with electrophysiological and optical recordings. ... more Surface maps of brain activity can be obtained with electrophysiological and optical recordings. However, there are no established methods for determining the reliability of maps of brain activity across subject groups or across tasks within the same subject. In this paper, we use bootstrapping to establish the reliability of the locations of maxima in maps of surface brain activity of individual subjects obtained with ERP and optical (EROS) recordings and report sample analyses for two data sets. Bootstrapping is a nonparametric method for estimating statistical accuracy from the data in a single sample. The distribution of the statistic of interest is estimated by constructing "bootstrap samples" from a pool of all available cases (with replacement). Many "bootstrap replications" are obtained by calculating the statistic of interest for each sample. In the case of brain activity, many (e.g., 10,000) amplitude distributions can be derived from the data of an individual subject. Frequency counts are then computed for each recording location to establish how many times that location corresponds to a maximum. The value obtained in this fashion represents an estimate of the reliability of the observation.

Neuropsychiatry, neuropsychology, and behavioral neurology, 1997

The hallmark symptom in probable Alzheimer's disease (PAD) is dramatic difficulty in storing ... more The hallmark symptom in probable Alzheimer's disease (PAD) is dramatic difficulty in storing and/or retrieving new information on tests of explicit or direct memory. However, in many studies of implicit or indirect memory, these same patients show repetition-priming magnitudes (i.e., facilitation of performance on the basis of previous experience) similar to that of normal controls. Recent studies of repetition priming have shown that PAD subjects have an intact event-related potential (ERP) repetition effect, which is thought to index indirect memory functioning. The present study was designed to test the effect of multiple repetitions of verbal stimuli on the ERPs of PAD patients. ERPs were recorded from 8 subjects with PAD, 8 age-matched elderly and 16 young healthy controls. Subjects were asked to make speeded but accurate choice responses to infrequently occurring animal words and frequently occurring nonanimal words, some of which repeated across three blocks of trials. Al...

Psychophysiology, 1994

A hypothesis of overfocused attention in obsessive‐compulsive disorder was investigated by measur... more A hypothesis of overfocused attention in obsessive‐compulsive disorder was investigated by measuring auditory event‐related potentials (ERPs) during a selective attention task. Unmedicated patients (n= 18) with this disorder showed significantly larger attention‐related processing negativity (PN), with earlier onset and longer duration, than did normal controls (n= 15). In the N200 region (160–250 ms), PN was larger in patients with fewer nonspecific neurological soft signs. This task, however, did not yield any group differences in mismatch negativity (N2a) or classical N200 (N2b). P300 amplitudes for attended targets were smaller for patient than normal groups, but the reverse was true for P300 and positive slow wave amplitudes for unattended nontargets. Collectively, these ERP abnormalities suggest a misallocation of cognitive resources. Because of the importance of the frontal lobe in the control of selective attention, PN enhancement in patients with obsessive‐compulsive disord...

Psychophysiology, 2003

The novelty P3 is an event-related potential component that is most often elicited by environment... more The novelty P3 is an event-related potential component that is most often elicited by environmental sounds within the "novelty oddball" paradigm. Within the context of this paradigm, it is not clear if the novelty P3 can be elicited by deviant stimuli regardless of whether they serve as target or nontarget deviants, or to what extent the physical characteristics of the stimulus contributes to the amplitude of the novelty P3. The current study examines this issue by systematically switching target and nontarget deviants between environmental sounds and tonal stimuli. Participants were 36 young adults. Auditory stimuli were 48 unique tones and 48 unique environmental sounds presented under three experimental conditions. The results showed that target and nontarget deviants elicited novelty P3s with anterior and posterior aspects. The major determinant of the extent of the anterior aspect was the degree of difference between the physical characteristics of the deviant stimuli and the standards. By contrast, the major determinant of the posterior aspect was the task relevance of the deviant stimuli.

Psychophysiology, 2010

According to the dual-mechanisms of cognitive control framework (DMC), older adults rely predomin... more According to the dual-mechanisms of cognitive control framework (DMC), older adults rely predominantly on reactive as opposed to proactive control. As a result, we expected elevated response conflict for older relative to younger adults with increasing task difficulty. Response-locked ERP activity was examined separately for fast and slow responses (representing proactive and reactive control, respectively) at low, medium, and high levels of difficulty. Older adults recruited reactive control more often than the young, as reflected by increased behavioral costs and enhanced pre-response negativity (PRN). No age differences in conflict detection (medial frontal negativity, MFN) were evident at low levels of difficulty, but response conflict increased along with difficulty for older adults. These data provide empirical support for the DMC suggesting that aging is associated with a less efficient reactive-control mode of processing.

NeuroImage, 2009

The auditory oddball task is a well-studied stimulus paradigm used to investigate the neural corr... more The auditory oddball task is a well-studied stimulus paradigm used to investigate the neural correlates of simple target detection. It elicits several classic event-related potentials (ERPs), the most prominent being the P300 which is seen as a neural correlate of subjects' detection of rare (target) stimuli. Though trial-averaging is typically used to identify and characterize such ERPs, their latency and amplitude can vary on a trial-to-trial basis reflecting variability in the underlying neural information processing. Here we simultaneously recorded EEG and fMRI during an auditory oddball task and identified cortical areas correlated with the trial-to-trial variability of task-discriminating EEG components. Unique to our approach is a linear multivariate method for identifying taskdiscriminating components within specific stimulus-or response-locked time windows. We find fMRI activations indicative of distinct processes that contribute to the single-trial variability during target detection. These regions are different from those found using standard, including trialaveraged, regressors. Of particular note is strong activation of the lateral occipital complex (LOC). The LOC was not seen when using traditional event-related regressors. Though LOC is typically associated with visual/spatial attention, its activation in an auditory oddball task, where attention can wax and wane from trial-to-trial, indicates it may be part of a more general attention network involved in allocating resources for target detection and decision making. Our results show that trial-to-trial variability in EEG components, acquired simultaneously with fMRI, can yield task-relevant BOLD activations that are otherwise unobservable using traditional fMRI analysis.

Neurobiology of Aging, 2002

Young (M ϭ 22) and elderly volunteers (M ϭ 74) participated in an ERP study that examined rule-ba... more Young (M ϭ 22) and elderly volunteers (M ϭ 74) participated in an ERP study that examined rule-based feature abstraction in the auditory modality. Stimuli were either a frequent ascending tone pair or an infrequent descending tone pair. Tone-pairs were presented under three conditions. Physical feature monaural (1 tone pair), abstract feature monaural (10 tone pairs), and abstract feature binaural (10 tone pairs). Volunteers watched a silent movie during ERP recordings. After completion of the ERP session all volunteers participated in a behavioral discrimination task. MMNs were elicited under all three conditions for the young. For the elderly, MMNs were elicited under both monaural conditions but not under binaural conditions. Behavioral discrimination was high under the physical feature condition but fell to near chance under the two rule-based feature conditions for both age groups. Thus rule-based neural representations were generated for both age groups under monaural conditions, but only for the young under binaural conditions, suggesting that there is an age-related decline in the efficacy of integrating multiple sources into a single auditory stream.

Human Brain Mapping, 2009

An important function of the brain's orienting response is to enable the evaluation of novel, env... more An important function of the brain's orienting response is to enable the evaluation of novel, environmental events in order to prepare for potential behavioral action. Here, we assessed the eventrelated hemodynamic (erfMRI) correlates of this phenomenon using unexpected (i.e., novel) environmental sounds presented within the context of an auditory novelty oddball paradigm. In ERP investigations of the novelty oddball, repetition of the identical novel sound leads to habituation of the novelty P3, an ERP sign of the orienting response. Repetition also leads to an enhancement of a subsequent positivity that appears to reflect semantic analysis of the environmental sounds. In this adaptation for erfMRI recording, frequent tones were intermixed randomly with infrequent target tones and equally infrequent novel, environmental sounds. Subjects responded via speeded button press to targets. To assess habituation, some of the environmental sounds were repeated two blocks after their initial presentation. As expected, novel sounds and target tones led to activation of widespread, but somewhat different, neural networks. Contrary to expectation, however, there were no significant areas in which activation was reduced in response to second compared to first presentations of the novel sounds. Conversely, novel sounds relative to target tones engendered activity in the inferior frontal gyrus (BA 45) consistent with semantic analysis of these events. We conclude that a key concomitant of the orienting response is the extraction of meaning, thereby enabling one to determine the significance of the environmental perturbation and take appropriate goal-directed action.

Brain Research, 2011

Behavioral studies show that no-longer-relevant information, although presumably removed from wor... more Behavioral studies show that no-longer-relevant information, although presumably removed from working memory (WM), still engenders proactive interference (PI). However, the timing of selecting items within WM and resolving PI is relatively unknown. To assess this, we recorded ERPs during WM from 20 young adults. In all conditions, a 4-digit display was followed by a cue indicating which digits to remember. In the selection condition, 2 digits were cued. The reaction time difference between the intrusion probe, a match of a to-be-rejected digit, and the non-intrusion probe, which did not match any of the 4 digits, was reliable, indicating a robust effect of PI. In the neutral-2 (remember 2 digits) and −4 (remember all 4) conditions, participants maintained the digits following the cue. Relative to neutral-4, selection elicited larger positivity at parietal sites (approximately 260 ms) and negativity at frontal sites (approximately 420 ms). Relative to the non-intrusion probe ERP, that to the intrusion probe was more negative over frontal scalp (approximately 500 ms). We conclude that initial selection occurs over parietal cortex and reflects top-down attention to task relevant items, whereas the subsequent negativity may reflect inhibition of no-longer-relevant items over frontal cortex. The probe-locked ERPs suggest that the frontal negativity (approximately 500 ms) reflects the final resolution of PI.

Brain Research, 2008

A critical function of the brain's orienting response is to evaluate novel environmental events i... more A critical function of the brain's orienting response is to evaluate novel environmental events in order to prepare for potential behavioral action. Here, measures of synchronization (power, coherence) and nonlinear cross-frequency phase coupling (m:n phase locking measured with bicoherence and crossbicoherence) were computed on 62-channel electroencephalographic (EEG) data during a paradigm in which unexpected, highly-deviant, novel sounds were randomly intermixed with frequent standard and infrequent target tones. Low frequency resolution analyses showed no significant changes in phase coupling for any stimulus type, though significant changes in power and synchrony did occur. High frequency resolution analyses, on the other hand, showed significant differences in phase coupling, but only for novel sounds compared to standard tones. Novel sounds elicited increased power and coherence in the delta band together with m:n phase locking (bicoherence) of delta:theta (1:3) and delta:alpha (1:4) rhythms in widespread fronto-central, right parietal, temporal, and occipital regions. Cross-bicoherence revealed that globally synchronized delta oscillations were phase coupled to theta oscillations in central regions and to alpha oscillations in right parietal and posterior regions. These results suggest that globally synchronized low frequency oscillations with phase coupling to more localized higher frequency oscillations provide a neural mechanism for the orienting response.

Biological Psychology, 1990

Event-related brain potentials (ERPs) were recorded from 10 young adults during a version of the ... more Event-related brain potentials (ERPs) were recorded from 10 young adults during a version of the continuous recognition memory paradigm. Words were presented after lags of either 2, 8 or 32 intervening items (equiprobable) following their first presentation, and subjects were required on each trial to make a choice: new (never presented previously) or old (previously presented) response. To assess the effect of probability of new to old items, words were presented in separate blocks with ratios of new to old of 2:1 and 1:1. Reaction time increased and successful recognition decreased systematically as the lag between first and second presentations of an item increased, supporting the distinction between primary (immediate memory) and secondary memory for verbal material. However, there were no systematic effects of item lag on the ERP components. ERPs to new items were characterized by larger N300 and smaller P300 amplitudes (from about 250 to 700 ms) than those to old items. These amplitude differences between old and new ERPs were interpreted as primarily reflecting repetition as opposed to semantic priming effects. These old/new effects did not interact with probability, suggesting that frequency of occurrence is not a major determinant the ERP old/new difference. Old items elicited a late negativity following the behavioral response that was interpreted as due to the presence of a "positive slow wave," with a frontally oriented distribution to new words that was absent in the ERPs to old words. Similarly, subtraction of ERPs elicited by new items that were subsequently unrecognized from those subsequently recognized, showed that underlying the ERP subsequent "memory effect" was a "frontal positive slow wave," dissociable from P300 on the basis of differences in scalp distribution. Since positive slow wave has been interpreted as reflecting "further processing," the data suggest that such processing, possibly similar to elaboration (Graf & Mandler, 1984), enhanced the probability of subsequent recognition.

Biological Psychiatry, 1992

Cerebral laterality in bipolar and unipolar major depression was compared using visual half-field... more Cerebral laterality in bipolar and unipolar major depression was compared using visual half-field and dichotic listening measures of perceptual asymmetry. The results replicate our prior finding of abnormal laterality in bipolar depressed patients on a visuospatial test. Bipolar patients (n-11) failed to show the left visual field (right hemisphere) advantage for dot enumeration seen for both unipolar patients (n-43) and normal controls (n = 24). Bipolar patients performed signi~cantly poorer than unipolar patients on normal controls for left visual field, but not right visual field stimuli. An electrophysiological correlate of abnormal visual field asymmetry in bipolar depression was found in brain event-related potentials recorded during audiospatial and temporal discrimination tasks. Bipolar patients had smaller NIO0 amplitudes for test stimuli in the left than right hemifieid, whereas unipolar patients and normals did not. The origins of left hemifield deficits in bipolar depression are discussed in terms of right-sided dysfunction of an arousal/attentional system involving temporoparietal and possibly frontal regions.

International Journal of Psychophysiology, 1999

Impairments of recognition memory for words and attenuation of the ERP 'old᎐new' effect have been... more Impairments of recognition memory for words and attenuation of the ERP 'old᎐new' effect have been found in patients with left medial temporal lobe damage. If left temporal lobe dysfunction in schizophrenia involves medial Ž. structures e.g. hippocampus , then schizophrenic patients might show similar abnormalities of verbal recognition memory. This study recorded ERPs from 30 electrode sites while subjects were engaged in a continuous word Ž. recognition memory task. Results are reported for 24 patients having a diagnosis of schizophrenia n 16 or Ž. schizoaffective disorder n 8 and 19 age-matched healthy controls. Both patients and controls showed the expected 'old᎐new' effect, with greater late positivity to correctly recognized old words at posterior sites, and there was also no significant difference between groups in P3 amplitude. However, accuracy of word recognition memory was poorer in patients than controls, and patients showed markedly smaller N2 amplitude. Reduced amplitudes of N2 Ž. and N2᎐P3 were associated with poorer performance, with highest correlations over the left inferior parietal N2 Ž. and left medial parietal N2᎐P3 region. Moreover, patients failed to show significantly greater left than right

NeuroImage, 2009

The auditory oddball task is a well-studied stimulus paradigm used to investigate the neural corr... more The auditory oddball task is a well-studied stimulus paradigm used to investigate the neural correlates of simple target detection. It elicits several classic event-related potentials (ERPs), the most prominent being the P300 which is seen as a neural correlate of subjects' detection of rare (target) stimuli. Though trial-averaging is typically used to identify and characterize such ERPs, their latency and amplitude can vary on a trial-to-trial basis reflecting variability in the underlying neural information processing. Here we simultaneously recorded EEG and fMRI during an auditory oddball task and identified cortical areas correlated with the trial-to-trial variability of task-discriminating EEG components. Unique to our approach is a linear multivariate method for identifying taskdiscriminating components within specific stimulus-or response-locked time windows. We find fMRI activations indicative of distinct processes that contribute to the single-trial variability during target detection. These regions are different from those found using standard, including trialaveraged, regressors. Of particular note is strong activation of the lateral occipital complex (LOC). The LOC was not seen when using traditional event-related regressors. Though LOC is typically associated with visual/spatial attention, its activation in an auditory oddball task, where attention can wax and wane from trial-to-trial, indicates it may be part of a more general attention network involved in allocating resources for target detection and decision making. Our results show that trial-to-trial variability in EEG components, acquired simultaneously with fMRI, can yield task-relevant BOLD activations that are otherwise unobservable using traditional fMRI analysis.

Biological Psychiatry, 1992

Cerebral laterality in bipolar and unipolar major depression was compared using visual half-field... more Cerebral laterality in bipolar and unipolar major depression was compared using visual half-field and dichotic listening measures of perceptual asymmetry. The results replicate our prior finding of abnormal laterality in bipolar depressed patients on a visuospatial test. Bipolar patients (n -11) failed to show the left visual field (right hemisphere) advantage for dot enumeration seen for both unipolar patients (n -43) and normal controls ( n = 24). Bipolar patients performed signi~cantly poorer than unipolar patients on normal controls for left visual field, but not right visual field stimuli. An electrophysiological correlate of abnormal visual field asymmetry in bipolar depression was found in brain event-related potentials recorded during audiospatial and temporal discrimination tasks. Bipolar patients had smaller NIO0 amplitudes for test stimuli in the left than right hemifieid, whereas unipolar patients and normals did not. The origins of left hemifield deficits in bipolar depression are discussed in terms of right-sided dysfunction of an arousal/attentional system involving temporoparietal and possibly frontal regions.

Biological Psychiatry, 1991

P3 latency, a brain event-related potential CERP~ correlate of stimulus evak~ation time, was meas... more P3 latency, a brain event-related potential CERP~ correlate of stimulus evak~ation time, was measured in 25 unmedk-ated depressed patients and 27 normal con-~ ='~.s d:~,';,,8 auditor 3, temporal and spatial discrimination tasks. Patients were divided into two subgroups, one having a a.,pical major depression (melancholia or simple mood reactive ~epressiom and one having an aO,pical depression. Typical depressives had abnorma~b¢ long P3 latency for the spatial task but not the temporal task. The)" also showed an abnormal lateral ao, mmeto', with longer P3 latency for stimuli in the right hemifieM than the left. In contrast, atypical depressives did not differ from normals in either respect. Longer P3 latency correlated with ratings of insomnia, while abnormal lateral ao'mmetr3' correlated with reduced right visual field advantage for ~qlables. The P3 latenc3' findings point to a task-related slowing of perceptual decisions in a subgroup of depression.

… and Clinical Neurophysiology/ …

In this overview of 7 studies, the scalp distribution of the P3b component (i.e. the P3 or P300) ... more In this overview of 7 studies, the scalp distribution of the P3b component (i.e. the P3 or P300) of the event-related potential elicited by target events in young and older adults was assessed. The target P3b data were recorded in either auditory oddball paradigms or in visual study tasks in which orienting activity was manipulated (as a within-subjects variable) in investigations of indirect memory. Some of the studies required choice reaction time responses, whereas others required responses only to the target stimuli. Motor response requirements had a profound effect on the P3b scalp distribution of older but not of younger subjects. The presence of a frontally oriented scalp focus in the topographies of the older adults in most of the tasks described here is consistent with older adults continuing to use prefrontal processes for stimuli that should have already been well encoded and/or categorized. However, although older subjects generally had different P3b scalp distributions than younger subjects, their scalp distributions were modulated similarly by task requirements. These data suggest that similar mechanisms modulate the scalp distribution of P3b in older compared to younger adults. However, in the older adult, these scalp distribution changes in response to task demands are superimposed on a frontally oriented scalp focus due to a putative frontal lobe contribution to target P3b topography.

Journal of Cognitive …, 1995

Behavior Research …, 1998

Surface maps of brain activity can be obtained with electrophysiological and optical recordings. ... more Surface maps of brain activity can be obtained with electrophysiological and optical recordings. However, there are no established methods for determining the reliability of maps of brain activity across subject groups or across tasks within the same subject. In this paper, we use bootstrapping to establish the reliability of the locations of maxima in maps of surface brain activity of individual subjects obtained with ERP and optical (EROS) recordings and report sample analyses for two data sets. Bootstrapping is a nonparametric method for estimating statistical accuracy from the data in a single sample. The distribution of the statistic of interest is estimated by constructing "bootstrap samples" from a pool of all available cases (with replacement). Many "bootstrap replications" are obtained by calculating the statistic of interest for each sample. In the case of brain activity, many (e.g., 10,000) amplitude distributions can be derived from the data of an individual subject. Frequency counts are then computed for each recording location to establish how many times that location corresponds to a maximum. The value obtained in this fashion represents an estimate of the reliability of the observation.