David Friedman

Episodic priming and memory for temporal source: event-related potentials reveal age-related differences in prefrontal functioning.

Event-related potentials (ERPs) were recorded from young (M = 25) and older (M = 71) adults during a recognition memory paradigm that assessed episodic priming. Participants studied two temporally distinct lists of sentences (each with two unassociated nouns). At test, in response to the nouns, participants made old-new, followed by remember (context)-know (familiarity) and source (i.e., list) judgments. Both young and older adults showed equivalent episodic priming effects. However, compared to the young adults, the older adults showed a greater source performance decrement than item memory performance decrement. Both age groups showed equivalent posterior-maximal old-new ERP effects. However, only the young produced a frontal-maximal, late onset old-new effect that differed as a function of subsequent list attribution. Because source memory is thought to be mediated by prefrontal cortex, we conclude that age-related memory differences may be due to a deficit in a prefrontal cortical system that underlies source memory and are not likely to be due to an age-related decline in episodic priming.

Cognition and Aging: A Highly Selective Overview of Event-Related Potential (ERP) Data

An overview of highly selected cognitive aging investigations of deviance detection, episodic memory and working memory reveals two primary themes: (1) when variability in elderly samples has been assessed, it has proven useful in understanding age-related changes in cognition; and (2) there is a frontal lobe contribution to at least some age-related changes in cognition. However, there are too few ERP age-related investigations of individual differences to determine whether the changes in patterns of ERP responding can be deemed “compensatory” or “inefficient.” It is suggested that, to the extent possible, future electrophysiological investigations of cognitive aging (as well as other physiological measurement techniques) include individual difference measures that will enable the determination of the implication of a given neural pattern in the genesis of a given, age-related behavioral outcome pattern.

Dissociations between memory for temporal order and recognition memory in aging.

Young and old subjects participated in an experiment in which trials testing memory for temporal order (recency memory) and recognition memory were randomly intermixed with study trials in a continuous sequence. A dissociation was found between recency and recognition memory performance for pictorial stimuli. Relative to young adults, older adults performed at chance on recency memory trials whereas they were not impaired on recognition memory. Recency performance was correlated with measures derived from the Wisconsin Card Sorting test, whereas recognition performance was not. The results are discussed in terms of the role of the frontal lobes in temporal-order memory and of possible frontal lobe deterioration in normal aging.

Event-related potentials in depression : influence of task, stimulus hemifield and clinical features on P3 latency

P3 latency, a brain event-related potential (ERP) correlate of stimulus evaluation time, was measured in 25 unmedicated depressed patients and 27 normal controls during auditory temporal and spatial discrimination tasks. Patients were divided into two subgroups, one having a typical major depression (melancholia or simple mood reactive depression) and one having an atypical depression. Typical depressives had abnormally long P3 latency for the spatial task but not the temporal task. They also showed an abnormal lateral asymmetry, with longer P3 latency for stimuli in the right hemifield 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 asymmetry correlated with reduced right visual field advantage for syllables. The P3 latency findings point to a task-related slowing of perceptual decisions in a subgroup of depression.

Event-related potentials in children at risk for schizophrenia during two versions of the continuous performance test

Event-related potentials (ERPs) were recorded from children of schizophrenic parents, children of parents with affective disorders, and children of parents without a history of psychiatric illness. ERPs were elicited during two versions of the continuous performance test (CPT), which differed in their level of processing complexity. The data were recorded from electrodes located at midline frontal, central, parietal, and occipital scalp sites. Diagnostic assessments of the parents were performed using the Schedule for Affective Disorders and Schizophrenia-Lifetime Version and Research Diagnostic Criteria. Clinical assessments of the children were made with a modified version of the Global Assessment Scale. ERP amplitudes for six electrophysiological events were compared among groups for target and nontarget stimuli using analyses of variance of both factor score and baseline to peak measures. There was one isolated between-group finding: frontal negative slow wave recorded at FZ was of greater magnitude in the high risk (HR) than in either the psychiatric (PC) or normal control (NC) groups. Since only a small percentage of children at risk will eventually develop schizophrenia, ERP amplitude deviance and frequency distribution analyses were also performed and compared among groups. ERP component amplitudes did not distinguish the groups when each component was considered separately. Deviance analyses, using a combination of the amplitudes of the six ERP components, also did not provide evidence of a deviant subgroup within any of the three groups. There appeared to be no relationship between ERP component amplitudes and behavioral adjustment in adolescence. Some evidence of a relationship between deviant attentional functioning and ERP component amplitude was found, but the pattern of findings within the attentionally deviant HR subgroup was opposite to that found for the HR group as a whole and more consistent with the pattern found for the NC group.

Abnormal cerebral laterality in bipolar depression : Convergence of behavioral and brain event-related potential findings

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 significantly 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 N100 amplitudes for test stimuli in the left than right hemifield, 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.

A longitudinal study relating P3 amplitude to schizophrenia spectrum disorders and to global personality functioning

Auditory and visual event-related potentials (ERPs) were recorded from first-degree relatives (adolescent offspring) of index cases with schizophrenic disorder, affective disorder, or no psychiatric disorder (normal controls) at a mean age of 15 years. Nearly a decade later, these subjects (at a mean age of 25 years) were evaluated for Research Diagnostic Criteria Schizophrenic Disorder, Schizoaffective Disorder, Unspecified Functional Psychosis, and for DSM-III-R Axis II schizophrenia-related traits and disorders including schizotypal, schizoid, and paranoid features. It was hypothesized, based on Duncan et al (1987a, Duncan 1988), that reduction of P3 amplitude in the auditory (but not the visual) modality would predict subsequent schizophrenic-related outcomes in subjects from the schizophrenic disorder parental group. This specific expectation was not statistically supported. An unanticipated and statistically robust result linking P3 decrements (in both auditory and visual modalities) with poorer Global Personality Functioning was observed for offspring from both psychiatric parental groups and the offspring of the normal control group. These data are consistent with the results of a large number of clinical studies of the P3 component that have demonstrated reductions in P3 amplitude in individuals expressing a wide range of behavioral dysfunctions. Their importance lies in the fact that these P3 amplitude decrements were detected long before the overt behavioral symptoms were identified, and were nonspecific with respect to parental psychiatric diagnostic group.

The Brain’s Orienting Response: An Event-Related Functional Magnetic Resonance Imaging Investigation

An important function of the brains orienting response is to enable the evaluation of novel, environmental events in order to prepare for potential behavioral action. Here, we assessed the event‐related 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. Hum Brain Mapp 2009.

Cross-frequency phase coupling of brain rhythms during the orienting response

A critical function of the brains 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 cross-bicoherence) 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.

ERPs during continuous recognition memory for words and pictures

Event-related brain potentials (ERPs) and performance measures were recorded from young adults during continuous recognition memory for word or picture representations of the same concepts. Subjects made speeded choice responses as to whether the item was “new” or “old,” with “old” items repeated after lags of 2,8, or 32 intervening stimuli following their first presentation. Longer lags were associated with poorer performance in words but not in pictures. A sequence of endogenous ERP components was responsive to repetition (old vs. new) and stimulus modality (pictures vs. words), and differed in scalp distribution as a function of both variables. The data suggest that multiple brain generators contribute to ERP repetition effects and support theoretical models that hypothesize processing differences between words and pictures.