Janet L. Shucard

Functional neuroimaging of attention in the auditory modality.

PREVIOUS functional neuroimaging studies of attention have emphasized the visual modality. We developed an auditory version of the continuous performance test (CPT) that included simple, focused and divided attention conditions. Positron emission tomographic (PET) scans were acquired during CPT performance in normal young adults and then submitted to statistical parametric mapping. Simple attention brought about a large region of activation involving the anterior cingulate gyrus and the right anterior/mesial frontal lobe. Focused and divided attention CPT conditions were compared but there were few significant differences. The findings are consistent with activation of an anterior attention network during auditory attention, without involvement of posterior attention structures which are more likely to vary in accordance with sensory modality.

Stimulus modality and Go/NoGo effects on P3 during parallel visual and auditory continuous performance tasks

Task and modality effects on P3 latency, amplitude, and scalp topography were studied during parallel versions of visual (VCPT) and auditory (ACPT) continuous performance tasks using a Go/NoGo paradigm (A-X CPT). Both the ACPT and VCPT incorporated five conditions including Go and NoGo stimulus sequences as well as three other nontarget conditions. The goal was to evaluate the functional significance and modality specificity of the P300 response and the NoGo P3. Analyses were performed using both raw and normalized data to make comparisons across modalities. For both modalities, the Target X (Go) and three nontarget conditions elicited maximum P3 amplitudes over the posterior scalp sites and qualified as classical P300 responses. The NoGo condition was associated with an increase in central-frontal amplitude compared to the Target X condition. The scalp topography of the P300/P3 for Go and NoGo conditions, as well as all other conditions, was the same for both modalities, supporting the modality independent nature of both P300 and the NoGo P3. Min-Max normalization of P3 amplitudes did not change the condition-topography relationships.

Auditory evoked potentials and sex-related differences in brain development

Abstract Auditory evoked potentials (AEPs) were obtained to probe tones which were delivered during the presentation of complex verbal and nonverbal auditory stimulation to 3-month-old infants. Significant sex-dependent AEP amplitude asymmetries were found. Females produced higher-amplitude responses from the left hemisphere and males produced higher-amplitude responses from the right hemisphere during both the verbal and nonverbal presentations. No significant AEP asymmetries were obtained in an independent group of infants that received only the probe tones. These findings are consistent with theories and behavioral data suggesting differences between males and females in the development of language and spatial functions.

An event-related potential study of attention deficits in posttraumatic stress disorder during auditory and visual Go/NoGo continuous performance tasks

Posttraumatic stress disorder (PTSD) is characterized by disturbances in attention, such as increased arousal and hypervigilance. This study examined the event-related potential (ERP) P3 component to target detection (Go), response inhibition (NoGo) and irrelevant nontarget stimuli during auditory and visual A-X continuous performance tasks. NoGo N2 amplitude effects were also analyzed. Participants were 23 Vietnam veterans with PTSD and 13 civilian controls. No group differences were present for N2 or P3 amplitude to Go and NoGo stimuli. The PTSD group, however, had longer P3 latency to NoGo stimuli than controls, regardless of modality. The PTSD group also had greater frontal P3 amplitude to irrelevant nontarget stimuli than controls. Significant P3 amplitude and latency findings were associated with higher hyperarousal and reexperiencing scores from the Clinician-Administered PTSD Scale. The findings suggest that attentional problems in PTSD are related to slowed central processing when response inhibition is required, and to an impaired ability to screen irrelevant information. This study provides further evidence that the attentional impairments in PTSD are not confined to trauma-related stimuli. Heightened arousal appears to enhance the attentional dysregulation seen in PTSD.

Sex-related differences in event-related potentials, face recognition, and facial affect processing in prepubertal children

Thirty-five prepubertal children, 17 boys and 18 girls, between the ages of 8 and 11 years, were studied to examine electrophysiological and cognitive sex differences during a face-recognition-memory (FRM) task and a facial-affect-identification task (FAIT). All participants were prepubertal, as determined by J. M. Tanners (1962) staging and endocrine evaluation. Sex-dependent event-related potential (ERP) amplitude asymmetries were found during FRM. Boys displayed greater right versus left ERP amplitude to auditory tone probes during the task, whereas girls displayed the opposite pattern. In addition, positive correlations were obtained between ERP amplitude during FRM and FAIT accuracy scores for boys, but not for girls. Results suggest that girls and boys may use different neuronal systems in the processing of faces and facial affect. Findings are consistent with developmental theories regarding sex differences in visuospatial processing.

Working memory and processing speed deficits in systemic lupus erythematosus as measured by the paced auditory serial addition test

As many as 66% of systemic lupus erythematosus (SLE) patients have been reported to have cognitive deficits. These deficits are often associated with information processing speed and working memory. Similarly, processing speed and working memory impairments are the hallmark of cognitive dysfunction in multiple sclerosis (MS). The Paced Auditory Serial Addition Test (PASAT) places high demands on processing speed and working memory. Fisk and Archibald, however, demonstrated that the total score of the PASAT does not accurately reflect impairments in these cognitive processes. They found that MS patients used a chunking strategy to obtain correct responses and reduce the cognitive demands of the task. In the present study, PASAT performance was examined for 45 SLE patients and 27 controls using alternative scoring procedures. Although the total number of correct responses did not differ between SLE and controls at the 2.4 or 2.0 s presentation rates, SLE patients had fewer dyads (correct consecutive responses) than controls at the faster rate, and more chunking responses than controls at both rates. Disease activity, disease duration, depression, fatigue, and corticosteroids could not account for these differences. The findings suggest that SLE patients, like MS patients, chunk responses more often than controls, and that this scoring procedure may better reflect the working memory and processing speed deficits present in SLE.

Working memory deficits in multiple sclerosis: Comparison between the n -back task and the Paced Auditory Serial Addition Test

Working memory (WM) deficits are common in multiple sclerosis (MS). The Paced Auditory Serial Addition Test (PASAT) is used frequently to measure WM in clinical settings. The n-back paradigm is used often in experimental studies of WM. One unique component of the n-back task is that it provides a measure of reaction time (RT), an additional behavioral index of processing speed and task difficulty. Despite the use of both tasks to measure WM, their common variance has not been documented. We tested 32 MS patients and 20 controls; performance measures were obtained for both tasks. Compared with controls, MS patients generally had poorer performance on both the PASAT and n-back task. MS patients also had slower RTs on the n-back than controls and showed more slowing than controls as a function of WM load. Correlational analyses showed a high correspondence between performance measures on the PASAT and n-back. Principal components analysis pointed to a common feature of the PASAT, n-back, and specific other neuropsychological measures, that is, processing speed. Although the PASAT and n-back were shown to have a significant amount of shared variance, each test has specific advantages and disadvantages for use in clinical populations.

Information processing deficits in multiple sclerosis: A matter of complexity

This study examined the relationship between processing speed (PS) and working memory (WM), as measured by performance on an n-back task, in relapsing-remitting multiple sclerosis (RRMS) patients. Simple PS was defined as reaction time (RT) on the 0-back task and complex PS was defined as RT on both the 1-back and 2-back tasks. Participants were administered all three n-back tasks (0-, 1-, and 2-back). Total correct responses, total dyads, and RTs were recorded. As expected, RT for all participants slowed as WM load increased. MS patients had slower RTs than controls across all tasks, and the difference between groups for RT was greatest during the 2-back task. When RT for simple PS (0-back) was parsed from the 1- and 2-back tasks, MS patients still showed impaired complex PS compared to controls. MS patients also made significantly fewer total correct responses and had fewer dyads than controls only on the 2-back task. These findings suggest that both WM and PS deficits are present in RRMS, and that as WM demand increases (from 1- to 2-back) both PS and WM deficits become more prominent.

Neuropsychological Impairment in Systemic Lupus Erythematosus: A Comparison with Multiple Sclerosis

In this manuscript, we review literature describing the neuropsychological and brain imaging characteristics of systemic lupus erythematosus (SLE) patients. The findings are compared and contrasted with multiple sclerosis (MS) studies, revealing similarities and differences of interest to clinicians and researchers. While cognitive impairment is somewhat less common in SLE than MS, the diseases share a similar cognitive profile with deficits most prominent on tests emphasizing the speed of information processing, working memory, and visual/spatial learning, and memory. In early or more mildly affected patients, diffuse white matter damage, which may not be apparent on conventional brain imaging, plays a major role in clinical presentation and cognitive testing. The causes of white matter damage are very different, however, and in later stages of the disease MS and SLE appear to give rise to different forms of cerebral pathology. MS may be characterized by increasing brain atrophy affecting especially the cortical and deep gray matter, at least after conversion to secondary progressive course. There is less evidence for neurodegenerative changes in SLE, but patients are increasingly at risk for cerebrovascular disease. We conclude by offering some suggestions for future clinical and imaging research.

Covert Auditory Attention Generates Activation in the Rostral/Dorsal Anterior Cingulate Cortex

The anterior cingulate cortex (ACC) is believed to mediate conscious information processing or high-capacity attention. However, previous functional imaging studies have largely relied on tasks that involve motor function as well as attention. The work from our group utilizing an auditory continuous performance task demonstrated increased activity in a caudal division of the ACC that borders the supplementary motor area (SMA). Activity in this region was attributed to motor responding as well as attention. In the present study, we used15O H2O positron emission tomography (PET) to map brain activation during nonmotor, covert auditory attention. Our hypothesis was that a different region within the ACC, anterior to the SMA, would be active during covert attention (CA). Six men and six women were asked to monitor aurally presented syllables presented at a 1-sec interstimulus interval. During the CA condition, subjects were asked to continuously discriminate target (.19 probability) from nontarget stimuli. Simultaneous recording of event-related potentials (ERPs) confirmed the discrimination of target and nontarget stimuli and the allocation of attention capacity. Comparison of the monitored versus nonmonitored presentation of stimuli demonstrated significant activity in a rostral/dorsal division of the right ACC, anterior to SMA. Other regions of activation included the lateral prefrontal cortex and posterior superior temporal gyrus in the left hemisphere, consistent with neurocognitive models of language and vigilance. We conclude that a rostral/dorsal subdivision of the right ACC is specific for conscious attention during auditory processing, in contrast to premotor response formation.