Biomedical subjects

Janet L Shucard

Publications and source records attributed to Janet L Shucard.

6 recordsLinked to original sources

PubMed2006

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.

Acoustic Stimulation↗

PubMed2004

The effects of covert attention and stimulus complexity on the P3 response during an auditory continuous performance task.

This study examined the effects of motor responding and stimulus complexity on the event-related potential (ERP) P3 amplitude and latency during an auditory continuous performance task (A-CPT). Subjects were presented with undegraded and degraded syllables during two experimental conditions. In the motor attention (MA) condition participants performed a button press to target syllables. In the covert attention (CA) condition, participants listened for target syllables without responding. The ERP P3 amplitude for targets during MA and CA showed the expected anterior-to-posterior scalp topography, with the greatest amplitude at Pz. Although amplitudes across all scalp sites were greater for MA than CA target P3 responses, both MA and CA targets had greater P3 amplitudes than the P3 for the nontarget syllables (NT). There was no effect of stimulus complexity (degraded vs. undegraded) on P3 amplitude. However, stimulus complexity did affect P3 latency. Degraded syllables elicited longer P3 latency than undegraded syllables for both the MA and CA conditions. The amplitude and topography findings show that when stimulus probability is controlled through the use of a CPT paradigm, a reliable P3 component is present even when the task does not require a motor response to target stimuli.

Acoustic Stimulation↗

PubMed2004

Do serum sodium levels predict febrile seizure recurrence within 24 hours?

The American Academy of Pediatrics Practice Parameter, The Neurodiagnostic Evaluation of a Child with a First Simple Febrile Seizure, does not recommend serum electrolytes be obtained routinely. Two reports from Europe, however, identified relative hyponatremia as a risk factor for febrile seizure recurrence within 24 hours. If confirmed, this would have potential impact on the approach to these patients. The charts of 175 sequential children ages 6 months to 5 years who presented to the Children's Hospital of Buffalo emergency room in 1999 with generalized seizures lasting less than 15 minutes were retrospectively reviewed. One hundred thirty-six patients were febrile and 39 (control group) were afebrile. Serum electrolytes were performed on all. The mean serum sodium for the 27 children with more than 1 febrile seizure in 24 hours (135.48 mmol/L) did not differ from those 109 febrile children whose seizures did not recur within 24 hours (135.56 mmol/L). Of interest, the mean serum sodium for the 109 children with simple febrile seizures, as well as those with recurrent "simple" febrile seizures were significantly lower than the control group of children with afebrile seizures. These findings reaffirm the recommendation of the American Academy of Pediatrics Practice Parameter to not routinely obtain electrolytes.

Biomarkers↗

PubMed2004

Tone probe event-related potential differences during a face recognition task in prepubertal children and Turner Syndrome girls.

Hormones have been shown to play a role in both cerebral development and neurocognitive function. Turner Syndrome (TS) provides the opportunity to study the effect of the lack of estrogen on neurocognitive development. In this study, event-related potential (ERP) differences were examined among 12 TS girls, 20 prepubertal control girls, and 20 prepubertal control boys during a face recognition memory task. Stage of puberty was determined by Tanner Scale rating and hormonal assay. ERPs to pairs of auditory probe stimuli were recorded from eight scalp sites while participants performed a faced recognition memory (FRM) task. For the N2 component of the ERP (which has previously been associated with evaluation of stimulus information, categorization difficulty, and attention), control boys displayed greater right versus left hemisphere amplitude, control girls displayed greater left versus right hemisphere amplitude, and there was no amplitude asymmetry for TS girls. Further, control girls had greater left hemisphere N2 amplitude than control boys and TS girls, and greater right hemisphere N2 amplitude than TS girls. The results suggest more right hemisphere activation during face recognition in boys, while the opposite pattern was present in control girls. In contrast, TS girls displayed no asymmetry, indicative of more uniform involvement of the left and right hemispheres during face recognition. These findings are consistent with differences in cortical organization related to face recognition memory processing among prepubertal control boys, girls, and TS girls. They also support the notion that sex differences in cognitive function are present prior to pubertal onset, and that lack of endogenous sex hormones (e.g., estrogen) during prenatal/perinatal development (i.e., for TS girls) may influence brain organization and, in turn, neurocognitive processes that relate to face recognition.

Acoustic Stimulation↗

PubMed2004

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.

Acoustic Stimulation↗

PubMed2002

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 used (15)O H(2)O 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.

Adult↗