EEG dipole analysis of motor-priming foreperiod activity reveals separate sources for motor and spatial attention components

OBJECTIVE: This study employed EEG source localisation procedures to study the contribution of motor preparatory and attentional processing to foreperiod activity in an S1-S2 motor priming task. METHODS: Behavioural and high-density event-related potential (ERP) data were recorded in an S1-S2 priming task where participants responded to S2 with a left or right-hand button press. S1 either provided information about response hand (informative) or ambiguous information (uninformative). RESULTS: Responses were significantly faster in informative trials compared with uninformative trials. Dipole source analysis of foreperiod lateralized ERPs revealed sources of motor preparatory activity in the dorsolateral premotor cortex (PMd) in line with previous work. In addition, two spatial attention components (ADAN, LDAP) were identified with generators in the PMd and occipitotemporal visual areas in the middle temporal (MT) region, respectively. Separation of motor-related and attentional PMd source locations was reliable along the rostral-caudal axis. CONCLUSIONS: The presence of attentional components in a motor priming paradigm supports the premotor theory of attention which suggests a close link between attention and motor preparatory processes. Separation of components in the premotor cortex is in accord with a functional division of PMd into rostral (higher-order processing) and caudal (motor-related processing) areas as suggested by imaging work. SIGNIFICANCE: A prime for response preparation is a trigger for separate, but closely linked, attention-related activity in premotor areas.     

Quantitative diagnostic performance of myocardial perfusion SPECT with attenuation correction in women.

Attenuation correction (AC) for myocardial perfusion SPECT (MPS) had not been evaluated separately in women despite specific considerations in this group because of breast photon attenuation. We aimed to evaluate the performance of AC in women by using automated quantitative analysis of MPS to avoid any bias. METHODS: Consecutive female patients--134 with a low likelihood (LLk) of coronary artery disease (CAD) and 114 with coronary angiography performed within less than 3 mo of MPS--who were referred for rest-stress electrocardiography-gated 99mTc-sestamibi MPS with AC were considered. Imaging data were evaluated for contour quality control. An additional 50 LLk studies in women were used to create equivalent normal limits for studies with AC and with no correction (NC). An experienced technologist unaware of the angiography and other results performed the contour quality control. All other processing was performed in a fully automated manner. Quantitative analysis was performed with the Cedars-Sinai myocardial perfusion analysis package. All automated segmental analyses were performed with the 17-segment, 5-point American Heart Association model. Summed stress scores (SSS) of > or =3 were considered abnormal. RESULTS: CAD (> or =70% stenosis) was present in 69 of 114 patients (60%). The normalcy rates were 93% for both NC and AC studies. The SSS for patients with CAD and without CAD for NC versus AC were 10.0 +/- 9.0 (mean +/- SD) versus 10.2 +/- 8.5 and 1.6 +/- 2.3 versus 1.8 +/- 2.5, respectively; P was not significant (NS) for all comparisons of NC versus AC. The SSS for LLk patients for NC versus AC were 0.51 +/- 1.0 versus 0.6 +/- 1.1, respectively; P was NS. The specificity for both NC and AC was 73%. The sensitivities for NC and AC were 80% and 81%, respectively, and the accuracies for NC and AC were 77% and 78%, respectively; P was NS for both comparisons. CONCLUSION: There are no significant diagnostic differences between automated quantitative MPS analyses performed in studies processed with and without AC in women.     

Double-stranded-RNA-dependent protein kinase and TAR RNA-binding protein form homo- and heterodimers in vivo.

The yeast two-hybrid system and far-Western protein blot analysis were used to demonstrate dimerization of human double-stranded RNA (dsRNA)-dependent protein kinase (PKR) in vivo and in vitro. A catalytically inactive mutant of PKR with a single amino acid substitution (K296R) was found to dimerize in vivo, and a mutant with a deletion of the catalytic domain of PKR retained the ability to dimerize. In contrast, deletion of the two dsRNA-binding motifs in the N-terminal regulatory domain of PKR abolished dimerization. In vitro dimerization of the dsRNA-binding domain required the presence of dsRNA. These results suggest that the binding of dsRNA by PKR is necessary for dimerization. The mammalian dsRNA-binding protein TRBP, originally identified on the basis of its ability to bind the transactivation region (TAR) of human immunodeficiency virus RNA, also dimerized with itself and with PKR in the yeast assay. Taken together, these results suggest that complexes consisting of different combinations of dsRNA-binding proteins may exist in vivo. Such complexes could mediate differential effects on gene expression and control of cell growth.     

Acute transverse myelitis in the emergency department: A case report and review of the literature

Acute transverse myelitis (ATM) is a neurologic condition that presents with bilateral lower extremity weakness and sensory loss associated with bowel and bladder dysfunction. Whereas the time of onset may be hours to days, the time to either partial or complete recovery may require months. The etiology is varied and may be idiopathic. Laboratory and radiographic evaluation may be nonrevealing. Corticosteriods have been used for treatment, but their efficacy is controversial. As illustrated by this case report, the essential aspect of the initial management of ATM is the elimination of potentially treatable causes.     

Metabolic and hemodynamic responses to concurrent voluntary arm crank and electrical stimulation leg cycle exercise in quadriplegics.

This study determined the metabolic and hemodynamic responses in eight spinal cord injured (SCI) quadriplegics (C5-C8/T1) performing subpeak arm crank exercise (ACE) alone, subpeak functional electrical stimulation leg cycle exercise (FES-LCE) alone, and subpeak FES-LCE concurrent with subpeak ACE (hybrid exercise). Subjects completed 10 minutes of each exercise mode during which steady-state oxygen uptake (VO2), pulmonary ventilation (VE), heart rate (HR), cardiac output (CO), stroke volume (SV), mean arterial pressure (MAP), arteriovenous oxygen difference (a-v O2 diff), and total peripheral resistance (TPR) were determined. Although mean VO2 for both ACE alone and FES-LCE alone was matched at 0.66 l/mi, individualized power outputs ranged from 0-30 W (mean = 19.4 +/- 1.3) and 0-12.2 W (mean = 2.3 +/- 0.6), respectively. Hybrid exercise elicited significantly higher VO2 (by 54 percent), VE (by 39-53 percent), HR (by 19-33 percent), and CO (by 33-47 percent), and significantly lower TPR (by 21-34 percent) than ACE or FES-LCE performed alone (P less than or equal to 0.05). Stroke volume was similar between hybrid exercise and FES-LCE alone, and these two exercise modes evoked a significantly higher SV (by 41-56 percent) than during ACE alone. These data clearly demonstrate that hybrid exercise creates a higher aerobic metabolic demand and cardiac-volume load in SCI quadriplegics than either subpeak levels of ACE or FES-LCE performed separately. Therefore, hybrid exercise may provide more advantageous central cardiovascular training effects in quadriplegics than either ACE or FES-LCE alone.