Primary aortoenteric fistula: computed tomographic diagnosis of an atypical presentation

A primary aortoenteric fistula is a potentially devastating complication of untreated aortic aneurysmal disease. The clinical presentation can be confusing, leading to a delay in diagnosis. Computed tomography (CT) can greatly assist in establishing the diagnosis. An unusual case of a primary aortoenteric fistula with an atypical presentation is described. The patient presented with symptoms indicating an exacerbation of recurrent nephrolithiasis. No clinical history of an abdominal aortic aneurysm or previous history of gastrointestinal hemorrhage was reported. A CT scan demonstrated extravasation of arterial contrast into the duodenum. The aorta was repaired with an in-line prosthetic graft. A review of the literature regarding this rare entity and surgical options are presented.

An ischemic skin lesion after chemoembolization of the right internal mammary artery in a patient with hepatocellular carcinoma

A huge nodular hepatocellular carcinoma located at the anterior superior portion of the left lobe in a patient with hepatocellular carcinoma was treated with transcatheter arterial chemoembolization through the left hepatic artery. Three months later, however, there was a re-elevation of the serum alpha-fetoprotein level and evidence of a marginal recurrence at the left side of the previously embolized tumor was noted on the postembolization computed tomographic scan. Although the hepatic artery was intact in the second hepatic arteriography, we found that the right internal mammary artery was feeding the recurred hepatocellular carcinoma. This internal mammary artery was successfully treated with Lipiodol-transcatheter arterial chemoembolization. However, an ischemic lesion occurred in the skin of the anterior chest and abdominal wall several days after internal mammary artery embolization. We report here a very rare case of ischemic skin lesion on the anterior chest and abdominal wall following transcatheter arterial chemoembolization of the right internal mammary artery. This internal mammary artery was embolized because it had developed a collateral tumor feeding vessel following the initial chemoembolization of a hepatocellular carcinoma.

Bidirectional case-crossover studies of air pollution: bias from skewed and incomplete waves

The case-crossover design compares exposures during the period of time of failure with one or more periods when failure did not occur and evaluates the potential excess risk using conditional logistic regression. In this simulation study, we applied several control sampling approaches to control for confounding by various temporal patterns of an exposure variable and evaluated the usefulness of symmetric bidirectional control strategies. We simulated true relative risks (RRs; true ss = 0.001) of deaths of 1.051 per 50-ppb increase of sulfur dioxide and included confounding by right- or left-skewed seasonal waves, linear long-term time trends, or a combination of both. The range of the estimated RRs from symmetric bidirectional control sampling approaches was 1.044 approximately 1. 056 at either a long-term trend or any skewed seasonal wave of SO(2) levels, which indicated the bidirectional control sampling methods would successfully control confounding by design. The simulations with bidirectional sampling, however, show that biases may occur if waves are incomplete (20-43% underestimated RRs). In conclusion, our simulations show that the symmetric bidirectional case-crossover design can substantially control for confounding by linear long-term trends and/or seasonality of an exposure variable by design as well. However, unidirectional control sampling would fail to control confounding by those variations of air pollution. Simulation results also show that even the bidirectional case-crossover design can be biased in a situation where the exposure variable shows incomplete cyclic waves, and therefore it cannot completely control for temporal confounding.

Nontumorous hepatic arterial-portal venous shunts: MR imaging findings

PURPOSE

To determine the magnetic resonance (MR) imaging findings of small nontumorous hepatic arterial-portal venous (arterioportal) shunts in the liver.

MATERIALS AND METHODS

MR images in 25 patients with 38 small nontumorous arterioportal shunts verified with surgery or follow-up imaging were included in this study. The causes of arterioportal shunts were iatrogenic causes in 11 patients and/or cirrhotic changes in the remaining patients. Nonenhanced T1- and T2-weighted images and multiphase contrast material-enhanced dynamic images were retrospectively reviewed and compared with conventional hepatic arteriograms to determine the MR characteristics related to the focal hemodynamic changes.

RESULTS

On arterial-dominant-phase dynamic MR images, 29 (76%) of the 38 arteriographically suggested nontumorous arterioportal shunts displayed abnormal findings distinguished against the surrounding hepatic parenchyma, including wedge-shaped (n = 14), nodular (n = 9), or irregularly outlined (n = 6) areas of focal contrast enhancement. The signal intensity on nonenhanced T1- and T2-weighted images of the corresponding areas appeared unremarkable except for three wedge-shaped high-signal-intensity areas (three [8%] of 38) on T2-weighted images accompanied by prolonged contrast enhancement. Most (24 [83%] of 29) areas of abnormal signal intensity were located at the periphery of the liver parenchyma.

CONCLUSION

A small nontumorous arterioportal shunt should be considered one of the causes of focal parenchymal hyperperfusion abnormalities on contrast-enhanced dynamic MR images of the liver in the absence of abnormal signal intensity on static MR images.

4-Hydroxybenzaldehyde from Gastrodia elata B1. is active in the antioxidation and GABAergic neuromodulation of the rat brain

Ether fraction of G. elata methanol extract significantly inhibited the recovery time and severity induced by pentylenetetrazole (PTZ) treatment. Pretreatment of ether fraction of G. elata methanol extract successfully prevented diminution of brain GABA level in subconvulsive dose of PTZ-treated rats. 4-Hydroxybenzaldehyde, an analogue of p-hydroxybenzyl alcohol, showed an inhibitory effect on the GABA transaminase, and its inhibitory activity was higher than that of valproic acid, a known anticonvulsant. In the brain of PTZ-treated rats, brain lipid peroxidation was significantly increased, while it recovered to the control level after treatment with 4-hydroxybenzaldehyde. It may be concluded that antioxidation and positive modulation of GABAergic neuromodulation of 4-hydroxybenzaldehyde partially contribute to an antiepileptic and anticonvulsive activity of G. elata B1.

Effects of deregulated Raf activation on integrin, cytokine-receptor expression and the induction of apoptosis in hematopoietic cells

The effects of deregulated Raf activation on the growth and differentiation of hematopoietic cells were investigated. The cytokine-dependent murine myeloid FDC-P1 and human erythroleukemic TF-1 cell lines were transformed to grow in response to deregulated Raf expression in the absence of exogenous cytokines. The conditionally active Raf proteins were regulated by beta-estradiol as cDNAs containing the Raf catalytic, but lacking negative-regulatory domains, were ligated to the hormone binding domain of the estrogen receptor (deltaRaf:ER). Continuous deltaRaf expression prevented apoptosis in the absence of exogenous cytokines and altered the morphology of the FD/deltaRaf:ER cells as they grew in large aggregated masses (>100 cells) whereas the parental cytokine-dependent FDC-P1 cells grew in smaller grape-like clusters (< 10 cells). FD/deltaRaf-1:ER cells growing in response to Raf activation displayed decreased levels of the Mac-2 and Mac-3 molecules on their cell surface. In contrast, when these cells were cultured in IL-3, higher levels of these adhesion molecules were detected. Expression of activated Raf oncoproteins also abrogated cytokine dependency and prevented apoptosis of TF-1 cells. Moreover, the differentiation status of these Raf-responsive cells was more immature upon Raf activation as culture with the differentiation-inducing agent phorbol 12 myristate 13-acetate (PMA) and beta-estradiol resulted in decreased levels of the CD11b and CD18 integrin molecules on the cell surface. In contrast when the Raf-responsive cells were induced to differentiate with PMA and GM-CSF, in the absence of deltaRaf:ER activation, increased levels of the CD11b and CD18 molecules were detected. Retinoic acid (RA) inhibited 3H-thymidine incorporation in response to GM-CSF. Interestingly, Raf activation counterbalanced the inhibition of DNA synthesis caused by RA but not PMA. Thus deregulated Raf expression can alter cytokine dependency, integrin expression and the stage of differentiation. These Raf-responsive cell lines will be useful in elucidating the roles of the MAP kinase cascade on hematopoietic cell differentiation and malignant transformation.

Abdominal tuberculous lymphadenopathy: MR imaging findings

BACKGROUND

The purpose of this study was to evaluate the utility of magnetic resonance imaging (MRI) as a diagnostic tool in abdominal tuberculous lymphadenopathy.

METHODS

MRI studies of 11 patients with histologically proven abdominal tuberculous lymphadenopathy were reviewed with regard to anatomic distribution, size, shape, degree, and pattern of enhancement and relation of the lesions to adjacent structures.

RESULTS

The most common site of involvement was the periportal area (n = 6), followed by the peripancreatic (n = 5), mesenteric (n = 1), and paraaortic (n = 1) areas. Eight patients were readily diagnosed as having tuberculous lymphadenopathy on abdominal computed tomography. Three patients had a heterogeneously enhancing masslike lesion adjacent to the pancreas and were initially diagnosed as having cystic tumor of the pancreas. On MRI, 11 lesions showed T1 iso- or hypointensity and central T2 hyperintensity. Two lesions showed T1 iso- or hypointensity and central T2 hypointensity. The lesions with different T2 signal intensities showed different patterns of enhancement on contrast-enhanced dynamic studies. The relations between the enlarged lymph nodes and adjacent bile ducts or vascular structures were well depicted on MRI.

CONCLUSION

MRI was useful in differentiating enlarged lymph nodes abutting the pancreas initially diagnosed as cystic neoplasms on abdominal computed tomography.

Air pollution and daily mortality in seven major cities of Korea, 1991-1997

The relationship between ambient air pollution and daily mortality in seven major cities of Korea for the period 1991-1997 was examined. These cities account for half of the Korean population (about 22 million). The observed concentrations of sulfur dioxide (SO(2), mean=23.3 ppb), ozone (O(3), mean=23.7 ppb), and total suspended particulates (TSP, mean=77.9 microg/m(3)) during the study period were at levels below Korea's current ambient air quality standards. Generalized additive models were applied to allow for the highly flexible fitting of seasonal and long-term time trends in air pollution as well as nonlinear associations with weather variables, such as air temperature and relative humidity. In city-specific analyses, an increase of 50 ppb of SO(2) corresponded to 1-12% more deaths, given constant weather conditions. The risk of all-cause mortality was estimated to increase by 0.5-4%, with an increase in the 2-day moving average of TSP levels equal to 100 microg/m(3). In multipollutant models with pooled data, we found that the estimated risk of death by SO(2) was notably unaffected by adding the other two pollutants (TSP and O(3)) to the model and was statistically significant in various regression models. The rate ratio (RR) for SO(2) remained elevated, indicating an excess mortality of 3% 50 ppb (RR=1.03; 95% CI, 1.01-1.05). TSP's effect on mortality maintained its significance with O(3), but not with SO(2). This implies that there may be collinearity problems where TSP and SO(2) are included in the same model or that TSP may function less than SO(2) as a surrogate for fine particles in the ambient air of Korea. In conclusion, increased mortality was associated with air pollution at SO(2) levels below the current recommendation for air quality. Further research is needed to clarify the relationship between SO(2) and fine particles in Korea.

Focal lesions in cirrhotic liver: comparing MR imaging during arterial portography with Gd-enhanced dynamic MR imaging

The purpose of this study was to document the additional value of MR imaging during arterial portography (MRAP) in patients examined with intravenous contrast-enhanced dynamic MR imaging for the assessment of focal lesions in patients with cirrhosis or chronic viral hepatitis. The MR images of 24 patients with 39 hepatocellular carcinomas and 18 benign hepatocellular nodules examined with dynamic MR imaging and MRAP within a 14-day interval were retrospectively reviewed. For 39 hepatocellular carcinomas, MRAP revealed 37 perfusion defects (95%), while dynamic MR imaging demonstrated 35 occurrences of nodular contrast-enhancement (90%) on arterial dominant phases. Among the 11 benign nodules misinterpreted as hepatocellular carcinoma due to their high signal intensities on arterial-dominant phases of dynamic MR imaging, eight (73%) showed intratumoral portal venous perfusion on MRAP and were regarded as benign nodules. As a result of its high sensitivity and its potential ability to enable differentiation of benign and malignant hepatocellular nodules, MRAP can be added to dynamic MR imaging for planning future management in patients with equivocal hepatocellular nodules in the cirrhotic liver.

Disruption of imprinted X inactivation by parent-of-origin effects at Tsix

In marsupials and in extraembryonic tissues of placental mammals, X inactivation is imprinted to occur on the paternal chromosome. Here, we find that imprinting is controlled by the antisense Xist gene, Tsix. Tsix is maternally expressed and mice carrying a Tsix deletion show normal paternal but impaired maternal transmission. Maternal inheritance occurs infrequently, with surviving progeny showing intrauterine growth retardation and reduced fertility. Transmission ratio distortion results from disrupted imprinting and postimplantation loss of mutant embryos. In contrast to effects in embryonic stem cells, deleting Tsix causes ectopic X inactivation in early male embryos and inactivation of both X chromosomes in female embryos, indicating that X chromosome counting cannot override Tsix imprinting. These results highlight differences between imprinted and random X inactivation but show that Tsix regulates both. We propose that an imprinting center lies within Tsix.

Cavernous hemangioma arising from the lesser omentum: MR findings

We report the magnetic resonance findings of an unusual hemangioma in the lesser omentum. A well-circumscribed, large mass was identified between the stomach and the left lobe of the liver, with compression of adjacent liver parenchyma. The mass showed low signal intensity (SI) on T1-weighted images, high SI on T2-weighted images with multiple septa, and slightly decreased SI on out-of-phase T1-weighted images. After gadolinium contrast administration, septa within the mass showed minimal enhancement on 30-s T1-weighted images and mild enhancement on 5-min T1-weighted images. The mass was histopathologically diagnosed as a cavernous hemangioma comprised of multiple vascular spaces, fibrotic tissue, and adipocytes.

Test-bolus injection for optimization of arterial phase imaging during contrast-enhanced hepatic MR imaging

Contrast enhancement during the dynamic MR imaging is important for the detection and characterization of focal liver lesions. The purpose of this study was to determine whether or not a timing examination with a injection of a 1.0-mL bolus of gadopentetate dimeglumine into the antecubital vein followed by rapid dynamic scanning and measurement of signal intensity of the aorta could help to obtain proper arterial-dominant phase images for the characterization of focal hepatic lesions during subsequent multiphase dynamic MR imaging. The imaging delay to acquisition of the first gadolinium-enhanced image for multiphase dynamic MR imaging was set to equal the time to peak aortic enhancement during the test examination. The first contrast-enhanced images of 80 patients with 160 focal liver lesions (hepatocellular carcinoma, n = 79; cavernous hemangioma, n = 51; metastatic tumor, n = 30) were then retrospectively reviewed. Peak aortic enhancement occurred between 10 and 28 seconds (mean, 16.5 seconds +/- 3.1) after starting the infusion of contrast material in 80 patients during the test-examination. Depending on the findings of intrahepatic vascular enhancement on the full-scale dynamic images, hepatic arterial phase (n = 11, 14%) or sinusoid phase (n = 65, 81%) imaging was obtained during the first gadolinium-enhanced acquisition in 76 (95%) of 80 patients. Three different lesions were well characterized and easily distinguished from each other (p < .0001) on the first-phase images depending on their enhancement pattern. In the majority of patients, timing examination with test-bolus injection was helpful in obtaining qualified images for the characterization of various focal lesions.

Local radiotherapy for unresectable hepatocellular carcinoma patients who failed with transcatheter arterial chemoembolization

PURPOSE

The purpose of this study was to investigate the efficacy of local radiotherapy (RT) as a salvage treatment for unresectable hepatocellular carcinoma (HCC) patients who failed with transcatheter arterial chemoembolization (TACE).

METHODS AND MATERIALS

Patients with unresectable HCC who had been treated with and eventually failed with TACE were eligible. The judgment of TACE failure was based on incomplete tumor filling of lipiodol-adriamycin mixture on either angiography or computed tomography (CT) scan. From January 1993 to December 1997, 27 patients were entered into this study. They had UICC Stage III (17) or IVA (10) disease, with a mean tumor size of 7.2 +/- 2.9 cm. Local RT was done, with a mean tumor dose of 51.8 +/- 7.9 Gy, in daily 1.8-Gy fractions using a 10- or 6-MV linear accelerator. Survival was calculated from both the diagnosis and the start of RT using the Kaplan-Meier method.

RESULTS

An objective response was observed in 16 of 24 patients (66.7%) including 1 CR. Intrahepatic metastasis was noted outside the RT field in 10 patients (37.0%). Extrahepatic distant metastasis occurred in 4 patients. Survival rates at 1, 2, and 3 years were 85. 2%, 58.1%, and 33.2%, respectively, from the diagnosis and 55.9%, 35. 7%, and 21.4%, respectively, from the start of RT. The median survivals were 26 months from the diagnosis and 14 months from the start of RT. Acute toxicity involved alteration in liver function test (13 patients) and thrombocytopenia (2 patients). Subacute and chronic toxicity involved gastroduodenal ulcer (3 patients) and duodenitis (2 patients). There was no treatment-related death.

CONCLUSION

In unresectable HCC patients who failed with TACE, local RT induced a substantial tumor response of 66.7%, with a 3-year survival rate of 21.4% and a median survival time of 14 months. Toxicity was significant but manageable. Although we do not know if there is survival benefit through this treatment, local RT in these patients seems to be valuable as a salvage for TACE-failed HCC.

Object and spatial alternation tasks with minimal delays activate the right anterior hippocampus proper in humans

Substantial evidence indicates that the hippocampus plays a critical role in long-term declarative memory. In contrast, the role of the human hippocampus in working memory, particularly when information needs to be maintained only for a few seconds, remains controversial. Using PET, we show robust activation of the right anterior hippocampus proper during the performance of both object and spatial alternation tasks. Hippocampal activation emerged even though subjects only had to remember a single, simple stimulus over a minimum delay of 1 s. No hippocampal activation occurred when the delay was increased to 5 s. This suggests that the role of the hippocampus in working memory is not to maintain information across a delay interval. Instead, its activity reflects a more transient function during encoding and/or retrieval. These data are among the first observations to demonstrate human hippocampal involvement in working memory.

Genetic engineering of drought resistant potato plants by introduction of the trehalose-6-phosphate synthase (TPS1) gene from Saccharomyces cerevisiae

In yeast, trehalose-6-phosphate synthase is a key enzyme for trehalose biosynthesis, encoded by the structural gene TPS1. Trehalose affects sugar metabolism as well as osmoprotection against several environmental stresses, such as heat and desiccation. The TPS1 gene of Saccharomyces cerevisiae was engineered under the control of the CaMV 35S promoter for constitutive expression in transgenic potato plants by Ti-plasmid of Agrobacterium-mediated transformation. The resulting TPS1 transgenic potato plants exhibited various morphological phenotypes in culture tubes, ranging from normal to severely retarded growth, including dwarfish growth, yellowish lancet-shaped leaves, and aberrant root development. However, the plants recovered from these negative growth effects when grown in a soil mixture. The TPS1 transgenic potato plants showed significantly increased drought resistance. These results suggest that the production of trehalose not only affects plant development but also improves drought tolerance.

The effect of mandibular third molar presence and position on the risk of an angle fracture

PURPOSE

This study assessed the relationship between the presence and position of mandibular third molars (M3) and angle fractures.

PATIENTS AND METHODS

A retrospective cohort study design and a sample composed of patients admitted for treatment of mandible fractures between January 1993 and April 1998 were used. Data sources were the patients' medical records and radiographs. The predictor variables were the presence and position of M3. M3 position was grouped into 9 categories based on the Pell and Gregory classification. The outcome variable was the presence of an angle fracture. Other study variables included age, sex, race, mechanism of injury, and fracture location.

RESULTS

The eligible sample was composed of 437 patients, of whom 367 had data available for analysis. Patients with M3 present had a 1.9 times (95% confidence interval = 1.2 to 2.9) greater chance of an angle fracture than patients without M3s (P = .003). There was a statistically significant variation in the risk for an angle fracture, depending on M3 position (P = .049).

CONCLUSION

The study results confirm other reports that patients with M3 present have an increased risk for angle fractures. Furthermore, it also showed that the risk for an angle fracture varied depending on M3 position.

O2 in Y2K: not an airtight case

During a bitterly cold Minnesota weekend, I holed up at home with two dogs and hot tea while reading and rereading the paper that “everyone is talking about.” The findings of Grief and coworkers now have received world-wide exposure. In consequence, anesthesiologists, surgeons, and infection control workers may be pondering how soon to start “putting everybody on 80% oxygen in the OR and recovery room.” The article is not perfect—it has some warts—yet it may stimulate timely reconsideration of four intertwined topics: the difficulty of detecting an incremental infection prevention effect in a clinical trial; the importance of designing such a trial so that the control-group treatment represents current best practice; the bittersweet vagaries of inductive inference that are inescapable whenever we generalize to our practices (non-research conditions) techniques reported from clinical trials (research conditions); and the absence of logical rules of engagement to follow at our own hospitals when a new infection control gimmick or gadget arrives on the scene.

Of course, I have already submitted my e-mail letter to the editor of the New England Journal of Medicine. What I could not cover within the 400-word limit of that forum inspired this essay.

The apparent effect of only a few hours' supplemental oxygen administration for colorectal surgical-incision infection prevention was astounding. The 50% reduction in infection risk seems almost too good to be true. There is a seductive charm when a single, simple, relatively cheap and safe process change gives that much outcome improvement.

Radiologic findings of Mirizzi syndrome with emphasis on MRI

We have reported a case of Mirizzi syndrome preoperatively diagnosed using MR cholangiopancreatography. MRCP and T2-weighted image using a single-shot fast spin-echo sequence accurately depicted all components of Mirizzi syndrome, including impacted stone in the neck of the gallbladder compressing the common hepatic duct and wall-thickening of the gallbladder without any evidence of malignancy. The combination of MRCP and T2-weighted image can be counted on to replace conventional modalities of diagnosing Mirizzi syndrome without any loss of diagnostic accuracy.

Applied pharmacoeconomics: modeling data from internal and external sources

The use and application of techniques for modeling data obtained from various data sources are discussed. Modeling with internal and external data has become a popular way for health care organizations to apply pharmacoeconomics to pharmacy practice. Modeling studies use existing clinical and epidemiologic data to project the effect of a clinical, policy, or medication decision on a patient, population, or organization. Although several modeling techniques have been used in health care, the most common approaches are to modify and adapt existing models or to develop a unique model to answer questions of interest in a specific practice setting. Typically, an economic model developed by adapting an existing one will use either the clinical decision-analysis or Markov modeling technique. Regardless of the technique used, external data must be carefully evaluated to ensure that the data are appropriate for use in making decisions at a specific organization. For example, cost data must be analyzed to ensure that the calculations are reproducible. Also, it must be acknowledged that this strategy may not always be appropriate. The use of modeling techniques can assist decision-makers in making more informed clinical, policy, and medication decisions in real-world settings. Caution is required when adapting and interpreting existing models to ensure appropriate application in a specific organization.

Homologous genomic fragments in the mouse pre-T cell receptor alpha (pTa) and Xist loci

We recently characterized a genomic region located upstream of the mouse pre-T cell receptor alpha (pTa) gene, which controls pTa expression in pre-T cells. We now report an unexpected homology between this region and a region in the mouse X chromosome inactivation center between the 3' end of the Xist gene and the start of an antisense transcript Tsix. The homology is extended over 4 kb of genomic sequence split by an expanded repeat region and is observed only in the mouse, not in the rat. Despite high sequence similarity to the pTa transcriptional enhancer, the homologous X chromosome fragment appears to have lost its enhancer activity. These data underscore the complex organization of the mouse genome and, in particular, of the X chromosome inactivation center.

Neuroanatomical correlates of the near response: voluntary modulation of accommodation/vergence in the human visual system

This study identifies brain regions participating in the execution of eye movements for voluntary positive accommodation (VPA) during open-loop vergence conditions. Neuronal activity was estimated by measurement of changes in regional cerebral blood flow (rCBF) with positron emission tomography and 15O-water. Thirteen naive volunteers viewed a checkerboard pattern with their dominant right eye, while a lens interrupted the line of gaze during alternate 1.5 s intervals. Three counterbalanced tasks required central fixation and viewing of a stationary checkerboard pattern: (i) through a 0.0 diopter (D) lens; (ii) through a -5.0-D lens while avoiding volitional accommodation and permitting blur; and (iii) through a -5. 0-D lens while maintaining maximal focus. The latter required large-amplitude, high-frequency VPA. As an additional control, seven of the subjects viewed passively a digitally blurred checkerboard through a 0.0-D lens as above. Optometric measurements confirmed normal visual acuity and ability to perform the focusing task (VPA). Large-amplitude saccadic eye movements, verified absent by electro-oculography, were inhibited by central fixation. Image averaging across subjects demonstrated multifocal changes in rCBF during VPA: striate and extrastriate visual cortices; superior temporal cortices; and cerebellar cortex and vermis. Decreases in rCBF occurred in the lateral intraparietal area, prefrontal and frontal and/or supplementary eye fields. Analysis of regions of interest in the visual cortex showed systematic and appropriate task dependence of rCBF. Activations may reflect sensorimotor processing along the reflex arc of the accommodation system, while deactivations may indicate inhibition of systems participating in visual search.