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T Ro

Publications and source records attributed to T Ro.

At least 19 recordsLinked to original sources
PubMed2001

Ipsilesional biases in saccades but not perception after lesions of the human inferior parietal lobule.

We examined the effects of chronic unilateral lesions to either the inferior parietal lobe, or to the dorsolateral prefrontal cortex including the frontal eye fields (FEFs), upon human visual perception and saccades in temporal-order-judgment (TOJ) tasks. Two visual events were presented on each trial, one in each hemifield at various stimulus onset asynchronies (SOAs). In the saccade task, patients moved their eyes to whichever stimulus attracted gaze first. In the perceptual-manual task, they pressed a button to indicate which stimulus was perceived first. Frontal patients showed appropriate TOJs for visual targets in both tasks. Parietal patients showed appropriate TOJs in the perceptual-manual but not the saccade task; their saccades tended to be ipsilesional unless the contralesional target led substantially. This reveals a bias in saccade choice after parietal damage that cannot be attributed to deficient visual perception. These results challenge previous claims that only anterior lesions produce motoric spatial biases in humans. However, they are in accord with recent neurophysiological evidence for parietal involvement in saccade generation, and also with suggestions that visuomotor transformations in the parietal lobe serving direct spatial motor responses can dissociate from conscious perception as indicated by indirect arbitrary responses.

Adult↗
PubMed2001

Changing faces: a detection advantage in the flicker paradigm.

Observers seem surprisingly poor at detecting changes in images following a large transient or flicker. In this study, we compared this change blindness phenomenon between human faces and other common objects (e.g., clothes). We found that changes were detected far more rapidly and accurately in faces than in other objects. This advantage for faces, however, was found only for upright faces in multiple-object arrays, and was completely eliminated when displays showed one photograph only or when the pictures were inverted. These results suggest a special role for faces in competition for visual attention, and provide support for previous claims that human faces are processed differently than stimuli that may be of less biological significance.

Awareness↗
PubMed2000

Inhibition of return in saccadic eye movements.

Inhibition of return (IOR) is a phenomenon in which responses generated to targets at previously attended locations are delayed. It has been suggested that IOR affords a mechanism for optimizing the inspection of novel locations and that it is generated by oculomotor reflexes mediated by the superior colliculus. In this investigation, we measured the effects of IOR on the metrics of saccadic eye movements made to novel and previously attended locations. Saccades made to cued target locations, as well as to other targets within the same hemifield, had longer latencies than saccades made towards the novel, uncued hemifield. We further found that the amplitudes of saccades towards the cued hemifield were more hypometric, but only when the amplitude could not be pre-programmed. These results provide evidence that IOR influences spatial, as well as temporal, parameters of saccadic eye movements and suggest that the exogenous orienting of attention, in addition to influencing target detection, also influences oculomotor programming.

Adult↗
PubMed1999

Localization of the human frontal eye fields and motor hand area with transcranial magnetic stimulation and magnetic resonance imaging.

We localized the neuroanatomical correlates for control of saccadic eye movements and for finger movements using a combined transcranial magnetic stimulation (TMS) and magnetic resonance imaging (MRI) approach. Two participants underwent TMS while performing an endogenous saccade task. The motor hand area was localized by TMS and the region anterior to it was mapped to identify the borders of a region where TMS produced delays in generating contralateral saccades. MRI scans were then obtained with fiducial markers placed over the motor hand area and 2 cm anterior to it, the common cortical region that produced saccadic delays in these two subjects. It was also shown that the structural anatomy of the hand area, physiologically defined by visible contractions of the contralateral hand following TMS, corresponded to the knob-like structure recently reported [18, 19]. These results demonstrate that TMS can be a precise, non-invasive tool for neuroanatomical mapping of cortical structures when combined with structural images of the brain.

Adult↗
PubMed1999

Interactions between color and word processing in a flanker task.

To examine interactions between color and word attributes, participants responded, either manually or vocally, to a central target (color patch or word) flanked by a Stroop stimulus. Color and word attributes of the flanker affected both vocal and manual responding to color patches. Color and word flankers also affected manual responding to word targets, but only word flanker affected vocal responding to word targets. These results are not consistent with models (e.g., translational models) of Stroop tasks, which posit that interactions between colors and words occur only when vocal responding is required.

Adult↗
PubMed1999

Aneurysmal bone cyst of the coronoid process of the mandible.

A rare case of an aneurysmal bone cyst (ABC) involving the right coronoid process of the mandible in a 12-year-old girl is presented. The characteristic features with fluid-fluid levels within the lesion observed on Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) was helpful in the preoperative diagnosis.

Bone Cysts, Aneurysmal↗
PubMed1999

Components of reflexive visual orienting to moving objects.

Posner and Cohen (1984) and Maylor (1985) initially observed that a luminance change produces both facilitatory and inhibitory effects on subsequent detection. While Posner and Cohen claimed that the facilitatory effect was mapped in retinotopic coordinates, they showed that inhibition of return (IOR) was mapped in "environmental coordinates." Tipper and colleagues (Tipper, Driver, & Weaver, 1991; Tipper et al., 1997; Tipper, Weaver, Jerreat, & Burak, 1994) and Abrams and Dobkin (1994b) have recently reported that IOR can be object based, but contradictory results have also been reported (Müller & von Mühlenen, 1996). Here we report six experiments showing that an uninformative peripheral cue can generate either facilitatory or inhibitory object-based effects that can tag moving objects and that can persist for several hundred milliseconds. Although the boundary conditions determining which effect will be manifest remain to be defined, the present results suggest that facilitation and inhibition are generated independently, rather than being components of the same biphasic process.

Adult↗
PubMed1998

Response channel activation and the temporoparietal junction.

When we learn to make one motor response to one visual stimulus and a different motor response to another, representations of these stimulus-response associations must be maintained to efficiently transduce perception into action. When an irrelevant distractor is presented adjacent to a target stimulus, interference is observed when the two stimuli are associated with conflicting responses, presumably due to response channel activation by the incompatible information. We have explored the neural bases of these interference effects. In a previous study, patients with hemispatial neglect showed normal interference from contralesional flankers. In another study, patients with lesions of the lateral prefrontal cortex were found not to show interference from distractors presented in the contralesional hemifield. The current study provided a more anatomically detailed investigation of the effects of posterior association cortex lesions on flanker interference. Patients with chronic, unilateral lesions involving the temporoparietal junction (TPJ), two of whom had hemispatial neglect, were compared with patients with lesions of the posterior association cortex not involving the TPJ. All patients performed a color discrimination task at fixation while a congruent or incongruent colored flanker was briefly presented (16.7 ms) in the adjacent contralesional or ipsilesional hemifield. Patients with TPJ lesions showed no interference effects from the contralesional flankers. These results suggest that the TPJ, in combination with the dorsolateral prefrontal cortex, is involved in transducing perception into action.

Aged↗
PubMed1997

Object-based facilitation and inhibition from visual orienting in the human split-brain.

Object-based attention was examined in 2 split-brain patients. A precued object could move within a visual field or cross the midline to the opposite field. Normal individuals show an inhibition in detecting signals in the cued object whether it moves within or between fields. Both patients showed this effect when the cued object moved within a visual field. When it crossed the midline into the opposite visual field, however, detection was faster in the cued box. These results reveal both facilitatory and inhibitory effects on attention that are object based and may last for several hundred milliseconds. However, the inhibition requires an intact corpus callosum for interhemispheric transfer, whereas the facilitation is transferred subcortically.

Adult↗
PubMed1996

Perception of geometric illusions in hemispatial neglect.

A patient with left hemispatial neglect, while completely unaware of features on the left side of figures, nevertheless perceived geometric illusions dependent on these features. Bisection errors were amplified not only by increasing line length, but also by perceived line length induced by these illusions. Bisection of Judd illusion figures was as much influenced by neglected features on the left as by perceived features on the right. These observations demonstrate that geometric illusions are generated through preattentive processes. They also suggest that in visual neglect there may be preattentive processing of location as well as shape information.

Brain↗
PubMed1996

Response channel activation and the lateral prefrontal cortex.

The role of lateral prefrontal cortex in transducing perception into action was studied in 10 patients with chronic, unilateral lesions. They identified colors in the center of a visual display, while a flanking, distractor color was presented simultaneously in either the ipsilesional or contralesional field. The flanker could be either the same color as the target, or incompatible with the correct response. The effects of compatible and incompatible flankers on reaction time (RT) served as a measure of response channel activation by the flanker. Flankers in the contralesional field influenced RT less than did those in the ipsilesional field. These results suggest that the lateral prefrontal cortex is involved in maintaining stimulus-response channels.

Adult↗
PubMed1995

Increased sensitivity to ipsilateral cutaneous stimuli following transcranial magnetic stimulation of the parietal lobe.

Transcranial magnetic stimulation of the sensorimotor cortex results in decreased sensitivity of threshold electrical stimuli to fingers of the contralateral hand. It has been suggested that one factor contributing to neglect contralateral to a unilateral parietal lesion is a release of the normal hemisphere from reciprocal interhemispheric inhibition by the damaged hemisphere. Consistent with this account, the current study demonstrated that transcranial magnetic stimulation over the parietal cortex results in increased sensitivity to cutaneous stimulation ipsilateral to the stimulation. The likely mechanism is a transcranial magnetic stimulation-induced transient dysfunction of the ipsilateral parietal cortex that then results in disinhibition of the contralateral parietal cortex.

Adolescent↗
PubMed1995

Pancreatic enlargement in obstructive jaundice. Effects of biliary stream diversion in humans.

To verify the influence of obstructive jaundice on pancreatic growth, the anteroposterior width of the pancreas was measured by computed tomography in 30 cholangiocarcinoma patients excluded patients with distal bile duct tumor (jaundice group) and 74 control subjects. Follow-up examinations were performed on 12 patients with and without internal biliary drainage to elucidate the temporal relationship between pancreatic enlargement and the diversion of the obstructed biliary stream. Histologic analysis on autopsy samples from 13 control and 10 jaundice cases also was performed. Mean pancreatic head and body widths in the jaundice group were 2.93 +/- 0.3 cm and 2.01 +/- 0.3 cm, respectively. These values were significantly greater than those of the controls (2.13 +/- 0.3 cm and 1.49 +/- 0.3 cm, P < 0.01). The glandular widths returned to their normal sizes following internal biliary drainage. No changes were seen in patients who underwent external drainage alone. Histologic examination revealed that enlargement of the acinar cells or of the islet of Langerhans was often seen in the jaundiced patients. Therefore obstructive jaundice is thought to cause pancreatic growth through a trophic effect by interrupting biliary circulation.

Aged↗
PubMed1995

Lymph-node metastases: efficacy for detection with helical CT in patients with gastric cancer.

PURPOSE: To determine the efficacy of helical computed tomography (CT) in the detection of lymphadenopathy in patients with gastric cancer. MATERIALS AND METHODS: Helical CT (5-mm section thickness, 5-mm/sec table incrementation) was performed in 58 patients (39 men, 19 women; mean age, 63.8 years) with gastric cancer; 1,082 lymph nodes (138 positive, 944 negative for metastasis) were resected at surgery. Findings at CT and resection were compared. Sensitivity for detecting lymph nodes was evaluated according to nodal size and presence of metastasis. RESULTS: Seven (1.1%) of 649 lymph nodes 1-4 mm, 160 (45.1%) of 355 nodes 5-9 mm, and 56 (72%) of 78 nodes larger than 9 mm were detected at CT. For nodes of at least 5 mm, sensitivity for detecting metastasis-positive nodes (79 [75.2%] of 105 nodes) was higher than that for detecting metastasis-negative nodes (137 [41.8%] of 328; P < .01). Differences between positive and negative nodes in CT attenuation (110 HU +/- 25 vs 66 HU +/- 32) and short-to-long axis ratios (0.81 +/- 0.15 vs 0.57 +/- 0.15; P < .001) were significant. CONCLUSION: Helical CT is effective for detection of metastatic lymphadenopathy from gastric cancer. CT attenuation and lymph-node configuration aid in diagnosis of malignant adenopathy.

Adult↗
PubMed1995

[Selective intra-arterial injection of calcium for localization of insulinomas: proposed new criteria].

To elucidate whether noninvasive arterial stimulation venous sampling (ASVS) is helpful for localizing insulinomas, calcium gluconate (0.02-0.025 mEq Ca2+/kg) was injected directly into the gastroduodenal, splenic and superior mesenteric arteries of six patients with episodic hypoglycemia. In all six patients, there was a greater than 26-fold increase in serum insulin levels in blood samples obtained from the hepatic vein after the infusion of calcium into the artery supplying the tumor. However, in four of the six patients, such an injection into an artery not supplying the tumor resulted in a greater than twofold increase in insulin concentration. Accurate localization of the insulinomas was verified at surgery in all patients. We believe that these false positive results were caused mainly by the influx of calcium via branches of intrapancreatic anastomoses. In order to minimize false positive results, we have recommended the following new criteria for ASVS: maximum insulin concentrations exceeding 150 microU/ml in blood samples obtained from the hepatic vein, and greater than twofold increases in insulin concentration. We concluded that noninvasive ASVS is helpful in determining the location of insulinomas.

Adult↗
PubMed1994

The dependence of two-dimensional shape perception on orientation.

While it is true that in daily life we generally recognize objects regardless of their orientation, previous experiments involving novel shapes indicate a decline in recognition when these are tested in altered orientation. Here the question is raised of whether there is a component of shape perception based purely on the geometry of an object, independent of orientation. By means of two tests designed to eliminate awareness of change of orientation, one more stringent than used heretofore, it was found that shape perception is dependent on orientation. The apparent contradiction between these findings and the apparent orientation-free character of recognition in daily life is discussed.

Female↗
PubMed1990

[Radiology of trigeminal neuralgia--with special reference to CT findings].

CT findings in ninety-nine patients with trigeminal neuralgia were reviewed. Brain tumors including three trigeminal neurinomas, three meningiomas, one epidermoid, one acoustic neurinoma, were found in eight cases as a cause of symptomatic trigeminal neuralgia. Among seventy-nine patients with idiopathic trigeminal neuralgia, four cases had vascular decompression surgery because of the tortuous, ectatic or anomalous vertebrobasilar artery. Among the other seventy-five non-surgical cases, seventeen cases showed the tortuous and/or ectatic vertebrobasilar artery on CT, and this group of patients showed slightly higher recurrence rate of trigeminal neuralgia after nerve block or medication compared with other non-surgical patients. CT is thought to be a useful screening imaging modality for evaluation of patients with trigeminal neuralgia, and angiography is required for precise evaluation of the compressing vessels when surgical treatment is contemplated.

Adult↗