The role of area 17 in visual imagery: convergent evidence from PET and rTMS.

Visual imagery is used in a wide range of mental activities, ranging from memory to reasoning, and also plays a role in perception proper. The contribution of early visual cortex, specifically Area 17, to visual mental imagery was examined by the use of two convergent techniques. In one, subjects closed their eyes during positron emission tomography (PET) while they visualized and compared properties (for example, relative length) of sets of stripes. The results showed that when people perform this task, Area 17 is activated. In the other, repetitive transcranial magnetic stimulation (rTMS) was applied to medial occipital cortex before presentation of the same task. Performance was impaired after rTMS compared with a sham control condition; similar results were obtained when the subjects performed the task by actually looking at the stimuli. In sum, the PET results showed that when patterns of stripes are visualized, Area 17 is activated, and the rTMS results showed that such activation underlies information processing.

The effect of visors on head and facial injury in National Hockey League players.

There has been an increase in the number of concussions sustained by players in the National Hockey League (NHL). While wearing a helmet is now required by the NHL, the face visor remains optional. It is unknown to what degree face visors influence concussion, other head injury and eye-injury rates at the professional level. Data from the 2001-2002 NHL season were examined. It was found that wearing a face visor did not significantly influence the prevalence of concussion. Visor protection did, however, minimise eye-injuries and other, non-concussion head injuries. These data suggest that, while a visor may prevent some head and eye-injuries, other measures may be necessary to reduce the number of concussions.

Tactile spatial resolution in blind braille readers.

OBJECTIVE: To determine if blind people have heightened tactile spatial acuity. BACKGROUND: Recently, studies using magnetic source imaging and somatosensory evoked potentials have shown that the cortical representation of the reading fingers of blind Braille readers is expanded compared to that of fingers of sighted subjects. Furthermore, the visual cortex is activated during certain tactile tasks in blind subjects but not sighted subjects. The authors hypothesized that the expanded cortical representation of fingers used in Braille reading may reflect an enhanced fidelity in the neural transmission of spatial details of a stimulus. If so, the quantitative limit of spatial acuity would be superior in blind people. METHODS: The authors employed a grating orientation discrimination task in which threshold performance is accounted for by the spatial resolution limits of the neural image evoked by a stimulus. The authors quantified the psychophysical limits of spatial acuity at the middle and index fingers of 15 blind Braille readers and 15 sighted control subjects. RESULTS: The mean grating orientation threshold was significantly (p = 0.03) lower in the blind group (1.04 mm) compared to the sighted group (1.46 mm). The self-reported dominant reading finger in blind subjects had a mean grating orientation threshold of 0.80 mm, which was significantly better than other fingers tested. Thresholds at non-Braille reading fingers in blind subjects averaged 1.12 mm, which were also superior to sighted subjects' performances. CONCLUSION: Superior tactile spatial acuity in blind Braille readers may represent an adaptive, behavioral correlate of cortical plasticity.

Hand response differences in a self-face identification task.

Evidence has indicated that the right frontal cortex is preferentially involved in self-face recognition. To test this further, we employed a face identification task and examined hand response differences (N=10). Pictures of famous faces were combined with pictures of the participants' faces (self) and their co-workers' faces (familiar). These images were presented as a 'movie' in which one face transformed into another. Under the first instruction set, the movies began with either the participant's face or a co-worker's face, and the sequences gradually morphed into a famous face. When told to stop the movie when the face in the sequence became famous, a significantly later 'frame' was identified when the movies were composed of self-faces and the participants responded with their left hand. When the movies started with the famous faces and participants had to stop the movie when it became their own or their familiar co-worker's image (Instruction set 2), a significantly earlier frame was identified in the 'Self: Left hand' condition. The data suggest that participants are inclined to identify images as their own when the right hemisphere is preferentially accessed.

Left hand advantage in a self-face recognition task.

Subjects were exposed to pictures of self and others (e.g., friend, stranger, and famous people) to determine if there was an advantage in reaction time and accuracy in identifying the self. It was found that upright and inverted self-faces were identified more rapidly than non-self faces when subjects responded with their left hand, which in other tasks has corresponded with contralateral hemispheric dominance. These data suggest that self-recognition may be correlated with neural activity in the right hemisphere, and that the differences observed may not be unique to self-face recognition. These results are in agreement with previous research indicating that self-directed awareness is correlated with right prefrontal activity.

Treatment of intermittent exotropia.

To study the long-range results of surgically treated intermittent exotropia, 100 consecutive patients have been followed up for an average of 6.1 years. In all cases, the initial procedure was bilateral recession of the lateral rectus muscles. The overall functional cure rate was 78%. To accomplish this result, 27 patients were operated on a second time, 21 for undercorrection and six for overcorrection. A number of patients cooperated very poorly or were lost to follow-up while still under treatment. Had these patients been eliminated from the series, the cure rate would have been greater than 90%. In this study, bilateral recession of the lateral rectus muscles corrected the distant measurement more than the near measurement only with the divergence excess type of deviation. Also, this procedure was not notably more effective with divergence excess than with basic-type intermittent exotropia.

Defective platelet aggregation to the calcium ionophore A23187 in a patient with a lifelong bleeding disorder.

A patient with a lifelong bleeding disorder is presented with a prolonged bleeding time and abnormal aggregation and secretion responses to arachidonic acid, thromboxane A2, PAF-acether and the divalent calcium ionophore A23187. Platelet alpha and dense granule contents and morphology appear normal. The proposed defect is due to an abnormality of a platelet intracellular calcium dependent process.

Alexia for Braille following bilateral occipital stroke in an early blind woman.

Recent functional imaging and neurophysiologic studies indicate that the occipital cortex may play a role in Braille reading in congenitally and early blind subjects. We report on a woman blind from birth who sustained bilateral occipital damage following an ischemic stroke. Prior to the stroke, the patient was a proficient Braille reader. Following the stroke, she was no longer able to read Braille yet her somatosensory perception appeared otherwise to be unchanged. This case supports the emerging evidence for the recruitment of striate and prestriate cortex for Braille reading in early blind subjects.

Modulation of corticospinal excitability by repetitive transcranial magnetic stimulation.

OBJECTIVE: Repetitive transcranial magnetic stimulation (rTMS) is able to modulate the corticospinal excitability and the effects appear to last beyond the duration of the rTMS itself. Different studies, employing different rTMS parameters, report different modulation of corticospinal excitability ranging from inhibition to facilitation. Intraindividual variability of these effects and their reproducibility are unclear. METHODS: We examined the modulatory effects of rTMS to the motor cortex at various frequencies (1, 10, 20 Hz) and at different time-points in twenty healthy volunteers. RESULTS: We observed significant inhibition of MEPs following 1 Hz rTMS and significant facilitation of MEPs following 20 Hz rTMS for both day1 and day 2. Interestingly, at 1 Hz and 20 Hz rTMS, the modulatory effect produced by rTMS was greater on day 2. However, there was no significant change in corticospinal excitability following 10 Hz rTMS neither on day 1 nor day 2. CONCLUSION: Our findings raise questions as to how stimulation parameters should be determined when conducting studies applying rTMS on multiple days, and in particular, studies exploring rTMS as a treatment modality in neuropsychiatric disorders.

Technique for construction of facial moulage.

A technique for fabrication of a facial moulage is described which is both simple and useful in preoperative evaluation for selected facial plastic-reconstructive procedures. There are many alternative methods and materials that could be used; the one described here is the one which best suits our needs. These techniques have been used by many people for many years and no claim is being made for any innovation in this regard. However, a simple, clear, step by step explanation of this technique is described.

Discrimination of spatial relations and features in faces: effects of inversion and viewing duration.

We studied discrimination of changes in eye position, mouth position, and eye colour at viewing durations ranging from 1 second to unlimited time. With upright faces, perception was rapid and did not improve above 2 seconds viewing time. Face inversion impaired discrimination of mouth position significantly, eye position slightly, but not eye colour. The 'inversion effect' for mouth position decreased with increasing stimulus duration, and disappeared when the subject knew that the only change in a trial was in mouth position. A subsequent experiment showed that the inversion impairment in the mouth region was not specific to spatial position but affected mouth colour to a lesser degree. When the mouth region was made more salient by increasing the frequency of mouth change trials, the inversion effect for mouth position decreased, and correlated with an increase in inversion effect for eye position but not eye colour. We conclude that the dominant effect of face inversion upon perception is decreased discrimination in less salient facial regions, that this impairment lessens with increasing viewing time, and that it affects both features and their spatial relations, though the effect on the latter is greater. These results are consistent with greater dependence on a serial component search strategy in inverted faces.

Pediatric mechanical ventilation technology.

An in-depth examination of ventilators currently marketed for the pediatric population and the technology associated with each is provided with this article. Also included is a discussion of an "ideal pediatric ventilator" and its application to the pediatric intensive care patient. Triggering, cycling, and limiting variability, costs, and special features currently available are detailed.

The surgical management of typhoid perforation in children.

Typhoid perforation still has a high mortality rate (19-59 per cent) and controversy regarding the management of patients with this complication still abounds. We report our experience of 26 children with histologically proven typhoid perforation with an operative mortality of 9.0 per cent. Timed surgery with ulcer excision, simple two-layer closure of the defect and copious peritoneal lavage were used.

The treatment of systemic lupus erythematosus (SLE) with the T-cell immunostimulant drug levamisole: A case report.

A 23-year-old woman with a nine-month history of SLE, uncontrolled with high daily doses of steroids, was treated with the T-cell immunostimulant drug, levamisole. Following a single oral three-day course of therapy with this agent her immunologic parameters and clinical manifestations underwent marked regression. Continuous two-weekly course of this drug at three days per course have allowed rapid reduction of her steroid and resulted in complete remission of her symptoms. The theoretical considerations for the use of levamisole dovetailed perfectly with the observed response to this agent.

Sclerotherapy for bleeding oesophageal varices--a fatal complication. A case report.

Although injection sclerotherapy for the control of bleeding varices is considered a relatively safe procedure, major complications can occur. A case is presented in which delayed perforation of the oesophagus due to ulceration led to a fatal outcome. The technique used and complications of the procedure are briefly discussed.