Identifying rate-limiting nodes in large-scale cortical networks for visuospatial processing: an illustration using fMRI

With the advent of functional neuroimaging techniques, in particular functional magnetic resonance imaging (fMRI), we have gained greater insight into the neural correlates of visuospatial function. However, it may not always be easy to identify the cerebral regions most specifically associated with performance on a given task. One approach is to examine the quantitative relationships between regional activation and behavioral performance measures. In the present study, we investigated the functional neuroanatomy of two different visuospatial processing tasks, judgement of line orientation and mental rotation. Twenty-four normal participants were scanned with fMRI using blocked periodic designs for experimental task presentation. Accuracy and reaction time (RT) to each trial of both activation and baseline conditions in each experiment was recorded. Both experiments activated dorsal and ventral visual cortical areas as well as dorsolateral prefrontal cortex. More regionally specific associations with task performance were identified by estimating the association between (sinusoidal) power of functional response and mean RT to the activation condition; a permutation test based on spatial statistics was used for inference. There was significant behavioral-physiological association in right ventral extrastriate cortex for the line orientation task and in bilateral (predominantly right) superior parietal lobule for the mental rotation task. Comparable associations were not found between power of response and RT to the baseline conditions of the tasks. These data suggest that one region in a neurocognitive network may be most strongly associated with behavioral performance and this may be regarded as the computationally least efficient or rate-limiting node of the network.

Hemispheric preference in visuospatial processing: a complementary approach with fMRI and lesion studies

Historically, the left cerebral hemisphere has been considered specialized for language, whereas the right cerebral hemisphere is aligned with spatial processes. However, studies have called into question adherence to this model and suggested that both hemispheres participate in language and spatial cognition. Using functional Magnetic Resonance Imaging (fMRI) and human brain lesion studies, we determined whether these complementary techniques could clarify issues of hemispheric dominance. Using a modified Benton Judgement of Line Orientation (JLO) test, considered a relatively pure spatial processing task, we found robust and significant (p < 0.0005) bilateral superior parietal lobe activation on fMRI in ten right-handed male adult volunteers. This was corroborated by lesion data in a cohort of 17 patients who showed significant JLO impairments after either right or left parietal lobe damage, with right parietal damage associated with somewhat more severe deficit. Detailed wavelet analysis of the fMRI time-series did, however, reveal a more dominant role of the right parietal lobe in "kick-starting" the task. To our knowledge, this is a novel way of using fMRI to address functional hemispheric differences in a cognitive task that is known to have bilateral representation.

Hemispheric preference in visuospatial processing: a complementary approach with fMRI and lesion studies

Historically, the left cerebral hemisphere has been considered specialized for language, whereas the right cerebral hemisphere is aligned with spatial processes. However, studies have called into question adherence to this model and suggested that both hemispheres participate in language and spatial cognition. Using functional Magnetic Resonance Imaging (fMRI) and human brain lesion studies, we determined whether these complementary techniques could clarify issues of hemispheric dominance. Using a modified Benton Judgement of Line Orientation (JLO) test, considered a relatively pure spatial processing task, we found robust and significant (p < 0.0005) bilateral superior parietal lobe activation on fMRI in ten right-handed male adult volunteers. This was corroborated by lesion data in a cohort of 17 patients who showed significant JLO impairments after either right or left parietal lobe damage, with right parietal damage associated with somewhat more severe deficit. Detailed wavelet analysis of the fMRI time-series did, however, reveal a more dominant role of the right parietal lobe in "kick-starting" the task. To our knowledge, this is a novel way of using fMRI to address functional hemispheric differences in a cognitive task that is known to have bilateral representation.

Cortical processing of human somatic and visceral sensation

Somatic sensation can be localized precisely, whereas localization of visceral sensation is vague, possibly reflecting differences in the pattern of somatic and visceral input to the cerebral cortex. We used functional magnetic resonance imaging to study the cortical processing of sensation arising from the proximal (somatic) and distal (visceral) esophagus in six healthy male subjects. Esophageal stimulation was performed by phasic distension of a 2 cm balloon at 0.5 Hz. For each esophageal region, five separate 30 sec periods of nonpainful distension were alternated with five periods of similar duration without distension. Gradient echoplanar images depicting bold contrast were acquired using a 1.5 T GE scanner. Distension of the proximal esophagus was localized precisely to the upper chest and was represented in the trunk region of the left primary somatosensory cortex. In contrast, distension of the distal esophagus was perceived diffusely over the lower chest and was represented bilaterally at the junction of the primary and secondary somatosensory cortices. Different activation patterns were also observed in the anterior cingulate gyrus with the proximal esophagus being represented in the right midanterior cingulate cortex (BA 24) and the distal esophagus in the perigenual area (BA32). Differences in the activation of the dorsolateral prefrontal cortex and cerebellum were also observed for the two esophageal regions. These findings suggest that cortical specialization in the sensory-discriminative, affective, and cognitive areas of the cortex accounts for the perceptual differences observed between the two sensory modalities.

Clinical evaluation of systemic doxycycline and ibuprofen administration as an adjunctive treatment for adult periodontitis

The objective of this study was to compare the efficacy of a systemic antibiotic (doxycycline) and a non-steroidal anti-inflammatory drug (ibuprofen), administered either separately or combined, as an adjunctive treatment of scaling/root planing (SRP). Thirty-two subjects diagnosed with generalized moderate adult periodontitis and having at least 2 teeth with > or =5 mm probing depth were randomly divided into 4 groups. Each group was treated with oral doxycycline and/or ibuprofen for 6 weeks as follows: group 1, doxycycline 200 mg the first day followed by 100 mg per day; group 2, ibuprofen 800 mg per day; group 3, doxycycline plus ibuprofen scheduled as in groups 1 and 2; group 4, one placebo capsule/day (control). A split mouth design was utilized in each subject such that half of the teeth received one session of scaling/root planing (SRP), while the other half received no SRP. Plaque index (PI), gingival index (GI), probing depth (PD), and clinical attachment level (CAL) using a customized acrylic stent were recorded at baseline and at 3, 6, 12, and 24 weeks following SRP. Analysis using ANOVA and Student t-test showed statistical significance (P< or =0.05) from baseline data in: 1) gains of 0.4 mm and 0.5 mm of CAL for groups 1 and 3, respectively; 2) reduction of 0.7 mm PD for group 3; 3) reduction of 0.4 and 0.1 GI scores for groups 1 and 3, respectively; and 4) gain of 0.5 mm CAL and reductions of 0.4 mm PD and 0.2 GI score for the SRP group when compared to the no SRP group at 24 weeks. It may be concluded that the adjunctive use of systemic doxycycline alone or in combination with ibuprofen results in a statistically significant, yet modest clinical, improvement beyond that obtained by scaling/root planing.

Amyloid angiopathy causing widespread miliary haemorrhages within the brain evident on MRI

The case of a 70-year-old woman with cerebral amyloid angiopathy (CAA) is presented. MRI of the head showed widespread miliary foci of haemorrhage within the cerebrum and cerebellum, with some additional linear lesions within the cerebral cortex and patchy lesions in the white matter. This is in contrast to the more usual pattern of intracranial haemorrhage in CAA, i.e., a lobar haematoma.

Preoperative endovascular embolisation of a vertebral haemangioma

We describe the successful relief of compression of the spinal cord due to a vertebral haemangioma by transcatheter embolisation using cyanoacrylate compounds before operation, and provide a brief review of the literature.

Ultrasound of the neonatal brain

Cranial ultrasound is currently the primary imaging modality employed in the assessment of the neonatal brain. Due to recent technological advances it is now possible to examine the developing cerebral surface, to assess sulcal-gyral maturation, and to investigate subtle changes in cerebral blood flow and parenchymal perfusion. This review discusses the currently accepted and the more controversial indications for neonatal transcranial ultrasound.

CT evaluation of treatment response in advanced gastric cancer

Ninety-one patients with advanced gastric carcinoma were followed by serial computed tomography (CT) in a phase II study using multi-agent chemotherapy. Regression of primary tumour was seen in 43, with complete resolution in 5 and > 50% regression in 29. Involvement of loco-regional lymph nodes was seen in 43 patients, with complete resolution in 16, and > 50% regression in 21. Hepatic metastases were seen in 40 patients, with complete resolution in three and > 50% regression in 17. Regression in other less common sites in the chest and abdomen were also documented. The pattern of maximum response in all sites of disease was seen within the first 12 weeks of chemotherapy. The difficulties of disease management are discussed and recommendations for CT evaluation in this group of patients are made.

Spontaneous rupture of the spleen in Legionnaires' disease

A case of Legionnaires' disease is described in a 63 year old man who presented with pneumonia and confusion. Eleven days after admission he became acutely hypotensive and attempts at resuscitation failed. Post-mortem examination revealed spontaneous splenic rupture and massive hepatocellular necrosis--an outcome that has not previously been associated with Legionnaires' disease.