Corpus callosum may be similar in children with ADHD and siblings of children with ADHD

No previous studies have used morphological neuroimaging to compare children with ADHD with siblings of children with ADHD. To test the hypothesis that the total size of the corpus callosum is altered in children with hyperkinetic disorder, the corpus callosum was outlined from a single midline protondensity weighted slice (containing the septum pellucidum). Fifteen boys with a refined phenotype of ADHD (mean age 10.2 years) and 15 healthy male siblings of children with ADHD (mean age 10.6 years) were enrolled in the study. The two groups were compared for global brain size and the callosal areas of Witelson. No significant differences were found between the study and comparison groups for any of the corpus callosum areas, even after age, global brain size, and handedness were covaried (using MANOVA). In addition, corpus callosum sizes do not seem to differ between children with ADHD and unaffected siblings of children with ADHD. Clinicians should not base their pathophysiological diagnosis of this disorder on an abnormality of callosal development.

Anti-CD8 treatment alters interleukin-4 but not interferon-gamma mRNA levels in murine sensory ganglia during herpes simplex virus infection. Brief report

Clearance of herpes simplex virus (HSV) from sensory ganglia of infected mice is dependent on CD8(+) cells but not on the death of infected neurons. The mechanism of action of CD8(+) cells in HSV infected ganglia is therefore unknown. The determine which cytokines might be involved in the CD8(+) cell dependent response to ganglionic HSV infection, IL-2, IL-4, IL-6, IL-10, and IFN-gamma mRNA levels were measured in infected ganglia from immunocompetent and anti-CD8 treated mice. Anti-CD8 treatment increased the abundance of mRNA encoding IL-4, and, to a lesser extent, IL-2, and IL-6. Significantly, IFN-gamma mRNA was not affected.

Physical map and characterization of transcripts in the candidate interval for familial chondrocalcinosis at chromosome 5p15.1

The gene for familial chondrocalcinosis (MIM 118600; gene symbol CCAL2) has been localized to a 0.8-cM interval on the short arm of chromosome 5, between the polymorphic microsatellite markers D5S416 and D5S2114. We have undertaken the physical and transcript mapping of this interval, as well as regions telomeric to the interval, in an attempt to define ultimately the gene for this disorder. The physical map is composed of YAC, BAC, PAC, and cosmid resources and spans a physical distance of approximately 0.3 Mb. Using cDNA selection, we have identified eight novel transcripts in and around the interval; two of the selected transcripts reside in the candidate interval. We have also more precisely placed several expressed sequence tags (ESTs) that were previously mapped by radiation hybrid analysis and were reported to reside in or near the candidate interval. Two of the ESTs analyzed overlap with the selected cDNAs that reside in the candidate interval. All of the selected cDNAs are expressed partial transcripts, as determined by Northern blot analysis, and using RT-PCR analysis, we have determined that the cDNAs that reside in the candidate interval are expressed in cartilage and synovium, tissues that are presumably relevant to the chondrocalcinosis phenotype.

Distinct hyperintense MRI signal changes in the corticospinal tracts of a patient with motor neuron disease

Neuroimaging in motor neuron disease (MND) is currently performed to exclude other pathologies, though abnormalities may be seen which are consistent with the diagnosis. We report a patient with rapidly progressive MND exhibiting extensive changes on a variety of contemporary magnetic resonance images, which is most likely to represent severe corticospinal tract degeneration.

Remission of inflammatory arthropathy in association with anti-CD20 therapy for non-Hodgkin's lymphoma

We describe a case involving a 53-yr-old male with a marginal zone B-cell lymphoma, associated with an IgM paraprotein and a rheumatoid factor-negative inflammatory polyarthropathy, treated with monoclonal anti-CD20 antibody. During the subsequent 12 weeks, evidence of synovitis reduced to a negligible level, despite no significant change in lymphoma bulk or paraprotein level. The relationship between the lymphoma and the arthropathy, and the likely mechanism of remission of the arthropathy, are discussed in the context of the potential value of anti-CD20 therapy in rheumatoid arthritis.

Diffusion tensor MRI assesses corticospinal tract damage in ALS

BACKGROUND

A number of neurophysiologic and neuroimaging techniques have been evaluated in the research setting to assess upper motor neuron (UMN) damage in ALS. Changes in tissue structure in the CNS modify the diffusional behavior of water molecules, which can be detected by diffusion tensor MRI.

OBJECTIVES

To explore the hypothesis that degeneration of the motor fibers in ALS would be reflected by changes in the diffusion characteristics of the white matter fibers in the posterior limb of the internal capsule and that these changes could be detected by diffusion tensor MRI.

METHODS

We studied 22 patients with El Escorial definite, probable, or possible ALS-11 with limb onset (mean age 54.5 +/- 10.7 years) and 11 with bulbar onset (mean age 49.6 +/- 11.7 years)-and compared them with 20 healthy, age-matched controls (mean age 46.0 +/- 12.6 years). We assessed central motor conduction time (CMCT), threshold to stimulation, and silent period using transcranial magnetic stimulation. Diffusion tensor MRI was performed using a 1.5-T GE Signa system (Milwaukee, WI) fitted with Advanced NMR hardware and software capable of producing echo planar MR images. Data were acquired from seven coronal slices centered to include the posterior limb of the internal capsule. Maps of the mean diffusivity, fractional anisotropy, and T2-weighted signal intensity were generated.

RESULTS

There were no differences between the subject groups on measures of CMCT, threshold to stimulation, and silent period. However, the CMCT correlated with clinical measures of UMN involvement. We found a significant increase in the mean diffusivity and reduction in fractional anisotropy along the corticospinal tracts between the three subject groups, most marked in the bulbar-onset group. The fractional anisotropy correlated with measures of disease severity and UMN involvement, whereas the mean diffusivity correlated with disease duration.

CONCLUSION

The results support the use of diffusion tensor MRI in detecting pathology of the corticospinal tracts in ALS.

Non-invasive assessment of axonal fiber connectivity in the human brain via diffusion tensor MRI

A technique for assessing in vivo fiber connectivity in the human brain is presented. The method utilizes a novel connectivity algorithm that operates in three spatial dimensions and uses estimates of fiber tract orientation and tissue anisotropy, obtained from diffusion tensor magnetic resonance imaging, to establish the pathways of fiber tracts. Sample in vivo connectivity images from healthy human brain are presented that demonstrate connections in the white matter tracts. White matter connectivity information is potentially of interest in the study of a range of neurological, psychiatric, and developmental disorders and shows promise for following the natural history of disease.

Restricted replication of herpes simplex virus in satellite glial cell cultures clonally derived from adult mice

To determine the possible influence of satellite glial cells on restricting the spread of herpes simplex virus in the peripheral nervous system, HSV replication was studied in clonally derived cultures of satellite glial cells from adult animals. Satellite cells were purified by exploiting their close anatomical association with primary sensory neurons. Dissociated neurons from dorsal root ganglia were micro-manipulated to remove all but one of the attached satellite cells and cultured in the presence of the mitogenic stimulators bovine pituitary extract and cholera toxin. Following a lag phase of 20-30 days some of the individual satellite cells began to proliferate. Initial cultures demonstrated bipolar morphology similar to cultured Schwann cells, some of which differentiated into large astrocytic whorl-like cells on subsequent passage. Immunocytochemical and molecular studies demonstrated that these cells, designated Sat.1, express glial fibrillary acidic protein, confirming their glial origin and by electron microscopy they were shown to be phagocytic. Under single step viral growth conditions Sat.1 cells were restrictive for HSV replication, producing in the order of 1000 times less infectious virus than Vero cells, a standard permissive cell line. These results suggest that satellite cells, which tightly encase sensory neurons, play a role in restricting interneural spread of HSV within the peripheral nervous system.

Cell surface expression of H2 antigens on primary sensory neurons in response to acute but not latent herpes simplex virus infection in vivo

CD8(+) T lymphocytes and class I major histocompatibility complex (MHC-I) molecules profoundly influence the severity of neuronal herpes simplex virus (HSV) infection in experimentally infected mice. Paradoxically, neurons are classically regarded as MHC-I deficient. However, it is shown here that H2-encoded heavy chains (alphaCs) and their associated light chain, beta2 microglobulin, are present on the surfaces of primary sensory neurons recovered from sensory ganglia within 1 to 2 weeks of HSV infection. During this time, some neurons are found to be tightly associated with T cells in vivo. Prior data showed that termination of productive HSV infection in the peripheral nervous system is not dependent on cell-mediated lysis of infected neurons. Consistent with these data, immunogold electron microscopy showed that the density of cell surface H2 on neurons is an order of magnitude lower than on satellite glia, which is predicted to favor a noncytolytic CD8 cell response.

Non-invasive assessment of axonal fiber connectivity in the human brain via diffusion tensor MRI

A technique for assessing in vivo fiber connectivity in the human brain is presented. The method utilizes a novel connectivity algorithm that operates in three spatial dimensions and uses estimates of fiber tract orientation and tissue anisotropy, obtained from diffusion tensor magnetic resonance imaging, to establish the pathways of fiber tracts. Sample in vivo connectivity images from healthy human brain are presented that demonstrate connections in the white matter tracts. White matter connectivity information is potentially of interest in the study of a range of neurological, psychiatric, and developmental disorders and shows promise for following the natural history of disease.

Golfalpha is expressed in primary sensory neurons outside of the olfactory neuroepithelium

Golfalpha is the alpha chain of a trimolecular stimulatory G protein originally described as the G protein responsible for signal transduction in odourant recognition within neurons of the olfactory neuroepithelium. While applying the technique of mRNA differential display to herpes simplex virus infected tissue, a partial cDNA clone corresponding to the mouse homologue of Golfalpha was isolated from sensory dorsal root ganglia. Levels of this transcript were reduced following viral infection and this reduction was enhanced in CD8(+) depleted mice. The presence of this G protein within sensory ganglia was confirmed with Northern blotting and PCR and in situ hybridization studies localised Golfalpha expression exclusively to neurons within this tissue.

Functional magnetic resonance imaging neuroactivation studies in normal subjects and subjects with the narcoleptic syndrome. Actions of modafinil

Functional magnetic resonance imaging (fMRI) can be used to detect regional brain responses to changes in sensory stimuli. We have used fMRI to determine the amount of visual and auditory cortical activation in 12 normal subjects and 12 subjects with the narcoleptic syndrome, using a multiplexed visual and auditory stimulation paradigm. In both normal and narcoleptic subjects, mean cortical activation levels during the presentation of periodic visual and auditory stimulation showed no appreciable differences with either age or sex. Normal subjects showed higher levels of visual activation at 10:00 hours than 15:00 hours, with a reverse pattern in narcoleptic subjects (P = 0.007). The group differences in spatial extent of cortical activation between control and narcoleptic subjects were small and statistically insignificant. The alerting action, and imaging response, to a single oral dose of the sleep-preventing drug modafinil 400 mg were then determined and compared with placebo in both the 12 normal (8 given modafinil, 4 placebo) and 12 narcoleptic subjects (8 modafinil, 4 placebo). Modafinil caused an increase in self-reported levels of alertness in 7 of 8 narcoleptic subjects, but there was no significant difference between mean pretreatment and post-treatment activation levels as determined by fMRI for either normal or narcoleptic syndrome subjects given modafinil. However, in the modafinil-treated group of 8 normal and 8 narcoleptic subjects, there was a clock time independent correlation between the initial level of activation as determined by the pretreatment scan and the post-treatment change in activation (visual, P = 0.002; and auditory, P = 0.001). No correlation was observed in placebo-treated subjects (P = 0.99 and 0.77, respectively). Although limited by the small number of subjects, and the lack of an objective measure of alertness, the findings of this study suggest that low cortical activation levels in both normal and narcoleptic subjects are increased following the administration of modafinil. Functional magnetic resonance imaging may be a valuable addition to established studies of attention.

Social intelligence in the normal and autistic brain: an fMRI study

There is increasing support for the existence of 'social intelligence' [Humphrey (1984) Consciousness Regained], independent of general intelligence. Brothers et al. 1990) J. Cog. Neurosci., 4, 107-118] proposed a network of neural regions that comprise the 'social brain': the orbito-frontal cortex (OFC), superior temporal gyrus (STG) and amygdala. We tested Brothers' theory by examining both normal subjects as well as patients with high-functioning autism or Asperger syndrome (AS), who are well known to have deficits in social intelligence, and perhaps deficits in amygdala function [Bauman & Kemper (1988) J. Neuropath. Exp. Neurol., 47, 369]. We used a test of judging from the expressions of another person's eyes what that other person might be thinking or feeling. Using functional magnetic resonance imaging (fMRI) we confirmed Brothers' prediction that the STG and amygdala show increased activation when using social intelligence. Some areas of the prefrontal cortex also showed activation. In contrast, patients with autism or AS activated the fronto-temporal regions but not the amygdala when making mentalistic inferences from the eyes. These results provide support for the social brain theory of normal function, and the amygdala theory of autism.

Hypofrontality in attention deficit hyperactivity disorder during higher-order motor control: a study with functional MRI

OBJECTIVE

Functional magnetic resonance imaging (MRI) was used to investigate the hypothesis that attention deficit hyperactivity disorder (ADHD) is associated with a dysfunction of prefrontal brain regions during motor response inhibition and motor timing.

METHOD

Generic brain activation of seven adolescent boys with ADHD was compared to that of nine comparison subjects equivalent in sex, age, and IQ while they were performing a stop task, requiring inhibition of a planned motor response, and a motor timing task, requiring timing of a motor response to a sensory cue.

RESULTS

The hyperactive adolescents showed lower power of response in the right mesial prefrontal cortex during both tasks and in the right inferior prefrontal cortex and left caudate during the stop task.

CONCLUSIONS

ADHD is associated with subnormal activation of the prefrontal systems responsible for higher-order motor control. Functional MRI is a feasible technique for investigation of neural correlates of ADHD.

Quality control for functional magnetic resonance imaging using automated data analysis and Shewhart charting

A data acquisition and analysis protocol for quality control (QC) of functional magnetic resonance imaging studies is presented. Two sets of data are acquired, single-timepoint data for measurement of signal-to-ghost and signal-to-noise ratios, and multiple-timepoint data for measurement of short-term drift. Since manual data analysis can be time consuming and an impediment to regular QC, an automated data processing scheme is presented. The use of automated Shewhart charting is proposed to identify significant changes in each parameter over the long term. The protocol has successfully identified system faults and deteriorations undetected by conventional QC.

Attenuated frontal activation in schizophrenia may be task dependent

Functional magnetic resonance imaging was used to examine the neural correlates of two linguistic tasks in schizophrenia.

METHOD

Five dextral male schizophrenic patients and five volunteers matched for demographic variables and task performance participated. Echoplanar images were acquired over 5 min at 1.5 T while subjects performed two paced, covert tasks; (1) verbal fluency: silent generation of words beginning with an aurally presented cue letter, contrasted with silent repetition of the aurally presented word 'rest'; (2) semantic decision: deciding whether a visually presented cue word was 'living or non-living' and silently articulating the response, contrasted with rest. Both tasks entailed language processing; only verbal fluency requires the intrinsic generation of verbal material. Between-group differences in the mean power of experimental response to the semantic decision task were identified by a one-way analysis of covariance (ANCOVA), with a measure of stimulus-correlated motion as a covariate. Voxels demonstrating a significant interaction between task and group were identified using a two-way ANCOVA.

RESULTS

In controls, both tasks were associated with activation of prefrontal cortex. In patients with schizophrenia there was a significantly reduced power of response in several prefrontal regions during verbal fluency relative to controls, a difference that was not evident for the semantic decision task. There was a significant group x task interaction in the left inferior frontal gyrus, left dorsolateral prefrontal cortex and the supplementary motor area at voxel and regional levels of analysis.

CONCLUSIONS

Attenuation of frontal activation during cognitive task performance in schizophrenia does not represent a fixed deficit in frontal function, but may depend on the specific cognitive demands of the experimental task employed.

Characterization of white matter damage in ischemic leukoaraiosis with diffusion tensor MRI

BACKGROUND AND PURPOSE

Information on the neuropathological changes underlying ischemic leukoaraiosis is only available postmortem, and there are limited data on histological appearances early in the disease. Diffusion tensor imaging allows determination of the directionality of diffusion, which is greater in the direction of white matter bundles. Therefore, the technique might be expected to show loss of anisotropy (directional diffusion) in leukoaraiosis.

METHODS

Nine patients with ischemic leukoaraiosis (radiological leukoaraiosis and clinical lacunar stroke) and 10 age-matched controls were studied. Diffusion tensor imaging was performed, and maps of diffusion trace and fractional anisotropy were constructed. Mean values of trace and fractional anisotropy were determined in standard regions of the anterior and posterior white matter in both hemispheres.

RESULTS

In all patients with ischemic leukoaraiosis, a characteristic abnormal pattern was found, with loss of anisotropy and increased trace in the white matter. For example, in the right anterior white matter mean (SD) trace/3 was 1.12 (0.33) x10(-3) mm2 s-1 in patients and 0.75 (0.11) in controls (P=0.001). In the same region, fractional anisotropy was 0.53 (0.11) in patients and 0.78 (0.09) in controls (P<0.001). Within the white matter regions, there was a strong negative correlation between mean diffusivity and anisotropy (r=-0.92, P<0.0001).

CONCLUSIONS

The characteristic pattern found on diffusion tensor imaging in this patient group is consistent with axonal loss and gliosis leading to impairment to and loss of directional diffusion. The "in vivo histological" information obtained may be useful in monitoring disease progression and in investigating the pathogenesis of the cognitive impairment that may be present.

The functional anatomy of the McCollough contingent colour after-effect

We report two functional magnetic resonance imaging (fMRI) experiments which reveal a cortical network activated when perceiving coloured grids, and experiencing the McCollough effect (ME). Our results show that perception of red-black and green-black grids activate the right fusiform gyrus (area V4) plus the left and right lingual gyri, right striate cortex (V1) and left insula. The ME activated the left anterior fusiform gyrus as well as the ventrolateral prefrontal cortex, and in common with colour perception, the left insula. These data confirm the critical role of the fusiform gyrus in actual and illusory colour perception as well as revealing localized frontal cortical activation associated with the ME, which would suggest that a 'top-down' mechanism is implicated in this illusion.

Herpes simplex virus genome isomerization: origins of adjacent long segments in concatemeric viral DNA

Herpes simplex virus type 1 DNA isomerization was studied by using a viral mutant, 5B8, lacking the unique SpeI site of its parent, SC16. In coinfected cells, SC16 genomic long segments flanked 5B8 genomes in all possible orientations with similar frequencies. Thus, recombination between progeny of different replication templates is sufficient to explain genomic isomerization.

Prefrontal involvement in "temporal bridging" and timing movement

Brain activity exclusively related to a temporal delay has rarely been investigated using modern brain imaging. In this study we exploited the temporal resolution of functional magnetic resonance imaging (fMRI) to characterise, by sinusoidal regression analysis, differential neuroactivation patterns induced in healthy subjects by two sensorimotor synchronization tasks different in their premovement delay of either 0.6 s or 5 s. The short event rate condition required rhythmic tapping, while the long event rate condition required timing of intermittent movements. Left rostral prefrontal cortex, medial frontal cortex, SMA and supramarginal gyrus demonstrated increased MR signal intensity during low frequency synchronization, suggesting that these brain regions form a distributed neural network for cognitive time management processes, such as time estimation and motor output timing. Medial frontal cortex showed a biphasic pattern of response during both synchronization conditions, presumably reflecting frequency-independent motor output related attention. As predicted, sensorimotor and visual association areas demonstrated increased MR signal intensity during high frequency synchronization.

Exploring the temporal nature of hemodynamic responses of cortical motor areas using functional MRI

OBJECTIVE

To use functional MRI (fMRI) to study grouped patterns of cerebral activation and the course of hemodynamic responses during performance of two activation tasks (paradigms) using a hand-held joystick to perform movements in a repetitively fixed direction and movements in freely selected random directions.

BACKGROUND

Evidence from lesion, electrophysiologic, and functional imaging studies implicates prefrontal and mesial frontal cortex in motor preparation and primary motor cortex in motor execution. fMRI can be used to study cerebral activation and has practical advantages over other methods of functional neuroimaging.

METHODS

We acquired 100 multislice T2*-weighted data sets from five healthy volunteers during performance of each paradigm using conventional fMRI. For each paradigm, rest and movement epochs were alternated every 30 seconds. After coregistration and spatial normalization, we combined the data for group studies. We used statistical parametric mapping to compare the early (first 15 seconds) components of the movement epochs with rest as well as the late (last 15 seconds) components of the movement epochs with rest.

RESULTS

During the early phase of both paradigms, significant activation was present in rostral and caudal mesial premotor cortex. Right prefrontal cortex was significantly activated during the early component of freely selected joystick movements. Activation of rostral supplementary motor area was maintained during the late component of freely selected movements but decreased during repetitively fixed movements. In contrast, significant activation in contralateral sensorimotor cortex was maintained during both early and late components of both paradigms.

CONCLUSIONS

fMRI can detect cortical activation. The temporal resolution of fMRI also allows adaptation of blood oxygenation level-dependent (BOLD) contrast signal to be detected in association cortex. However, the level of BOLD contrast signal in primary motor cortex remained significantly elevated throughout task performance.

Residual processing of chromatic signals in the absence of a geniculostriate projection

We have investigated the residual processing of chromatic signals in a subject with unilateral damage to the primary visual cortex using psychophysical, pupillometric and functional magnetic resonance imaging (fMRI) methods. Of particular interest was to establish the correlation between the subject's ability to make use of chromatic signals in the blind hemifield to discriminate between different coloured targets, the corresponding residual pupil colour responses and the level and location of cortical activation generated by the same stimuli as revealed by fMRI. The results obtained using the three different experimental approaches are consistent and suggest that retrograde degeneration of thalamic and retinal chromatic processing mechanisms caused by damage to the primary visual cortex in man does not abolish completely the ability to process chromatic signals particularly when large, long-wavelength stimuli are employed.

Residual processing of chromatic signals in the absence of a geniculostriate projection

We have investigated the residual processing of chromatic signals in a subject with unilateral damage to the primary visual cortex using psychophysical, pupillometric and functional magnetic resonance imaging (fMRI) methods. Of particular interest was to establish the correlation between the subject's ability to make use of chromatic signals in the blind hemifield to discriminate between different coloured targets, the corresponding residual pupil colour responses and the level and location of cortical activation generated by the same stimuli as revealed by fMRI. The results obtained using the three different experimental approaches are consistent and suggest that retrograde degeneration of thalamic and retinal chromatic processing mechanisms caused by damage to the primary visual cortex in man does not abolish completely the ability to process chromatic signals particularly when large, long-wavelength stimuli are employed.