Edward J. Modestino

A Retrospective Survey of Childhood ADHD Symptomatology Among Adult Narcoleptics

Objective: This study examined the retrospective history of childhood ADHD symptomatology in an adult narcoleptic population (Narcolepsy Group [NG]: n = 161) compared with a control group (CG: n = 117). Method: Both groups completed the Wender Utah Rating Scale (WURS), a retrospective self-report questionnaire indicating the presence of childhood ADHD symptomatology in adults. Results: Childhood ADHD symptoms were significantly greater in NG than CG (p < .001). Joint prevalence calculations of childhood ADHD symptomatology in NG were more than 8 to 15 times greater than expected. Among NG, those individuals with a greater score on the WURS, indicative of childhood ADHD symptomatology, also had shorter sleep onsets on the Multiple Sleep Latency Test, a common objective measure of sleepiness, t(97) = −7.11, p < .05. Conclusion: It appears that self-reported childhood ADHD symptomatology history among adult narcoleptics is common. Future research is warranted with adult narcoleptics to elucidate the true nature of this.

Functional magnetic resonance imaging of the visual system.

Functional magnetic resonance imaging (fMRI), which is a technique useful for non-invasive mapping of brain function, is well suited for studying the visual system. This review highlights current clinical applications and research studies involving patients with visual deficits. Relevant reports regarding the investigation of the brains role in visual processing and some newer fMRI techniques are also reviewed. Functional magnetic resonance imaging has been used for presurgical mapping of visual cortex in patients with brain lesions and for studying patients with amblyopia, optic neuritis, and residual vision in homonymous hemianopia. Retinotopic borders, motion processing, and visual attention have been the topics of several fMRI studies. These reports suggest that fMRI can be useful in clinical and research studies in patients with visual deficits.

Reproducibility of visual activation during checkerboard stimulation in functional magnetic resonance imaging at 4 Tesla.

PURPOSE To investigate the reproducibility of visual activation by checkerboard stimulation, we used functional magnetic resonance imaging (fMRI) at 4 Tesla (T). METHODS Four subjects were studied with fMRI at 4 T during checkerboard visual stimulation. The functional images were realigned and spatially normalized to the standard brain. For each subject, statistical parametric maps were made for each study, and the reproducibility was determined based on the number of supra-threshold voxels (Z > 3.5, 4.5, and 5.5). RESULTS The mean ratio for the number of supra-threshold (Z > 4.5) voxels was 0.75, and the mean ratio for the overlapping voxels was 0.61. Restricting the region of interest within the posterior half of the brain improved reproducibility values at the low threshold (Z > 3.5), but did not improve the values at the higher thresholds. CONCLUSIONS Despite the fact that more than half of the supra-threshold voxels were found to be active for the repeated scans, visual activation with checkerboard stimulation seems to be less reproducible than that by flash stimulation.

Decreased Lateral Geniculate Nucleus Activation in Retrogeniculate Hemianopia Demonstrated by Functional Magnetic Resonance Imaging at 4 Tesla

Functional magnetic resonance imaging (fMRI) can detect lateral geniculate nucleus (LGN) activation. We studied LGN function in 5 patients with retrogeniculate homonymous hemianopia using fMRI at 4.0 Tesla during binocular visual stimulation. Decreased activation of visual cortex and LGN on the side of the lesion was observed in all 5 patients. These findings suggest that retrogeniculate lesions are associated with decreased activation of the LGN, due to retrograde degeneration or a functional decrease caused by decreased feedback from ipsilateral visual cortex.

Magno- and Parvocellular Visual Cortex Activation in Anisometropic Amblyopia, as Studied with Functional Magnetic Resonance Imaging

Purpose: We studied the functional magnetic resonance imaging (fMRI) of the visual cortex in order to activate preferentially the parvocellular (PC) or the magnocellular (MC) visual system by manipulation of the spatiotemporal characteristics of the stimuli. Then we applied this technique to a patient with amblyopia to see how these two visual systems are affected in amblyopia. Methods: We acquired the fMRI at 1.5 T in 8 normal subjects and in one patient with anisometropic amblyopia, each receiving their best refractive correction. Each subject underwent experimentation under five conditions. The MC stimulus had a low contrast, a large check size, and a high temporal frequency. The PC stimulus had a high contrast, a small check size, and a low temporal frequency. After the activation in each condition had been determined by contrasting the visual stimulation conditions with the condition at rest, the inter-eye difference was determined. Results: In normal subjects, the activation map showed different visual areas as well as some overlap between the MC and PC stimuli, and similar visual cortex activations were obtained under the right-eye and the left-eye stimulation conditions. In the patient with amblyopia, the inter-eye difference was within a 95% confidence interval for the MC stimulation, but not for the PC stimulation. Conclusions: Our fMRI results show a good localization of the activity in the MC and PC pathways, and they are consistent with the findings in the literature, suggesting that the PC visual pathway is primarily defective in amblyopia.

Recognition of objects in non-canonical views: a functional MRI study.

Background: The neural correlate of object recognition in non-canonical views is uncertain, but there is evidence for involvement of neural pathways, possibly separate from those used for object recognition in canonical views. Methods: Boxcar functional MRI (fMRI) techniques were used to detect neural activity while eight normal subjects were instructed to identify digital photographs of objects in non-canonical and canonical orientations. Results: The right angular gyrus, the left inferior temporal gyrus, and the right cerebellum showed significant fMRI activity during non-canonical as opposed to canonical viewing. Conclusions: Subjects recognizing objects in non-canonical orientations engage in a process separate from, or in addition to, the process used in recognizing objects in canonical orientations.

Functional magnetic resonance imaging of lateral geniculate nucleus and visual cortex at 4 Tesla in a patient with homonymous hemianopia

We present the functional magnetic resonance imaging findings at 4 Tesla in a 49-year-old male patient with a right thalamic tumor and left homonymous hemianopia. Markedly asymmetric activation of the lateral geniculate nucleus and visual cortex was found, and a pregeniculate or geniculate lesion was suspected from these findings. Functional magnetic resonance imaging at a high magnetic field can be useful in localizing a lesion responsible for visual loss.

Neural correlate of vernier acuity tasks assessed by functional MRI (FMRI).

Vernier acuity refers to the ability to discern a small offset within a line. However, while Vernier acuity has been extensively studied psychophysically, its neural correlates are uncertain. Based upon previous psychophysical and electrophysiologic data, we hypothesized that extrastriate areas of the brain would be involved in Vernier acuity tasks, so we designed event-related functional MRI (fMRI) paradigms to identify cortical regions of the brain involved in this behavior. Normal subjects identified suprathreshold and subthreshold Vernier offsets. The results suggest a cortical network including frontal, parietal, occipital, and cerebellar regions subserves the observation, processing, interpretation, and acknowledgment of briefly presented Vernier offsets.

Reward Deficiency Syndrome: Attentional/Arousal Subtypes, Limitations of Current Diagnostic Nosology, and Future Research.

We theorise that in some cases Attention Deficit Hyperactivity Disorder (ADHD) predisposes to narcolepsy and hypersomnia, and that there may be a shared pathophysiology with various addictions [Reward Deficiency Syndrome (RDS)]. Reticence to acknowledge such connections may be due to a narrow nosological framework. Additionally, we theorise that the development of narcolepsy on a baseline of ADHD/RDS leads to an additional assault on the dopaminergic reward system in such individuals. In this study, we propose to test these hypotheses by using a combination of broad genetic screening, and neuroimaging with and without pharmacological intervention, in those with pure ADHD, pure narcolepsy, and the combined ADHD-narcolepsy phenotype. Results of this proposed study may reveal a common pathophysiology of ADHD, narcolepsy and RDS, and perhaps an additional compromise to the reward system in those with combined ADHD-narcolepsy. If the evidence supports the hypothesis that indeed there is a shared pathophysiology for narcolepsy with RDS and thus its subtype ADHD, early intervention/preventative treatment amongst those with ADHD may be beneficial with the putative dopaminergic compound KB220Z™.