Visual tasks that are perceptually diverse might be expected to elicit unique evoked-potential waveforms that exhibit differing topographic maps. To investigate this possibility, multichannel ...visual-evoked potentials (VEPs) were recorded in response to several dot spatial localization stimuli that are physically similar yet produce different percepts (vernier offsets, steroscopic disparity, bisection, orientation, and relative displacement) to determine if the unique percepts arising from these stimuli reflect the activation of different cortical neural populations. The resulting evoked potentials were all similar in waveform, although the stereoscopic VEPs were relatively delayed. Topographic maps of the evoked-potential activity to each stimulus revealed a late major component with two independent foci: one 7 or more centimeters above the inion lateral to the midline, and the other at least 6 cm lateral to OZ. The scalp localization of both peaks was independent of both the position of the stimulus in the visual field and the particular stimulus cue presented. An asymmetric response to pattern appearance vs. disappearance indicated strong pattern specificity for each stimulus type except unreferenced motion. The timing of the VEP responses and relative insensitivity to retinal locus of stimulation suggest the involvement of higher cortical areas. The two map foci might be interpreted as activation of inferotemporal and parietal cortices whose roles are thought to be visual object interpretation and spatial attention and localization, respectively.
A young scientist reported severe headaches emanating from behind one eye with an associated intermittent monocular blur. The monocular near cross-cylinder test revealed an accommodative fluctuation ...of one eye alone with a range of approximately 3 D. Referral to a neuro-ophthalmologist failed to produce a diagnosis for the disorder. A subsequent routine visit to a dentist provided a diagnosis of Costen's temporomandibular joint (TMJ) syndrome, a condition that is commonly misdiagnosed as a variety of neurological and vascular disorders.
Special Assessment Procedures Maino, Dominick; Bartuccio, Mary; Taub, Marc B
Visual Diagnosis and Care of the Patient with Special Needs,
2012
Book Chapter
Hyperacuity thresholds of a few arc seconds can be achieved psychophysically for a variety of spatial localization tasks. The present experiments show that evoked potentials can be elicited in ...response to the introduction of vernier offsets, but not by the introduction of other cues to hyperacuity such as bisection or relative pattern motion, although each of these cues is equally salient psychophysically. Moreover, vernier acuity measurements and the evoked potentials elicited in response to vernier offsets are strongly degraded by the introduction of flanking stimuli 2-4 min from the vernier target. This suggests that the hyperacuity VEP is a cortical correlate of a very specific type of hyperacuity, that produced by vernier offsets (colinearity failure).
Frequently, during the course of total shoulder arthroplasty, the measurement of the patient’s native glenoid is between the available prosthetic glenoid sizes. Technically, it may be easier for the ...surgeon to implant a smaller glenoid component. Currently, there is no information regarding the difference in joint stability by use of glenoid components of different sizes. Stability ratio measurements were performed by use of a multiaxis testing machine with 3 different glenoid sizes (small, medium, and large) and compared by use of analysis of variance and the Tukey HSD test. Changes in the size of the glenoid component were found to have a significant effect on the stability ratio. At a load of 50 N, the stability ratio increased by 18% from the small to the medium glenoid component and by 15% from the medium to the large glenoid in the superoinferior axis. In the anteroposterior axis, the stability ratio increased by 17% from small to medium and by 10% from medium to large. The results from this study indicate a modest increase in stability when one chooses the larger of the 2 glenoid components.
Two synthetic immunodominant and nonencephalitogenic peptides of myelin basic protein, N1-20 and AcN9-20, effectively compete with an encephalitogenic peptide, AcN1-11, in an in vitro T-cell response ...restricted by class II major histocompatibility complex products (I-Au). These mutant peptide constructs, which do not occur in nature, also compete with the self-antigen for the in vivo induction of T cells primed with the encephalitogen AcN1-11. By using these nonpathogenic competitor peptides, it is possible to prevent the development of a prototypic T-cell-mediated autoimmune disease, experimental allergic encephalomyelitis. These results suggest possibilities for the utilization of competitor peptides for therapy of T-cell-mediated autoimmune diseases linked to specific major histocompatibility complex genes.
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