Direction-specific deficits in horizontal optokinetic nystagmus following removal of visual cortex in the cat.
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Animals↗
Biomedical subjects
C C Wood
Publications and source records attributed to C C Wood.
Auditory evoked potentials during speech perception.
Neural responses evoked by the same binaural speech signal were recorded from ten right-handed subjects during two auditory identification tasks. One task required analysis of acoustic parameters important for making a linguistic distinction, while the other task required analysis of an acoustic parameter which provides no linguistic information at the phoneme level. In the time interval between stimulus onset and the subjects' identification responses, evoked potentials from the two tasks were significantly different over the left hemisphere but identical over the right hemisphere. These results indicate that different neural events occur in the left hemisphere during analysis of linguistic versus nonlinguistic parameters of the same acoustic signal.
Adolescent↗
The influence of carbon dioxide on the interchange of ions between the corpuscles and the serum of blood.
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Journal Article↗
Nonlinear analysis of biological systems using short M-sequences and sparse-stimulation techniques.
The m-sequence pseudorandom signal has been shown to be a more effective probing signal than traditional Gaussian white noise for studying nonlinear biological systems using cross-correlation techniques. The effectiveness is evidenced by the high signal-to-noise (S/N) ratio and speed of data acquisition. However, the "anomalies" that occur in the estimations of the cross-correlations represent an obstacle that prevents m-sequences from being more widely used for studying nonlinear systems. The sparse-stimulation method for measuring system kernels can help alleviate estimation errors caused by anomalies. In this paper, a "padded sparse-stimulation" method is evaluated, a modification of the "inserted sparse-stimulation" technique introduced by Sutter, along with a short m-sequence as a probing signal. Computer simulations show that both the "padded" and "inserted" methods can effectively eliminate the anomalies in the calculation of the second-order kernel, even when short m-sequences were used (length of 1023 for a binary m-sequence, and 728 for a ternary m-sequence). Preliminary experimental data from neuromagnetic studies of the human visual system are also presented, demonstrating that the system kernels can be measured with high signal-to-noise (S/N) ratios using short m-sequences.
Computer Simulation↗
Potentials evoked in human and monkey medial temporal lobe during auditory and visual oddball paradigms.
Event-related potentials (ERPs) were recorded from epileptic patients with electrodes chronically implanted in the medial temporal lobe (MTL) and other intracranial locations, and from monkeys with epidural, transcortical, and MTL electrodes. For both humans and monkeys, the eliciting events consisted of trains of auditory or visual stimuli in which a random 10-20% deviated in pitch or pattern from the remaining stimuli. The distribution of ERPs elicited by the rare (oddball) stimuli in both species was similar, consisting of a P3 recorded from the scalp or cortical surface and a slightly later, but temporally overlapping, focal negativity in the hippocampus and nearby MTL structures. The similarity between the patterns of ERPs in humans and monkeys establishes the feasibility of studying the electrogenesis of P3-like activity with detailed intracranial recordings in an animal model. The data also establish that the MTL ERPs in human patients represent a normal neurophysiological process unrelated to epilepsy.
Acoustic Stimulation↗
The relationship between human long-latency somatosensory evoked potentials recorded from the cortical surface and from the scalp.
In scalp recordings, stimulation of the median nerve evokes a number of long-latency (40-300 msec) somatosensory evoked potentials (SEPs) whose neural origins are unknown. We attempted to infer the generators of these potentials by comparing them with SEPs recorded from the cortical surface or from within the brain. SEPs recorded from contralateral sensorimotor cortex can be characterized as "precentral," "postcentral," or "pericentral." The scalp-recorded P45, N60 and P100 potentials appear to correspond to the pericentral P50, N90 and P190 potentials and are probably generated mainly in contralateral area 1 of somatosensory cortex. The scalp-recorded N70-P70 appear to correspond to the precentral and postcentral N80-P80 and are generated mainly in contralateral area 3b of somatosensory cortex. The scalp-recorded N120-P120 appear to correspond to the intracranial N100-P100 and are probably generated bilaterally in the second somatosensory areas. N140 and P190 (the "vertex potentials") are probably generated bilaterally in the frontal lobes, including orbito-frontal, lateral and mesial (supplementary motor area) cortex. The supplementary sensory area probably generates long-latency SEPs, but preliminary recordings have yet to confirm this assumption. Most of the proposed correspondences are speculative because the different conditions under which scalp and intracranial recordings are obtained make comparison difficult. Human recordings using chronically implanted cortical surface electrodes, and monkey studies of SEPs which appear to be analogs of the human potentials, should provide better answers regarding the precise generators of human long-latency SEPs.
Adolescent↗
Retinotopic organization of human visual cortex: departures from the classical model.
Retinotopic mapping strategies similar to those used for invasive electrophysiological studies to identify multiple visual areas in monkeys have been adapted for noninvasive studies in humans, using magnetic recordings of brain activity in conjunction with anatomical magnetic resonance imaging. The retinotopic organization of the primary visual area (V1) in the left hemisphere of human subjects was examined by presenting a small patterned stimuli near the vertical and horizontal meridians in the lower right visual field. In contrast with the classical model of V1 retinotopy, our results suggest that the representation of the horizontal meridian does not necessarily correspond in a one-to-one manner with the base of the calcarine fissure and that some lower field stimuli can activate regions in the lower bank of the fissure. The results also indicate significant individual variability in the details of how V1 maps around the calcarine fissure.
Brain Mapping↗
Biogeographic implications of cytochrome b sequences and allozymes in sockeye (Oncorhynchus nerka).
Nucleotide sequence and restriction site analyses of the cytochrome b gene of mitochondrial DNA revealed three relatively common haplotypes among sockeye salmon (N = 80) from eight populations representing four major drainages from Kamchatka (Russia), Alaska, and British Columbia. Macrogeographic variation in mtDNA was compared to that of three variable allozyme loci assayed for a much larger number of fish (N = 779). Sockeye from the Fraser River drainage of British Columbia were distinct from those from the other three drainages in both analyses. The GT haplotype was found in all four populations, but the GC haplotype was absent from the Fraser River (southern) drainage and present in the three northern drainages. The AC haplotype was common in the Fraser River drainage (frequency = 0.4), rare in the Skeena River drainage of British Columbia (0.1), and absent from the Alaskan and Russian samples. Cluster analysis (UPGMA) of allozyme allele frequencies showed a similar pattern of divergence with the populations from the Fraser River drainage being most divergent and clustering at an identity value of 0.93 with the rest of the populations. Five of the remaining six populations clustered at or above an identity value of 0.99. These data, combined with allozyme data for sockeye and mitochondrial DNA data for chinook salmon and the Steller sea lion, indicate the presence of a phylogeographic break between northern and southern populations ostensibly derived from glacial refugia in Beringia and the Columbia River, respectively.
Animals↗
Ipratropium bromide nasal spray 0.03% provides additional relief from rhinorrhea when combined with terfenadine in perennial rhinitis patients; a randomized, double-blind, active-controlled trial.
Medical treatment of perennial rhinitis is aimed at providing symptomatic relief of individual symptoms. Multiple agents are administered when no single agent provides complete relief. Studies assessing the benefit/risk of combined therapy are important, especially for newly available agents such as ipratropium bromide nasal spray, a topical anticholinergic agent approved for the treatment of rhinorrhea in allergic and nonallergic perennial rhinitis. The objective was to determine whether the combined use of ipratropium bromide nasal spray 0.03% (42 mcg per nostril) administered three times daily with a nonsedating antihistamine (terfenadine, 60 mg administered twice daily) is safe and provides greater clinical benefit than use of the placebo nasal spray plus terfenadine. Our method was a multicenter, 6-week, double-blind, randomized, active-controlled, crossover trial of 205 patients with perennial rhinitis (114 allergic and 91 nonallergic), 18 to 75 years of age, who had clinically significant rhinorrhea. After a 1-week run-in period, patients were treated for 2 weeks with one of the two treatment regimens, followed by a 1-week washout period, and then were treated for another 2 weeks with the other treatment regimen. Daily diary symptoms scores of rhinorrhea, congestion, and sneezing were obtained, as well as biweekly patient and physician global assessments of treatment effectiveness of each of the nasal symptoms. Ipratropium bromide nasal spray plus terfenadine was more effective than vehicle plus terfenadine in reducing the average severity (38% versus 28%) and duration (46% versus 30%) of rhinorrhea during the 2 weeks of treatment from baseline (p < 0.05). The advantage of ipratropium bromide nasal spray plus terfenadine was evident by the second day of treatment and continued throughout the 2-week treatment period. Of patients who responded more to one treatment than another, 69% responded to ipratropium bromide nasal spray plus terfenadine, compared to 31% to vehicle plus terfenadine (p < 0.05). Both physicians and patients rated control of rhinorrhea and sneezing by ipratropium bromide nasal spray plus terfenadine as superior to vehicle plus terfenadine (p < 0.05). The symptom of congestion was controlled equally well by both treatments. Combined active therapy was well tolerated with no increase in adverse events over that seen previously with ipratropium bromide nasal spray alone. The combination of ipratropium bromide nasal spray with terfenadine is more effective than vehicle plus terfenadine for the treatment of rhinorrhea, and does not result in a potentiation of adverse drug reactions.
Administration, Intranasal↗
The anticholinergic agent, ipratropium bromide, is useful in the treatment of rhinorrhea associated with perennial allergic rhinitis.
The effects of the new ipratropium bromide nasal spray on rhinorrhea associated with perennial allergic rhinitis were studied in 219 patients over eight weeks in a multicenter, randomized, double-blind trial. The purpose of the study was to determine whether the new spray reduces nasal hypersecretion in allergic patients without causing excessive dryness or other potential cholinergic side effects. The investigators compared two doses of the spray (42 or 84 mcg/nostril t.i.d.) to placebo. Two hundred and nineteen patients were admitted to the study; 176 completed it. Study design included one week of screening to confirm a diagnosis of perennial allergic rhinitis with clinically significant rhinorrhea, one week of single-blind treatment with a placebo consisting of the saline vehicle of the spray, an eight-week double-blind treatment-comparison period, and one week of follow-up without treatment. Both doses of ipratropium bromide nasal spray significantly reduced the hypersecretion associated with PAR, compared with placebo. The two doses of active drug were equally effective. Treatment differences were noticeable during the first week and remained relatively stable during the eight-week treatment period. There was no evidence of nasal rebound after discontinuation of treatment. The incidence of side effects was comparable to placebo. The spray was well-tolerated, and was not associated with any significant adverse events.
Adolescent↗
Noninvasive preoperative cortical localization by magnetic source imaging.
The authors successfully used magnetoencephalography and MR data to localize the sensorimotor cortex in two patients prior to neurosurgery; preoperative localization influenced surgical management.
Adult↗