Strategies for optical control and simultaneous electrical readout of extended cortical circuits.

BACKGROUND: To dissect the intricate workings of neural circuits, it is essential to gain precise control over subsets of neurons while retaining the ability to monitor larger-scale circuit dynamics. This requires the ability to both evoke and record neural activity simultaneously with high spatial and temporal resolution. NEW METHOD: In this paper we present approaches that address this need by combining micro-electrocorticography (µECoG) with optogenetics in ways that avoid photovoltaic artifacts. RESULTS: We demonstrate that variations of this approach are broadly applicable across three commonly studied mammalian species - mouse, rat, and macaque monkey - and that the recorded µECoG signal shows complex spectral and spatio-temporal patterns in response to optical stimulation. COMPARISON WITH EXISTING METHODS: While optogenetics provides the ability to excite or inhibit neural subpopulations in a targeted fashion, large-scale recording of resulting neural activity remains challenging. Recent advances in optical physiology, such as genetically encoded Ca(2+) indicators, are promising but currently do not allow simultaneous recordings from extended cortical areas due to limitations in optical imaging hardware. CONCLUSIONS: We demonstrate techniques for the large-scale simultaneous interrogation of cortical circuits in three commonly used mammalian species.

Primate reaching cued by multichannel spatiotemporal cortical microstimulation.

Both humans and animals can discriminate signals delivered to sensory areas of their brains using electrical microstimulation. This opens the possibility of creating an artificial sensory channel that could be implemented in neuroprosthetic devices. Although microstimulation delivered through multiple implanted electrodes could be beneficial for this purpose, appropriate microstimulation protocols have not been developed. Here, we report a series of experiments in which owl monkeys performed reaching movements guided by spatiotemporal patterns of cortical microstimulation delivered to primary somatosensory cortex through chronically implanted multielectrode arrays. The monkeys learned to discriminate microstimulation patterns, and their ability to learn new patterns and new behavioral rules improved during several months of testing. Significantly, information was conveyed to the brain through the interplay of microstimulation patterns delivered to multiple electrodes and the temporal order in which these electrodes were stimulated. This suggests multichannel microstimulation as a viable means of sensorizing neural prostheses.

Deadbeat dads or inept states? A comparison of child support enforcement systems.

This article provides information on the effectiveness of state child support enforcement systems. We use individual level data from the Child Support Supplements of the Current Population Surveys (1978-1992) to create an index of state effectiveness that captures success at securing child support awards, setting award levels, and collecting obligations. We identify states that were performing above or below the national average in the late 1980s to early 1990s and states that showed substantial improvement or decline in child support effectiveness during the 1980s. Identifying successful states will help researchers to determine what policies and practices are associated with successful enforcement. These variations in state effectiveness also suggest that low levels of child support are not due to deadbeat dads alone but also to inept states.

Cranial/cervical nerve dysfunction after carotid endarterectomy.

PURPOSE: The purpose of this article is to review the results of patients who had cranial and cervical nerve dysfunction after undergoing carotid endarterectomy. METHODS: The prospective study reviewed 183 consecutive carotid endarterectomies. Preoperative and postoperative cranial nerve assessments were accomplished on all patients. Neurologic evaluation included direct fiberoptic laryngoscopy. Patients found to be neurologically intact had no further follow-up. Patients with postoperative neuropraxia were entered into regular long-term follow-up to assess delayed recovery. RESULTS: Twenty-six (14.2%) nerve injuries were identified in 21 patients. There were 14 recurrent laryngeal, 8 hypoglossal, 2 marginal mandibular, and 2 greater auricular nerve dysfunctions. Two patients were lost to follow-up. Eighteen (9.8%) nerve injuries were transient, whereas two (1.1%) were permanent. Four patients are currently undergoing extended follow-up to assess delayed recovery. Two patients with recurrent laryngeal nerve dysfunction were found to have prolonged full recovery intervals: 20 months and 50 months, respectively. CONCLUSIONS: The incidence of focal neuropraxia after carotid endarterectomy is presented. Most injuries are transient. However, permanent injuries can lead to significant disability. Extended follow-up will identify the small subset of patients with delayed complete nerve recovery.

Trends in child support outcomes.

This paper examines trends in child support award rates, award amounts, and receipts. We investigate four hypotheses that have been proposed to explain the downward trend in these outcomes during the 1980s: (1) changes in the demographic composition of the population eligible for child support, (2) increases in mothers' income, (3) decreases in fathers' income, and (4) inflation. Our results indicate that trends in nonmarital fertility can explain much of the decline in award rates. The steady downward trend in fathers' incomes during the 1980s also explains a considerable portion of the decline in award rates, award amounts, and receipts. Our results are also consistent with the notion that persistent money illusion is responsible for the decline in real child support awards.

Carotid duplex scan versus angiography in evaluation of carotid artery disease.

Angiography is presently felt to be the most accurate means of evaluating the carotid artery bifurcation, and is required preoperatively by most vascular surgeons. Arterial digital subtraction angiography (DSA) is the method commonly used. Angiography, however, is expensive and invasive, with significant morbidity and mortality. Duplex scanning (DS) has gained acceptance as a screening technique and has recently been advocated as the sole preoperative study in several centers because it is non-invasive and has an accuracy that is equal to or better than angiography. This study preoperatively evaluated 41 carotid arteries in 38 patients by arterial digital subtraction angiography and duplex scanning, and the results were compared to the surgical specimen. One artery was excluded because of an inadequate duplex scan, leaving 40 arteries studied by both techniques. Forty arteries (100%) studied by duplex scans corresponded with the surgical specimen, whereas only 31 arteries (77.5%) studied by DSA corresponded with the surgical specimen. Nine arteries (22.5%) studied by DSA had stenosis at the time of surgery significantly greater than predicted by DSA. Three arteries (7%) were felt to be normal by DSA, but had approximately 80 per cent stenosis by DS and at surgery. Our findings indicate that duplex scanning at our institution is more accurate than arterial DSA in determining percent diameter stenosis and plaque morphology of carotid arteries.

Immunoregulatory effects of Borrelia burgdorferi on T-B cell interactions.

Late stages of Lyme borreliosis are characterized by a disproportionate inflammatory response presumably elicited by only minute amounts of persisting antigen. To explore the possibility that amplification mechanisms of the immune response shape disease manifestations, we studied immunoregulatory properties of Borrelia burgdorferi antigens and analyzed whether they influence B cell-T cell cooperation. B. burgdorferi was found to induce peripheral resting B cells to function as effective antigen presenting cells for B. burgdorferi sonicate (Bb) and unrelated third party antigens. Morphologically and phenotypically, pulsed B cells represented small resting B cells and did not acquire activation markers. These data suggest that distinct antigen-presenting cells are involved in B. burgdorferi induced immune responses. B lymphocytes may play a crucial role in amplifying T cell responses, especially by recruiting antigen specific and nonspecific T cells to regions where minute amounts of spirochetal antigens are present.

The influence of resident surgical training on outcome of carotid endarterectomy in a teaching hospital.

Eighty-two consecutive patients who underwent 101 consecutive carotid endarterectomies (CEA) between 1982 and the first half of 1986 were evaluated. All of the operations were performed by fourth and fifth year general surgical residents under direct staff supervision. Hemispheric symptoms were present in 75 percent, and 64 per cent had a stenosis of 70 per cent or greater. In 24 per cent of the CEA, the indication for operation was a completed stroke. The operative stroke rate was 3 per cent and the mortality rate, 1 per cent. At a mean follow-up period of 17.4 months, no strokes had occurred, and the restenosis rate was 4 per cent over-all and 1 per cent in primary simple CEA. These results of CEA in a teaching hospital are excellent and indicate no compromise in patient care related to resident surgeons performing the procedures.