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BACKGROUND: In Canada, the annual incidence rates of West Nile virus (WNV) illness have fluctuated over the last 15 years. Ontario is one of the provinces in Canada most affected by WNV and, as a result, has implemented robust mosquito and human surveillance programs. OBJECTIVE: To summarize and discuss the epidemiology of WNV illness in Ontario, Canada in 2017, with comparisons to previous years. METHODS: Case data were obtained from the provincial integrated Public Health Information System. Provincial and public health unit (PHU)-specific incidence rates by year were calculated using population data extracted from intelliHEALTH Ontario. RESULTS: In 2017, the incidence of WNV illness in Ontario was 1.1 cases per 100,000 population, with 158 confirmed and probable cases reported by 27 of the province's 36 PHUs. This is the highest rate since 2013, but less than the rate in 2012 (2.0 cases per 100,000 population). Incidence rates in 2017 were highest in Windsor-Essex County and in PHUs in eastern Ontario. While the seasonality is consistent with previous years, the number of cases reported between July and September 2017 was above expected. Most cases were in older age groups (median: 58 years old) and males (59.5% of provincial total); cases with severe outcomes (neurological complications, hospitalizations, deaths) were also disproportionately in older males. CONCLUSION: WNV illness continues to be an ongoing burden in Ontario. The increase in the number of cases reported in 2017, and the increased number of PHUs reporting cases, suggests changing and expanding risk levels in Ontario. Continued mosquito and human surveillance, increased awareness of preventive measures, and early recognition and treatment are needed to mitigate the impact of WNV infections.

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BACKGROUND: Lyme disease is an infection caused by the spirochete Borrelia burgdorferi and, in most of North America, is transmitted by the blacklegged tick Ixodes scapularis. Climate change has contributed to the expansion of the geographic range of blacklegged ticks in Ontario, increasing the risk of Lyme disease for Ontarians. OBJECTIVE: To identify the number of cases and incidence rates, as well as the geographic, seasonal and demographic distribution of Lyme disease cases reported in Ontario in 2017, with comparisons to historical trends. METHODS: Data for confirmed and probable Lyme disease cases with episode dates from January 1, 2012, through December 31, 2017, were extracted from the integrated Public Health Information System (iPHIS). Data included public health unit (PHU) of residence, episode date, age and sex. Population data from Statistics Canada were used to calculate provincial and PHU-specific incidence rates per 100,000 population. The number of cases reported in 2017 by PHU of residence, month of occurrence, age and sex was compared to the 5-year averages for the period 2012-2016. RESULTS: There were 959 probable and confirmed cases of Lyme disease reported in Ontario in 2017. This was three times higher than the 5-year (2012-2016) average of 313. The provincial incidence rate for 2017 was 6.7 cases per 100,000 population, although this varied markedly by PHU. The highest incidence rates were found in Leeds-Grenville and Lanark District (128.8 cases per 100,000), Kingston-Frontenac, Lennox and Addington (87.2 cases per 100,000), Hastings and Prince Edward Counties (28.6 cases per 100,000), Ottawa (18.1 cases per 100,000) and Eastern Ontario (13.5 cases per 100,000). Cases occurred mostly from June through September, were most common among males, and those aged 5-14 and 50-69 years. CONCLUSION: In 2017, Lyme disease incidence showed a marked increase in Ontario, especially in the eastern part of the province. If current weather and climate trends continue, blacklegged ticks carrying tick-borne pathogens, such as those causing Lyme disease, will continue to spread into suitable habitat. Monitoring the extent of this geographic spread will inform future clinical and public health actions to detect and mitigate the impact of Lyme disease in Ontario.

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By 2013, the number of confirmed rabid animals in Ontario had decreased to unprecedented low numbers, yet the expected decrease in the number of courses of rabies post-exposure prophylaxis (RPEP) administered did not occur consistent with the decrease in animal rabies cases (Figure ). This prompted a review of the reasons that RPEP was administered in Ontario. This study provides a descriptive analysis of the exposure incidents resulting in RPEP administration in Ontario during 2013 using data obtained from the integrated Public Health Information System, a Web-based disease surveillance system. Findings from the study revealed that the number of RPEP courses administered could be reduced, without increased risk of rabies, through the following strategies: (i) Education and resources for public health staff and healthcare providers who assess animal exposures to improve interpretation of guidelines for RPEP administration. (ii) Refinement of guidelines for public health staff and healthcare providers to ensure that they support detailed consideration of the circumstances of the exposure in order to assist with the risk assessment. Guidelines should also support completion of a risk assessment when exposures to skunks, foxes, raccoons and other wild carnivores are provoked by the victim, as opposed to automatically providing RPEP as recommended by current guidelines. (iii) Public education strategies to prevent exposures to animals (e.g., do not touch unattended animals, bat proofing your house, proper removal of bats from the house). (iv) Defining the criteria to declare a jurisdiction rabies-free. (v) Exploring strategies to improve surveillance for rabid animals.

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In Ontario, Canada, the implementation of an annual rabies control programme in wildlife that began in 1989 resulted in a marked, steady decrease in the number of animal rabies cases. The number of animal rabies cases decreased from 1870 in 1989 to 183 in 2000 (Nunan et al., 2002 Emerg Infect Dis 8, 214). In our study period, the number of animal rabies cases continued to decrease from 210 in 2001 to 28 in 2012. The marked decrease in animal rabies cases since 1989 has resulted in a decrease in the risk of human infection. A concomitant decrease in the number of rabies post-exposure prophylaxis (RPEP) administered was anticipated but failed to occur. The mean rate of RPEP, 13.9 RPEP administered per 100,000 persons, from 2001-2012 was approximately the same as the rate in the 1990 s. Two possible reasons that the rate of RPEP administration has not decreased include strict adherence to RPEP recommendations and administration of RPEP when it is not recommended. A reduction in the number of RPEP administered, consistent with the decrease in the animal rabies cases, would provide some financial savings for the government. Ideally, an increased use of the risk assessment approach in keeping with recent guidelines, rather than adhering to previous prescriptive recommendations for RPEP administration, coupled with a continuing low incidence of animal rabies cases will result in decreased, and yet appropriate, use of RPEP. Consideration should be given to identify how guidelines could be revised to more effectively target high-risk exposures and reduce the administration of RPEP for instances in which the risk of rabies virus exposure is exceedingly low.

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Although the response of human cutaneous mechanoreceptors to controlled stimuli is well studied, it is not clear how these peripheral signals may be reflected in neuronal activity of the human CNS. We now test the hypothesis that individual neurons in the human thalamic principal somatic sensory nucleus [ventral caudal (Vc)] respond selectively to the optimal stimulus for one of the four mechanoreceptors. The optimal stimuli for particular mechanoreceptors were defined as follows: Pacinian corpuscles (PC), vibration at 128 Hz; rapidly adapting (RA), vibration at 32 or 64 Hz; slowly adapting type 1 (SA1), edge; slowly adapting type 2 (SA2), skin stretch. Nineteen neurons had a significant response to at least one optimal stimulus, and 17 had a significantly greater response to one stimulus than to the other three, including 7 PC-related, 7 RA-like, 3 SA1-like, and 2 SA2-like neurons. One of each of the SA1- and SA2-like thalamic neurons responded to vibration with firing rates that were lower than those to edge or stretch but not significantly. Except in the case of PC-related neurons, the receptive field (RF) sizes were larger for these thalamic neurons than for the corresponding mechanoreceptor. Von Frey thresholds were higher than those for the corresponding human RA and SA1 mechanoreceptors. These results suggest that there is a convergence of pathways transmitting input from multiple mechanoreceptors of one type on single thalamic neurons via the dorsal columns. They are also consistent with the presence of primate thalamic elements of modality and somatotopic isorepresentation.

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We investigated whether synchrony between neuronal spike trains is affected by the animal's attentional state. Cross-correlation functions between pairs of spike trains in the second somatosensory cortex (SII) of three macaque monkeys trained to switch attention between a visual task and a tactile task were computed. We previously showed that the majority of recorded neuron pairs (66%) in SII cortex fire synchronously while the animals performed either task and that in a subset of neuron pairs (17%), the degree of synchrony was affected by the animal's attentional state. Of the neuron pairs that showed changes in synchrony with attention, about 80% showed increased synchrony when the animal attended to the tactile stimulus. Here, we show that peak correlation typically occurred at a delay <25 ms; most commonly the delay was close to zero. Half-widths of the correlation peaks were distributed between a few milliseconds and hundreds of milliseconds, with the majority lying <100 ms and the mode of the distribution around 20-30 ms. Maximal change in synchrony occurred mainly during the periods when the stimulus was present, and synchrony usually increased when attention was on the tactile stimulus. If periods of elevated firing rates around the motor response times were removed from the analysis, the percentage of pairs that changed the degree of synchrony with attention more than doubled (from 35 to 72%). The observed effects did not depend on details of the statistical criteria or of the time window used in the analysis.

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We investigated the extent to which subjects' ability to perceive the fine spatial structure of a stimulus depends on its temporal properties (namely the frequency at which it vibrates). Subjects were presented with static or vibrating gratings that varied in spatial period (1-8 mm) and vibratory frequency (5-80 Hz) and judged the orientation of the gratings, presented either parallel or perpendicular to the long axis of the finger. We found that the grating orientation threshold (GOT)-the spatial period at which subjects can reliably discriminate the orientation of the grating-increased as the vibratory frequency of the gratings increased. As the spatial modulation of SA1 and RA afferent fibers has been found to be independent of vibratory frequency, the frequency dependence of spatial acuity cannot be attributed to changes in the quality of the peripheral signal. Furthermore, we found GOTs to be relatively independent of stimulus amplitude, so the low spatial acuity at high flutter frequencies does not appear to be due to an inadequacy in the strength of the afferent response at those frequencies. We hypothesized that the RA signal, the strength of which increases with vibratory frequency, interfered with the spatially modulated signal conveyed by SA1 fibers. Consistent with this hypothesis, we found that adapting RA afferent fibers improved spatial acuity, as gauged by GOTs, at the high flutter frequencies.

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SA1 and RA afferent fibers differ both in their ability to convey information about the fine spatial structure of tactile stimuli and in their frequency sensitivity profiles. In the present study, we investigated the extent to which the spatial resolution of the signal conveyed by SA1 and RA fibers depends on the temporal properties of the stimulus. To that end, we recorded the responses evoked in SA1 and RA fibers of macaques by static and vibrating gratings that varied in spatial period, vibratory frequency, and amplitude. Gratings were oriented either parallel to the long axis of the finger (vertical) or perpendicular to it (horizontal). We examined the degree to which afferent responses were dependent on the spatial period, vibratory frequency, amplitude, and orientation of the gratings. We found that the spatial modulation of the afferent responses increased as the spatial period of the gratings increased; the spatial modulation was the same for static and vibrating gratings, despite large differences in evoked spike rates; the spatial modulation in SA1 responses was independent of stimulus amplitude over the range of amplitudes tested, whereas RA modulation decreased slightly as the stimulus amplitude increased; vertical gratings evoked stronger and more highly modulated responses than horizontal gratings; the modulation in SA1 responses was higher than that in RA responses at all frequencies and amplitudes. The behavioral consequences of these neurophysiological findings are examined in a companion paper.

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Extended suprathreshold vibratory stimulation applied to the skin results in a desensitization of cutaneous mechanoreceptive afferents. In a companion paper, we describe the dependence of the threshold shift on the parameters of the adapting stimulus and discuss neural mechanisms underlying afferent adaptation. Here we describe the time-course of afferent adaptation and recovery. We found that absolute and entrainment thresholds rise and fall exponentially during adaptation and recovery with time constants that vary with fiber type. slowly adapting type I (SA1) afferents adapt most rapidly, and pacinian (PC) afferents adapt most slowly, whereas rapidly adapting (RA) afferents exhibit intermediate rates of adaptation; SA1 fibers also recover more rapidly from adaptation than RA and PC fibers. We also showed that threshold adaptation is accompanied by a shift in the timing of the spikes within individual cycles of the adapting stimulus (i.e., a shift in the impulse phase). We invoked an integrate-and-fire model to explore possible mechanisms underlying afferent adaptation. Finally, we found that the time-course of afferent adaptation is more rapid than that of its psychophysical counterpart, as is the time-course of recovery from adaptation, suggesting that central factors play a role in the psychophysical phenomenon.

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The objective of this study was to investigate the effects of extended suprathreshold vibratory stimulation on the sensitivity of slowly adapting type 1 (SA1), rapidly adapting (RA), and Pacinian (PC) afferents. To that end, an algorithm was developed to track afferent absolute (I0) and entrainment (I1) thresholds as they change over time. We recorded afferent responses to periliminal vibratory test stimuli, which were interleaved with intense vibratory conditioning stimuli during the adaptation period of each experimental run. From these measurements, the algorithm allowed us to infer changes in the afferents' sensitivity. We investigated the stimulus parameters that affect adaptation by assessing the degree to which adaptation depends on the amplitude and frequency of the adapting stimulus. For all three afferent types, I0 and I1 increased with increasing adaptation frequency and amplitude. The degree of adaptation seems to be independent of the firing rate evoked in the afferent by the conditioning stimulus. In the analysis, we distinguished between additive adaptation (in which I0 and I1 shift equally) and multiplicative effects (in which the ratio I1/I0 remains constant). RA threshold shifts are almost perfectly additive. SA1 threshold shifts are close to additive and far from multiplicative (I1 threshold shifts are twice the I0 shifts). PC shifts are more difficult to classify. We used an integrate-and-fire model to study the possible neural mechanisms. A change in transducer gain predicts a multiplicative change in I0 and I1 and is thus ruled out as a mechanism underlying SA1 and RA adaptation. A change in the resting action potential threshold predicts equal, additive change in I0 and I1 and thus accounts well for RA adaptation. A change in the degree of refractoriness during the relative refractory period predicts an additional change in I1 such as that observed for SA1 fibers. We infer that adaptation is caused by an increase in spiking thresholds produced by ion flow through transducer channels in the receptor membrane. In a companion paper, we describe the time-course of vibratory adaptation and recovery for SA1, RA, and PC fibers.

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Combined psychophysical and neurophysiological research has resulted in a relatively complete picture of the neural mechanisms of tactile perception. The results support the idea that each of the four mechanoreceptive afferent systems innervating the hand serves a distinctly different perceptual function, and that tactile perception can be understood as the sum of these functions. Furthermore, the receptors in each of those systems seem to be specialized for their assigned perceptual function.

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Combined psychophysical and neurophysiological studies have shown that the perceived roughness of surfaces with element spacings of >1 mm is based on spatial variation in the firing rates of slowly adapting type 1 (SA1) afferents (mean absolute difference in firing rates between SA1 afferents with receptive fields separated by approximately 2 mm). The question addressed here is whether this mechanism accounts for the perceived roughness of surfaces with element spacings of <1 mm. Twenty triangular and trapezoidal gratings plus a smooth surface were used as stimulus patterns [spatial periods, 0.1-2.0 mm; groove widths (GWs), 0.1-2.0 mm; and ridge widths (RWs), 0-1.0 mm]. In the human psychophysical studies, we found that the following equation described the mean roughness magnitude estimates of the subjects accurately (0.99 correlation): 0.2 + 1.6GW - 0.5RW - 0.25GW(2). In the neurophysiological studies, these surfaces were scanned across the receptive fields of SA1, rapidly adapting, and Pacinian (PC) afferents, innervating the glabrous skin of anesthetized macaque monkeys. SA1 spatial variation was highly correlated (0.97) with human roughness judgments. There was no consistent relationship between PC responses and roughness judgments; PC afferents responded strongly and almost equally to all of the patterns. Spatial variation in SA1 firing rates is the only neural code that accounts for the perceived roughness of surfaces with finely and coarsely spaced elements. When surface elements are widely spaced, the spatial variation in firing rates is determined primarily by the surface pattern; when the elements are finely spaced, the variation in firing rates between SA1 afferents is determined by stochastic variation in spike rates.

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The spatial acuity of the index, middle, and ring distal finger pads of eight right-handed men, aged 22 to 57 years, was measured by using gratings and raised letters. Acuity declined significantly from the index to the middle finger and from the middle to the ring finger. There were no significant differences between homologous fingers of the two hands. Letter recognition and grating orientation threshold measures were highly correlated.

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We recorded action potentials from three RA fibers innervating primate fingerpad, while applying electrotactile (electrocutaneous) stimulation. Negative pulses required 1.3-1.5 times more current than positive ones for entrainment. The strength-duration time constant was approximately 151 micros. Suprathreshold sinusoidal vibration synchronized to 30-Hz electrotactile pulses changed the electrotactile entrainment current slightly, indicating a possible electrical-mechanical transduction interaction.

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A potentially powerful information processing strategy in the brain is to take advantage of the temporal structure of neuronal spike trains. An increase in synchrony within the neural representation of an object or location increases the efficacy of that neural representation at the next synaptic stage in the brain; thus, increasing synchrony is a candidate for the neural correlate of attentional selection. We investigated the synchronous firing of pairs of neurons in the secondary somatosensory cortex (SII) of three monkeys trained to switch attention between a visual task and a tactile discrimination task. We found that most neuron pairs in SII cortex fired synchronously and, furthermore, that the degree of synchrony was affected by the monkey's attentional state. In the monkey performing the most difficult task, 35% of neuron pairs that fired synchronously changed their degree of synchrony when the monkey switched attention between the tactile and visual tasks. Synchrony increased in 80% and decreased in 20% of neuron pairs affected by attention.

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This is the third in a series of studies of the neural representation of tactile spatial form in somatosensory cortical area 3b of the alert monkey. We previously studied the spatial structure of >350 fingerpad receptive fields (RFs) with random-dot patterns scanned in one direction () and at varying velocities (). Those studies showed that area 3b RFs have a wide range of spatial structures that are virtually unaffected by changes in scanning velocity. In this study, 62 area 3b neurons were studied with three to eight scanning directions (58 with four or more directions). The data from all three studies are described accurately by an RF model with three components: (1) a single, central excitatory region of short duration, (2) one or more inhibitory regions, also of short duration, that are adjacent to and nearly synchronous with the excitation, and (3) a region of inhibition that overlaps the excitation partially or totally and is temporally delayed with respect to the first two components. The mean correlation between the observed RFs and the RFs predicted by this three-component model was 0.81. The three-component RFs also predicted orientation sensitivity and preferred orientation to a scanned bar accurately. The orientation sensitivity was determined most strongly by the intensity of the coincident RF inhibition in relation to the excitation. Both orientation sensitivity and this ratio were stronger in the supragranular and infragranular layers than in layer IV.

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Four types of mechanoreceptive afferents innervate the glabrous skin of the hand. Evidence from more than three decades of combined psychophysical and neurophysiological research supports the idea that each afferent type serves a distinctly different sensory function and that these functions explain most of tactual perceptual function. The available evidence supports the following hypotheses: (1) The slowly adapting type 1 system provides the information on which form and texture perception are based. (2) The cutaneous rapidly adapting system provides information about minute skin motion and, thereby, plays a critical role in grip control. (3) The Pacinian system is responsible for the detection and perception of distant events by vibrations transmitted through objects, probes, and tools held in the hand. (4) The slowly adapting type 2 system provides information for the perception of hand conformation and for the perception of forces acting on the hand. The authors review the evidence on which these hypotheses are based. They also review the role of proprioceptive afferents in the perception of hand conformation because they appear to play a significant role along with cutaneous afferents.

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Twenty-four slowly adapting type 1 (SA1) and 26 rapidly adapting (RA) cutaneous mechanoreceptive afferents in the rhesus monkey were studied with an array of independently controlled, punctate probes that covered an entire fingerpad. Each afferent had a receptive field (RF) on a single fingerpad and was studied at 73 skin sites (50 mm2). The entire array was lowered to 1.6 mm below the point of initial skin contact (the background indentation) before delivering single-probe indentations. SA1 and RA responses differed in several ways. 1) SA1 RF boundaries were affected much less by indentation depth than were RA boundaries, and the SA1 RF areas were much more uniform in size. The mean SA1 RF area grew from 5.1 to 8.8 mm2 as the indentation depth increased from 50 to 500 microm; the mean RA RF area grew from 5.5 to 22.4 mm2 over the same intensity range. 2) SA1 RFs were more elongated than RA RFs. Elongated RFs were oriented in all directions relative to the skin ridges and the finger axis. 3) SA1 impulse rates were linear functions of indentation depth at all probe locations in the RF; RA responses tended toward saturation beginning at 100 microm indentation depth when the probe was over the HS. Similarities between SA1 and RA responses were that 1) both were extremely repeatable with SDs < 1 impulse per trial and 2) both had population responses (number of impulses) that were nearly linear functions of indentation depth. However, SA1s represented increasing indentation depth by increasing impulse rates in a small, relatively constant group of afferents, whereas the RAs represented increasing indentation depth predominantly by the recruitment of new afferents at a distance.

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Twenty-four slowly adapting type 1 (SA1) and 26 rapidly adapting (RA) cutaneous mechanoreceptive afferents in the rhesus monkey were studied with an array of independently controlled, punctate probes that covered an entire fingerpad. Each afferent had a receptive field (RF) on a single fingerpad and was studied at 73 skin sites (50 mm2). The entire array was lowered to 1.6 to 3.0 mm below the point of initial skin contact (the background indentation) before delivering indentations with one to seven probes. Indentations were generally limited to 100 microm to minimize gross mechanical interactions. There were two major, new findings. 1) The discharge rates of both SA1 and RA afferents were strongly affected by the number of probes indenting the RF simultaneously. The effect was exponential. Each increase in probe number reduced the response by 24% in SA1 and 12% in RA afferents on average. When seven probes indented the skin simultaneously, the impulse rates in SA1 and RA afferents were reduced to 20 and 40% of the rates evoked by a single probe at the hot spot (all indentations were 100 microm). This shows that before any synaptic interaction in the CNS there is already a mechanism analogous to surround inhibition that suppresses an afferent's responses to uniform indentation and makes it especially sensitive to deviations from spatial uniformity. 2) The responses of both SA1 and RA afferents were independent of background array depth over the range from 1.6 to 3 mm below the point of initial skin contact. This shows that the neural responses to elements raised above a background are independent of the applied force over a wide range of forces. To relate the background depths to indentation force and to compare humans and monkeys, we studied the biomechanics of indentation with a uniform surface. A remarkable result is that the force-displacement relationships in humans and monkeys were the same; the skin is highly compliant for the first 2-3 mm of indentation and then becomes much stiffer. The results were the same in alert humans and monkeys and in monkeys anesthetized with pentobarbital. Ketamine anesthesia made the skin much stiffer and reduced the compliant range substantially.

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