Arousal systems.

Recent advances in neural and behavioural pharmacology, and in intracellular recording suggest that arousal during the awake state may be regulated by multiple, interdependent neurotransmitter systems that originate in the brainstem or hypothalamus, and project to subcortical and cortical sites. We discuss efforts to determine the mechanisms by which these systems extent their effects, and the roles that they play in the control of arousal.

Norepinephrine and acetylcholine mediation of the components of reflexive attention: implications for attention deficit disorders.

Attention deficit hyperactivity disorders (ADHD) create major learning barriers for children and significant social and legal handicaps for adults worldwide. Important advances in the genetic basis of the disease have been made, but reliable, biological, diagnostic markers remain elusive. This review takes the position that future progress in treating the core symptom of attention deficits requires a clearer understanding of the neuroscience of attention in normal individuals. Two important achievements in this direction have been the development of tasks that identify activity in the orienting, alerting and conflict networks, and the identification of neurotransmitters that mediate these components. The proven ability of these tasks to identify and characterize response components of "normal" attention argues that they could be used advantageously with patient populations. The categorization of neurotransmitter abnormalities in those with ADHD could clarify whether attention deficits occur within or across attention networks. To realize these goals, we evaluate laboratory studies of attention in humans and animals that address the underlying neurotransmitter systems, primarily norepinephrine and acetylcholine. We propose that key facts about deficits in reflexive and voluntary attention may be understood by a model that includes deficits in brain norepinephrine release and its effects on cholinergic activity in the parietal cortex.

Cholinergic modulation of covert attention in the rat.

RATIONALE: Nicotine is known to facilitate attentional processing, but its role in processing spatial and non-spatial cues is not well established in rodents. OBJECTIVE: These experiments tested the hypothesis that nicotine facilitates the orienting of attention in space but has no effect on non-spatial cues and that the benefits are blocked by the nicotinic antagonist mecamylamine. METHODS: Eight male rats were trained to insert their noses in an opening, which triggered the presentation of cue and target lights in a modified covert orienting task. Four types of trials were presented: valid cues (cue and target lights on the same side of the nose hole), invalid cues (cue and targets on opposite sides), double cues (both cue lights illuminated, target on either side), and no cue (cue lights omitted, targets on either side). The reaction time required to withdraw the nose from the fixation hole (RT) and the time for the rat to move to the feeder (MT) were measured. RESULTS: Nicotine decreased all RTs in a dose-dependent manner but significantly lowered the invalid cue RTs and the validity effect (invalid-valid cue RT). Mecamylamine slowed RTs in a dose-dependent fashion and reduced the validity effect by significantly slowing the valid cue RTs. With mixtures of a fixed strength of nicotine and an increasing dose of mecamylamine, RTs showed nicotine-like effects at low doses and mecamylamine-like effects at high doses. Neither of these drugs had a major effect on non-orienting trials (double and no cue RTs), and the alerting effect (no cue RTs-double cue RTs). CONCLUSIONS: Taken together with recent work in humans and non-human primates, these results suggest that the nicotinic cholinergic modulation of visual covert orienting is conserved across species despite different ecological niches.

Alteration of brain noradrenergic activity in rhesus monkeys affects the alerting component of covert orienting.

Experiments were conducted to elucidate the role of the noradrenergic neurotransmitter system in arousal and the orienting of attention. Rhesus monkeys were trained to perform a peripherally cued, covert orienting task for juice reward, and their manual reaction times (RTs) to visual stimuli were measured. The effects of parenteral injections of the alpha-2 adrenergic agonists clonidine and guanfacine, and normal saline were compared on the covert task. We assessed 1) overall error rates, 2) the difference in RTs between validly and invalidly cued trials (validity effect), 3) the difference in RTs between neutral and no-cue trials (alerting effect), 4) target location (visual field), and 5) cue-target interval. Changes in noradrenaline levels produced by clonidine (and to a lesser extent guanfacine) significantly decreased the alerting effect, and lowered RTs to stimuli in the left visual field, but did not change the validity effect, suggesting that noradrenaline is involved in maintaining non-spatial, sensory readiness to external cues but not in the shifting of the attentional focus.

Scopolamine slows the orienting of attention in primates to cued visual targets.

The cholinergic agonist nicotine facilitates visuospatial attention shifting, but the role of muscarinic cholinergic drugs in this behavior is unclear. In order to establish the generality of cholinergic action in attention shifting, we administered the muscarinic antagonist scopolamine to two rhesus monkeys trained to perform a cued target detection (Posner) task. In this task, monkeys signaled the detection of a peripheral visual target by releasing a switch and their reaction times were measured. The location of the target's appearance was preceded by a cue that was either valid (target and cue in the same spatial location), invalid (target and cue to opposite hemifields), spatially uninformative (cues in both hemifields, target to one hemifield), or omitted altogether. Scopolamine produced a dose-dependent increase in all reaction times and a decrease in accuracy. The slowing was most prominent for valid cues in either visual field. However, slowing did not occur in trials whose cues lacked spatial information, or in tasks in which attention was directed to events at the fixation point, whether or not peripheral distractors were present. These results provide additional support for the hypothesis that acetylcholine plays a key role in reflexive attention shifting to peripheral visual targets.

Effects of altering brain cholinergic activity on covert orienting of attention: comparison of monkey and human performance.

Experiments were conducted to elucidate the role of the cholinergic neurotransmitter system in arousal and the orienting of attention to peripheral targets. Rhesus monkeys and humans fixated a visual stimulus and responded to the onset of visual targets presented randomly in two visual field locations. The target was preceded by a valid cue (cue and target at the same location), an invalid cue (cue and target to opposite locations), a double cue (cues to both spatial locations, target to one), or, the cue was omitted (no-cue, target to either location). Reaction times (RTs) to the onset of the target were recorded. For monkeys, systemic injections of nicotine (0.003-0.012 mg/kg) or atropine (0.001-0.01 mg/kg), but not saline control injections, reduced mean RTs for all trials, indicating general behavioral stimulation. In addition, nicotine significantly reduced RTs for invalid trials but had little additional effect on those for valid, double, or no-cue trials. Virtually identical effects were observed for human chronic tobacco smokers in performing the same task following cigarette smoking. Injections of atropine in monkeys had no effect on RTs for valid or invalid trials but significantly slowed RTs in double-cue trials that did not require the orienting of attention. These results suggest that in both species, the nicotinic cholinergic system may play a role in automatic sensory orienting. In addition, the muscarinic system may play a role in alerting to visual stimuli in monkeys.

Visual orienting and alerting in rhesus monkeys: comparison with humans.

The behavioral capacities of the rhesus monkey for several sensory and cognitive tasks appear quite similar to those of humans. To evaluate the monkey's attentional capacities, we have compared monkey and human performance on a visuospatial attentional task, the cued target detection (CTD) paradigm. Animals were trained to fixate a small spot of light while a cue and a subsequent target, are flashed in the visual periphery. In valid trials, the cue and target appeared in the same spatial location; in invalid trials, the cue and target appeared in the opposite location; in double trials, two cues were presented and the target appeared in one of their locations; in no-cue trials, the cue was omitted and the target appeared in one location. In addition, we varied cognitive control over the task initiation by making the trial onset either self-paced or computer-paced. Reaction times (RTs) to target presentation, response accuracy, and frequency of aborted trials were measured for all subjects. No significant species differences were found for the patterns of RTs for different trial types or for attentional dynamics, as indexed by the decreases in RT with increasing cue-target interval. However, humans and non-human primates reacted differently to changes in cognitive control. Humans shows significant increases in no-cue trial RTs in the auto-paced task compared to the self-paced, but no differences in overall RT between tasks; monkeys showed a significant faster overall RT for the self-paced than the computer-paced task, but no difference between no-cue RTs. The performance differences between species may be related to the training history of the animals or to known anatomical differences in cortical organization, especially in the parietal lobe.

Saccades induced by stimulation of the frontal eye fields: interaction with voluntary and reflexive eye movements.

Saccadic eye movements were evoked in alert monkeys by electrical stimulation of the frontal eye fields (FEF). The interaction of FEF movements with voluntary saccades, pursuit, and vestibular nystagmus (VN) was examined. An FEF saccade in one direction could be evoked as little as 10 msec after the onset of a natural rapid movement (saccade, fast phase of VN) in the opposite direction. Thus, refractory periods between similar eye movements are directionally specific. The frequency of evoked FEF saccades following natural slow movements (pursuit, slow phase of VN) in either direction was reduced as though saccade thresholds were elevated. The FEF appears capable of modulating any ongoing eye movement.

The influence of the visual cortex on the spatiotemporal response properties of lateral geniculate nucleus cells.

Previous studies of the cortical input to the mammalian dorsal lateral geniculate nucleus (LGN) have identified a number of possible functions for the corticogeniculate pathway, including alteration of LGN spatial frequency selectivity and facilitation of both binocular interactions and orientation selectivity. These changes may be due to either a tonic or a phasic cortical facilitation or both. The temporal differences between each of these inputs suggests that their impact on LGN cell temporal tuning should be unique. To test this hypothesis, we reversibly blocked the visual cortex (VI) and measured the effects on several indices of the temporal properties of LGN cells, including peak frequency, bandwidth, and response phase. Macaque monkeys were anesthetized and paralyzed during single cell recording from the LGN while area VI was cryogenically deactivated. Single-cell responses were visually evoked with drifting, luminance-modulated, sine-wave gratings and discrete-Fourier analyzed. Cortical cooling produced statistically significant increases or decreases in response amplitude in 64% of cells recorded. In most cases, alterations in response amplitude occurred for stimuli that varied in spatial as well as temporal frequency. For those cells influenced by changes in stimulus temporal frequency, the majority showed changes over a broad range of frequencies. A minority of cells showed changes in either peak temporal tuning or temporal frequency bandwidth. Response phase angles for all temporal frequencies tested were unaffected by cortical cooling. Overall, these results suggest that the cortical input may alter the temporal response properties of LGN cells, perhaps by tonic, but not exclusively excitatory, corticofugal influences.

Spatial contrast sensitivity: effects of peripheral field stimulation during monocular and dichoptic viewing.

This report examines whether a radial grating with a blank 2 deg central aperture viewed with one eye can affect contrast sensitivity for foveally-viewed, counterphasing or stationary, sine-wave gratings seen with the other eye. We find that the moving radial grating preferentially raises the threshold for the low spatial frequencies of the counterphasing but not the stationary foveal stimulus. These results closely parallel recent primate electrophysiological work which suggests that visual stimulation of the peripheral field with a moving radial grating can activate inhibitory corticofugal influences on lateral geniculate neurons. The current data are evaluated in terms of a model which suggests that the peripheral stimulus activates corticofugal mechanisms.

Head-related transfer functions of the Rhesus monkey.

Head-related transfer functions (HRTFs) are direction-specific acoustic filters formed by the head, the pinnae and the ear canals. They can be used to assess acoustical cues available for sound localization and to construct virtual auditory environments. We measured the HRTFs of three anesthetized Rhesus monkeys (Macaca mulatta) from 591 locations in the frontal hemisphere ranging from -90 degrees (left) to 90 degrees (right) in azimuth and -60 degrees (down) to 90 degrees (up) in elevation for frequencies between 0.5 and 15 kHz. Acoustic validation of the HRTFs shows good agreement between free field and virtual sound sources. Monaural spectra exhibit deep notches at frequencies above 9 kHz, providing putative cues for elevation discrimination. Interaural level differences (ILDs) and interaural time differences (ITDs) generally vary monotonically with azimuth between 0.5 and 8 kHz, suggesting that these two cues can be used to discriminate azimuthal position. Comparison with published subsets of HRTFs from squirrel monkeys (Saimiri sciureus) shows good agreement. Comparison with published human HRTFs from the frontal hemisphere demonstrates overall similarity in the patterns of ILD and ITD, suggesting that the Rhesus monkey is a good acoustic model for these two sound localization cues in humans. Finally, the measured ITDs in the horizontal plane agree well between -40 degrees and 40 degrees in azimuth with those calculated from a spherical head model with a radius of 52 mm, one-half the interaural distance of the monkey.

Attention as a target of intoxication: insights and methods from studies of drug abuse.

A symposium was convened to discuss recent developments in the assessment of attention and the effects of drugs and toxic chemicals on attention at the 17th annual meeting of the Behavioral Toxicology Society on May 1, 1999, in Research Triangle Park, NC. Speakers addressed issues including the methodology of assessing cognitive function, the neurobiology of specific aspects of attention, the dual roles of attention as a target of intoxication and as a mediating variable in the development of addiction to psychoactive drugs, the changes in attention that accompany neuropsychological disorders of schizophrenia, senile dementia of the Alzheimer type and attention deficit hyperactivity disorder, and potential therapies for these disorders. This article provides an overview of the objectives of the symposium, followed by summaries of each of the talks given.

Nucleotide sequence of the internal transcribed spacers and 5.8S region of ribosomal DNA in Pinus pinea L.

The nucleotide sequence of the first internal transcribed spacer (ITS1) belonging to different ribosomal RNA genes from Pinus pinea are reported. The analyzed ITS1 can be distinguished on the basis of their length, being one 2631 bp and the other 271 bp long. Nucleotide comparison of these regions did not show appreciable sequence homology. The larger ITS1 contains five tandem arranged subrepeats with size ranging between 219 bp and 237 bp. The nucleotide sequence of the 5.8S and the ITS2 regions belonging to the larger ribosomal RNA gene are also reported.

Ribosomal RNA genes of Phaseolus coccineus. IV. Structure and comparative-analysis of the intergenic spacer: possible involvement of some nucleotides in the transcription control of coding sequences. Sequence of the intergenic spacer of ribosomal genes.

The sequence of the intergenic spacer (IGS) of Phaseolus coccineus is determined. The IGS contains three distinct regions: Region A, constant in length; Region B, heterogeneous in length among genes, including two very similar segments 162 and 177 bp long, repeated two and nine times respectively in the investigated clone; Region C, constant in length, comprising five islands. The putative promoters and the sites of termination, processing and methylation are detected by a comparison with other plant systems.

Quantitative immunohistochemical assessment of IgA, IgM, IgG and antigen-specific immunoglobulin secreting plasma cells in pig small intestinal lamina propria.

Intestinal immune response plays an important defensive role for pathogens, particularly for those transmitted by the oro-faecal route or for foecal shedding modulation. This work examined three parts of intestine from twelve gilts experimentally infected with PCV2-spiked semen, six vaccinated (V group) and six unvaccinated (NV group) against PCV2, 29 and 53 days post infection (DPI). An immunohistochemical investigation for IgA-, IgG- and IgM-antibody bearing plasma cells (PCs) was run on intestinal samples coupled with a sandwich immunohistochemical method to reveal anti-PCV2 antibody-secreting PCs. Plasma cell density was compared in the two groups of animals at 29 and 53 DPI. The IgA, IgG and IgM PC density did not differ between groups but displayed an increase from the upper (villus) to the lower part of the crypts while a decreasing trend in PC density was identified from duodenum to ileum. In the NV group, no increase in anti-PCV2 PC density was demonstrable in the two sampling moment: the amounts of lamina propria PCV2-specific antibody-producing PCs remained constant, 10.55 ± 4.24 and 10.06 ± 5.01 at 29 DPI and 53 DPI, respectively. In the V group a significant increase in PCV2-specific antibody-producing PCs was observed over time. The amounts of PCV2-specific antibody-producing PCs increased from 9.37 ± 13.36 at 29 DPI to 18.76 ± 15.83 at 53 DPI. The data on IgA, IgM and IgG PC counts can be considered reference values in a population of adult pigs. The sandwich method can be proposed as a technique able to identify specific antibody-secreting PCs in formalin-fixed paraffin-embedded tissues. A practical application of the sandwich method is the demonstration of a "booster-like" response of the lamina propria in vaccinated compared to unvaccinated animals. After virus challenge, vaccination induced an increase in the number of PCs containing specific anti-PCV2 antibodies at the level of intestinal mucosa.

Paracetamol-codeine compared to ketorolac for pain control in the Emergency Department.

OBJECTIVE: Paracetamol /codeine has shown a strong analgesic activity in several studies conducted among different kind of subjects, including those with trauma. Nevertheless, its efficacy in patients accessing the Emergency Department (ED) for different kind of pain has never been tested. PATIENTS AND METHODS: This is a cross-sectional, observational, prospective, cohort study. Inclusion criteria were patients > 18 year old presenting to the ED for localized traumatic or inflammatory pain involving only extremities. Numeric scale (NRS) was recorded thirty minutes and two hours after the administration of the analgesic therapy, consisting of 15 mg of ketorolac or 1000 mg/60 mg of paracetamol/ codeine, both orally. RESULTS: Two-hundred patients were consecutively enrolled; 87 were treated with paracetamol/codeine and 113 with ketorolac. The combination paracetamol/codeine resulted to be not inferior to ketorolac in non-traumatic pain group and trauma group (p = 0.635 and p = 0.482, respectively). Compared to ketorolac, the combination paracetamol/codeine exerted a significantly higher analgesic activity in patients with fractures and muscular pain (p = 0.044) and was more effective in acute pain (p = 0.002), with a significant effect two hours after the administration (p = 0.029). CONCLUSIONS: Paracetamol/codeine is equivalent to ketorolac in non-traumatic pain and post-traumatic pain, but is superior in acute pain and in patients with fractures and muscular pain. Those results play in favor of the use of the combination paracetamol/codeine in patients accessing the ED for non-traumatic or traumatic pain of the extremities.