Opiate receptor gradients in monkey cerebral cortex: correspondence with sensory processing hierarchies

Adding Prefrontal Transcranial Direct Current Stimulation Before Occipital Nerve Stimulation in Fibromyalgia

OBJECTIVES

Fibromyalgia (FM) is a type of chronic musculoskeletal pain without a clear peripheral origin of nociception, often associated with depression. The underlying pathophysiology involves changes in a functional network that is related to pain and emotional processing in the central nervous system. Transcranial direct current stimulation (tDCS) targeting the dorsolateral prefrontal cortex or the occipital nerve (ON) is a noninvasive neuromodulation technique capable of improving fibromyalgia symptoms. This study aims to test the effect of combining 2 targets of stimulation using tDCS.

MATERIALS AND METHODS

We applied ON-tDCS in isolation or coupled with pre-ONS right-anode bifrontal tDCS and assessed its effect on fibromyalgia using the Fibromyalgia Impact Questionnaire, the Beck Depression Inventory, and Numeric Rating Scale for pain scores. These measures were compared with a sham control group using repeated measures analysis of variance.

RESULTS

The interaction effect of stimulation trials and the protocols of sham versus ON-tDCS were significant for the impact, distress, and pain caused by fibromyalgia (P<0.05). The interaction effect of trials and protocols of sham versus ON-tDCS with bifrontal tDCS was significant for distress (P<0.01), and it showed a trend of improvement for impact and pain (P<0.1). On the basis of the nonsignificant interaction effect of ON-tDCS versus ON-tDCS with bifrontal tDCS (P>0.1), adding bifrontal tDCS was found not to improve the treatment effect of ON-tDCS in any of the tested clinical outcome measures.

DISCUSSION

This study suggests that adding right-anode bifrontal tDCS to ONS has no added benefit in improving fibromyalgia-related symptoms.

The Neural Correlates of Humor Creativity

Unlike passive humor appreciation, the neural correlates of real-time humor creation have been unexplored. As a case study for creativity, humor generation uniquely affords a reliable assessment of a creative product’s quality with a clear and relatively rapid beginning and end, rendering it amenable to neuroimaging that has the potential for reflecting individual differences in expertise. Professional and amateur “improv” comedians and controls viewed New Yorker cartoon drawings while being scanned. For each drawing, they were instructed to generate either a humorous or a mundane caption. Greater comedic experience was associated with decreased activation in the striatum and medial prefrontal cortex (mPFC), but increased activation in temporal association regions (TMP). Less experienced comedians manifested greater activation of mPFC, reflecting their deliberate search through TMP association space. Professionals, by contrast, tend to reap the fruits of their spontaneous associations with reduced reliance on top-down guided search.

Neuromodulatory Basis of Emotion

The neural basis of emotion can be found in both the neural computation and the neuromodulation of the neural substrate that mediates behavior. I review the experimental evidence showing the involvement of the hypothalamus, the amygdala, and the prefrontal cortex in emotion. For each of these structures, I show the important role of various neuromodulatory systems in mediating emotional behavior. Generalizing, I suggest that behavioral complexity is caused partly by the diversity and intensity of neuromodulation and hence depends on emotional contexts. Rooting the emotional state in neuromodulatory phenomena allows for its quantitative and scientific study and possibly its characterization. NEUROSCIENTIST 5:283-294, 1999

Human, Nature, Dynamism: The Effects of Content and Movement Perception on Brain Activations during the Aesthetic Judgment of Representational Paintings

Movement perception and its role in aesthetic experience have been often studied, within empirical aesthetics, in relation to the human body. No such specificity has been defined in neuroimaging studies with respect to contents lacking a human form. The aim of this work was to explore, through functional magnetic imaging (f MRI), how perceived movement is processed during the aesthetic judgment of paintings using two types of content: human subjects and scenes of nature. Participants, untutored in the arts, were shown the stimuli and asked to make aesthetic judgments. Additionally, they were instructed to observe the paintings and to rate their perceived movement in separate blocks. Observation highlighted spontaneous processes associated with aesthetic experience, whereas movement judgment outlined activations specifically related to movement processing. The ratings recorded during aesthetic judgment revealed that nature scenes received higher scored than human content paintings. The imaging data showed similar activation, relative to baseline, for all stimuli in the three tasks, including activation of occipito-temporal areas, posterior parietal, and premotor cortices. Contrast analyses within aesthetic judgment task showed that human content activated, relative to nature, precuneus, fusiform gyrus, and posterior temporal areas, whose activation was prominent for dynamic human paintings. In contrast, nature scenes activated, relative to human stimuli, occipital and posterior parietal cortex/precuneus, involved in visuospatial exploration and pragmatic coding of movement, as well as central insula. Static nature paintings further activated, relative to dynamic nature stimuli, central and posterior insula. Besides insular activation, which was specific for aesthetic judgment, we found a large overlap in the activation pattern characterizing each stimulus dimension (content and dynamism) across observation, aesthetic judgment, and movement judgment tasks. These findings support the idea that the aesthetic evaluation of artworks depicting both human subjects and nature scenes involves a motor component, and that the associated neural processes occur quite spontaneously in the viewer. Furthermore, considering the functional roles of posterior and central insula, we suggest that nature paintings may evoke aesthetic processes requiring an additional proprioceptive and sensori-motor component implemented by “motor accessibility” to the represented scenario, which is needed to judge the aesthetic value of the observed painting.

Ha ha! versus aha! a direct comparison of humor to nonhumorous insight for determining the neural correlates of mirth

While humor typically involves a surprising discovery, not all discoveries are perceived as humorous or lead to a feeling of mirth. Is there a difference in the neural signature of humorous versus nonhumorous discovery? Subjects viewed drawings that were uninterpretable until a caption was presented that provided either: 1) a nonhumorous interpretation (or insight) of an object from an unusual or partial view (UV) or 2) a humorous interpretation (HU) of the image achieved by linking remote and unexpected concepts. fMRI activation elicited by the UV captions was a subset of that elicited by the humorous HU captions, with only the latter showing activity in the temporal poles and temporo-occipital junction (linking remote concepts), and medial prefrontal cortex (unexpected reward). Mirth may be a consequence of the linking of remote ideas producing high-and unexpected-activation in association and classical reward areas. We suggest that this process is mediated by opioid activity as part of a system rewarding attention to novel information.

WIN 44,441: A Stereospecific and Long-Acting Narcotic Antagonist

The opiate antagonist WIN 44,441-3 is a potent, stereospecific antagonist of mu, delta, and kappa opiate receptors. This antagonist activity is of long duration (> 4 h) with no agonist activity being observed. It therefore appears that WIN 44,441-3 will be a useful long-acting opiate antagonist for in vivo studies.

The experience of art: insights from neuroimaging

The experience of art is a complex one. It emerges from the interaction of multiple cognitive and affective processes. Neuropsychological and neuroimaging studies are revealing the broadly distributed network of brain regions upon which it relies. This network can be divided into three functional components: (i) prefrontal, parietal, and temporal cortical regions support evaluative judgment, attentional processing, and memory retrieval; (ii) the reward circuit, including cortical, subcortical regions, and some of its regulators, is involved in the generation of pleasurable feelings and emotions, and the valuation and anticipation of reward; and (iii) attentional modulation of activity in low-, mid-, and high-level cortical sensory regions enhances the perceptual processing of certain features, relations, locations, or objects. Understanding how these regions act in concert to produce unique and moving art experiences and determining the impact of personal and cultural meaning and context on this network the biological foundation of the experience of art--remain future challenges.

Cerebral decreases in opioid receptor binding in patients with central neuropathic pain measured by [11 C]diprenorphine binding and PET

Central neuropathic pain (CNP) is pain resulting from damage to the central nervous system. Up till now, it has not been possible to identify a common lesion or pharmacological deficit in these patients. This preliminary study in a group of patients with CNP with predominantly post-stroke pain, demonstrates that there is significantly less opioid receptor binding in a number of cortical and sub-cortical structures that are mostly, but not exclusively, within the medial pain system in patients compared to age-matched pain-free controls. The reductions in opioid receptor binding within the medial system were observed mainly in the dorsolateral (Brodman area 10) and anterior cingulate (Brodman area 24 with some extension into area 23) and insula cortices and the thalamus. There were also reductions in the lateral pain system within the inferior parietal cortex (Brodman area 40). These changes in binding could not be accounted for by the cerebral lesions shown by CT or MRI, which were outside the areas of reduced binding and the human pain system. To our knowledge this is the first systematic demonstration of a reduction in opioid receptor-binding capacity in neurones within the human nociceptive system in patients with CNP. This may be a key common factor resulting in undamped nociceptor activity within some of the structures that are predominantly within the medial nociceptive system. If confirmed, these findings may explain why certain patients with CNP require high doses of synthetic opiates to achieve optimum analgesia. The findings also raise the possibility of new pharmacological approaches to treatment.

The neural basis for shape preferences

Several dimensions of shape, such as curvature or taper, can be regarded as extending from a singular (S) or 0 value (e.g., a straight contour with 0 curvature or parallel contours with a 0 angle of convergence) to an infinity of non-singular (NS) values (e.g., curves and non-parallel contours). As orientation in depth is varied, an S value remains S, and a NS value will vary but will remain NS. Infant and adult human participants viewed pairs of geons where one member had an S and the other had a NS value on a given shape dimension, e.g., a cylinder vs. a cone. Both adults and infants looked first, and adults looked longer at the NS geons. The NS geons also produced greater fMRI activation in shape selective cortex (LOC), a result consistent with the greater single unit activity in macaque IT produced by those geons (Kayaert et al., 2005). That NS stimuli elicit higher neural activity and attract eye movements may account for search asymmetries in that these stimuli pop out from their S distractors but not the reverse. A positive association between greater activation in higher-level areas of the ventral pathway and visual preference has been demonstrated previously for real world scenes (Yue, Vessel, & Biederman, 2007) and may reflect the workings of a motivational system that leads humans to seek novel but richly interpretable information.

Spinogenesis and Pruning in the Anterior Ventral Inferotemporal Cortex of the Macaque Monkey: An Intracellular Injection Study of Layer III Pyramidal Cells

Pyramidal cells grow and mature at different rates among different cortical areas in the macaque monkey. In particular, differences across the areas have been reported in both the timing and magnitude of growth, branching, spinogenesis, and pruning in the basal dendritic trees of cells in layer III. Presently available data suggest that these different growth profiles reflect the type of functions performed by these cells in the adult brain. However, to date, studies have focused on only a relatively few cortical areas. In the present investigation we quantified the growth of the dendritic trees of layer III pyramidal cells in the anterior ventral portion of cytoarchitectonic area TE (TEav) to better comprehend developmental trends in the cerebral cortex. We quantified the growth and branching of the dendrities, and spinogenesis and pruning of spines, from post-natal day 2 (PND2) to four and a half years of age. We found that the dendritic trees increase in size from PND2 to 7 months of age and thereafter became smaller. The dendritic trees became increasingly more branched from PND2 into adulthood. There was a two-fold increase in the number of spines in the basal dendritic trees of pyramidal cells from PND2 to 3.5 months of age and then a 10% net decrease in spine number into adulthood. Thus, the growth profile of layer III pyramidal cells in the anterior ventral portion of the inferotemporal cortex differs to that in other cortical areas associated with visual processing.

Corticotropin and beta-endorphin-like materials are native to unicellular organisms

Multiple molecular forms of immunoreactive corticotropin (ACTH) and beta-endorphin were present in extracts of a unicellular eukaryote (Tetrahymena pyriformis). One form of immunoreactive ACTH reacted similarly with two different ACTH antisera (one specific for the 11-24 sequence and the other with determinants within sequences 1-14 and 17-39) and migrated with synthetic hACTH-(1-39) in a gel filtration system. This form also exhibited ACTH bioactivity in a dispersed rat adrenal cell bioassay system, with a mean immunoassay/bioassay ratio of 1.5. Gel filtration revealed multiple size classes of immunoreactive beta-endorphin; a major peak of radioreceptor activity was detected which exhibited a K(av) similar to that of authentic beta-endorphin. A major portion of immunoreactive beta-endorphin-sized material exhibited retention times similar to those of synthetic human and camel beta-endorphin upon reverse-phase high-pressure liquid chromatography. These distinctive properties and specificities would seem to exclude the presence of limited homologies with sequences present in other proteins. High molecular weight material containing both ACTH and beta-endorphin antigenic determinants was also demonstrated, suggesting, but not proving, the presence of a common precursor molecule.

The scope of neuroethology

Neuroethology, an interdisciplinary subdivision of neuroscience, has emerged in recent years. Since 1976 there has been a regular session under this heading at the annual meeting of the Society for Neuroscience. In 1980 two introductory texts in English were published on the subject (Ewert 1980; Guthrie 1980), and a third (Camhi 1984) was published recently. There is widespread interest in neural mechanisms underlying behavior, but they encompass such a vast array of often unrelated topics that proponents do not share common goals. This article describes the emergence of ethology as a discipline, pointing out that its practitioners were successful because they confined their research to stereotyped, complex, nonlearned, innate behavioral acts. A limited number of profoundly significant principles emerged. Each of these is redefined. The major concepts of earlier ethology were embodied in a simple hydraulic model used by Konrad Lorenz in 1949 (Lorenz 1950). It is pointed out that this model implies the existence of common neurophysiological mechanisms and neuronal circuitry. This model has now been made obsolete by neurophysiological progress, but with appropriate modifications an updated version may still be useful in focusing attention on possible principles. The initial aim of neuroethology should be to examine the neurophysiological events in a variety of behaviors, exhibited by diverse animals from different phyla, which meet the criteria of innate behavioral acts. The behaviors should be sufficiently complex to interest ethologists, yet they should be addressable with neurophysiological methods down to the cellular level. In the case of vertebrates this may mean working with brain slices as well as whole animals, but for some invertebrates recording should be possible in the nearly intact animal during execution of the behavior. The work will be exacting and very difficult, and it is not likely to get done at all unless neuroethologists recognize that they should both train and discipline themselves and restrict their attention to welldefined goals.

Toward an understanding of flow in video games

In the domain of computer games, research into the interaction between player and game has centred on 'enjoyment', often drawing in particular on optimal experience research and Csikszentmihalyi's 'Flow theory'. Flow is a well-established construct for examining experience in any setting and its application to game-play is intuitive. Nevertheless, it's not immediately obvious how to translate between the flow construct and an operative description of game-play. Previous research has attempted this translation through analogy. In this article we propose a practical, integrated approach for analysis of the mechanics and aesthetics of game-play, which helps develop deeper insights into the capacity for flow within games.

The relationship between player and game, characterized by learning and enjoyment, is central to our analysis. We begin by framing that relationship within Cowley's user-system-experience (USE) model, and expand this into an information systems framework, which enables a practical mapping of flow onto game-play. We believe this approach enhances our understanding of a player's interaction with a game and provides useful insights for games' researchers seeking to devise mechanisms to adapt game-play to individual players.

Blind or Deaf? A Matter of Aesthetics

Blind or deaf? Surprisingly, a small but noticeable minority, 17%, opted for blindness. Another 6% were indifferent. For these individuals (23% of the sample), the loss of the aesthetic experience—music—was given relatively greater weight than the loss of the practical-conversation. This was not a symmetric effect in that those who opted for being deaf did not place greater value on the aesthetic aspects of vision compared to those who opted for being blind. What predicts the preference for being blind was not the amount of time spent listening to music but the extent to which one formally studied, created, and played music and experienced intense emotions when engaged by music.

The neural basis of scene preferences

What is the neural correlate of preference that governs our spontaneous selection of visual information? With a rapid, event-related functional magnetic resonance imaging design, we showed that the viewing of highly preferred compared to less preferred scenes (as assessed by participant ratings) was associated with greater blood-oxygen level dependent responses in the right parahippocampal cortex but not in the lateral occipital complex, ruling out feed forward and attentional effects. Highly preferred images also produced greater activation in the ventral striatum, suggesting that perceptual preference might engage the conventional reward system. These results are consistent with the hypothesis that high activity in the parahippocampal cortex, an area with a high density of cortical mu-opioid receptors, may be experienced as cognitively pleasurable.

Attention to pain localization and unpleasantness discriminates the functions of the medial and lateral pain systems

Functional imaging studies have identified a matrix of structures in the brain that respond to noxious stimuli. Within this matrix, a division of function between sensory-discriminative and affective responses has so far been demonstrated by manipulating either pain intensity or unpleasantness under hypnosis in two different normal volunteer groups studied on separate occasions. Our study used positron emission tomography (PET) to demonstrate this division of function under more natural conditions in a healthy group of volunteers, using a CO(2) laser to provide nociceptive stimuli that selectively activate A-delta and C-fibres without contamination by touch sensations. We measured the differential cerebral responses to noxious and innocuous laser stimuli during conditions of selective attention to either the unpleasantness or location of the stimuli. Attention to location increased responses in the contralateral (right) primary somatosensory and inferior parietal cortices. This result implies that these components of the lateral pain system are concerned mainly with the localization of pain. In contrast, attention to unpleasantness increased responses in bilateral perigenual cingulate and orbitofrontal cortices, contralateral (right) amygdala, ipsilateral (left) hypothalamus, posterior insula, M1 and frontal pole. These areas comprise key components of the medial pain and neuroendocrine systems and the results suggest that they have a role in the affective response to pain. Our results indicate the importance of attentional effects on the pattern of nociceptive processing in the brain. They also provide the first clear demonstration, within a single experiment, of a major division of function within the neural pain matrix.

Neuropsychological correlates of opioid dependence and withdrawal

Severity of opioid dependence, and performance on two successive runs of the Wisconsin Card Sorting Test (WCST), were assessed in 39 right-handed male and female methadone patients who had been randomly assigned to either a recently dosed (n=21) or 24 hr abstinent (n=18) condition. Results indicated that severity of opioid dependence was positively correlated with perseverative responses and errors on the second run of the WCST, p<.05. Further, controlling for the effect of dependence severity, patients in early methadone withdrawal made selectively more perseverative responses and errors than did recently dosed patients, p<.05, with no difference on nonperseverative errors. Findings were consistent with the hypothesis that opioid dependence, like alcoholism and cocaine addiction, is associated with disruption of executive cognitive functions mediated by the prefrontal cortex.

Distribution of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate-type glutamate receptor subunits (GluR2/3) along the ventral visual pathway in the monkey

By using immunohistochemical methods, we examined the distribution of cells expressing subunits of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA)-selective glutamate receptors (GluR2/3) in the cortical areas of the occipitotemporal pathway in monkeys. GluR2/3-immunoreactive (-ir) cells were primarily pyramidal cells; this category, however, also included large stellate cells in layer IVB of the striate cortex (V1) and fusiform cells in layer VI of all the areas examined. GluR2/3 immunoreactivity differed among the areas in laminar distribution and intensity. In V1, GluR2/3-ir cells were identified mainly in layers II, III, IVB, and VI. The prestriate areas V2 and V4 and the inferior temporal areas TEO and TE contained GluR2/3-ir cells in layers II, III, and VI. In the TE, GluR2/3-ir cells were also abundant in layer V. In area 36 of the perirhinal cortex, neurons in layers II, III, V, and VI were labeled in a similar manner to the TE labeling, but with greater staining intensity and numbers, especially in layer V. Thus, GluR2/3 immunoreactivity increased rostrally along the pathway. Within V1 and V2, cells strongly stained for GluR2/3 formed clusters that colocalized with cytochrome oxidase (CO)-rich regions. These distinct laminar and regional distribution patterns of GluR2/3 expression may contribute to the specific physiological properties of neurons within various visual areas and compartments.

Reward deficiency syndrome: a biogenetic model for the diagnosis and treatment of impulsive, addictive, and compulsive behaviors

The dopaminergic system, and in particular the dopamine D2 receptor, has been implicated in reward mechanisms. The net effect of neurotransmitter interaction at the mesolimbic brain region induces "reward" when dopamine (DA) is released from the neuron at the nucleus accumbens and interacts with a dopamine D2 receptor. "The reward cascade" involves the release of serotonin, which in turn at the hypothalmus stimulates enkephalin, which in turn inhibits GABA at the substania nigra, which in turn fine tunes the amount of DA released at the nucleus accumbens or "reward site." It is well known that under normal conditions in the reward site DA works to maintain our normal drives. In fact, DA has become to be known as the "pleasure molecule" and/or the "antistress molecule." When DA is released into the synapse, it stimulates a number a DA receptors (D1-D5) which results in increased feelings of well-being and stress reduction. A consensus of the literature suggests that when there is a dysfunction in the brain reward cascade, which could be caused by certain genetic variants (polygenic), especially in the DA system causing a hypodopaminergic trait, the brain of that person requires a DA fix to feel good. This trait leads to multiple drug-seeking behavior. This is so because alcohol, cocaine, heroin, marijuana, nicotine, and glucose all cause activation and neuronal release of brain DA, which could heal the abnormal cravings. Certainly after ten years of study we could say with confidence that carriers of the DAD2 receptor A1 allele have compromised D2 receptors. Therefore lack of D2 receptors causes individuals to have a high risk for multiple addictive, impulsive and compulsive behavioral propensities, such as severe alcoholism, cocaine, heroin, marijuana and nicotine use, glucose bingeing, pathological gambling, sex addiction, ADHD, Tourette's Syndrome, autism, chronic violence, posttraumatic stress disorder, schizoid/avoidant cluster, conduct disorder and antisocial behavior. In order to explain the breakdown of the reward cascade due to both multiple genes and environmental stimuli (pleiotropism) and resultant aberrant behaviors, Blum united this hypodopaminergic trait under the rubric of a reward deficiency syndrome.

Neurochemical gradients along monkey sensory cortical pathways: calbindin-immunoreactive pyramidal neurons in layers II and III

We examined the distribution of neurons containing immunoreactivity for three calcium-binding proteins, calbindin, parvalbumin and calretinin, as well as nonphosphorylated neurofilament protein, in cortical areas along the ventral and dorsal cortical visual pathways, and in ventrally-directed somatosensory and auditory cortical pathways. Calbindin-immunoreactive pyramidal neurons showed the most prominent regional differences. They were largely restricted to layers II and III and their number monotonically increased from the primary sensory areas to the anteroventral areas along the ventral visual pathway and along the ventrally-directed somatosensory and auditory pathways. The number of calbindin-immunoreactive pyramidal neurons in layers II and III also increased along the dorsal visual pathway, but the number in the last recognized stage of the dorsal visual pathway (area 7a) was significantly smaller than that at the corresponding stage in the ventral visual pathway (TE). The number of calbindin-immunoreactive pyramidal neurons was highest in layers II and III of areas 35/36, TG, and TF/TH, which represent terminal cortical regions of the pathways. These results show neurochemical differences between cortical areas located at early and late stages along serial corticocortical pathways, as well as confirming differences between pyramidal neurons in the supragranular and infragranular layers.

Brain opioid receptor density relates to stereotypies in chronically stressed pigs

Opioid receptor densities were measured in the hippocampus of chronically stressed (tethered) pigs to study the involvement of endogenous opioid systems in stereotypy performance. Three groups of animals were housed tethered for 2 (n=12), 5.5 (n=12) and 8-9 months (n=8), respectively, and the intensity of stereotypy performance was determined. Opioid receptor densities were measured post mortem using membrane binding assays with [(3)H]naloxone as a ligand. A negative correlation was found between the density of opioid receptors and the intensity of stereotypy performance in the animals that had been housed tethered for 2 months. This correlation seemed to disappear with increasing duration of tethered housing. The data further suggest that, associated with the duration of tediered housing, there was a gradual decrease in the density of opioid receptors in the left hippocampal lobe of the low-stereotyping animals, but not in the right lobe, nor in the left and right lobes of the high-stereotypers. This suggests that chronic stress leads to a (asymmetrically expressed) progressive loss of opioid receptors in the hippocampus, and that stereotypies exert a mitigating effect on stress-induced changes in opioid receptor densities, supporting the hypothesis that stereotypies help the animals cope wife the adverse effects of chronic stress.

Intrinsic Connections in the macaque inferior temporal cortex

Intrinsic connections in the inferior temporal cortex were analyzed by making extracellular injections of biocytin in Japanese macaques. Analysis was focused mainly on the dorsal part of area TE, in which a functional columnar organization has been shown. Interlaminar connections were analyzed in coronal section after laminar-specific microinjections, and intralaminar connections were examined from tangential sections. After injections at various depths in the dorsal TE, both axons and cell bodies were strongly labeled above or below the injection site in a columnar appearance. Axons from layer 3 ran in bundles towards the white matter and gave off prominent collaterals in layer 5. Ascending axons from lower to upper layers were also present (e.g., layers 4, 5, and 6 to layer 3). In tangential sections, there were abundant axons running parallel to the pia mater. These horizontal axons, particularly those in layers 2 and 3, produced patches of terminals 0.5 +/- 0.1 mm (mean +/- s.d.) in size and cylindrical in shape, spanning layers 1-3 or even to layers 4 and 5. In the tangential plane, they were distributed in an anisotropic manner around the injection. The farthest patch appeared at 4 mm from the injection site. The center-to-center distance between nearest-neighbor patches was 0.7 +/- 0.3 mm. These patches were found only within the dorsal TE and did not extend into the lower bank of the superior temporal sulcus or into the ventral part of area TE. Area TEO, which is a major afferent source to area TE, had axonal patches with spacing similar to those in area TE but with smaller sizes (0.4 +/- 0.1 mm). The results show that intrinsic horizontal axons both in area TE and in area TEO arborize in a patchy manner, as has been reported for several other cortical areas. In are TE, the size and spacing of the terminal patches match those of columns with similar stimulus selectivity. Thus, these patches may be related to the functional modularity in area TE. Vertical connections across layers and cylindrical patches of horizontal axons most likely contribute to the shared stimulus selectivity among cells within a column.

Reversal of visuospatial deficit on the Clock Drawing Test in Parkinson's disease by treatment with weak electromagnetic fields

Visuospatial deficits are among the most frequently encountered abnormalities in neuropsychological testing of patients with Parkinson's disease, being present in up to 90% of cases. Clinically, impairment of visuospatial functions may not be noted by Parkinsonian patients but may contribute to various functional disabilities including frequent falls, difficulties operating a vehicle, ambulating, and dressing. I have reported recently that treatment with external electromagnetic fields (EMFs) in the picotesla (pT) range intensity is an effective nonpharmacological modality in the management of the motor and various cognitive deficits of Parkinsonism including visuoperceptive and visuospatial functions. The present communication concerns four fully medicated Parkinsonian patients who, in response to treatment with EMFs, exhibited reversal of visuospatial impairments as demonstrated on the Clock Drawing Test. Specifically, prior to treatment with EMFs these patients demonstrated a visuospatial deficit which was evident by the placement of the numbers on the clock distant from the periphery. Following a series of treatments with EMFs this visuospatial deficit was corrected. The report supports prior observations demonstrating that externally applied pT range intensity EMFs may bring about reversal of visuospatial deficits in Parkinsonian patients which usually are not improved by treatment with dopaminergic or anticholinergic drugs.

The opiate system in invertebrates

The presence in diverse species of a similar mode of communication, that of a soluble messenger binding to a receptor, raises the question as to whether the specific components of this system are equally widespread. Do invertebrates use the same hormones and receptors as vertebrates do? Invertebrates ranging from unicellular organisms to insects have been shown to contain opiate-like peptides and binding sites, and they exhibit biological responses to opiates. However, critical genetic data are lacking. It is not known how signal systems arise phylogenetically, but it is conceivable that signal molecules that are already present cause the formation of their own receptors from membrane proteins.

Comparison of bolus and infusion methods for receptor quantitation: application to [18F]cyclofoxy and positron emission tomography

Positron emission tomography studies with the opiate antagonist [18F]cyclofoxy ([18F]CF) were performed in baboons. Bolus injection studies demonstrated initial uptake dependent on blood flow. The late uptake showed highest binding in caudate nuclei, amygdala, thalamus, and brainstem and the least accumulation in cerebellum. By 60 min postinjection, regional brain radioactivity cleared at the same rate as metabolite-corrected plasma, i.e., transient equilibrium was achieved. Compartmental modeling methods were applied to time-activity curves from brain and metabolite-corrected plasma. Individual rate constants were estimated with poor precision. The model estimate of the total volume of distribution (VT), representing the ratio of tissue radioactivity to metabolite-corrected plasma at equilibrium, was reliably determined. The apparent volume of distribution (Va), the concentration ratio of tissue to metabolite-corrected plasma during transient equilibrium, was compared with the fitted VT values to determine if single-scan methods could provide accurate receptor measurements. Va significantly overestimated VT and produced artificially high image contrast. These differences were predicted by compartment model theory and were caused by a plasma clearance rate that was close to the slowest tissue clearance rate. To develop a simple method to measure VT, an infusion protocol consisting of bolus plus continuous infusion (B/I) of CF was designed and applied in a separate set of studies. The Va values from the B/I studies agreed with the VT values from both B/I and bolus studies. This infusion approach can produce accurate receptor measurements and has the potential to shorten scan time and simplify the acquisition and processing of scan and blood data.

Naloxone prevents interruption of parturition and increases plasma oxytocin following environmental disturbance in parturient sows

Experiments in rodents have suggested that environmental disturbance can disrupt parturition through an opioid-mediated inhibition of oxytocin secretion. To test this hypothesis in a large animal model, 14 primiparous female pigs were allowed to commence parturition in a strawed pen. Five of these gilts were allowed to continue parturition undisturbed in this pen, while the remainder were moved to a farrowing crate immediately after the birth of the first piglet. At this time, pigs were injected subcutaneously with either the opioid antagonist naloxone (n = 4; dose 1 mg/kg body weight) or saline (n = 5). Whereas the undisturbed pigs all gave birth to a second piglet within 53 min, in three of the five disturbed and saline-treated pigs no further births occurred for 2 h, at which time oxytocin was administered subcutaneously to restart parturition. By contrast, all of the naloxone-treated pigs gave birth spontaneously within 2 h, although mean interbirth intervals were still prolonged compared to undisturbed pigs. In a second experiment, nine primiparous female pigs with chronic catheters preplaced in the external jugular vein were similarly moved after the birth of their first piglet and either injected with naloxone (n = 5) or saline (n = 4). Again, parturition was interrupted in three out of four saline-treated animals for at least 2.5 h, but resumed promptly when exogenous oxytocin was administered. Plasma concentrations of oxytocin in these pigs were significantly lower than in naloxone-treated pigs, five out of six of which gave birth spontaneously to one or more piglets within 2.5 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Habituation-like decrease in the responses of neurons in inferior temporal cortex of the macaque

In both anesthetized and behaving macaques, we examined the responses of neurons in the inferior temporal cortex (IT) to repeated presentation of a visual stimulus. In anesthetized animals, the responsiveness of IT neurons decreased with repeated stimulus presentation at interstimulus intervals (ISIs) of 2-12 s but not at 20 s. Responsiveness recovered after a 5-min period of no stimulus presentation. The response decrement was similar in anesthetized and awake animals at a 2-s ISI, but at a 6-s ISI, response decrement in the awake animal was much less.

Effects of opioid be drugs on auditory evoked potentials suggest a role of lateral olivocochlear dynorphins in auditory function

Multiple gene products of opioid peptide families (e.g., enkephalins, dynorphins) with differing opioid receptor specificities are present within olivocochlear efferent terminals. Enkephalins activate mu- and delta-opioid receptors, and are generally inhibitory in the nervous system, and dynorphins are kappa-receptor agonists, which may be excitatory to postsynaptic neurons. We have examined the effects of intravenously administered opioid agonists and antagonists on click-evoked N1 and N2 amplitudes and latencies of the compound action potential in the chinchilla recorded at the round window. Parenteral administration of the opioid receptor antagonist naloxone or the potent mu-receptor agonist fentanyl did not alter N1 and N2 amplitudes or latencies. The kappa-receptor agonist, mu-receptor antagonist pentazocine caused marked increases in N1 and N2 amplitudes over baseline values at threshold intensities. These effects were not abolished by naloxone. No effects were seen on the cochlear microphonic, supporting a site of action of these effects at the lateral olivocochlear efferent terminals on auditory nerve dendrites under inner hair cells. Similar results were obtained when far field auditory evoked responses were recorded. Results were obtained under ketamine/pentobarbital anesthesia, which provided stable recording baselines in contrast to tiletamine/zolezepam/pentobarbital, with which an upward drift in auditory potentials was observed. This stimulatory action of kappa-agonists on auditory-evoked potential amplitudes appears to represent a physiological role of the lateral olivocochlear efferent innervation. The different neurotransmitters of the olivocochlear efferents (e.g. enkephalins, dynorphins, acetylcholine) may have antagonistic actions on auditory potentials, as may the lateral and medial systems themselves.

Naloxone effects on the visual evoked potentials recorded from the main and accessory visual pathways of the cat

1. The effects produced by repetitive i.v. administration of naloxone (1, 2 or 4 mg/kg) on the visual evoked potentials (VEPs) recorded along the main and accessory visual pathways were investigated in a modified "encéphale isolé" cat preparation. 2. Naloxone provoked a progressive amplitude enhancement and latency reduction of some components, depending on the structure analyzed, the dose used and the number of administrations applied. Electroretinogram (ERG) and N1-P1 VEP components of optic chiasm (OCh), lateral geniculate body (LGB) and visual cortex (VC) did not present significant changes. 3. Late-latency components (more than 200 msec) appeared in the VEPs of LGB and VC, mainly when 4 mg/kg were used. 4. Our results suggest that endogenous opioids have a modulatory role in the processing of sensory information at different levels of the visual system.

EEG power and coherence while male adults watch emotional video films

Quantitative EEG analysis recorded at F3, F4, T3, T4, P3, P4 was performed for a group of healthy right-handed male adults (n = 9) viewing video films varying in their inductiveness on the affective valence dimension. Digital EOG-correction permitted the inclusion of trials with eye movements. Muscle artifacts were statistically treated by means of analysis of covariance (ANCOVA). The configuration of topographically motivated EEG parameters corresponded to the subjective valence rating of different video films. Low broad band coherences (COHs) ranked films along the subjective ratings within each hemisphere by the fronto-temporal COHs and interhemispherically by the T4-T3 COH, as did, restricted to the right hemisphere, similarity of beta 2 band power topography over time. High frequencies may be involved in the processing and low frequencies in the transmission of differential affective information, which to integrate seemed to utilize resources of both hemispheres. Alpha 2 and beta 1 COHs were sensitive to variations in an integrality/disassociation dimension with regard to the arrangement of verbal-visual affective cues. Power fluctuations at frontal leads pointed to difficulties in interpreting interhemispheric EEG asymmetries in emotion research, if information on time dynamics is discarded.

Dominant mice show much lower concentrations of methionine-enkephalin in brain tissue than subordinates: cause or effect?

Possible relationships between dominance rank and brain methionine-enkephalin content were studied by using a method of consecutive rank determination in groups of mice reassembled according to their initial ordinal dominance rank. Thus, 10 groups of 3 Balb/c AnN mice of identical ordinal rank were formed with the consecutive dominants of 3 groups of 10 mice. Dominant, subdominant, subordinate and non-aggressive mice were recognized in these groups. Rank order was strongly correlated with brain Met-enkephalin content. Dominant mice contain less than a fourth Met-enkephalin immunologic reactivity in the brainstem and about half the forebrain concentration than subordinates. Brainstem Met-enkephalin correlated with the final ordinal rank and, accordingly, it was found to decrease exponentially after mice acquired alpha-dominance status. Different concentrations in the forebrain correlated with the initial but not the final ordinal rank and, therefore, probably preceded dominance status.

Regional distribution of binding sites for neuropeptide Y in cat and monkey visual cortex determined by in vitro receptor autoradiography

The goal of this study was to elucidate the precise regional and laminar distribution of neuropeptide Y (NPY) binding sites in feline and primate visual cortex. By means of in vitro receptor autoradiography, NPY binding sites in primate and feline visual cortex were specifically labeled with 3H-NPY. In cat area 17, the highest density of NPY-binding sites was present in lamina I and the upper half of lamina II. The density then gradually decreased towards lamina VI. Areas 18 and 19 exhibited a similar binding site-density profile. The decrease in density from superficial to deep layers was more gradual in area 18 than in areas 17 and 19. In monkey primary visual cortex (V1), layer IVc presented a high concentration of NPY binding sites, in addition to a dense zone of binding sites in layer I. Monkey secondary visual cortex (V2) displays a similar dense zone in layer I, but lacks such high density of NPY binding sites in layer IV. Therefore, the border between primary and secondary visual cortex coincides with the abrupt disappearance of this latter high density in layer IV. In cat as well as in monkey visual cortex, no significant differences were found between regions representing central vision and those representing the peripheral parts of the visual field. Comparison of our results for NPY binding sites with the distribution of alpha 1-adrenergic receptors, as recently described by Rakic et al. (J. Neurosci. 8(10):3670-3690, 1988) for primate and Parkinson et al. (Brain Res. 457:70-78, 1988) for feline visual cortex, revealed that those two patterns are very similar.

Three-dimensional distribution of 3H-naloxone binding to opiate receptors in the human fetal and infant brainstem

Despite the putative role of opioids in disorders of the developing human brainstem, little is known about the distribution and ontogeny of opioid-specific perikarya, fibers, terminals, and/or receptors in human fetuses and infants. This study provides baseline information about the quantitative distribution of opiate receptors in the human fetal and infant brainstem. Brainstem sections were analyzed from three fetuses, 19-21 weeks gestation, and seven infants, 45-68 postconceptional weeks, in whom the postmortem interval was less than or equal to 12 hours. Opiate receptors were localized by autoradiographic methods with the radiolabelled antagonist 3H-naloxone. Computer-based methods permitted quantitation of 3H-naloxone binding in specific nuclei, as well as three-dimensional reconstructions of binding patterns. High 3H-naloxone binding corresponds primarily to sensory and limbic nuclei, and to nuclei whose functions are known to be influenced by opioids, e.g., trigeminal nucleus (pain), nucleus tractus solitarii and nucleus parabrachialis medialis (cardio-respiration), and locus coeruleus (arousal). The regional distribution of opiate receptors as determined by 3H-naloxone binding is similar in human infants to that reported in human adults and animals and corresponds most closely to that of mu receptors. We found, however, that opiate receptor binding is high in the fetal and infant inferior olive, in comparison to low binding reported in this site in adult humans, primates, and rodents. In addition, opiate receptors are sparse in the fetal and infant substantia nigra, as in reports of the adult human substantia nigra, compared to moderate densities reported in primates and rodents. By midgestation, the regional distribution of 3H-naloxone binding in human fetuses is similar, but not identical, to that in infants. Highest 3H-naloxone binding occurs in the inferior olive in fetuses at midgestation, compared to the interpeduncular nucleus in infants. Tritiated naloxone binding quantitatively decreases in virtually all nuclei sampled over the last trimester, but not to the same degree. The most substantial binding decrease (two- to fourfold) occurs in the inferior olive and may reflect programmed regressive events, e.g., neuronal loss, during its development. Definitive developmental trends in 3H-naloxone binding are not observed in the postnatal period studied. The heterogeneous distribution of opiate binding in individual brainstem nuclei underscores the need for volumetric sampling in quantitative studies.