4,958 research outputs found
Aspetti anatomici del riflesso otticocinetico
No full textAspetti anatomici del riflesso otticocinetico- Cenni storici e definizioni- Connessioni- Cenni di ultrastruttura e neurochimic
Visual corticopontine projections in the guinea pig: an autoradiographic study
No full textThe goal of this study is to characterize the anatomical organization of the visual cortical output to the basal pontine nuclei in the guinea pig. Data from the Literature show that guinea pigs exhibit different optokinetic oculomotor behaviors with respect to rats and rabbits. Namely, they present a fast rise in eye movement velocity at stimulus onset and a better performance in monocular horizontal stimulation. Possible differences in the visual corticopontocerebellar pathway might explain these peculiarities. The pontine projections from the primary visual cortex were studied with the method of the anterograde axonal transport of [H-3]leucine. The terminal labeling forms prominent patches, ipsilaterally to the cortical injection, throughout the rostrocaudal extent of the pontine nuclei, predominantly in the dorsolateral region. At the intermediate rostrocaudal level, some foci of labeling are found ventrolaterally as well. Sparse fields are present also in the medial pontine nuclei and in the nucleus reticularis tegmenti pontis, but only when the injection site extends to secondary visual areas, either lateral or medial. The present description of the corticopontine projections in guinea pigs is in substantial agreement with the projections previously described in rats, with a few differences, namely: (1) the recipient area extends more caudally; (2) secondary visual areas project to the nucleus reticularis tegmenti pontis
Functional activity mapping of brainstem nociceptive networks in animals
No full textIn this paper, we review blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) studies addressing the neural correlates of touch, thermosensation, pain and the mechanisms of their cognitive modulation in healthy human subjects. There is evidence that fMRI signal changes can be elicited in the parietal cortex by stimulation of single mechanoceptive afferent fibers at suprathreshold intensities for conscious perception. Positive linear relationships between the amplitude or the spatial extents of BOLD fMRI signal changes, stimulus intensity and the perceived touch or pain intensity have been described in different brain areas. Some recent fMRI studies addressed the role of cortical areas in somatosensory perception by comparing the time course of cortical activity evoked by different kinds of stimuli with the temporal features of touch, heat or pain perception. Moreover, parametric single-trial functional MRI designs have been adopted in order to disentangle subprocesses within the nociceptive system.Available evidence suggest that studies that combine fMRI with psychophysical methods may provide a valuable approach for understanding complex perceptual mechanisms and top-down modulation of the somatosensory system by cognitive factors specifically related to selective attention and to anticipation. The brain networks underlying somatosensory perception are complex and highly distributed. A deeper understanding of perceptual-related brain mechanisms therefore requires new approaches suited to investigate the spatial and temporal dynamics of activation in different brain regions and their functional interaction
Fisiologia per la pratica infermieristica
No full textQuesto testo, frutto dell'esperienza didattica degli autori con studenti di scienze infermieristiche appartenenti a corsi di studio di vari livelli, presenta una visione completa della fisiologia e dedica un'attenzione particolare a come i principi fisiologici discussi possono guidare la pratica infermieristica.I contenuti, corredati da numerose illustrazioni a colori, riflettono le concezioni più attuali sulla prestazione dell’assistenza sanitaria e si adattano perfettamente ai nuovi curricula del corso di laurea in infermieristica.La struttura a quattro colori del volume è particolarmente curata per permettere al lettore di individuare con facilità le diverse parti che compongono il testo: le osservazioni relative allo sviluppo, i suggerimenti per la pratica infermieristica e gli argomenti relativi alla pratica clinica che, integrati con i principi anatomici e fisiologici, consentono una migliore comprensione dell’argomento trattato
Pain Anticipation in the Cingulate Gyrus
No full textThroughout this chapter, we focus mainly on theinvolvement of the cingulate cortex in the anticipationof somatosensory input and specifi cally of pain. Thisissue has important theoretical and clinical implications,given the role of the cingulate cortex in themechanisms of pain and analgesia (see Chapters 14and 15). A specifi c question is that whether anticipationis able to affect the activity of pain-related populationsin the cingulate cortex and in the pain matrix in general.Indeed, it has long been hypothesized (James 1892)that essentially the same brain regions were implicatedboth in the anticipation and in the perception of astimulus; this hypothesis has now been directly testedby electrophysiological and functional imaging studiesin humans and non-human primates. Also, whenappropriate, we will briefl y compare the activity ofthe cingulate cortex during anticipation of painand during anticipation of other aversive or rewardevents. The specifi c goals of this chapter include thefollowing:1 Assess electrophysiological evidence of neurons activeduring pain anticipation in the cingulate cortex.2 Evaluate evidence from functional imaging studiesof activity changes related to somatosensory anticipationin different portions of the cingulate gyrus inhealthy volunteers and in pain patients.3 Appraise the modulation of basal- and stimulusevokedactivity of pain-related populations in thecingulate cortex and in other pain-related areas.4 Consider anticipation of pain and analgesia in termsof the potential underlying mechanisms and cingulatecircuits
Neglect syndrome for aversive stimuli in a Macaque monkey with dorsomedial frontal cortex lesion
No full textAfter a session of unit activity recording, one of our monkeys presented an epileptic attack, which provoked contralateral tilting movements. The following days, the animal performed saccades and fixation tasks correctly in all directions, while contralateral arm reaching movements were severely impaired. To establish if the neurological lesion had changed the orienting performance we considered two types of stimuli, pleasant and aversive. Pleasant stimuli, presented in the ipsilateral or contralateral hemifield, readily drew the attention of the animal. If the same stimuli were presented simultaneously in both hemifields, the monkey oriented itself only toward the ipsilateral one. Aversive stimuli evoked an aggressive reaction only when the stimulus was localized in the ipsilateral hemifield. The animal clearly neglected the aversive stimulus presented in the contralateral hemifield. The animal recovered completely in 30 days. The postmortem examination revealed a lesion in the dorsomedial frontal cortex. The combined attentional and motor deficits suggest that this area may be involved in the preparation and execution of movements triggered by the affective meaning of the stimulus. (C) 1998 Elsevier Science Ltd. All rights reserved
Fisiologia Umana: Un approccio integrato
No full textVi sono oggi opportunità straordinarie per un proficuo studio delle funzioni del corpo umano. Gli studenti talvolta guardano alla fisiologia come a una materia "morta", in cui non resta più nulla da scoprire. In effetti, un tempo si pensava che decodificcando l'intero genoma umano avremmo avuto la chiave del segreto della vita. Tuttavia, questa visione riduzionistica della biologia ha forti limiti. Gli organismi viventi sono molto di più di una semplice somma di parti. Ora, alle soglie del XXI secolo, i biologi molecolari chiedono aiuto ai fisiologi per la comprensione della funzione delle molecole nell'organismo in toto
Hypnotic susceptibility modulates brain activity related to experimental placebo analgesia
No full textIdentifying personality traits and neural signatures that predict placebo responsiveness is important, both on theoretical and practical grounds. In the present functional magnetic resonance imaging (fMRI) study, we performed multiple-regression interaction analysis to investigate whether hypnotic susceptibility (HS), a cognitive trait referring to the responsiveness to suggestions, explains interindividual differences in the neural mechanisms related to conditioned placebo analgesia in healthy volunteers. HS was not related to the overall strength of placebo analgesia. However, we found several HS-related differences in the patterns of fMRI activity and seed-based functional connectivity that accompanied placebo analgesia. Specifically, in subjects with higher HS, the placebo response was related to increased anticipatory activity in a right dorsolateral prefrontal cortex focus, and to reduced functional connectivity of that focus with brain regions related to emotional and evaluative pain processing (anterior mid-cingulate cortex/medial prefrontal cortex); an opposite pattern of fMRI activity and functional connectivity was found in subjects with lower HS. During pain perception, activity in the regions reflecting attention/arousal (bilateral anterior thalamus/left caudate) and self-related processing (left precuneus and bilateral posterior temporal foci) was negatively related to the strength of the analgesic placebo response in subjects with higher HS, but not in subjects with lower HS. These findings highlight HS influences on brain circuits related to the placebo analgesic effects. More generally, they demonstrate that different neural mechanisms can be involved in placebo responsiveness, depending on individual cognitive traits
Projections from visual areas of the cerebral cortex to pretectal nuclear complex, terminal accessory optic nuclei, and superior colliculus in macaque monkey
No full textThe purpose of this study was to analyze the projections from visually related areas of the cerebral cortex of rhesus monkey to subcortical nuclei involved in eye-movement control; i.e., the pretectal nuclear complex, the terminal nuclei of the accessory optic system (AOS), and the superior colliculus (SC). The anterograde tracer H-3-leucine was pressure injected bilaterally into the cortex of six monkeys (for a total of 12 cases) involving the primary visual cortex (area 17); the medial prestriate cortex (medial 18/19); dorsomedial area 19; the caudal portion of the cortex of the superior temporal sulcus, upper bank (cytoarchitectural area OAa) and lower bank (area PGa); the lower bank of the caudal lateral intraparietal sulcus (area POa); and the inferior parietal lobule (area 7). The results revealed that the pretectal nucleus of the optic tract received inputs from medial prestriate cortex, dorsomedial part of area 19, OAa, and PGa. The posterior pretectal nucleus received sparse projections from area 7 and the cortex lining the intraparietal sulcus (dorsomedial part of area 19 and POa). The pretectal olivary nucleus was targeted by neurons in cortex of dorsomedial area 19, and the anterior pretectal nucleus was targeted by neurons in both dorsomedial 19 and area 7. The nuclei of the AOS (dorsal terminal; lateral terminal; and interstitial nuclei of the superior fasciculus, posterior and medial fibers) received projections exclusively from areas OAa and PGa. Furthermore, in one case with PGa injection, the medial terminal nucleus, dorsal portion, was also labeled. The visual cortical areas studied projected differentially upon the SC laminae. The primary visual area 17 projected only to the superficial laminae, i.e., stratum zonale (SZ), stratum griseum superficiale (SGS), and stratum opticum (SO). On the other hand, the medial portion of the prestriate cortex and caudal OAa and PGa targeted the superficial and intermediate laminae, i.e., SZ, SGS, SO, and stratum griseum intermediale (SGI), whereas caudal area POa projected primarily to the intermediate layer SGI. Rostral area 7 (mainly 7b) neurons terminated in the stratum album intermediale (SAI); no SC terminals were found in a case in which caudal area 7 (mainly 7a) was injected
KAINIC ACID DIFFERENTLY AFFECTS RETINAL PROJECTIONS TO DIFFERENT PRETECTAL NUCLEI
No full textKainic acid (KA) damages retinal cells, thus impairing axonal anterograde transport of labeled aminoacids when injected intravitreally. In this study, Long-Evans rats were injected with KA into one eye, and seven days later were binocularly injected with C-14-valine. The extent of residual retinal afferents to two pretectal nuclei was calculated as the percentage of the contralateral, intact side. Projections to the nucleus of the optic tract (first relay station of the optokinetic pathway) appear significantly more affected than those to the olivary pretectal nucleus (involved in the pupillary light response). These results suggest a correlation between the functional properties of retinal ganglion cells and distinctive biochemical characteristics, such as their susceptibility to KA
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