47,330 research outputs found
Isospora atrata (Apicomplexa, Eimeridae): a new coccidium isolated from Carduelis atrata (Passeriformes, Fringillidae)
No full textLarge numbers of coccidian oocysts belonging to the genus Isospora were obtained from the intestinal contents of 98 Carduelis atrata imported into Italy from South America during the months of August through December 1994. The oocysts are subspherical and average 21 X 20.3 mu m (19.4-23.5 mu m X 18.5-22 mu m), have a bilayered wail, and an oval polar granule (rarely two). The sporocysts are elliptical and measure 18.8 mu m X 10.3 mu m (17.5-18.94 mu m X 9.5-11.0 mu m). The Stieda body protrudes slightly from the end of the sporocyst. A large sporocyst residuum is present, consisting of many granules that may be in a compact mass or scattered. Since this Isospora sp.does not resemble any other species of Isospora previously described from birds of the genus Carduelis, it has been named Isospora atrata n. sp. after the host. Disseminated asexual stages were found in mononuclear cells derived from formalin-fixed post mortem material, suggesting this coccidian may represent an Atoxoplasma-like parasite. Four coccidia-free Serinus canarius L. cohabitated for a lone period (4 mo) with infected C. atrata but oocysts were never found in the stool of these birds
Respiratory phases modulate heartbeat-evoked cortical responses
No full textHeartbeat Evoked Responses (HERs) are EEG event-related potentials time-locked to the heartbeat that reflect the cortical processing of cardiac activity. HER amplitude has been related to various behavioural measures of interoception, but the reliability of such findings is controversial, given possible confounding effects driven by the electric cardiac field, as well as by other somatosensory or interoceptive factors. One of such interoceptive factors may be the respiratory phase. In fact, despite recent studies demonstrating optimized neural processing of incoming exteroceptive (sensory) information during inhalation, virtually nothing is known about mechanisms through which respiratory activity influences incoming interoceptive (cardiac) information. We simultaneously recorded 64-channel EEG, cardiac and respiratory activity in 20 healthy volunteers during an eyes-open resting state. We extracted HERs detected during inspiratory (when respiratory activity is at maximum) and post-expiratory (when respiratory activity is at a minimum) phases. In order to reduce cardiac field artefacts, HERs were time-locked to the T-peak and pruned with ICA-based procedures. HERs were compared performing a repeated-measures, two-tailed
cluster mass permutation test (10 000 permutations), including all time points between 80 and 350 ms post T-peak. We found that respiratory phases modulate HER amplitude, which was significantly higher during post-expiratory phases as compared to inspiratory phases, in a time window ranging from 176ms to 254ms post T-peak. This “respiratory HER effect” was detected in central and parietal areas known to be involved in various experimentally-induced HER modulations. Present finding indicates an often-unnoticed influence of respiration on cardiac interoception, suggesting increased neural processing of the heartbeat during post-expiratory phases, when respiratory interoceptive afference is at a minimum, as compared to inspiratory phases. Finally, starting from recent studies that independently showed that cardiac interoceptive accuracy increased during breath-holding and is predicted by HER amplitude, we conducted another study investigating if: i) the performance on the heartbeat tapping task changes depending on the specific respiratory
phase, and ii) these changes correlate with the “respiratory HER effect”
Environmental control and psychosis-relevant traits modulate the prospective sense of agency in non-clinical individuals
No full textThe sense of agency concerns the experience of being the source of one's own actions and their consequences. An altered sense of agency can occur due to task automation and in psychosis. We tested in a non-clinical sample the hypothesis that reducing voluntary task control diminishes intentional binding as an implicit indicator of the sense of agency, possibly interacting with psychosis-relevant personality traits. Agent-device interactions were manipulated obtaining positive-control (voluntary interaction), no-control (automation), and negative-control (device-commanded interaction) groups. The main results showed reduced prospective intentional binding (predictive coding of action consequences) in the no-control and negative-control groups, compared to the positive-control group. Psychosis-like experiences covaried positively with intentional binding in the no-control group, but negatively in the negative-control group. Moreover, positive-social traits were associated with increased intentional binding in the positive-control group. These findings demonstrate the interplay between environmental and individual differences variables in establishing the implicit sense of agency
Heartfelt choices: The influence of cardiac phase on free-choice actions
No full textThe influence of cardiac phases on cognitive and sensorimotor functions is noteworthy. Specifically, during systole, as opposed to diastole, there is an observed enhancement in tasks demanding the suppression of instructed responses. This suggests that systole contributes to inhibitory control in motor functions. However, the extent to which systolic inhibition is significant in volitional free-choice actions, such as choosing to execute or refrain from a cue-initiated response, remains to be clarified. To fill this gap in the current literature, the purpose of this study was to test whether during the systole phase, compared with the diastole phase, the tendency to enact volitional actions decreased due to the systolic inhibitory effect. We used a modified version of the Go/No-Go task with an added condition for volitional free-choice actions, where participants could decide whether to respond or not, to test whether systolic inhibition could affect the volitional decision to act. The results showed that participants' responses were less frequent in systole than in diastole in the volitional action condition. Then, to test the robustness of the cardiac effect on volitional actions, we used two established manipulations: the Straw Breathing Manipulation and the Cold Pressor Test, which were able to induce anxiety and increase the heart rate, respectively. Results showed that the systole/diastole difference in the number of volitional action trials in which participants decided to respond tended to remain the same despite all manipulations. Overall, our results provide convergent evidence for the effect of the heart on the decision to act, an effect that appears independent of manipulations of both the physiological and psychological state of the individual
Isospora thibetana n. sp. (Apicomplexa, Eimeriidae), a parasite of the Tibetan siskin (Serinus thibetanus equals Carduelis thibetanus) (Passeriformes, Fringillidae)
No full textTibetan siskins are birds native to the Himalayan region often imported into Italy for commercial purposes. Fecal examination of 45 imported subjects with clinical signs of diarrhoea revealed the presence of a large number of coccidian oocysts. After sporulation, accomplished by mixing feces with 2.5 % (w/v) acqueous K2Cr2O7 at room temperature (22 degrees C +/- 1 degrees C), exogenous stages of an Isospora species were revealed. The oocysts of this Isospora are spherical, have a bilayered colorless wall, and average 23.24 mu m x 23.05 mu m: oocyst residuum and micropyle an absent, while an oval polar granule is rarely present. The elliptical sporocysts average 18.44 mu m x 10.97 mu m and the Stieda body protrudes slightly from the end of the sporocyst. A spherical sporocyst residuum is present though it sometimes consists of scattered granules. The spindle-shaped sporozoites average 11.53 mu m x 2.86 mu m, and have two refractile bodies. The taxonomic position of the tibetan siskin is controversial. Some authors include this species in the genus Serinus, while others include it in the genus Carduelis. The coccidian species isolated from these tibetan siskins was, for this reason, compared with the Isospora species previously described both in the genus Carduelis and in the genus Serinus. As a result of this comparison a new species, Isospora thibetana, was named. In the intestine of dead subjects, oocysts were found only in the ileum where the mucosa was greatly thickened and presented a heavy leucocytic infiltration consisting mainly of lympho-monocytic cells. A similar infiltration was observed in liver and lungs as well
In vitro and ex vivo evaluation of the anti-Giardia duodenalis activity of the supernatant of SLAB51 (SivoyTM)
No full textThe effects on Giardia duodenalis growth (G), adherence (A), and viability (V) of SivoyTM
probiotic supernatant were evaluated in vitro and ex vivo. SivoyTM (101 UFC) was in vitro
cultured and the obtained supernatant was filtered, adjusted at pH 7, and added (100 μl/ml) as
such (FS) or after heat-treatment to G. duodenalis (5×104) cultures in TYI-S-33 medium.
Negative and metronidazole 20 μg/ml (M) treated controls were used. Ex vivo, five- 1 cm long
mice duodenal portions were cultivated in standard conditions with 5X105 G. duodenalis
trophozoites/ml, while to further five duodenal portions similarly cultured and infected, FS 200μl
was added. After 12 and 18h, samples were fixed in 10% buffered formalin and histologically
processed to score Giardia infection and cell damage. Cells proliferation/apoptosis were scored
by TUNEL, Caspase–3, and Ki67 tests. All data, in triplicate, were statistically evaluated (P<
0.05). Results showed that FS significantly reduced Giardia G and V respect to negative
controls but its efficacy was lower than that of M, while the inhibition of A was similar to that of
M. Moreover, the effects of FS were significantly lowered by heat-treatment and the reduction
was statistically higher at 90°C than at 56°C, indicating a heat-sensitive nature of active FS
compounds. In ex vivo trials, in intestinal sections treated with FS respect to untreated controls
viable G. duodenalis trophozoites and enterocyte TUNEL+ and Caspase-3 expression were
significantly reduced, while enterocyte Ki67 expression was significantly increased, confirming
the anti-G. duodenalis activity of FS observed in vitro
Slow Resting State Fluctuations Enhance Neuronal and Behavioral Responses to Looming Sounds
No full textWe investigate both experimentally and using a computational model how the power of the electroencephalogram (EEG) recorded in human subjects tracks the presentation of sounds with acoustic intensities that increase exponentially (looming) or remain constant (flat). We focus on the link between this EEG tracking response, behavioral reaction times and the time scale of fluctuations in the resting state, which show considerable inter-subject variability. Looming sounds are shown to generally elicit a sustained power increase in the alpha and beta frequency bands. In contrast, flat sounds only elicit a transient upsurge at frequencies ranging from 7 to 45 Hz. Likewise, reaction times (RTs) in an audio-tactile task at different latencies from sound onset also present significant differences between sound types. RTs decrease with increasing looming intensities, i.e. as the sense of urgency increases, but remain constant with stationary flat intensities. We define the reaction time variation or “gain” during looming sound presentation, and show that higher RT gains are associated with stronger correlations between EEG power responses and sound intensity. Higher RT gain further entails higher relative power differences between loom and flat in the alpha and beta bands. The full-width-at-half-maximum of the autocorrelation function of the eyes-closed resting state EEG also increases with RT gain. The effects are topographically located over the central and frontal electrodes. A computational model reveals that the increase in stimulus–response correlation in subjects with slower resting state fluctuations is expected when EEG power fluctuations at each electrode and in a given band are viewed as simple coupled low-pass filtered noise processes jointly driven by the sound intensity. The model assumes that the strength of stimulus-power coupling is proportional to RT gain in different coupling scenarios, suggesting a mechanism by which slower resting state fluctuations enhance EEG response and shorten reaction times
Walking-related locomotion is facilitated by the perception of distant targets in the extrapersonal space
No full textThe Gibsonian notion of affordance has been massively employed in cognitive sciences to characterize the tight interdependence between hand-related actions, manipulable objects and peripersonal space. A behavioural facilitation effect, indeed, is observed for grasping actions directed to objects located in the ‘reachable’ peripersonal space. Relevantly, this relationship is supported by dedicated neural systems in the brain. The original notion of affordance, however, was directly inspired by real-time interactions between animals and their extended natural environment. Consistently, also the extrapersonal space representation can be significantly modulated by action-related factors, and the brain contains dedicated systems for the representation of topographical space and navigation. Here we examined whether a facilitation effect could be also described for a walking-related action in the far extrapersonal space. To this aim, we employed a go/no-go paradigm requiring subjects to execute a footstep ahead in response to pictures of a virtual reality environment containing objects located at different distances (near, far) and eccentricities (central, peripheral). A walking-related, facilitation effect for distant extrapersonal locations was found, suggesting an automatic trigger of walking by positions that preferentially guide spatial exploration. Based on the parallelism with the literature on micro-affordances, we propose that this effect can be described in terms of “macro-affordances”
Formazione on line: Coerenza interna e validità convergente della scala del senso di comunità in corsi online
No full textIl Senso di Comunità (SdC), ovvero la percezione di similarità e interdipendenza che si
sviluppa tra i membri di un gruppo, è considerato nella formazione on line uno dei
fattori che contribuiscono significativamente alla qualità dell’apprendimento e alla
soddisfazione degli studenti. La sua valutazione può essere indicata anche per
identificare le condizioni organizzative che possono effettivamente supportare il SdC,
come ad esempio la modalità di interazione (asincrona vs. asincrona e sincrona) e le
caratteristiche del contesto del corso (ad. es. totalmente on-line vs. blended). In accordo
al modello di McMillan e Chavis (1986), è stata recentemente predisposta la Scala del
SdC in Corsi on line (SSCC; Perrucci et al., 2008, 2009). Con la presente indagine si è
voluto verificarne coerenza interna e validità convergente-divergente rispetto a test che
misurano il SdC e costrutti affini ma distinti.
Duecentottantasei frequentanti di corsi on line, casualmente suddivisi in due sub-gruppi
(1 e 2) entro ogni corso, hanno compilato l’SSCC e altri due questionari già validati e
opportunamente adattati dagli Autori della presente indagine al contesto della
formazione on line: Scala Italiana del Senso di Comunità (Prezza et al., 1999) e Scala
Multidimensionale del Sostegno Sociale Percepito (Zimet et al., 1988), sub-gruppo 1;
Classroom Community Scale (Rovai, 2002) e Questionario sull’Identità Sociale
(Cameron, 2004), sub-gruppo 2.
Il coefficiente di alfa di Cronbach e i pattern di correlazioni tra l’SSCC e le altre scale
permettono di affermare che l’SSCC è attendibile nel misurare il SdC in corsi on line e
valido nel discriminarlo da costrutti simili. Ulteriori indagini sulle proprietà
psicometriche consentiranno di verificare se la struttura fattoriale dell’SSCC è in
accordo con le dimensioni ipotizzate dal modello di McMillan e Chavis (1986)
Respiratory rhythm and multisensory perception
No full textIntroduction: The brain continuously processes information coming from both the external environment and visceral signals generated by the body. This constant information exchange between the body and the brain allows rhythmic signals originating from the heart and lungs, among others, to influence perception. In previous work, we have shown that cardiac cycle phase interacts with multisensory integration, i.e., the non-linear combination of information coming from multiple senses. Here, we investigated respiratory modulations of reaction times and multisensory integration in a simple detection task. Methods: Forty healthy participants were presented with unimodal (Auditory, Visual, Tactile) and bimodal (Audio-Tactile, Audio-Visual, Visuo-Tactile) stimuli while respiratory activity was recorded. Linear mixed effects models were performed on reaction times and the Race Model Inequality approach was employed to quantify multisensory integration, with a specific focus on respiratory phases. Results: First, respiration was found to significantly modulate reaction times irrespective of the stimulus type, with distinct temporal dynamics for unimodal and bimodal stimuli. Notably, reaction times were slower during the expiration-to-inspiration phase. Then, the Race Model Inequality analysis revealed higher multisensory integration for Audio-Tactile and Audio-Visual stimuli during expiration-toinspiration phase. Participants also adapted their respiratory cycle, as their response onsets preferentially occurred during early expiration. Discussion: These findings indicate that respiration is not merely a bottom-up mechanism but is actively adjusted to optimize the signalto-noise balance between interoceptive and exteroceptive signals. From a predictive processing perspective, these results suggest that respiration acts as a "master clock" aligning external information sampling with fluctuating states of neural excitability. This intricate interplay between respiration and neural processes sheds light on the dynamic nature of multisensory integration and its modulation by peripheral factors
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