Skrjabinodon castillensis (Nematode: Pharyngodonidae) parasitizing Liolaemus gracielae lizard (Squamata: Iguania: Liolaemidae) from Argentina.

Skrjabinodon castillensis is mentioned and illustrated here, based on specimens found in the large intestines of Liolaemus gracielae (Squamata: Liolaemidae) collected in San Juan province, Argentina. The species found is assigned to Skrjabinodon based lateral alae present in males. Lateral alae beginning midway between lips and nerve ring and ending just posterior to first pair of caudal papillae. In males, caudal alae absent, paired caudal papillae present. The species recorded in this study differs from all other species assigned to Skrjabinodon by morphology and number of tail filament spines. Skrjabinodon castillensis is the ninth species from the Neotropical realm and the only species of this genus known from Argentina.

Skrjabinodon castillensis n. sp. (Nematoda:Pharyngodonidae) from the Homonota horrida and H.darwinii (Squamata: Phyllodactylidae) from Argentina and key for the Neotropical species of the genus Skrjabinodon.

Skrjabinodon castillensis n. sp. is described and illustrated here, based on specimens found in the large intestines of Homonota horrida (province San Juan) and Homonota darwinii (province Neuquén) (Squamata: Phyllodactylidae) from Argentina. The new species is assigned to Skrjabinodon based lateral alae present in males, absent in females. Lateral alae beginning midway between lips and nerve ring and ending just posterior to first pair of caudal papillae. Females with vulva near esophageal bulb. In males, caudal alae absent, paired caudal papillae present. Skrjabinodon castillensis n. sp. represents the 9th species from the Neotropical realm. The new species differs from all other species assigned to Skrjabinodon by morphology of tail filament and number of tail filament spines. Skrjabinodon castillensis n. sp. is the only species of this genus known from Argentina. A key to the species of Skrjabinodon in the Neotropical realm is provided.

First record of Amblyomma tigrinum (Acari: Ixodidae) on puma (Puma concolor) in Argentina and new associations for carnivores in San Juan province.

Amblyomma tigrinum is a tick species widely distributed in South America. In Argentina, it has been recorded to occur in nearly all phytogeographic regions, exhibiting its plasticity to different types of environments. This tick is of medical and veterinary importance because its adult stages have been recorded primarily in mammals, including humans. Specifically in San Juan province, records of A. tigrinum are almost non-existent, with only two mentions, but which have no indication of host or specific place of collection. For this reason, the goal of this study is to report the first case of A. tigrinum in Argentina, as well as two new parasite-host associations of the adult tick in other carnivores in San Juan. We analyzed two individuals, one puma and one fox, which arrived at the Wildlife Rehabilitation, Environmental Education and Responsible Recreation Center (Parque Faunistico). Moreover, we analyzed one canid specimen obtained during a field sampling event. Our results indicated new records for San Juan province of A. tigrinum parasitizing Canis familiaris and Lycalopex gymnocercus, in addition to the first record for Argentina of this tick parasitizing a Puma concolor individual. The present study affords novel information about natural associations for carnivore hosts in San Juan province, and the first record of this tick on a puma for Argentina. Thus, we are contributing to the knowledge of parasite-host relationships on the group of carnivores in Argentina.

Checklist of nematode parasites of reptiles from Argentina.

A summary of the parasitic nematodes of reptiles from Argentina is presented. It is a compilation of 29 parasitological papers published between 1992 and May 2020. This review includes information about 40 species of reptiles (4 snakes, 3 turtles, 1 anfisbaenian and 32 lizards). Twenty-six nematodes species have been reported from reptiles. The present review provides data on hosts, geographical distribution and site of infection. A host/parasite list is also provided.

Abnormal distraction and load-specific connectivity during working memory in cognitively normal Parkinson's disease.

Visuospatial working memory impairments are common in Parkinson's disease (PD), yet the underlying neural mechanisms are poorly understood. The present study investigated abnormalities in context-dependent functional connectivity of working memory hubs in PD. Cognitively normal PD and control participants underwent fMRI while performing a visuospatial working memory task. To identify sources of dysfunction, distraction, and load-modulated connectivity were disentangled for encoding and retrieval phases of the task. Despite normal working memory performance in PD, two features of abnormal connectivity were observed, one due to a loss in normal context-related connectivity and another related to upregulated connectivity of hubs for which the controls did not exhibit context-dependent connectivity. During encoding, striatal-prefrontal coupling was lost in PD, both during distraction and high memory loads. However, long-range connectivity of prefrontal, medial temporal and occipital hubs was upregulated in a context-specific manner. Memory retrieval was characterized by different aberrant connectivity patterns, wherein precuneus connectivity was upregulated during distraction, whereas prefrontal couplings were lost as memory load approached capacity limits. Features of abnormal functional connectivity in PD had pathological and compensatory influences as they correlated with poorer working memory or better visuospatial skills. The results offer new insights into working memory-related signatures of aberrant cortico-cortical and corticostriatal functional connections, which may portend future declines in different facets of working memory.

Description of Ornithodoros montensis n. sp. (Acari, Ixodida: Argasidae), a parasite of the toad Rhinella arenarum (Amphibia, Anura: Bufonidae) in the Monte Desert of Argentina.

A new tick species of the genus Ornithodoros (Acari: Argasidae) was described from larvae collected on the toad Rhinella arenarum in a locality from Argentina belonging to the Monte Biogeographic Province. Ornithodoros montensis n. sp. was described based on morphological traits and sequences of the mitochondrial 16S rRNA gene. The diagnostic characters for this species are a combination of idiosoma oval, dorsal plate pyriform with posterior margin slightly concave, dorsal surface with 17 pairs of setae (7 anterolateral, 4 to 5 central and 5 to 6 posterolateral), ventral surface with 6 pairs of setae and 1 pair on anal valves, three pairs of sternal setae, postcoxal setae absent, and hypostome pointed apically with dental formula 3/3 in the anterior half and 2/2 posteriorly almost to base. Phylogenetic analysis of 16S rDNA sequences and a principal component analysis based on morphometric characters provided additional support to the description of O. montensis as an independent lineage within the genus Ornithodoros. Larvae of O. montensis are phylogenetically closely related to O. puertoricensis, O. rioplatensis, O. talaje s.s., O. guaporensis, O. hasei and O. atacamensis, all of them belonging to the "O. talaje group".

New association between Amblyomma parvitarsum (Acari: Ixodidae) and the endemic lizard Liolaemus eleodori (Iguania: Liolaemidae) in Argentina

Records of lizard parasitizing ticks in Argentina are scarce and incomplete. We recorded a new population of Liolaemus eleodori, a lizard endemic to Argentina, parasitized by the hard tick Amblyomma parvitarsum. Hence, the objective of this study is to report this new association and enhance knowledge about its parasitism on reptiles of Argentina. To do this, we researched ectoparasitic loads. We determined different ecological predictors: intensity, mean intensity and prevalence. Our results provide the first data on the parasitism of nymphal stages on this lizard. We found a tick prevalence of 91.6% and a mean intensity of 2.45. Considering sexes, mean intensity was higher in females than in males. The gular region and lower ventral abdomen were the highest parasitized anatomical regions. This new record of the host-parasite association suggests that this relationship is not accidental, with this lizard species being central to the tick's life cycle. Probably, the microhabitat of this lizard species is essential for the tick to reach high prevalence. Our study represents an important contribution and provides additional information on parasitism in lizards of Argentina.

Altered Functional Interactions of Inhibition Regions in Cognitively Normal Parkinson's Disease.

Deficient inhibitory control in Parkinson's disease (PD) is often observed in situations requiring inhibition of impulsive or prepotent behaviors. Although activation of the right-hemisphere frontal-basal ganglia response inhibition network is partly altered in PD, disturbances in interactions of these regions are poorly understood, especially in patients without cognitive impairment. The present study investigated context-dependent connectivity of response inhibition regions in PD patients with normal cognition and control participants who underwent fMRI while performing a stop signal task. PD participants were tested off antiparkinsonian medication. To determine if functional disturbances depended on underlying brain structure, aberrant connectivity was correlated with brain volume and white-matter tissue diffusivity. We found no group differences in response inhibition proficiency. Yet the PD group showed functional reorganization in the long-range connectivity of inhibition regions, despite preserved within network connectivity. Successful inhibition in PD differed from the controls by strengthened connectivity of cortical regions, namely the right dorsolateral prefrontal cortex, pre-supplementary motor area and right caudal inferior frontal gyrus, largely with ventral and dorsal attention regions, but also the substantia nigra and default mode network regions. Successful inhibition in controls was distinguished by strengthened connectivity of the right rostral inferior frontal gyrus and subcortical inhibition nodes (right caudate, substantia nigra, and subthalamic nucleus). In both groups, the strength of context-dependent connectivity correlated with various indices of response inhibition performance. Mechanisms that may underlie aberrantly stronger context-specific connectivity include reduced coherence within reorganized systems, compensatory mechanisms, and/or the reorganization of intrinsic networks. In PD, but not controls, abnormally strengthened connectivity was linked to individual differences in underlying brain volumes and tissue diffusivity, despite no group differences in structural variables. The pattern of structural-functional associations suggested that subtle decreases in tissue diffusivity of underlying tracts and posterior cortical volumes may undermine the enhancement of normal cortical-striatal connectivity or cause strengthening in cortical-cortical connectivity. These novel findings demonstrate that functionally reorganized interactions of inhibition regions predates the development of inhibition deficits and clinically significant cognitive impairment in PD. We speculate that altered interactions of inhibition regions with attention-related networks and the dopaminergic system may presage future decline in inhibitory control.

Aberrant Intrinsic Activity and Connectivity in Cognitively Normal Parkinson's Disease.

Disturbances in intrinsic activity during resting-state functional MRI (rsfMRI) are common in Parkinson's disease (PD), but have largely been studied in a priori defined subnetworks. The cognitive significance of abnormal intrinsic activity is also poorly understood, as are abnormalities that precede the onset of mild cognitive impairment. To address these limitations, we leveraged three different analytic approaches to identify disturbances in rsfMRI metrics in 31 cognitively normal PD patients (PD-CN) and 30 healthy adults. Subjects were screened for mild cognitive impairment using the Movement Disorders Society Task Force Level II criteria. Whole-brain data-driven analytic approaches first analyzed the amplitude of low-frequency intrinsic fluctuations (ALFF) and regional homogeneity (ReHo), a measure of local connectivity amongst functionally similar regions. We then examined if regional disturbances in these metrics altered functional connectivity with other brain regions. We also investigated if abnormal rsfMRI metrics in PD-CN were related to brain atrophy and executive, visual organization, and episodic memory functioning. The results revealed abnormally increased and decreased ALFF and ReHo in PD-CN patients within the default mode network (posterior cingulate, inferior parietal cortex, parahippocampus, entorhinal cortex), sensorimotor cortex (primary motor, pre/post-central gyrus), basal ganglia (putamen, caudate), and posterior cerebellar lobule VII, which mediates cognition. For default mode network regions, we also observed a compound profile of altered ALFF and ReHo. Most regional disturbances in ALFF and ReHo were associated with strengthened long-range interactions in PD-CN, notably with regions in different networks. Stronger long-range functional connectivity in PD-CN was also partly expanded to connections that were outside the networks of the control group. Abnormally increased activity and functional connectivity appeared to have a pathological, rather than compensatory influence on cognitive abilities tested in this study. Receiver operating curve analyses demonstrated excellent sensitivity (≥90%) of rsfMRI variables in distinguishing patients from controls, but poor accuracy for brain volume and cognitive variables. Altogether these results provide new insights into the topology, cognitive relevance, and sensitivity of aberrant intrinsic activity and connectivity that precedes clinically significant cognitive impairment. Longitudinal studies are needed to determine if these neurocognitive associations presage the development of future mild cognitive impairment or dementia.

Dissociation of Neural Mechanisms for Intersensory Timing Deficits in Parkinson's Disease.

This study investigated the ability of individuals with Parkinson's disease (PD) to synthesize temporal information across the senses, namely audition and vision. Auditory signals (A) are perceived as lasting longer than visual signals (V) when they are compared together, since attentsion is captured and sustained more easily than for visual information. We used the audiovisual illusion to probe for disturbances in brain networks that govern the resolution of time in two intersensory conditions that putatively differ in their attention demands. PD patients and controls judged the relative duration of successively presented pairs of unimodal (AA, VV) and crossmodal (VA, AV) signals whilst undergoing fMRI. There were four main findings. First, underestimation of time was exaggerated in PD when timing depended on controlled attention (AV), whereas subtle deficits were found when audition dominated and attention was more easily sustained (VA). Second, group differences in regional activation were observed only for the AV-unimodal comparison, where the PD group failed to modulate basal ganglia, anterior insula, and inferior cerebellum activity in accord with the timing condition. Third, the intersensory timing conditions were dissociated by patterns of abnormal functional connectivity. When intersensory timing emphasized controlled attention, patients showed weakened connectivity of the cortico-thalamus-basal ganglia (CTBG) circuit and the anterior insula with widespread cortical regions, yet enhanced cerebellar connectivity. When audition dominated intersensory timing, patients showed enhanced connectivity of CTBG elements, the anterior insula, and the cerebellum with the caudate tail and frontal cortex. Fourth, abnormal connectivity measures showed excellent sensitivity and specificity in accurately classifying subjects. The results demonstrate that intersensory timing deficits in PD were well characterized by context-dependent patterns of functional connectivity within a presumed core timing system (CTBG) and a ventral attention hub (anterior insula), and enhanced cerebellar connectivity irrespective of the hypothesized attention demands of timing.

Neural underpinnings of distortions in the experience of time across senses.

Auditory signals (A) are perceived as lasting longer than visual signals (V) of the same physical duration when they are compared together. Despite considerable debate about how this illusion arises psychologically, the neural underpinnings have not been studied. We used functional magnetic resonance imaging (fMRI) to investigate the neural bases of audiovisual temporal distortions and more generally, intersensory timing. Adults underwent fMRI while judging the relative duration of successively presented standard interval-comparison interval (CI) pairs, which were unimodal (A-A, V-V) or crossmodal (V-A, A-V). Mechanisms of time dilation and compression were identified by comparing the two crossmodal pairs. Mechanisms of intersensory timing were identified by comparing the unimodal and crossmodal conditions. The behavioral results showed that auditory CIs were perceived as lasting longer than visual CIs. There were three novel fMRI results. First, time dilation and compression were distinguished by differential activation of higher-sensory areas (superior temporal, posterior insula, middle occipital), which typically showed stronger effective connectivity when time was dilated (V-A). Second, when time was compressed (A-V) activation was greater in frontal cognitive-control centers, which guide decision making. These areas did not exhibit effective connectivity. Third, intrasensory timing was distinguished from intersensory timing partly by decreased striatal and increased superior parietal activation. These regions showed stronger connectivity with visual, memory, and cognitive-control centers during intersensory timing. Altogether, the results indicate that time dilation and compression arise from the connectivity strength of higher-sensory systems with other areas. Conversely, more extensive network interactions are needed with core timing (striatum) and attention (superior parietal) centers to integrate time codes for intersensory signals.

Neurobehavioral mechanisms of temporal processing deficits in Parkinson's disease.

BACKGROUND: Parkinson's disease (PD) disrupts temporal processing, but the neuronal sources of deficits and their response to dopamine (DA) therapy are not understood. Though the striatum and DA transmission are thought to be essential for timekeeping, potential working memory (WM) and executive problems could also disrupt timing. METHODOLOGY/FINDINGS: The present study addressed these issues by testing controls and PD volunteers 'on' and 'off' DA therapy as they underwent fMRI while performing a time-perception task. To distinguish systems associated with abnormalities in temporal and non-temporal processes, we separated brain activity during encoding and decision-making phases of a trial. Whereas both phases involved timekeeping, the encoding and decision phases emphasized WM and executive processes, respectively. The methods enabled exploration of both the amplitude and temporal dynamics of neural activity. First, we found that time-perception deficits were associated with striatal, cortical, and cerebellar dysfunction. Unlike studies of timed movement, our results could not be attributed to traditional roles of the striatum and cerebellum in movement. Second, for the first time we identified temporal and non-temporal sources of impaired time perception. Striatal dysfunction was found during both phases consistent with its role in timekeeping. Activation was also abnormal in a WM network (middle-frontal and parietal cortex, lateral cerebellum) during encoding and a network that modulates executive and memory functions (parahippocampus, posterior cingulate) during decision making. Third, hypoactivation typified neuronal dysfunction in PD, but was sometimes characterized by abnormal temporal dynamics (e.g., lagged, prolonged) that were not due to longer response times. Finally, DA therapy did not alleviate timing deficits. CONCLUSIONS/SIGNIFICANCE: Our findings indicate that impaired timing in PD arises from nigrostriatal and mesocortical dysfunction in systems that mediate temporal and non-temporal control-processes. However, time perception impairments were not improved by DA treatment, likely due to inadequate restoration of neuronal activity and perhaps corticostriatal effective-connectivity.

From sensory processes to conscious perception.

In recent years, cognitive neuroscientists have began to explore the process of how sensory information gains access to awareness. To further probe this process, event-related functional magnetic resonance imaging (fMRI) was used while testing subjects with a paradigm known as the "attentional blink." In this paradigm, visually presented information sporadically fails to reach awareness. It was found that the magnitude and time course of activation within the anterior cingulate (BA 32), medial prefrontal cortex (BA 9), and frontopolar cortex (BA 10) predicted whether or not information was consciously perceived during the critical period for the attentional blink. These results are discussed in light of a neural framework for conscious processing.