Description of Evandromyia cristacapita sp. nov., a new sand fly species of the Argentinian Chaco.

A new species of phlebotomine sand fly collected in the rural and peri-urban areas of wet and dry subregions of the Chaco Province, Argentina, is described. Illustrations of male and female adults are presented. Morphological characters allow the inclusion of the new species within the Evandromyia genus, Barrettomyia subgenus, Cortelezzii series (Diptera: Psychodidae). Furthermore, we present an identification key for the Cortelezzii series of the Barrettomyia subgenus with a new distinct species complex for its correct identification. The species was denominated as Evandromyia cristacapita sp. nov.

Temporal distribution of, and effect of anthropic modifications on, phlebotomine populations in the Chaco Bioregion, Argentina.

Migonemyia migonei is the predominant species in the dry ecoregion and Nyssomyia neivai in the humid region, although co-dominance in humid highly modified areas could be observed. Vector abundance seems to be modulated by environmental anthropization, as the abundance and predominance of Ny. neiviai and Mg. migonei increased in highly modified areas. In Humid Chaco, the risk of human-vector contact would be present throughout the year, being particularly high in spring/summer, and in Dry Chaco, the risk would be restricted to temperate and humid months.

Cross-modal comparisons of stimulus specificity and commonality in phonological processing.

Phonological processing is a fundamental ability which underlies language comprehension. Functional neuroanatomy of phonology constitutes a matter of ongoing debate. In the present study, subjects performed visual (rhyme detection) and auditory (identification of spoken words starting with a given consonant) tasks that were contrasted with matched nonverbal tasks. We identified regions critical for phonological processing which were either stimulus specific or supramodal. The results revealed a high degree of modality specificity in both visual and auditory networks. Moreover, we observed a modality independent region in the left middle temporal gyrus (MTG)/superior temporal sulcus (STS), between a more anterior temporal area with auditory specificity and a more posterior temporal area with visual specificity. This dissociation in functional neuroanatomy suggests that this area may be a core region for supramodal phonological processing, acting as a gateway between spatially separate, but stimulus specific, phonological processes and more general linguistic functions.

Changes in fMRI BOLD response to increasing and decreasing task difficulty during auditory perception of temporal order.

We have discovered changes in brain activation during difficult and easy milliseconds timing. Structures engaged in difficult and easier auditory temporal-order judgment were identified in 17 young healthy listeners presented with paired-white-noises of different durations. Within each pair, a short (10 ms) and a long (50 ms) noise was separated by a silent gap of 10, 60 or 160 ms, corresponding to three levels of task difficulty, i.e. difficult, moderate and easy conditions, respectively. A block design paradigm was applied. In temporal-order judgment task subjects were required to define the order of noises within each pair, i.e. short-long or long-short. In the control task they only detected the presentation of the stimulus pair. A multiple regression with 'task difficulty' as a regressor ('difficult', 'moderate', 'easy') showed dynamic changes in neural activity. Increasing activations accompanying increased task difficulty were found in both bilateral inferior parietal lobuli and inferior frontal gyri, thus, in classic regions related to attentional and working memory processes. Conversely, decreased task difficulty was accompanied by increasing involvement of more specific timing areas, namely bilateral medial frontal gyri and left cerebellum. These findings strongly suggest engagement of different neural networks in difficult or easier timing and indicate a framework for understanding timing representation in the brain.

Towards electrophysiological correlates of auditory perception of temporal order.

Recent studies have postulated that the temporal order (TO) of two successive events can be correctly identified if they are separated by an inter-stimulus interval (ISI) of at least 30 ms duration. Using Auditory Evoked Potentials, we tested 21 students for the cortical activation associated with TO detection of two successively presented tones in either 'easy' (ISI=60 ms) or 'difficult' (ISI=10 ms) conditions. The amplitude of P2 component was related to difficulty of TO perception and was significantly higher in 'difficult' than 'easy' condition. Moreover, in 'difficult' condition the correlation analyses revealed a negative association at both Fz and Cz electrodes between P2 amplitudes and the correctness level. Correct responses in this condition were accompanied by lower P2 amplitudes than the incorrect ones.

Auditory perception of temporal order in humans: the effect of age, gender, listener practice and stimulus presentation mode.

The temporal order (TO) of two auditory stimuli can be reported correctly when they are separated by a gap of approximate 30 ms. Since no clear evidence on individual differences in human sequencing abilities exists, we tested the effect of subjects' age and gender, as well as physical properties of presented stimuli and listener practice on the perception of TO. In two experiments, young and elderly listeners reported the TO of two clicks or tones. The TO threshold (i.e. the minimum temporal gap required to report the stimulus order at 75% correctness) was lower in young than elderly listeners, in men than women and for tones than clicks. Age-related deterioration depended on the physical properties of presented stimuli, remaining resistant to both gender and practice.

Deficits of non-verbal auditory perception in postlingually deaf humans using cochlear implants.

Temporal integration in the time domain of a few seconds was investigated with a subjective accentuation paradigm in 11 monochannel cochlear implant users, who showed auditory comprehension deficits. While listening to metronome beats generated at various frequencies, patients were asked to accentuate mentally every n-th beat and create an individual rhythmic pattern. The extent of temporal integration was defined as the duration of perceptual units consisting of subjectively grouped beats at particular metronome frequencies. The results indicate that there is reduced capacity for temporal integration in implant recipients, particularly for lower metronome frequencies, in comparison to normally hearing. These observations point to the coincidence of specific temporal processing disorders and deficits in auditory comprehension after cochlear implantation.

Conscious control of movements: increase of temporal precision in voluntarily delayed actions.

The variability of simple actions with response to auditory stimuli was studied under different delay conditions. Subjects reacted as fast as possible or with a defined time delay (from 250 to 750 ms) to a tone switching off by pressing a response-key with the left index finger (controlled by the right hemisphere) or with the right one (left hemisphere). For short delays (requested response times below 350 ms) variability of responses was much larger then for longer delays (above 350 ms), especially for the right hand. Thus, precise temporal control on consciously mediated actions sets only in after a rather long delay (in some cases after half a second). Neuronal mechanisms underlying conscious temporal control of actions appear to be different for the two hemispheres.

Hemispheric specialisation for self-paced motor sequences.

Temporal aspects of motor control were investigated in patients with infarction to the brain with two finger-tapping tests. In the self-paced tapping task patients with cortical left-hemispheric lesions were slowed down and patients with left-hemispheric subcortical injuries were consistently faster as compared with control subjects and patients with right hemispheric cortical lesions. The results point to the dominant control of the left-hemisphere in voluntarily timed action and to a special time range of 250-300 ms involved in motor behaviour.

[Assessment of blood flow velocity during cognitive stimulation in persons with suspected hydrocephalus]. / Badanie predkosci przeplywu krwi w czasie stymulacji poznawczej u osób z podejrzeniem wodoglowia.

The aim of this work is to evaluate middle cerebral arteries (MCA) blood flow velocity changes during performance of linguistic and visuospatial cognitive tasks. Two groups were investigated: eight patients with suspected hydrocephalus without perceptible cognitive disturbances, and eight healthy persons. Blood flow velocity in left and right MCA was recorded with transcranial Doppler sonography while the examined patients were performing three different tasks. The analysis of the results showed differences between the groups concerning both increase of blood flow velocity values and performance patterns. Compared to healthy individuals less increase in blood flow velocity during performance of all tasks and no difference in haemodynamic changes between both hemispheres during task performance were observed in patients with hydrocephalus. The results obtained suggest, that the pattern of functional lateralization in brain in patients with suspected hydrocephalus is probably changed.

Auditory temporal-order judgement is impaired in patients with cortical lesions in posterior regions of the left hemisphere.

Auditory temporal-order judgement was investigated in patients suffering from unilateral focal brain lesions, localized in anterior or posterior regions of the left hemisphere (LH) (resulting in non-fluent or fluent aphasia, respectively), or in predominantly subcortical regions of this hemisphere (without aphasic syndromes) and in anterior or posterior regions of the right hemisphere. The temporal order threshold was measured as the minimum time interval between two clicks presented consecutively and binaurally via headphones (one to each ear) that was necessary for a subject to indicate the temporal order of the two stimuli. Only the patient group with fluent aphasia showed a significantly increased mean temporal-order threshold as compared to the controls. Our results indicate that fine temporal resolution for auditory stimuli is predominantly associated with posterior regions of the LH.

[Dynamics of blood flow velocity in middle cerebral arteries in dyslexic persons]. / Dynamika przeplywu krwi w tetnicach srodkowych mózgu u osób z dysleksja.

The aim of our study was to investigate the blood flow in middle cerebral arteries during the different forms of cognitive activity in dyslectic persons. Two group of subjects were tested. The first group consisted of 10 students with school difficulties, diagnosed neuropsychologically as having a particular form of dyslexia, i.e. dysgraphy or dysorthography. 6 of them were right lateralized and 4--left lateralized. The second contained 10 students without such problems. 7 of them were right lateralized and 3--left lateralized. We used four kinds of cognitive tasks, during which the blood flow velocity in MCA in left and right hemisphere was measured with the Transcranial Doppler method. The analysis of the results showed differences between the groups of blood flow velocity levels, without a difference in performance profile. The dysgraphic persons had significantly higher blood flow velocity in the right hemisphere compared to the reference group. The results suggest particularly important role of right hemisphere in dyslexic persons, which is consistent with results obtained by other authors. The analysis of lateralization showed that this factor influences significantly the blood flow velocity level--the left lateralized persons showed lower rise of blood flow velocity than the right lateralized, regardless of the kind of task and measured hemisphere.

Temporal constraints of perceiving, generating, and integrating information: Clinical indications.

Neuropsychological research on temporal constraints of perception and motor performance can add important information to research on human behavior. Without considering temporal mechanisms of perceiving, generating, and updating information, brain mechanisms can never be fully understood. In this study temporal aspects of performance in psychophysical experiments on three different temporal levels (around 30 ms, 300 ms, and 3000 ms) were investigated in patients with acquired brain lesions and a control group without neurological deficits. The patients had acquired focal brain lesions in: anterior (pre-central) regions of the left hemisphere (with non-fluent aphasia), posterior (post-central) regions of the left hemisphere (with fluent aphasia), the left hemipshere in predominantly subcortical regions (without aphasia), or anterior (pre-central) or posterior (post-central) regions of the right hemipshere. Perception of temporal order (20 to 60 ms) was impaired in patients with left-hemispheric post-central lesions; repetitive voluntary action (300 to 500 ms) was affected mostly in patients with left hemi-spheric lesions, both pre-central and post-central; and a deficit in integrating (2000 ms to 3000 ms) information was most pronounced in patients with left and right pre-central lesions. These findings provide insight into the associations between different levels of temporal organisation and circumscribed regions of the neocortex.

Temporal integration in a subjective accentuation task as a function of child cognitive development.

We have previously shown that temporal integration in the domain of a few seconds may be studied using a subjective accentuation paradigm. Here we report developmental effects on the limits of this temporal integration in 9-10-year-olds in comparison with 13-14-year-olds. The task was to listen to a string of identical metronome beats and mentally bind the presented beats by subjectively accentuating every second, third or nth beat. The integration interval length was defined as the number of stimuli mentally connected multiplied by the temporal interval between two successive beats. For the lowest stimulus frequency integration intervals were approximately 3 s for the older and 2.2 s for the younger children. For higher frequencies integration intervals got systematically shorter, but being always longer for the older age group. It is suggested that the prefrontal region is responsible for this developmental effect. The expansion of temporal integration correlates with cognitive development in the investigated phase of ontogenesis.

Temporal processing disorders in patients with Broca's aphasia.

We report an association between a language deficit following brain lesion and a new strategy in temporal integration. Patients with different brain lesions mentally grouped sequences of identical acoustic stimuli generated at various frequencies. They were asked while listening to the stimuli to accentuate every second, third or other stimulus to create an individual rhythmic pattern. After each sequence patients reported how many stimuli they had united into a perceptual unit. The integration interval was defined as the number of reported stimuli multiplied by the temporal interval between two successive stimuli. Results indicate different integration strategies depending on the lesion site, i.e. Broca's aphasics behaving differently than all other patient groups. At lower frequencies they showed longer, at higher frequencies they displayed shorter integration. From this observation we conclude that the Broca's patients acquired a new strategy because of the lesion; they relied on mental counting and less on automatic temporal integration, which is usually the case.

Hemispheric asymmetries in stutterers: disorder severity and neuroticism?

This study tests the hypothesis that there is atypical brain asymmetry in stuttering children. In particular the association of both severity of stuttering and neuroticism with cerebral laterality in perception of visuospatial material is tested. Subjects were asked to recognize faces presented laterally in the left or right visual field and point to the exposed stimuli on response cards containing three different faces. Recognition errors committed in the left and right field presentations were analyzed. In fluent speakers and in moderately neurotic stutterers, fewer errors were found for the right hemisphere independently of their neuroticism score; in contrast, stutterers with a high neuroticism score showed fewer errors for the left hemisphere. The latter was true regardless of severity of stuttering. The study suggests a close link between atypical hemispheric dominance in the face recognition test and the emotional state in stutterers as defined by their neuroticism score. This characteristic may be related to the negative emotional reactions demonstrated relatively often by stuttering individuals. In highly neurotic stutterers, the negative affective states might be associated with disturbances of right hemisphere functioning and related to an atypical asymmetry pattern in the processing of right-hemispheric stimuli. These results illustrate the importance of controlling for subject-related factors while conducting and interpreting investigations on stutterers.

The effect of auditory experience on hemispheric asymmetry in a post-lingually deaf child: a case study.

We have previously shown that cerebral asymmetry in congenitally deaf children differs from that observed in normal hearing children. The effect of early auditory experiences on this process was investigated in a 14 year-old boy who had completely lost his hearing at the age of 5 due to meningitis. His recognition of laterally projected words and faces was compared with that of 18 congenitally deaf and 18 normal hearing children. In the word recognition test, a right hemisphere advantage was found in the patient and in congenitally deaf subjects and a left hemisphere advantage in normal hearing subjects. In the face recognition test, the left hemisphere was more proficient in the patient and the right hemisphere in normal hearing subjects. There was no hemispheric difference in the congenitally deaf. While hemispheric asymmetry has an ontogenetic base, these findings suggest that the degree and nature of such asymmetries can be influenced by environmental factors during development.

Temporal constraints in processing of nonverbal rhythmic patterns.

This study investigates the effect of a mental content of presented stimuli, normal aging and individual differences in cognitive abilities on temporal limits of an integration mechanism. Younger and older subject grouped together the beats generated by a metronome. Subjects were asked to listen to the beats of a metronome and to accentuate mentally every second, third, fourth...etc. beat, to create a subjective rhythm. This rhythm exists, in fact, only in subjects' mind and not objectively. Subjects reported verbally how many clicks they were able to integrate into a perceptual unit. On this basis, the time interval during which subjects were able to integrate temporally separated stimuli was calculated (number of beats reported as being integrated x time distance between beats) for different metronome frequencies. The results show, firstly, that the length of integration periods significantly depends on the frequency of presented metronome beats. When the frequency of metronome beats is high, the time interval during which the subjects integrate beats into a single perceptual unit is shorter. Secondly, older adults integrate information during a longer time interval than younger ones. Thirdly, the length of an integration period is related to a subjects' level of cognitive ability. These results suggest that the length of an integration period is not a constant, stable feature, but varies across the life span depending on the mental content of the information presented and individual factors.

Individual differences in the functional asymmetry of the human brain.

Standard models of hemispheric asymmetry assume the dychotomous division of functional competence between the two hemispheres. Individual subjects, however, often do not fit such prototypical patterns and show great variation with respect to the functional differentiation of their hemispheres. The present paper reviews the results of some of our investigations on the effect of various subject related factors on brain lateralization. Among these individual experience, gender and handedness seem to be of most significance.