The Role of the Primary Sensory Cortices in Early Language Processing.

The results of this magnetoencephalography study challenge two long-standing assumptions regarding the brain mechanisms of language processing: First, that linguistic processing proper follows sensory feature processing effected by bilateral activation of the primary sensory cortices that lasts about 100 msec from stimulus onset. Second, that subsequent linguistic processing is effected by left hemisphere networks outside the primary sensory areas, including Broca's and Wernicke's association cortices. Here we present evidence that linguistic analysis begins almost synchronously with sensory, prelinguistic verbal input analysis and that the primary cortices are also engaged in these linguistic analyses and become, consequently, part of the left hemisphere language network during language tasks. These findings call for extensive revision of our conception of linguistic processing in the brain

Muscular effort increases hand-blink reflex magnitude.

Defensive motor responses elicited by sudden environmental stimuli are finely modulated by their behavioural relevance to maximise the organism's survival. One such response, the blink reflex evoked by intense electrical stimulation of the median nerve (Hand-Blink Reflex; HBR), has been extensively used to derive fine-grained maps of defensive peripersonal space. However, as other subcortical reflexes, the HBR might also be modulated by lower-level factors that do not bear direct relevance to the defensive value of blinking, thus posing methodological and interpretive problems. Here, we tested whether HBR magnitude is affected by the muscular effort present when holding the hand in certain postures. We found that HBR magnitude increases with muscular effort, an effect most likely mediated by the increased corticospinal drive. However, we found strong evidence that this effect is substantially smaller than the well-known effect of eye-hand proximity on HBR magnitude. Nonetheless, care should be taken in future experiments to avoid erroneous interpretations of the effects of muscular effort as indicators of behaviour relevance

Saliency Detection as a Reactive Process: Unexpected Sensory Events Evoke Corticomuscular Coupling.

Survival in a fast-changing environment requires animals not only to detect unexpected sensory events, but also to react. In humans, these salient sensory events generate large electrocortical responses, which have been traditionally interpreted within the sensory domain. Here we describe a basic physiological mechanism coupling saliency-related cortical responses with motor output. In four experiments conducted on 70 healthy participants, we show that salient substartle sensory stimuli modulate isometric force exertion by human participants, and that this modulation is tightly coupled with electrocortical activity elicited by the same stimuli. We obtained four main results. First, the force modulation follows a complex triphasic pattern consisting of alternating decreases and increases of force, time-locked to stimulus onset. Second, this modulation occurs regardless of the sensory modality of the eliciting stimulus. Third, the magnitude of the force modulation is predicted by the amplitude of the electrocortical activity elicited by the same stimuli. Fourth, both neural and motor effects are not reflexive but depend on contextual factors. Together, these results indicate that sudden environmental stimuli have an immediate effect on motor processing, through a tight corticomuscular coupling. These observations suggest that saliency detection is not merely perceptive but reactive, preparing the animal for subsequent appropriate actions.SIGNIFICANCE STATEMENT Salient events occurring in the environment, regardless of their modalities, elicit large electrical brain responses, dominated by a widespread "vertex" negative-positive potential. This response is the largest synchronization of neural activity that can be recorded from a healthy human being. Current interpretations assume that this vertex potential reflects sensory processes. Contrary to this general assumption, we show that the vertex potential is strongly coupled with a modulation of muscular activity that follows the same pattern. Both the vertex potential and its motor effects are not reflexive but strongly depend on contextual factors. These results reconceptualize the significance of these evoked electrocortical responses, suggesting that saliency detection is not merely perceptive but reactive, preparing the animal for subsequent appropriate actions

Ultralow-frequency neural entrainment to pain

Nervous systems exploit regularities in the sensory environment to predict sensory input, adjust behavior, and thereby maximize fitness. Entrainment of neural oscillations allows retaining temporal regularities of sensory information, a prerequisite for prediction. Entrainment has been extensively described at the frequencies of periodic inputs most commonly present in visual and auditory landscapes (e.g., >0.5 Hz). An open question is whether neural entrainment also occurs for regularities at much longer timescales. Here, we exploited the fact that the temporal dynamics of thermal stimuli in natural environment can unfold very slowly. We show that ultralow-frequency neural oscillations preserved a long-lasting trace of sensory information through neural entrainment to periodic thermo-nociceptive input as low as 0.1 Hz. Importantly, revealing the functional significance of this phenomenon, both power and phase of the entrainment predicted individual pain sensitivity. In contrast, periodic auditory input at the same ultralow frequency did not entrain ultralow-frequency oscillations. These results demonstrate that a functionally significant neural entrainment can occur at temporal scales far longer than those commonly explored. The non-supramodal nature of our results suggests that ultralow-frequency entrainment might be tuned to the temporal scale of the statistical regularities characteristic of different sensory modalities

Inhibitory control ability moderates the relationship between internet addiction and inattention in ADHD in a community sample

Internet addiction (IA) has been related to psychiatric problems such as ADHD. However, it is not known exactly how this relationship operates, although most research shows that both people with ADHD and IA have inhibitory control (IC) deficit. This study aimed to investigate whether IC mediates or moderates the relationship. 76 non-clinically diagnosed participants were recruited. They performed the Stroop task and completed the Young's Internet Addiction Test, Adult ADHD Self-Report Scale Symptom Checklist and a Demographic Information Form. Consistent with previous research, the results show that while total ADHD/inattention was correlated with IA, hyperactivity/impulsivity was not. In contrast with some previous research, Stroop task performance (measured via reaction times and pupil dilation) did not differ between low and high IA groups, nor low and high inattention groups. Despite neither inattention nor IA between associated with IC impairments, the relationship between inattention and IA was shown to be moderated by Stroop task performance in that the relationship was present mainly in those who experience high and moderate IC deficits. This finding could have implications for both ADHD and IA at higher levels of severity and could help guide prevention and treatment options in those most vulnerable to IA

Trait-level non-clinical ADHD symptoms in a community sample and their association with technology addictions

An increasing number of studies have reported the existence of ADHD symptoms to be risk factors for technology addictions among young adults. In contrast to previous studies, the aim of the present study was to examine different dimensions of technology addiction in a community sample of adults and to examine their association with the individual trait-level ADHD symptoms of inattention and hyperactivity-impulsivity. A community sample of one hundred and fifty adults were recruited to participate in this study via convenience sampling. Participants completed the Adult ADHD Self-Report Scale Symptom Checklist, the Bergen Social Media Addiction Scale, the Smartphone Addiction Scale, Young’s Internet Addiction Test, the Compulsive Online Shopping Scale, and a Demographic Information Form. Composite ADHD score, inattention and hyperactivity/impulsivity were positively associated with technology addictions (internet, social media, smartphone, and online shopping addiction). Hierarchical regression analysis revealed inattention and hyperactivity-impulsivity were predictors of social media addiction and smartphone addiction, whereas they were not for online shopping addiction. Furthermore, inattention was the only predictor of internet addiction. People with non-clinical, trait-level ADHD, especially those showing a preponderance of inattention symptoms appear to be more vulnerable to developing some forms of technology addiction

The effect of salient stimuli on neural oscillations, isometric force, and their coupling.

Survival in a suddenly-changing environment requires animals not only to detect salient stimuli, but also to promptly respond to them by initiating or revising ongoing motor processes. We recently discovered that the large vertex brain potentials elicited by sudden supramodal stimuli are strongly coupled with a multiphasic modulation of isometric force, a phenomenon that we named cortico-muscular resonance (CMR). Here, we extend our investigation of the CMR to the time-frequency domain. We show that (i) both somatosensory and auditory stimuli evoke a number of phase-locked and non-phase-locked modulations of EEG spectral power. Remarkably, (ii) some of these phase-locked and non-phase-locked modulations are also present in the Force spectral power. Finally, (iii) EEG and Force time-frequency responses are correlated in two distinct regions of the power spectrum. An early, low-frequency region (∼4 Hz) reflects the previously-described coupling between the phase-locked EEG vertex potential and force modulations. A late, higher-frequency region (beta-band, ∼20 Hz) reflects a second coupling between the non-phase-locked increase of power observed in both EEG and Force. In both time-frequency regions, coupling was maximal over the sensorimotor cortex contralateral to the hand exerting the force, suggesting an effect of the stimuli on the tonic corticospinal drive. Thus, stimulus-induced CMR occurs across at least two different types of cortical activities, whose functional significance in relation to the motor system should be investigated further. We propose that these different types of corticomuscular coupling are important to alter motor behaviour in response to salient environmental events

Υπολογισμός του διαθλαστικού σφάλματος με χρήση αναλυτών μετώπου κύματος

Visual performance is defined by how well a visual task of interest can be performed by a given individual. Therefore, the purpose of a conventional, ophthalmic refraction of the eye is to determine that combination of spherical and cylindrical lenses which optimizes visual acuity. This study is concerned with the problem of objectively determining the best correction of an eye from measurements of wavefront aberrations. The wavefront aberration is a function that characterizes the image-forming properties of any optical system (Born & Wolf, 1985). It is defined as the optical deviation of the wavefront along a certain ray from the perfect spherical wavefront. A Hartmann-Shack wavefront sensor was used to measure the monochromatic wave aberrations of the subjects. We determined the accuracy of two groups of objective methods for predicting the results of conventional, sphero-cylindrical refraction from wavefront aberrations in a population of 81 eyes. All metrics used in this study are mathematical functions that have as input the normalized Zernike expansion coefficients and as output a single value. The second group of metrics, as opposed to the first on, included the Stiles-Crawford apodization filter in the calculations. We investigate whether the predictions from these methods were improved. Accuracy for predicting defocus varied from 0.28D to 0.4D across methods. Objective determined defocus was significantly correlated with the subjective sphere. The metric mVSMTF, which included the Contrast Sensitivity Function in its calculations, was one of the most precise methods and exhibited the optimal performance. It is important to mention that we introduced a new metric, called weightedMTF, which proved good predictor of optical quality. This metric was inspired by mVSMTF but it differs significantly as it includes the impact of higher spatial frequencies. Inclusion of Stiles-Crawford improved the predictions from all metrics. All metrics discussed were calculated both for monochromatic and polychromatic light. The link between visual performance and optical quality of the eye enjoys a renewed interest. However, visual perception is highly subjective and involves many aspects of image quality. Therefore, it may be unrealistic to suppose that one single metric will capture all aspects of image quality. Instead, multivariate metrics may be needed to adequately predict the visual effects caused by optical defects of the eye and to prescribe the ideal correction.Η γνώση των οφθαλμικών εκτροπών είναι σημαντική αν θέλουμε να απαντήσουμε σε θεμελιώδη ερωτήματα της επιστήμης της όρασης και σε εφαρμοσμένα ερωτήματα στην κλινική άσκηση της οπτομετρίας και της οφθαλμολογίας. Με την παρούσα εργασία γίνεται προσπάθεια να προσδιοριστεί η κατάλληλη αντικειμενική μέθοδος προσδιορισμού της υποκειμενικής διάθλασης μέσω της μέτρησης των οφθαλμικών εκτροπών και να διευκολυνθεί η διερεύνηση κάποιων από τα ερωτήματα που απασχολούν τους ερευνητές της όρασης. Η εκτροπή μετώπου κύματος είναι μία συνάρτηση που χαρακτηρίζει τις απεικονιστικές ιδιότητες κάθε οπτικού συστήματος (Born & Wolf, 1985). Ορίζεται ως η απόκλιση ενός μετώπου κύματος με εκτροπές από το ιδανικό σφαιρικό μέτωπο κύματος. Οι μονοχρωματικές εκτροπές μετρήθηκαν με ένα εκτροπόμετρο Hartmann-Shack σε ένα πληθυσμό 81 οφθαλμών. Ορίστηκαν δύο ομάδες μετρικών, ικανών να προβλέπουν τη συμβατική σφαιροκυλινδρική διόρθωση. Όλες οι μετρικές ήταν μαθηματικές συναρτήσεις που είχαν ως είσοδο τα πολυώνυμα Zernike και ως έξοδο μία μόνο τιμή. Οι δύο ομάδες διέφεραν μεταξύ τους μόνο στο ότι η δεύτερη συμπεριλάμβανε στους υπολογισμούς την Stiles-Crawford apodization συνάρτηση. Η ακρίβεια πρόβλεψης του σφαιρικού διαθλαστικού σφάλματος από τις μετρικές ήταν 0.28D έως 0.4D. Το αντικειμενικά υπολογισμένο σφαιρικό διαθλαστικό σφάλμα εμφάνισε εξαιρετική συσχέτιση με το υποκειμενικό σφαίρωμα. Η μετρική (mVSMTF) που συμπεριλάμβανε στον υπολογισμό της τη συνάρτηση του Contrast Sensitivity Function ήταν μία από τις πιο ακριβείς και επέδειξε τη βέλτιστη συμπεριφορά. Ορίσαμε μία νέα μετρική, την weightedMTF, η οποία δίνει βαρύτητα σε υψηλότερες χωρικές συχνότητες, αποδείχθηκε πολύ καλή όσο αφορά την πρόβλεψη του υποκειμενικού διαθλαστικού σφάλματος. Η εισαγωγή του Stiles-Crawford βελτίωσε τις προβλέψεις για όλες τις μετρικές. Όλες οι μετρικές εξετάστηκαν για μονοχρωματικές και πολυχρωματικές συνθήκες. Τα αποτελέσματα της μελέτης είναι ικανοποιητικά, ωστόσο είναι αναγκαίο κάποιος να αναγνωρίσει ότι η οπτική αντίληψη δεν είναι μία μηχανική καταγραφή στοιχείων αλλά μάλλον μια σύλληψη σύνθετων οπτικών σχέσεων και είναι ουτοπικό να θεωρηθεί ότι μία μόνο μετρική μπορεί να αιχμαλωτίσει την ποιότητα ενός τέλειου ειδώλου

Νευροφυσιολογική μελέτη εγκεφάλου πιθήκου κατά την εκτέλεση κινήσεων προς στόχους

In the past, we demonstrated that the neural system which supports both the generation of an action and the perception of the same action performed by another subject encompasses widespread areas in a parieto-frontal cortical network. In the present study we examined whether this system that helps match action perception to action generation extends beyond these areas to early visual cortices. We applied the quantitative autoradiographic method of [14C]- deoxyglucose, combined with cytoarchitectonic identification of cortical areas, to explore early visual cortical areas throughout the cortex of the occipital operculum, lunate and inferior occipital sulci of twelve adult female monkeys (Macaca mulatta) performing three behavioural tasks: (a) grasping-in-the-light (Gl), (b) grasping-observation (O), and (c) grasping-in-the-dark (Gd). In order to disambiguate the effects of the purposely reaching/grasping action from the effects of (a) the non-goal-directed biological-motion elicited by a purposelessly moving forelimb in front of the monkey, and (b) the visual stimulation induced by mere presentation of the 3D-object, we compared the functional activity in the Gl and O monkeys with that in two arm-motion control (Cm) monkeys. To reveal the effects induced by reaching-to-grasp in the dark, we compared the functional activity in the two Gd monkeys with that in two control-in-the-dark monkeys (Cd). In order to reveal the effects induced by the behavioural tasks, we produced and compared twodimensional reconstructions (2D-maps) of the spatio-intensive pattern of metabolic activity (LCGU values in #mol/100 g/min) throughout the full extent of the visual areas V1, V2, V3, V3A, and V4. During grasping-in-the-light increased metabolic activity was evident in extrastriate areas V3d, V3A and V4 with the two segments of area V3d, the occipito-parietal reflecting peripheral vision and the occipito-temporal reflecting central vision being equally activated. During grasping-observation, area V4 was not activated, marginal activation was displayed in the representation of the central visual field of area V1 and significant activation was displayed in areas V3d and V3A with the occipito-temporal region of area V3d being more activated than the occipito-parietal. During grasping-in-the-dark activation was observed in areas V1, V2, V3A, and V3v. Area V3d was markedly activated in its occipito-parietal segment, contrary to the occipito-temporal which was not activated. According to our previous proposal, the activations induced by grasping-observation in the parietal and motor cortex imply that observation of an action corresponds to simulation of its overt counterpart. Based on our present findings, we suggest that the activation of areas V3d and V3A for action-observation and for action-execution in the dark reflects the processing of visual information xv Summary related to the mental simulation of the action. Area V3 may relay to the motor system, via the parieto-frontal visuo-motor stream, visuospatial information required for the reaching component of the action and 3D-object-related information useful for the grasping constituent. Therefore, as the somatotopic activation of the primary somatosensory cortex during action-observation in our previous study supported an introspective kinesthetic feeling of the movement by the observer in a first person perspective, the activation of the early visual cortices during action-generation in the dark in the present study supports an internalized visual representation of the spatial-location and the 3D-form of the invisible object to be reached and grasped, i.e. visual imagery during action control