Pietro Avanzini

The Dynamics of Sensorimotor Cortical Oscillations during the Observation of Hand Movements: An EEG Study

Background The observation of action done by others determines a desynchronization of the rhythms recorded from cortical central regions. Here, we examined whether the observation of different types of hand movements (target directed, non-target directed, cyclic and non-cyclic) elicits different EEG cortical temporal patterns. Methodology Video-clips of four types of hand movements were shown to right-handed healthy participants. Two were target directed (grasping and pointing) motor acts; two were non-target directed (supinating and clenching) movements. Grasping and supinating were performed once, while pointing and clenching twice (cyclic movements). High-density EEG was recorded and analyzed by means of wavelet transform, subdividing the time course in time bins of 200 ms. The observation of all presented movements produced a desynchronization of alpha and beta rhythms in central and parietal regions. The rhythms desynchronized as soon as the hand movement started, the nadir being reached around 700 ms after movement onset. At the end of the movement, a large power rebound occurred for all bands. Target and non-target directed movements produced an alpha band desynchronization in the central electrodes at the same time, but with a stronger desynchronization and a prolonged rebound for target directed motor acts. Most interestingly, there was a clear correlation between the velocity profile of the observed movements and beta band modulation. Significance Our data show that the observation of motor acts determines a modulation of cortical rhythm analogous to that occurring during motor act execution. In particular, the cortical motor system closely follows the velocity of the observed movements. This finding provides strong evidence for the presence in humans of a mechanism (mirror mechanism) mapping action observation on action execution motor programs.

Melanopsin retinal ganglion cell loss in Alzheimer disease

Melanopsin retinal ganglion cells (mRGCs) are photoreceptors driving circadian photoentrainment, and circadian dysfunction characterizes Alzheimer disease (AD). We investigated mRGCs in AD, hypothesizing that they contribute to circadian dysfunction.

The visual system in eyelid myoclonia with absences.

To investigate the functional and structural brain correlates of eyelid myoclonus and absence seizures triggered by eye closure (eye closure sensitivity [ECS]).

Four-dimensional maps of the human somatosensory system

Significance Here, we show how anatomical and functional data recorded from patients undergoing stereo-EEG can be combined to generate highly resolved four-dimensional maps of human cortical processing. We used this technique, which provides spatial maps of the active cortical nodes at a millisecond scale, to depict the somatosensory processing following electrical stimulation of the median nerve in nearly 100 patients. The results showed that human somatosensory system encompasses a widespread cortical network including a phasic component, centered on primary somatosensory cortex and neighboring motor, premotor, and inferior parietal regions, as well as a tonic component, centered on the opercular and insular areas, lasting more than 200 ms. A fine-grained description of the spatiotemporal dynamics of human brain activity is a major goal of neuroscientific research. Limitations in spatial and temporal resolution of available noninvasive recording and imaging techniques have hindered so far the acquisition of precise, comprehensive four-dimensional maps of human neural activity. The present study combines anatomical and functional data from intracerebral recordings of nearly 100 patients, to generate highly resolved four-dimensional maps of human cortical processing of nonpainful somatosensory stimuli. These maps indicate that the human somatosensory system devoted to the hand encompasses a widespread network covering more than 10% of the cortical surface of both hemispheres. This network includes phasic components, centered on primary somatosensory cortex and neighboring motor, premotor, and inferior parietal regions, and tonic components, centered on opercular and insular areas, and involving human parietal rostroventral area and ventral medial-superior-temporal area. The technique described opens new avenues for investigating the neural basis of all levels of cortical processing in humans.

Spatiotemporal dynamics during processing of abstract and concrete verbs: an ERP study.

Different accounts have been proposed to explain the nature of concept representations. Embodied accounts claim a key involvement of sensory-motor systems during semantic processing while more traditional accounts posit that concepts are abstract mental entities independent of perceptual and motor brain systems. While the involvement of sensory-motor areas in concrete language processing is supported by a large number of studies, this involvement is far from being established when considering abstract language. The present study addressed abstract and concrete verb processing, by investigating the spatiotemporal dynamics of evoked responses by means of high density EEG while participants performed a semantic decision task. In addition, RTs to the same set of stimuli were collected. In both early and late time intervals, ERP scalp topography significantly differed according to word categories. Concrete verbs showed involvement of parieto-frontal networks for action, according to the implied body effector. In contrast, abstract verbs recruited mostly frontal regions outside the motor system, suggesting a non-motor semantic processing for this category. In addition, differently from what has been reported during action observation, the parietal recruitment related to concrete verbs presentation followed the frontal one. The present findings suggest that action word semantic is grounded in sensory-motor systems, provided a bodily effector is specified, while abstract concepts׳ representation cannot be easily explained by a motor embodiment.

Human cortical activity evoked by gaze shift observation: An intracranial EEG study

While is widely accepted that the posterior temporal region is activated during the observation of faces showing gaze shifts, it is still unclear whether its activity is stronger while observing direct or averted gaze. Furthermore, despite its assessed role in social cognition, studies describing an enhanced activity of the posterior temporal region during the observation of gaze aversion interpreted this activity in terms of spatial attention toward the target direction. This spatial attention interpretation is not easily reconcilable with the role of the posterior temporal region in social cognition, and an overarching view of its global cognitive function would be much more preferable. Here we used intracranial EEG to assess the precise spatial localization of the gaze shifts coding in the posterior temporal region, to assess its selectivity for direct versus averted gaze and to distinguish between a spatial‐attentional and a social interpretations of gaze aversion. We found stronger activation during gaze aversion than direct gaze and lateral side switch observation, the latter indicating that the crucial aspect of gaze aversion is the prior presence of the eye contact and its interruption, and not the gaze direction. These results suggest a more social‐oriented interpretation based on the view that among humans, gaze aversion signals a negative relational evaluation in social interaction. Hum Brain Mapp 35:1515–1528, 2014.

Causality within the Epileptic Network: An EEG-fMRI Study Validated by Intracranial EEG.

Accurate localization of the Seizure Onset Zone (SOZ) is crucial in patients with drug-resistance focal epilepsy. EEG with fMRI recording (EEG-fMRI) has been proposed as a complementary non-invasive tool, which can give useful additional information in the pre-surgical work-up. However, fMRI maps related to interictal epileptiform activities (IED) often show multiple regions of signal change, or “networks,” rather than highly focal ones. Effective connectivity approaches like Dynamic Causal Modeling (DCM) applied to fMRI data potentially offers a framework to address which brain regions drives the generation of seizures and IED within an epileptic network. Here, we present a first attempt to validate DCM on EEG-fMRI data in one patient affected by frontal lobe epilepsy. Pre-surgical EEG-fMRI demonstrated two distinct clusters of blood oxygenation level dependent (BOLD) signal increases linked to IED, one located in the left frontal pole and the other in the ipsilateral dorso-lateral frontal cortex. DCM of the IED-related BOLD signal favored a model corresponding to the left dorso-lateral frontal cortex as driver of changes in the fronto-polar region. The validity of DCM was supported by: (a) the results of two different non-invasive analysis obtained on the same dataset: EEG source imaging (ESI), and “psycho-physiological interaction” analysis; (b) the failure of a first surgical intervention limited to the fronto-polar region; (c) the results of the intracranial EEG monitoring performed after the first surgical intervention confirming a SOZ located over the dorso-lateral frontal cortex. These results add evidence that EEG-fMRI together with advanced methods of BOLD signal analysis is a promising tool that can give relevant information within the epilepsy surgery diagnostic work-up.

Sequencing biological and physical events affects specific frequency bands within the human premotor cortex: an intracerebral EEG study.

Evidence that the human premotor cortex (PMC) is activated by cognitive functions involving the motor domain is classically explained as the reactivation of a motor program decoupled from its executive functions, and exploited for different purposes by means of a motor simulation. In contrast, the evidence that PMC contributes to the sequencing of non-biological events cannot be explained by the simulationist theory. Here we investigated how motor simulation and event sequencing coexist within the PMC and how these mechanisms interact when both functions are executed. We asked patients with depth electrodes implanted in the PMC to passively observe a randomized arrangement of images depicting biological actions and physical events and, in a second block, to sequence them in the correct order. This task allowed us to disambiguate between the simple observation of actions, their sequencing (recruiting different motor simulation processes), as well as the sequencing of non-biological events (recruiting a sequencer mechanism non dependant on motor simulation). We analysed the response of the gamma, alpha and beta frequency bands to evaluate the contribution of each brain rhythm to the observation and sequencing of both biological and non-biological stimuli. We found that motor simulation (biological>physical) and event sequencing (sequencing>observation) differently affect the three investigated frequency bands: motor simulation was reflected on the gamma and, partially, in the beta, but not in the alpha band. In contrast, event sequencing was also reflected on the alpha band.

Ictal involvement of the nigrostriatal system in subtle seizures of ring chromosome 20 epilepsy

Studies in animal models and patients with epilepsy have suggested that basal ganglia circuits may control epileptic seizures and that striatal dopaminergic transmission may play a role in seizure modulation and interruption. Chromosome 20 [r(20)] syndrome is a well‐defined chromosomal disorder characterized by epilepsy, mild‐to‐moderate mental retardation, and lack of recognizable dysmorphic features. Epilepsy is often the most important clinical manifestation of the syndrome, with prolonged episodes of nonconvulsive status epilepticus suggesting dysfunction in the seizure control system. We present the ictal blood oxygen level–dependent (BOLD) changes in brief seizures recorded by means of electroencephalography–functional magnetic resonance imaging (EEG‐fMRI) coregistration in a patient with [r(20)] syndrome. We observed ictal BOLD increments in a cortical‐subcortical network involving substantia nigrastriatum and frontal cortex. At present, this is the first functional neuroimaging evidence of the involvement of the nigrostriatal system during ictal EEG discharges in [r(20)] syndrome supporting a role of the basal ganglia circuits in human epileptic seizures.

Cognitive abilities in siblings of children with autism spectrum disorders

Abstract The aim of the present study was to assess the cognitive profiles of children with autistic spectrum disorder and of their healthy siblings (Siblings). With the term cognitive profile, we indicate the relationship extant among the values of verbal and performance subtests of the Wechsler Intelligence Scale. The conducted statistical analyses indicated that, although siblings showed a normal intelligent quotient and did not differ in this aspect from typically developing group, their cognitive profile was amazingly similar to that of their relatives affected by autism. A k-means clustering analysis on the values of single subtests further confirmed this result, showing a clear separation between typically developing children on the one side, and autistics and their siblings on the other. We suggest that the common cognitive profile observed in autistic children and their siblings could represent a marker of liability to autism and, thus, a possible intermediate phenotype of this syndrome.