Lorenzo Sani

Neural correlates of spatial working memory in humans: A functional magnetic resonance imaging study comparing visual and tactile processes

Recent studies of neural correlates of working memory components have identified both low-level perceptual processes and higher-order supramodal mechanisms through which sensory information can be integrated and manipulated. In addition to the primary sensory cortices, working memory relies on a widely distributed neural system of higher-order association areas that includes posterior parietal and occipital areas, and on prefrontal cortex for maintaining and manipulating information. The present study was designed to determine brain patterns of neural response to the same spatial working memory task presented either visually or in a tactile format, and to evaluate the relationship between spatial processing in the visual and tactile sensory modalities. Brain activity during visual and tactile spatial working memory tasks was measured in six young right-handed healthy male volunteers by using functional magnetic resonance imaging. Results indicated that similar fronto-parietal networks were recruited during spatial information processing across the two sensory modalities-specifically the posterior parietal cortex, the dorsolateral prefrontal cortex and the anterior cingulate cortex. These findings provide a neurobiological support to behavioral observations by indicating that common cerebral regions subserve generation of higher order mental representations involved in working memory independently from a specific sensory modality.

Do We Really Need Vision? How Blind People “See” the Actions of Others

Observing and learning actions and behaviors from others, a mechanism crucial for survival and social interaction, engages the mirror neuron system. To determine whether vision is a necessary prerequisite for the human mirror system to develop and function, we used functional magnetic resonance imaging to compare brain activity in congenitally blind individuals during the auditory presentation of hand-executed actions or environmental sounds, and the motor pantomime of manipulation tasks, with that in sighted volunteers, who additionally performed a visual action recognition task. Congenitally blind individuals activated a premotor–temporoparietal cortical network in response to aurally presented actions that overlapped both with mirror system areas found in sighted subjects in response to visually and aurally presented stimuli, and with the brain response elicited by motor pantomime of the same actions. Furthermore, the mirror system cortex showed a significantly greater response to motor familiar than to unfamiliar action sounds in both sighted and blind individuals. Thus, the mirror system in humans can develop in the absence of sight. The results in blind individuals demonstrate that the sound of an action engages the mirror system for action schemas that have not been learned through the visual modality and that this activity is not mediated by visual imagery. These findings indicate that the mirror system is based on supramodal sensory representations of actions and, furthermore, that these abstract representations allow individuals with no visual experience to interact effectively with others.

How skill expertise shapes the brain functional architecture: an fMRI study of visuo-spatial and motor processing in professional racing-car and naive drivers.

The present study was designed to investigate the brain functional architecture that subserves visuo-spatial and motor processing in highly skilled individuals. By using functional magnetic resonance imaging (fMRI), we measured brain activity while eleven Formula racing-car drivers and eleven ‘naïve’ volunteers performed a motor reaction and a visuo-spatial task. Tasks were set at a relatively low level of difficulty such to ensure a similar performance in the two groups and thus avoid any potential confounding effects on brain activity due to discrepancies in task execution. The brain functional organization was analyzed in terms of regional brain response, inter-regional interactions and blood oxygen level dependent (BOLD) signal variability. While performance levels were equal in the two groups, as compared to naïve drivers, professional drivers showed a smaller volume recruitment of task-related regions, stronger connections among task-related areas, and an increased information integration as reflected by a higher signal temporal variability. In conclusion, our results demonstrate that, as compared to naïve subjects, the brain functional architecture sustaining visuo-motor processing in professional racing-car drivers, trained to perform at the highest levels under extremely demanding conditions, undergoes both ‘quantitative’ and ‘qualitative’ modifications that are evident even when the brain is engaged in relatively simple, non-demanding tasks. These results provide novel evidence in favor of an increased ‘neural efficiency’ in the brain of highly skilled individuals.

Effects of visual experience on the human MT+ functional connectivity networks: an fMRI study of motion perception in sighted and congenitally blind individuals

Human middle temporal complex (hMT+) responds also to the perception of non-visual motion in both sighted and early blind individuals, indicating a supramodal organization. Visual experience, however, leads to a segregation of hMT+ into a more anterior subregion, involved in the supramodal representation of motion, and a posterior subregion that processes visual motion only. In contrast, in congenitally blind subjects tactile motion activates the full extent of hMT+. Here, we used fMRI to investigate brain areas functionally connected with the two hMT+ subregions (seeds) during visual and tactile motion in sighted and blind individuals. A common functional connectivity network for motion processing, including bilateral ventral and dorsal extrastriate, inferior frontal, middle and inferior temporal areas, correlated with the two hMT+ seeds both in sighted and blind individuals during either visual or tactile motion, independently from the sensory modality through which the information was acquired. Moreover, ventral premotor, somatosensory, and posterior parietal areas correlated only with the anterior but not with the posterior portion of hMT+ in sighted subjects, and with both hMT+ seeds in blind subjects. Furthermore, a correlation between middle temporal and occipital areas with primary somatosensory seeds was demonstrated across conditions in both sighted and blind individuals, suggesting a cortico-cortical pathway that conveys non-visual information from somatosensory cortex, through posterior parietal regions, to ventral extrastriate cortex. These findings expand our knowledge about the development of the functional organization within hMT+ by showing that distinct patterns of brain functional correlations originate from the anterior and posterior hMT+ subregions as a result of visual experience.

How the brain heals emotional wounds: the functional neuroanatomy of forgiveness

In life, everyone goes through hurtful events caused by significant others: a deceiving friend, a betraying partner, or an unjustly blaming parent. In response to painful emotions, individuals may react with anger, hostility, and the desire for revenge. As an alternative, they may decide to forgive the wrongdoer and relinquish resentment. In the present study, we examined the brain correlates of forgiveness using functional Magnetic Resonance Imaging (fMRI). Healthy participants were induced to imagine social scenarios that described emotionally hurtful events followed by the indication to either forgive the imagined offenders, or harbor a grudge toward them. Subjects rated their imaginative skills, levels of anger, frustration, and/or relief when imagining negative events as well as following forgiveness. Forgiveness was associated with positive emotional states as compared to unforgiveness. Granting forgiveness was associated with activations in a brain network involved in theory of mind, empathy, and the regulation of affect through cognition, which comprised the precuneus, right inferior parietal regions, and the dorsolateral prefrontal cortex. Our results uncovered the neuronal basis of reappraisal-driven forgiveness, and extend extant data on emotional regulation to the resolution of anger and resentment following negative interpersonal events.

It's not all in your car: functional and structural correlates of exceptional driving skills in professional racers

Driving is a complex behavior that requires the integration of multiple cognitive functions. While many studies have investigated brain activity related to driving simulation under distinct conditions, little is known about the brain morphological and functional architecture in professional competitive driving, which requires exceptional motor and navigational skills. Here, 11 professional racing-car drivers and 11 “naïve” volunteers underwent both structural and functional brain magnetic resonance imaging (MRI) scans. Subjects were presented with short movies depicting a Formula One car racing in four different official circuits. Brain activity was assessed in terms of regional response, using an Inter-Subject Correlation (ISC) approach, and regional interactions by mean of functional connectivity. In addition, voxel-based morphometry (VBM) was used to identify specific structural differences between the two groups and potential interactions with functional differences detected by the ISC analysis. Relative to non-experienced drivers, professional drivers showed a more consistent recruitment of motor control and spatial navigation devoted areas, including premotor/motor cortex, striatum, anterior, and posterior cingulate cortex and retrosplenial cortex, precuneus, middle temporal cortex, and parahippocampus. Moreover, some of these brain regions, including the retrosplenial cortex, also had an increased gray matter density in professional car drivers. Furthermore, the retrosplenial cortex, which has been previously associated with the storage of observer-independent spatial maps, revealed a specific correlation with the individual drivers success in official competitions. These findings indicate that the brain functional and structural organization in highly trained racing-car drivers differs from that of subjects with an ordinary driving experience, suggesting that specific anatomo-functional changes may subtend the attainment of exceptional driving performance.

Functional inhibition of the human middle temporal cortex affects non-visual motion perception: a repetitive transcranial magnetic stimulation study during tactile speed discrimination

The visual motion-responsive middle temporal complex (hMT+) is activated during tactile and aural motion discrimination in both sighted and congenitally blind individuals, suggesting a supramodal organization of this area. Specifically, non-visual motion processing has been found to activate the more anterior portion of the hMT+. In the present study, repetitive transcranial magnetic stimulation (rTMS) was used to determine whether this more anterior portion of hMT+ truly plays a functional role in tactile motion processing. Sixteen blindfolded, young, healthy volunteers were asked to detect changes in the rotation velocity of a random Braille-like dot pattern by using the index or middle finger of their right hand. rTMS was applied for 600 ms (10 Hz, 110% motor threshold), 200 ms after the stimulus onset with a figure-of-eight coil over either the anterior portion of hMT+ or a midline parieto-occipital site (as a control). Accuracy and reaction times were significantly impaired only when TMS was applied on hMT+, but not on the control area. These results indicate that the recruitment of hMT+ is necessary for tactile motion processing, and thus corroborate the hypothesis of a ‘supramodal’ functional organization for this sensory motion processing area.

Functional Exploration Studies of Supramodal Organization in the Human Extrastriate Cortex

In the context of the Touch-Hapsys project, our group investigated whether the two main components of the cortical visual systems, i.e., the ventral ”what” pathway and the dorsal ”where” pathways, are devoted merely to the processing of visual information or rather they are organized in a supramodal fashion, that is, they are able to process information independently from the sensory modality through which such an information reaches the brain. Sighted and congenitally blind individuals underwent fMRI scan examinations while performing distinct visual and/or tactile experimental tasks involving object recognition, movement detection and spatial localization. These functional studies revealed that both sighted subjects and individuals with no previous visual experience rely on these supramodal brain areas of the ventral and dorsal extrastriate cortex to acquire normal knowledge about objects and interact effectively with the surrounding world.

Combination of event-related potentials and functional magnetic resonance imaging during single-letter reading

This work proposes a mathematical approach for combining event-related potentials (ERPs) and functional magnetic resonance images (fMRI). Data were separately recorded during the same event-related experimental design, consisting of visually presented single letters and non-alphabetic symbols, that had to be either simply observed (passive condition) or read aloud (active condition). This protocol was useful for exploring the neural correlates of reading processes. Healthy adults participated in the experiment. Averaged ERPs were decomposed by independent component analysis; low resolution electromagnetic tomography (LORETA) was applied to estimate the current density distribution maps of each independent component. fMRI images time series were analyzed by multiple linear regression. ERP-fMRI correspondence was quantified by computing the Euclidean distance between LORETA local maxima and clusters of significantly activated fMRI voxels. During reading aloud of letters, that is clearly the task most similar to natural reading conditions, significant electrical and hemodynamic response was observed in the left medial frontal gyrus (BA 6) and left middle temporal gyrus (BA 22/39) just before articulation and in the bilateral middle superior temporal gyrus (BA 22/37) during and after verbal-motor production. These results indicate that the middle-superior temporal gyrus plays a crucial and multifunctional role in grapheme-phoneme matching