Parietal/premotor lesions effects on visuomotor cognition in neuro-oncology patients: A multimodal study

Background: Assessing prior to surgery the functionality of brain areas exposed near the tumor requires a multimodal approach that combines the use of neuropsychological testing and fMRI tasks. Paradigms based on motor imagery, which corresponds to the ability to mentally evoke a movement, in the absence of actual action execution, can be used to test sensorimotor areas and the functionality of mental motor representations. Methods: The most commonly used paradigm is the Limb Laterality Recognition Task (LLRT), requiring judgments about whether a limb belongs to the left or right side of the body. The group studied included 38 patients with high-grade (N = 21), low-grade (N = 11) gliomas and meningiomas (N = 6) in areas anterior (N = 21) and posterior (N = 17) to the central sulcus. Patients before surgery underwent neuropsychological assessment and fMRI. They performed the LLRT as an fMRI task. Accuracy, and neuroimaging data were collected and combined in a multimodal study. Structural MRI data analyses were performed by subtracting the overlap of volumes of interest (VOIs) plotted on lesions from the impaired patient group vs the overlap of VOIs from the spared group. The fMRI analyses were performed comparing the impaired patients and spared group. Results: In general, patients were within normal limits on many neuropsychological screening tests. Compared with the control group, 17/38 patients had significantly different performance. The subtraction between the VOIs overlay of the impaired patients' group vs. the VOIs overlay of the spared group revealed that the areas maximally involved by lesions in the impaired patients' group were the right postcentral gyrus, right inferior parietal lobe, right supramarginal gyrus, right precentral gyrus, paracentral lobule, left postcentral gyrus, right superior parietal lobe, left inferior parietal lobe, and left superior and middle frontal gyrus. Analysis of the fMRI data showed which of these areas contributes to a correct LLRT performance. The task (vs. rest) in the group comparison (spared vs. impaired patients) activated a cluster in the left inferior parietal lobe. Conclusion: Underlying the altered performance at LLRT in patients with lesions to the parietal and premotor areas of the right and left hemispheres is a difference in activation of the left inferior parietal lobe. This region is involved in visuomotor processes and those related to motor attention, movement selection, and motor planning

Identifying environmental sounds: a multimodal mapping study

Our environment is full of auditory events such as warnings or hazards, and their correct recognition is essential. We explored environmental sound (ES) recognition in a series of studies. In study 1 we performed an Activation Likelihood Estimation (ALE) meta-Analysis of neuroimaging studies addressing ES processing to delineate the network of areas consistently involved in ES processing. In study 2 we reported a series of 7 neurosurgical patients with lesions involving the areas found consistently activated by the ALE meta-analysis and tested their ES recognition abilities. In study 3 we investigated how the areas involved in ES might be functionally deregulated as an effect of lesion by performing an fMRI study on patients (in comparison to healthy controls). Areas found to be consistently activated in the ALE quantitative meta-analysis involved the STG/MTG, insula/rolandic operculum, parahippocampal gyrus and inferior frontal gyrus complex bilaterally. Some of these areas were found modulated by design choices, e.g., type of task, type of control condition, type of stimuli. Patients with lesions in these areas of the left and the right hemisphere had an impaired ES recognition. The most frequently lesioned area corresponded to the hippocampus/insula/superior temporal gyrus. For the most part, the patients’ responses were unrelated to the target sounds or were semantically related to the target sounds. The other type of responses were: auditorily related, semantically and auditorily related, and I don't Know answers. The fMRI evidenced deregulations of the activation reported in the right IFG and in the STG bilaterally and in the left insula. We showed that some of these clusters of activation truly reflect ES processing, whereas others are related to design choices. Our results allowed a parcelization of the activation found along the MTG/STG are

Attempts at memory control induce dysfunctional brain activation profiles in Generalized Anxiety Disorder: An exploratory fMRI study

Suppression of aversive memories through memory control has historically been proposed as a central psychological defense mechanism. Inability to suppress memories is considered a central psychological trait in several psychiatric disorders, including Generalized Anxiety Disorder (GAD). Yet, few studies have attempted the focused identification of dysfunctional brain activation profiles when patients with Generalized Anxiety Disorders attempt memory control. Using a well-characterized behavioral paradigm we studied brain activation profiles in a group of adult GAD patients and well-matched healthy controls (HC). Participants learned word-association pairs before imaging. During fMRI when presented with one word of the pair, they were instructed to either suppress memory of, or retrieve the paired word. Subsequent behavioral testing indicated both GAD and HC were able to engage in the task, but attempts at memory control (suppression or retrieval) during fMRI revealed vastly different activation profiles. GAD were characterized by substantive hypo-activation signatures during both types of memory control, with effects particularly strong during suppression in brain regions including the dorsal anterior cingulate and the ventral prefrontal cortex. Attempts at memory control in GAD fail to engage brain regions to the same extent HC, providing a putative neuronal signature for a well-established psychological characteristic of the illness

Common and different neural markers in major depression and anxiety disorders: A pilot structural magnetic resonance imaging study.

Although anxiety and depression often co-occur and share some clinical features, it is still unclear if they are neurobiologically distinct or similar processes. In this study, we explored common and specific cortical morphology alterations in depression and anxiety disorders. Magnetic Resonance Imaging data were acquired from 13 Major Depressive Disorder (MDD), 11 Generalized Anxiety Disorder (GAD), 11 Panic Disorder (PD) patients and 21 healthy controls (HC). Regional cortical thickness, surface area (SA), volume and gyrification were measured and compared among groups. We found left orbitofrontal thinning in all patient groups, as well as disease-specific alterations. MDD showed volume deficits in left precentral gyrus compared to all groups, volume and area deficits in right fusiform gyrus compared to GAD and HC. GAD showed lower SA than MDD and PD in right superior parietal cortex, higher gyrification than HC in right frontal gyrus. PD showed higher gyrification in left superior parietal cortex when compared to MDD and higher SA in left postcentral gyrus compared to all groups. Our results suggest that clinical phenotypic similarities between major depression and anxiety disorders might rely on common prefrontal alterations. Frontotemporal and parietal abnormalities may represent unique biological signatures of depression and anxiety

Single-Trial Characterization of BOLD fMRI Responses by Self-Organizing Neural Networks

Functional magnetic resonance imaging (fMRI) plays a dominant role in human brain mapping studies. As of today, no standards exist for processing fMRI data and analysis techniques are often associated to the different stimulation paradigms used to acquire functional data. Being able to estimate the hemodynamic response following a single execution of a task permits to characterize its relationship to different aspects of the stimulus, and of the subject’s performance. This works is aimed to test a strategy for the characterization of single trial-related BOLD fMRI responses based on the self-organizing maps method of Kohonen (SOMs). Analysis have been carried out on synthetic fMRI images modeling activation and on data from a single-event fMRI experiment on one human subject performing a basic motor task. Results were able to define the potentiality range for this data-driven methodology in monitoring the evolution of the BOLD response deriving from a single stimulation

Percept-related activity in the human somatosensory system: functional magnetic resonance imaging studies

In this paper, we review blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) studies addressing the neural correlates of touch, thermosensation, pain and the mechanisms of their cognitive modulation in healthy human subjects. There is evidence that fMRI signal changes can be elicited in the parietal cortex by stimulation of single mechanoceptive afferent fibers at suprathreshold intensities for conscious perception. Positive linear relationships between the amplitude or the spatial extents of BOLD fMRI signal changes, stimulus intensity and the perceived touch or pain intensity have been described in different brain areas. Some recent fMRI studies addressed the role of cortical areas in somatosensory perception by comparing the time course of cortical activity evoked by different kinds of stimuli with the temporal features of touch, heat or pain perception. Moreover, parametric single-trial functional MRI designs have been adopted in order to disentangle subprocesses within the nociceptive system. Available evidence suggest that studies that combine fMRI with psychophysical methods may provide a valuable approach for understanding complex perceptual mechanisms and top-down modulation of the somatosensory system by cognitive factors specifically related to selective attention and to anticipation. The brain networks underlying somatosensory perception are complex and highly distributed. A deeper understanding of perceptual-related brain mechanisms therefore requires new approaches suited to investigate the spatial and temporal dynamics of activation in different brain regions and their functional interaction

An ARX model-based approach to trial by trial identification of fMRI-BOLD responses

Being able to estimate the fMRI-BOLD response following a single task or stimulus is certainly of value, since it allows to characterize its relationship to different aspects either of the stimulus, or of the subject's performance. In order to detect and characterize BOLD responses in single trials, we developed and validated a procedure based on an AutoRegressive model with eXogenous Input (ARX). The use of an individual exogenous input for each voxel makes the modeling sensitive enough to reveal differences across regions, avoiding any a priori assumption about the reference signal. The detection of variability across trials is ensured by a suitable choice, for each voxel, of the order of the moving average, which in our implementation determines the relative delay between the recorded and the reference signal. This is a quality useful in finding different time profiles of activation from high temporal resolution fMRI data. The results obtained from simulated fMRI data resulting from synthetic activations in actual noise indicate that such approach allows to evaluate important features of the response, such as the time to onset, and time to peak. Moreover, the results obtained from real high temporal resolution fMRI data acquired at l.5 T during a motor task are consistent with previous knowledge about the responses of different cortical areas in motor programming and execution. The proposed procedure should also prove useful as a pre-processing step in different approaches to the analysis of fMRI data

Preoperative plasticity in the functional naming network of patients with left insular gliomas

Plasticity could take place as a compensatory process following brain glioma growth. Only a few studies specifically explored plasticity in patients affected by a glioma invading the left insula; even more, plasticity of the insular cortex in task-based functional language network is almost unexplored.In the current study, we explored potential plasticity in a consecutive series of 22 patients affected by a glioma centered to the left insula, by comparing their preoperative object-naming functional network with that of a group of healthy controls. After having controlled for demographic variables, fMRI results showed that patients vs. controls activated a cluster in the right, contralesional pars triangularis including the Broca’s area. On the other hand, controls did not significantly activate any brain region more than patients. At behavioral level, patients retained a generally preserved naming performance as well as a proficient language processing profile.These findings suggest that involvement of language-specific areas in the healthy hemisphere could help compensate for the left, affected insula, thus allowing preservation of the naming functions. Results are commented in relation to lesion site, naming performance, and potential relevance for neurosurgery

Analisi di dati fMRI-BOLD a singolo evento: un approccio con reti neurali non supervisionate

Negli studi di risonanza magnetica funzionale (fMRI) cerebrale hanno assunto particolare rilevanza i protocolli di stimolazione basati su singoli eventi. Nel lavoro viene descritta una strategia di analisi di dati fMRI-BOLD, con lo scopo di rilevare il profilo temporale della risposta ad ogni singola stimolazione, nelle diverse aree cerebrali coinvolte. Il metodo si avvale di una fase di pre-elaborazione dei dati finalizzata ad incrementare il basso contrasto segnale-rumore tipico di dati derivanti da un singolo evento e di una fase di classificazione, caratterizzazione e localizzazione delle risposte realizzata implementando una rete neurale basata sull\u2019algoritmo di Kohonen delle mappe auto-organizzanti (SOMs). I risultati, ottenuti sia su immagini fMRI simulate, che su dati reali relativi ad un soggetto umano, mostrano la validita\u2019 di questo approccio guidato dai dati nell\u2019identificazione delle risposte ad una singola stimolazione e ne forniscono i limiti di applicabilita\u2019