Action execution and recognition: a neuropsychological analysis

Humans appear to show an innate tendency to imitate, and this may provide one of the foundations of social communication. Several studies have been carried out in social and cognitive science in order to understand how imitation works, which parts of the brain are involved, and what the role of imitation might be in social behaviour. Previous brain imaging and neuropsychological studies report data that favour a dual process account of imitation, according to which actions are imitated through different mechanisms on the basis of whether they are meaningful and familiar (MF actions) or meaningless/unfamiliar (ML actions). However many questions remain to be clarified – such as which brain areas mediate these different actions. In addition to the distinction between MF and ML gestures, there is considerable interest in the production of different types of known gestures – particularly between actions involving tools (i.e. transitive actions) and those subserving communicative (intransitive) gestures, and in how the production of these gestures relates to the processes involved in recognizing the gestures as input. This thesis reports a neuropsychological examination of the functional and neural bases of imitation using converging data from behavioural studies with different patient groups (stroke patients, patients with Parkinson’s Disease, PD) and structural brain imaging (particularly using voxel-based morphometric [VBM] analyses) to examine lesion-symptom relations. The first empirical chapter (Chapter 2) describes a neuropsychological study on the recognition and production of MF actions and the imitation of ML gestures, in patients with unilateral left or rightside brain damage (respectively: LBD and RBD patients). At a group level, LBD patient were worse in imitation than RBD patients only when novel transitive actions had to be reproduced, when both LBD and RBD differed from healthy participants, while intransitive gestures were generally easier to be executed. Also both transitive and intransitive action imitation tasks were correlated to action recognition. At a single subject level, however, there was evidence for some dissociated symptoms, suggesting that at least partially different mechanisms mediate the imitation of transitive and intransitive gestures and gesture production as opposed to recognition. Chapter 3 presents a first attempt to use VBM to evaluate the relations between brain lesions and the symptoms of apraxia, contrasting the imitation of meaningful (familiar) and meaningless (unfamiliar) transitive and intransitive actions in a consecutive series of brain damaged patients. Chapters 4 and 5 describe two investigations where VBM was again used in a large-scale lesionsymptom analysis of deficits in i) the recognition and generation to command of MF actions and the imitation of ML actions, and ii) the generation to command of different types of learned action (transitive or intransitive gestures). All three investigations using VBM revealed common and differential neural substrates involved in the execution of the tasks considered, and the data are compatible with a model which posits that different processes are involved in MF and ML action execution, as well as in action understanding. The results also suggest that the distinction between transitive and intransitive actions may be included in an action reproduction system. In the final empirical chapter (Chapter 6), I report a study on PD patients tested for imitation of transitive and intransitive MF and ML actions, also relating their performance to the neurological/peripheral symptoms of the disease. This study revealed that PD patients were impaired in imitation, and they also had different pattern of deficit for transitive and intransitive actions. The correlation with peripheral symptoms was not significant, though there were correlations with underlying cognitive processes likely to support action production. Chapter 7 summarizes the different results and links them back to functional and neural accounts of action recognition, production and imitation. The relations between action production and recognition and other cognitive processes are discussed, as are methodological issues concerning lesion-symptom mapping

Neural correlates of transitive and intransitive action imitation:an investigation using voxel-based morphometry

AbstractThe ability to reproduce visually presented actions has been studied through neuropsychological observations of patients with ideomotor apraxia. These studies include attempts to understand the neural basis of action reproduction based on lesion–symptom mapping in different patient groups. While there is a convergence of evidence that areas in the parietal and frontal lobes within the left hemisphere are involved in the imitation of a variety of actions, questions remain about whether the results generalize beyond the imitation of tool use and whether the presence of a strong grasp component of the action is critical. Here we used voxel-based lesion–symptom mapping to assess the neural substrates of imitating meaningful (familiar, MF) and meaningless (unfamiliar, ML) tool-related (transitive) and non-tool related (intransitive) actions. The analysis showed that the left parietal cortex was involved in the imitation of transitive gestures, regardless of whether they were meaningful or not. In addition there was poor reproduction of meaningless actions (both transitive and intransitive) following damage of the right frontal cortex. These findings suggest a role of right frontal regions in processing of unfamiliar actions

Age-dependent changes of thinking about verbs

We investigated the knowledge of emotional and motor verbs in children andadolescents from three age ranges (8\u201311, 12\u201315, 16\u201319 years). Participants estimatedthe verbs familiarity, age of acquisition, valence, arousal, imageability, and motor- andemotion-relatedness. Participants were familiar with theverbs in our dataset. The younger(8\u201311) attributed an emotional character to the verbs less frequently than the middle(12\u201315) and the older (16\u201319) groups. In the 8\u201311 group malesrated the verbs asemotion-related less frequently than females. Results indicate that processing verbalconcepts as emotion-related develops gradually, and after12\u201315 is rather stable. The ageof acquisition (AoA) develops late: the older (16\u201319) had a higher awareness in reportingthat they learnt the verbs earlier as compared to the estimations made by the younger(8\u201311 and 12\u201315). AoA positively correlated with attribution of emotion relatednessmeaning that emotion-related verbs were learned later. Arousal was comparable acrossages. Also it increased when attributing motor relatednessto verbs and decreasedwhen attributing emotion relatedness. Reporting the verbs\u2019 affective valence (happy vs.unhappy) changes with age: younger (8\u201311) judged the verbs generally more \u201chappy\u201dthan both the older groups. Instead the middle and the older group did not showdifferences. Happiness increased when processing the verbs as motor related anddecreased when processing the verbs as emotion related. Ageaffected imageability:the younger (8\u201311) considered the verbs easier to be imagined than the two oldergroups, suggesting that at this age vividness estimation isstill rough, while after 12\u201315 isstable as the 12\u201315 and 15\u201319 group did not differ. Imageability predicted arousal, AoA,emotion- and motor-relatedness indicating that this indexinfluences the way verbs areprocessed. Imageability was positively correlated to emotion relatedness, indicating thatsuch verbs were harder to be imagined, and negatively to motor relatedness. Imageablitypositively correlated with valence meaning that verbs receiving positive valence were alsothose that were hard to be imagined, and negatively correlated with arousal, meaning thatverbs that were harder to be imagined elicited low physiological activation. Our resultsgive an insight in the development of emotional and motor-related verbs representations

Intervención económica de la Corte Constitucional, argumentos y debate de su viabilidad

En Colombia la Constitución es norma de normas, es la norma suprema dentro del ordenamiento positivo de modo que sus disposiciones deberán ser aplicadas siempre que se presente incompatibilidad con otras normas jurídicas. Por tal motivo, es la norma suprema rectora del ordenamiento jurídico del Estado y de las actuaciones de los órganos y actividades del poder público. La guardia de su integridad y supremacía se le confiere a la Corte Constitucional, que en el nuevo ordenamiento asume la función que desde 1910 le correspondía a la Sala Plena de la Corte Suprema de Justicia

Effects of age and gender on neural correlates of emotion imagery

Mental imagery is part of people's own internal processing and plays an important role in everyday life, cognition and pathology. The neural network supporting mental imagery is bottom-up modulated by the imagery content. Here, we examined the complex associations of gender and age with the neural mechanisms underlying emotion imagery. We assessed the brain circuits involved in emotion mental imagery (vs. action imagery), controlled by a letter detection task on the same stimuli, chosen to ensure attention to the stimuli and to discourage imagery, in 91 men and women aged 14-65 years using fMRI. In women, compared with men, emotion imagery significantly increased activation within the right putamen, which is involved in emotional processing. Increasing age, significantly decreased mental imagery-related activation in the left insula and cingulate cortex, areas involved in awareness of ones' internal states, and it significantly decreased emotion verbs-related activation in the left putamen, which is part of the limbic system. This finding suggests a top-down mechanism by which gender and age, in interaction with bottom-up effect of type of stimulus, or directly, can modulate the brain mechanisms underlying mental imagery

Automatic classification of autism spectrum disorder in children using cortical thickness and support vector machine

Objective: Autism spectrum disorder (ASD) is a neurodevelopmental condition with a heterogeneous phenotype. The role of biomarkers in ASD diagnosis has been highlighted; cortical thickness has proved to be involved in the etiopathogenesis of ASD core symptoms. We apply support vector machine, a supervised machine learning method, in order to identify specific cortical thickness alterations in ASD subjects. Methods: A sample of 76 subjects (9.5 \ub1 3.4 years old) has been selected, 40 diagnosed with ASD and 36 typically developed subjects. All children underwent a magnetic resonance imaging (MRI) examination; T1-MPRAGE sequences were analyzed to extract features for the characterization and parcellation of regions of interests (ROI); average cortical thickness (CT) has been measured for each ROI. For the classification process, the extracted features were used as input for a classifier to identify ASD subjects through a "learning by example" procedure; the features with best performance was then selected by "greedy forward-feature selection." Finally, this model underwent a leave-one-out cross-validation approach. Results: From the training set of 68 ROIs, five ROIs reached accuracies of over 70%. After this phase, we used a recursive feature selection process in order to identify the eight features with the best accuracy (84.2%). CT resulted higher in ASD compared to controls in all the ROIs identified at the end of the process. Conclusion: We found increased CT in various brain regions in ASD subjects, confirming their role in the pathogenesis of this condition. Considering the brain development curve during ages, these changes in CT may normalize during development. Further validation on a larger sample is required

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

Longitudinal investigation of the parietal lobe anatomy in bipolar disorder and its association with general functioning

The parietal lobe (PL) supports cognitive domains, including attention and memory, which are impaired in bipolar disorder (BD). Although cross-sectional voxel-based morphometry studies found reduced PL grey matter (GM) in BD, none has longitudinally focused on PL anatomy in BD, relating it to patients? functioning. Thirty-eight right-handed BD patients and 42 matched healthy subjects (HS) underwent a Magnetic Resonance Imaging (MRI) scan at baseline. Seventeen BD patients and 16 matched HS underwent a follow-up MRI. PL white matter (WM) and GM volumes were measured. The trajectory of parietal volumes over time and the possible relation with the global functioning were investigated in both BD patients and HS. At baseline, BD patients showed significant reduced PL WM and GM and different WM laterality compared with HS. Furthermore, smaller PL WM volumes predicted lower global functioning in BD, but not in HS. At follow-up, although BD patients reported reduced PL WM compared with HS, no different pattern of volume changes over time was detected between groups. This study suggests the involvement of the PL in the pathophysiology of BD. In particular, PL WM reductions seem to predict an impairment in general functioning in BD and might represent a marker of functional outcome

Increased gyrification in schizophrenia and non affective first episode of psychosis

Prefrontal cortex gyrification has been suggested to be altered in patients with schizophrenia and first episode psychosis. Therefore, it may represent a possible trait marker for these illnesses and an indirect evidence of a disrupted underlying connectivity. The aim of this study was to add further evidence to the existing literature on the role of prefrontal gyrification in psychosis by carrying out a study on a sizeable sample of chronic patients with schizophrenia and non-affective first-episode psychosis (FEP-NA) patients. Methods: Seventy-two patients with schizophrenia, 51 FEP-NA patients (12 who later develop schizophrenia) and 95 healthy controls (HC) underwent magnetic resonance imaging (MRI). Cortical folding was quantified using the automated gyrification index (GI). GI values were compared among groups and related to clinical variables. Results: Both FEP-NA and patients with schizophrenia showed a higher mean prefrontal GI compared to HC (all p. <. 0.05). Interestingly, no differences have been observed between the two patients groups as well as between FEP-NA patients who did and did not develop schizophrenia. Conclusions: Our results suggest the presence of a shared aberrant prefrontal GI in subjects with both schizophrenia and first-episode psychosis. These findings support the hypothesis that altered GI represents a neurodevelopmental trait marker for psychosis, which may be involved in the associated neurocognitive deficits