Role of inhibitory neurons in temporal correlations of critical and supercritical spontaneous activity

Experimental and numerical results suggest that the brain can be viewed as a system acting close to a critical point, as confirmed by scale-free distributions of relevant quantities in a variety of different systems and models. Less attention has received the investigation of the temporal correlation functions in brain activity in different, healthy and pathological, conditions. Here we perform this analysis by means of a model with short and long-term plasticity which implements the novel feature of different recovery rates for excitatory and inhibitory neurons, found experimentally. We evidence the important role played by inhibitory neurons in the supercritical state: We detect an unexpected oscillatory behaviour of the correlation decay, whose frequency depends on the fraction of inhibitory neurons and their connectivity degree. This behaviour can be rationalized by the observation that bursts in activity become more frequent and with a smaller amplitude as inhibition becomes more relevant.Comment: 15 pages, 6 figure

Neural correlates of apathy in patients with neurodegenerative disorders: an activation likelihood estimation (ALE) meta-analysis

Apathy is commonly reported in Alzheimer’s Disease (AD), Fronto-Temporal Dementia (FTD) and Parkinson’s Disease (PD). In our meta-analysis we analysed a total of 41 studies to identify brain patterns associated with apathy. For these purposes we used activation likelihood estimation meta-analyses. Our main overall analysis showed that apathy is associated to hypometabolism and a decreased gray matter volume in the left inferior frontal gyrus (BA 45, 46). Disorder-specific analyses, not performed by means of meta-analysis, because of the small number of studies, but by means a label-based review, revealed an altered brain perfusion and decreased gray matter volume in anterior cingulate cortex (BA 24, 32) in AD patients and a decreased gray matter volume in inferior frontal gyrus (BA 44, 45) and parietal cortex (BA 40) in FTD patients. These findings suggest that apathy is mainly associated with a cortical dysfunction of areas involved in executive-cognitive processing (i.e. action planning) and emotional regulation (auto-activation and reward processing). Knowledge about the neural underpinnings of apathy is crucial for understanding its clinical characteristics in neurodegenerative diseases and for developing novel strategies of treatment in clinical practice

The Addenbrooke’s Cognitive Examination Revised (ACE-R) and its sub-scores: normative values in an Italian population sample

BACKGROUND A complex relationship exists between postural control and cognition in the elderly. Namely, neural mechanisms that are required for the regulation of posture have been variably associated with cognitive dysfunctions. Parkinson's disease (PD) is the second most common neurodegenerative disease among the elderly, and it has been associated with both cognitive and postural abnormalities such as Pisa syndrome (PS). Although its onset has been considered to be multifactorial, the pathophysiological mechanisms underpinning PS are still not fully explained. Until now, no study investigated the possible contribution of cognitive dysfunction to occurrence of PS in PD. PATIENTS AND METHODS: Twenty PD patients with PS and 20 PD patients without PS were enrolled. All patients with PD underwent neuropsychological battery to assess behavioural disturbances, memory, attention, frontal/executive and visuospatial functions. RESULTS: The two groups did not differ on demographic features, age at PD onset and disease duration, whereas they significantly differed on UPDRS-Part III, and levodopa-equivalent daily dose (LEDD). MANCOVA with above-mentioned clinical variable as covariates revealed significant differences on tasks tapping verbal long-term memory, and attentional and visuoperceptual abilities between groups. The binary logistic regression revealed that higher LEDD and lower performance on visuospatial task (Benton Judgment of Lines Orientation test) significantly predicted occurrence of PS. CONCLUSION: Our results revealed a significant association of PS with altered attention and visuoperceptual functions in PD, suggesting that the occurrence of PS may be associated with alteration of both frontal-striatal systems and posterior cortical areas

The Body Across Adulthood: On the Relation Between Interoception and Body Representations

Interoceptive information plays a pivotal role in building body representations (BR), but the association between interoception and the different types of BR in healthy individuals has never been systematically investigated. Thus, this study aimed to explore the association between BR and interoceptive sensibility (IS) throughout adulthood. One hundred thirty-seven healthy participants (50 aged from 18 to 40 years old; 50 aged from 41 to 60 years old; and 37 over 60 years old) were given a self-report tool for assessing IS (the Self-Awareness Questionnaire; SAQ), and a specific battery including tasks evaluating three different BR (i.e., the body schema, using the Hand Laterality Task; the body structural representation, using the Frontal Body Evocation task, FBE; and body semantics, using the Object-Body Part Association Task) as well as control tasks (i.e., tasks with non-body stimuli). The older age group (aged over 60 years old) showed lower performances on the tasks probing the body schema and body structural representation than younger groups (aged 18 to 40 and 41 to 60 years old). More interestingly, worse performances on a task assessing the body schema were significantly associated with higher IS with older age, suggesting that higher awareness of one’s inner body sensations would decrease the plasticity of this BR. These findings are interpreted according to the neuropsychological model of BR development and the effects of aging on the brain.</jats:p

Neural substrates of interoceptive sensibility: An integrated study in normal and pathological functioning

In early studies interoception strictly referred to the awareness of visceral sensations, but recent theories have expanded this concept to denote the ongoing status of the body, including somatosensory feelings. Here, we integrated data from normal and pathological functioning to disclose neural underpinnings of interoceptive sensibility, taking into account the crucial distinction between visceral and somatosensory feelings. Twenty-seven healthy young individuals underwent structural MRI (including T1w images and DTI). Voxel-wise ana-lyses of the gyrification index (GI) and fractional anisotropy (FA) data were performed to assess the relation between interoceptive sensibility and surface morphometry and anatomical connectivity. Thirty-three unilateral brain-damaged patients took part in this study for Voxel-Based Lesion-Symptom Mapping (VLSM) and track-wise hodological lesion-deficit analysis (TWH). All participants completed the Self-Awareness Questionnaire (SAQ), a self-report tool assessing interoceptive sensibility of visceral (F1) and somatosensory feelings (F2). Tract-Based Spatial Statistics showed that F2 was positively associated with FA in the bilateral anterior thalamic radiation, corticospinal tract, cingulum, forceps, inferior longitudinal, fronto-occipital, superior longitudinal, and uncinate fasciculi; no significant association was detected for F1. However, F1 was positively associated with GI in the left anterior cingulate cortex. VLSM showed that F1 mainly relies on the right posterior insula, whereas F2 is related mostly to subcortical nuclei and surrounding white matter in the right hemisphere. Accordingly, patients with disconnection of the anterior thalamic projection, corticospinal tract, inferior fronto-occipital, inferior longitu-dinal, uncinate and superior longitudinal fasciculus III showed lower scores on F2. Overall, results support the dissociation between interoceptive sensibility of visceral and somatosensory feelings

Neuropsychological Correlates of Theory of Mind Deficits in Patients With Multiple Sclerosis

Background: Theory of mind (ToM) is the ability to understand and interpret another person's beliefs, intentions (cognitive ToM) and emotions (affective ToM). Objective: To explore affective and cognitive ToM and their neuropsychological correlates in patients affected by multiple sclerosis (MS). Material and Method: Forty MS patients and 40 matched control individuals underwent tasks assessing cognitive (the ToM Pictures Sequencing Task and the Advanced Test of ToM) and affective ToM (the Reading the Mind in the Eyes Task and the Emotion Attribution Task), in both verbal and nonverbal modality, a comprehensive neuropsychological battery, and questionnaires for behavioral disorders. Results: MS patients performed significantly worse than controls on tasks assessing cognitive and affective ToM, in verbal and nonverbal modality. Moreover, MS patients achieved significantly lower scores on tests assessing visuospatial learning and speed of spatial information processing, and significantly higher scores on scales for alexithymia and depression with respect to controls. After covarying for cognitive and behavioral variables different in the 2 groups, the differences between patients and controls on ToM tasks remained significant. ToM abilities were significantly related to executive functions, but not to depressive, anxious and apathetic symptoms. Higher alexithymia scores were associated with poor recognition of others' mental states. Conclusion: The findings demonstrated that both affective and cognitive aspects of ToM are impaired in nondemented and mildly to moderately disabled MS and suggest that impaired social cognition can occur independently from behavioral disorders. (PsycINFO Database Recor