Pietro Pietrini

The functional organization of human extrastriate cortex: a PET-rCBF study of selective attention to faces and locations

The functional dissociation of human extrastriate cortical processing streams for the perception of face identity and location was investigated in healthy men by measuring visual task-related changes in regional cerebral blood flow (rCBF) with positron emission tomography (PET) and H2(15)O. Separate scans were obtained while subjects performed face matching, location matching, or sensorimotor control tasks. The matching tasks used identical stimuli for some scans and stimuli of equivalent visual complexity for others. Face matching was associated with selective rCBF increases in the fusiform gyrus in occipital and occipitotemporal cortex bilaterally and in a right prefrontal area in the inferior frontal gyrus. Location matching was associated with selective rCBF increases in dorsal occipital, superior parietal, and intraparietal sulcus cortex bilaterally and in dorsal right premotor cortex. Decreases in rCBF, relative to the sensorimotor control task, were observed for both matching tasks in auditory, auditory association, somatosensory, and midcingulate cortex. These results suggest that, within a sensory modality, selective attention is associated with increased activity in those cortical areas that process the attended information but is not associated with decreased activity in areas that process unattended visual information. Selective attention to one sensory modality, on the other hand, is associated with decreased activity in cortical areas dedicated to processing input from other sensory modalities. Direct comparison of our results with those from other PET-rCBF studies of extrastriate cortex demonstrates agreement in the localization of cortical areas mediating face and location perception and dissociations between these areas and those mediating the perception of color and motion.

Forgiveness, Health, and Well-Being: A Review of Evidence for Emotional Versus Decisional Forgiveness, Dispositional Forgivingness, and Reduced Unforgiveness

The extant data linking forgiveness to health and well-being point to the role of emotional forgiveness, particularly when it becomes a pattern in dispositional forgivingness. Both are important antagonists to the negative affect of unforgiveness and agonists for positive affect. One key distinction emerging in the literature is between decisional and emotional forgiveness. Decisional forgiveness is a behavioral intention to resist an unforgiving stance and to respond differently toward a transgressor. Emotional forgiveness is the replacement of negative unforgiving emotions with positive other-oriented emotions. Emotional forgiveness involves psychophysiological changes, and it has more direct health and well-being consequences. While some benefits of forgiveness and forgivingness emerge merely because they reduce unforgiveness, some benefits appear to be more forgiveness specific. We review research on peripheral and central nervous system correlates of forgiveness, as well as existing interventions to promote forgiveness within divergent health settings. Finally, we propose a research agenda.

Tau gene mutation G389R causes a tauopathy with abundant pick body-like inclusions and axonal deposits.

Exonic and intronic mutations in Tau cause familial neurodegenerative syndromes characterized by frontotemporal dementia and dysfunction of multiple cortical and subcortical circuits. Here we describe a G389R mutation in exon 13 of Tau. When 38 years old, the proband presented with progressive aphasia and memory disturbance, followed by apathy, indifference, and hyperphagia. Repeated magnetic resonance imaging showed the dramatic progression of cerebral atrophy. Positron emission tomography revealed marked glucose hypometabolism that was most severe in left frontal, temporal, and parietal cortical regions. Rigidity, pyramidal signs and profound dementia progressed until death at 43 years of age. A paternal uncle, who had died at 43 years of age, had presented with similar symptoms. The probands brain showed numerous tau-immunoreactive Pick body-like inclusions in the neocortex and the fascia dentata of the hippocampus. In addition, large numbers of tau-positive filamentous inclusions were present in axons in the frontal, temporal, and parietal lobes. Immunoblot analysis of sarkosyl-insoluble tau showed 2 major bands of 60 and 64 kDa. Upon dephosphorylation, these bands resolved into 4 bands consisting of three- and four-repeat tau isoforms. Most isolated tau filaments were straight and resembled filaments found in Alzheimer disease and some frontotemporal dementias with tau mutations. A smaller number of twisted filaments was also observed. Biochemically, recombinant tau proteins with the G389R mutation showed a reduced ability to promote microtubule assembly, suggesting that this may be the primary effect of the mutation. Taken together, the present findings indicate that the G389R mutation in Tau can cause a dementing condition that closely resembles Picks disease.

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.

Where the brain appreciates the moral of a story

To identify the distributed brain regions used for appreciating the grammatical, semantic and thematic aspects of a story, regional cerebral blood flow was measured with positron emission tomography in nine normal volunteers during the reading of Aesops fables. In four conditions, subjects had to monitor the fables for font changes, grammatical errors, a semantic feature associated with a fable character, and the moral of the fable. Both right and left prefrontal cortices were consistently, but selectively, activated across the grammatical, semantic, and moral conditions. In particular, appreciating the moral of a story required activating a distributed set of brain regions in the right hemisphere which included the temporal and prefrontal cortices. These findings emphasize that story processing engages a widely distributed network of brain regions, a subset of which become preferentially active during the processing of a specific aspect of the text.

Imagery and spatial processes in blindness and visual impairment.

The objective of this review is to examine and evaluate recent findings on cognitive functioning (in particular imagery processes) in individuals with congenital visual impairments, including total blindness, low-vision and monocular vision. As one might expect, the performance of blind individuals in many behaviours and tasks requiring imagery can be inferior to that of sighted subjects; however, surprisingly often this is not the case. Interestingly, there is evidence that the blind often employ different cognitive mechanisms than sighted subjects, suggesting that compensatory mechanisms can overcome the limitations of sight loss. Taken together, these studies suggest that the nature of perceptual input on which we commonly rely strongly affects the organization of our mental processes. We also review recent neuroimaging studies on the neural correlates of sensory perception and mental imagery in visually impaired individuals that have cast light on the plastic functional reorganization mechanisms associated with visual deprivation.

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.

Beyond visual, aural and haptic movement perception: hMT+ is activated by electrotactile motion stimulation of the tongue in sighted and in congenitally blind individuals

The motion-sensitive middle temporal cortex (hMT+ complex) responds also to non-visual motion stimulation conveyed through the tactile and auditory modalities, both in sighted and in congenitally blind individuals. This indicates that hMT+ is truly responsive to motion-related information regardless of visual experience and the sensory modality through which such information is carried to the brain. Here we determined whether the hMT+ complex responds to motion perception per se, that is, motion not perceived through the visual, haptic or aural modalities. Using functional magnetic resonance imaging (fMRI), we investigated brain responses in eight congenitally blind and nine sighted volunteers who had been trained to use the tongue display unit (TDU), a sensory substitution device which converts visual information into electrotactile pulses delivered to the tongue, to resolve a tactile motion discrimination task. Stimuli consisted of either static dots, dots moving coherently or dots moving in random directions. Both groups learned the task at the same rate and activated the hMT+ complex during tactile motion discrimination, although at different anatomical locations. Furthermore, the congenitally blind subjects showed additional activations within the dorsal extrastriate cortical pathway. These results extend previous data in support of the supramodal functional organization of hMT+ complex by showing that this cortical area processes motion-related information per se, that is, motion stimuli that are not visual in nature and that are administered to body structures that, in humans, are not primarily devoted to movement perception or spatial location, such as the tongue. In line with previous studies, the differential activations between sighted and congenitally blind individuals indicate that lack of vision leads to functional rearrangements of these supramodal cortical areas.

Early detection of Alzheimer's disease : a statistical approach using positron emission tomographic data

Correlational analysis of regional cerebral glucose metabolism (rCMRglc) obtained by high-resolution positron emission tomography (PET) has demonstrated reduced neocortical rCMRglc interactions in mildly/moderately demented patients with probable Alzheimers disease (AD). Thus, identification of individual differences in patterns of rCMRglc interactions may be important for the early detection of AD, particularly among individuals at greater risk for developing AD (e.g., those with a family history of AD). Recently, a statistical procedure, using multiple regression and discriminant analysis, was developed to assess individual differences in patterns of rCMRglc interdependencies. We applied this new statistical procedure to resting rCMRglc PET data from mildly/moderately demented patients with probable AD and age/sex-matched controls. The aims of the study were to identify a discriminant function that would (a) distinguish patients from controls and (b) identify an AD pattern in an individual at risk for AD with isolated memory impairment whose initial PET scan showed minor abnormalities, but whose second scan showed parietal hypometabolism, coincident with further cognitive decline. Two discriminant functions, reflecting interactions involving regions most involved in reduced correlations in probable AD, correctly classified 87% of the patients and controls, and successfully identified the first scan of the at-risk individual as AD (probability >0.70). The results suggest that this statistical approach may be useful for the early detection of AD.

Differential modulation of neural activity throughout the distributed neural system for face perception in patients with Social Phobia and healthy subjects

Social Phobia (SP) is a marked and persistent fear of social or performance situations in which the person is exposed to unfamiliar people or to possible scrutiny by others. Faces of others are perceived as threatening by social phobic patients (SPP). To investigate how face processing is altered in the distributed neural system for face perception in Social Phobia, we designed an event-related fMRI study in which Healthy Controls (HC) and SPP were presented with angry, fearful, disgusted, happy and neutral faces and scrambled pictures (visual baseline). As compared to HC, SPP showed increased neural activity not only in regions involved in emotional processing including left amygdala and insula, as expected from previous reports, but also in the bilateral superior temporal sulcus (STS), a part of the core system for face perception that is involved in the evaluation of expression and personal traits. In addition SPP showed a significantly weaker activation in the left fusiform gyrus, left dorsolateral prefrontal cortex, and bilateral intraparietal sulcus as compared to HC. These effects were found not only in response to emotional faces but also to neutral faces as compared to scrambled pictures. Thus, SPP showed enhanced activity in brain areas related to processing of information about emotional expression and personality traits. In contrast, brain activity was decreased in areas for attention and for processing other information from the face, perhaps as a result of a feeling of wariness. These results indicate a differential modulation of neural activity throughout the different parts of the distributed neural system for face perception in SPP as compared to HC.