Simone Pernigo

The Neural Basis of Body Form and Body Action Agnosia

Visual analysis of faces and nonfacial body stimuli brings about neural activity in different cortical areas. Moreover, processing body form and body action relies on distinct neural substrates. Although brain lesion studies show specific face processing deficits, neuropsychological evidence for defective recognition of nonfacial body parts is lacking. By combining psychophysics studies with lesion-mapping techniques, we found that lesions of ventromedial, occipitotemporal areas induce face and body recognition deficits while lesions involving extrastriate body area seem causatively associated with impaired recognition of body but not of face and object stimuli. We also found that body form and body action recognition deficits can be double dissociated and are causatively associated with lesions to extrastriate body area and ventral premotor cortex, respectively. Our study reports two category-specific visual deficits, called body form and body action agnosia, and highlights their neural underpinnings.

Phenomenology and neural correlates of implicit and emergent motor awareness in patients with anosognosia for hemiplegia

Anosognosia for hemiplegia (AH) is characterized by a lack of awareness of motor disorders and appears associated with fronto-temporal-parietal damage. Neuropsychological evidence indicates that behavioral indices of residual forms of motor awareness may co-exist with explicit denial of impairment. Here we explore whether the attempt by AH patients to perform an action may disclose residual forms of motor awareness and whether such forms are underpinned by different neural structures. Twelve hemiplegic patients affected by AH were tested in tasks assessing: (i) implicit awareness (IA), indexed by discrepancies between verbal reports and actual motor behavior; (ii) emergent awareness (EA), indexed by increased verbal awareness induced by the attempt to perform actions. IA and EA were found in five and three patients, respectively. Lesion analysis indicates that while the lack of IA is associated with damage to subcortical white matter anterior to the basal ganglia, lack of EA is linked to damage to cortical regions including insulo-frontal, temporal and parietal structures. Our results indicate that deficits in explicit and implicit awareness are associated with lesions involving different cortico-subcortical structures. Moreover, the results show that the attempt to perform an action may ameliorate body awareness deficits and have implications for rehabilitation.

Vision of the body modulates processing in primary somatosensory cortex

Viewing the body affects somatosensory processing, even when entirely non-informative about stimulation. While several studies have reported effects of viewing the body on cortical processing of touch and pain, the neural locus of this modulation remains unclear. We investigated whether seeing the body modulates processing in primary somatosensory cortex (SI) by measuring short-latency somatosensory evoked-potentials (SEPs) elicited by electrical stimulation of the median nerve while participants looked directly at their stimulated hand or at a non-hand object. Vision of the body produced a clear reduction of the P27 component of the SEP recorded over contralateral parietal channels, which is known to reflect processing in SI. These results provide the first direct evidence that seeing the body modulates processing in SI and demonstrate that vision can affect even the earliest stages of cortical somatosensory processing.

Visual body recognition in a prosopagnosic patient

Conspicuous deficits in face recognition characterize prosopagnosia. Information on whether agnosic deficits may extend to non-facial body parts is lacking. Here we report the neuropsychological description of FM, a patient affected by a complete deficit in face recognition in the presence of mild clinical signs of visual object agnosia. His deficit involves both overt and covert recognition of faces (i.e. recognition of familiar faces, but also categorization of faces for gender or age) as well as the visual mental imagery of faces. By means of a series of matching-to-sample tasks we investigated: (i) a possible association between prosopagnosia and disorders in visual body perception; (ii) the effect of the emotional content of stimuli on the visual discrimination of faces, bodies and objects; (iii) the existence of a dissociation between identity recognition and the emotional discrimination of faces and bodies. Our results document, for the first time, the co-occurrence of body agnosia, i.e. the visual inability to discriminate body forms and body actions, and prosopagnosia. Moreover, the results show better performance in the discrimination of emotional face and body expressions with respect to body identity and neutral actions. Since FMs lesions involve bilateral fusiform areas, it is unlikely that the amygdala-temporal projections explain the relative sparing of emotion discrimination performance. Indeed, the emotional content of the stimuli did not improve the discrimination of their identity. The results hint at the existence of two segregated brain networks involved in identity and emotional discrimination that are at least partially shared by face and body processing.

Massive somatic deafferentation and motor deefferentation of the lower part of the body impair its visual recognition: A psychophysical study of patients with spinal cord injury

Embodied cognition theories postulate that perceiving and understanding the body states of other individuals are underpinned by the neural structures activated during first‐hand experience of the same states. This suggests that one’s own sensorimotor system may be used to identify the actions and sensations of others. Virtual and real brain lesion studies show that visual processing of body action and body form relies upon neural activity in the ventral premotor and the extrastriate body areas, respectively. We explored whether visual body perception may also be altered in the absence of damage to the above cortical regions by testing healthy controls and spinal cord injury (SCI) patients whose brain was unable to receive somatic information from and send motor commands to the lower limbs. Participants performed tasks investigating the ability to visually discriminate changes in the form or action of body parts affected by somatosensory and motor disconnection. SCI patients showed a specific, cross‐modal deficit in the visual recognition of the disconnected lower body parts. This deficit affected both body action and body form perception, hinting at a pervasive influence of ongoing body signals on the brain network dedicated to visual body processing. Testing SCI patients who did or did not practise sports allowed us to test the influence of motor practice on visual body recognition. We found better upper body action recognition in sport‐practising SCI patients, indicating that motor practice is useful for maintaining visual representation of actions after deafferentation and deefferentation. This may be a potential resource to be exploited for rehabilitation.

Cognitive Stimulation in a-MCI: An Experimental Study

Nowadays, preventing the effects of mental decline is an international priority, but there is little research into cognitive training in mild cognitive impairment (MCI). We present the results of a program aimed at teaching memory strategies and improving metacognitive abilities. This was associated with training to ameliorate caregivers’ assistance. Two groups (A and B) were compared in a crossover design. After the first evaluation, group A (but not B) participated in a 6-month cognitive stimulation program. After a second assessment, only B received treatment and then a final evaluation was carried out on both the groups. The results show that (1) both the groups improved their performance as an effect of training; (2) improvements are specific to the functions trained; (3) in the interval without intervention, performance of group B worsened; and (4) group A has maintained their results over time. In conclusion, our results show that specific training may reduce memory impairment in MCI.

Anosognosia for apraxia: Experimental evidence for defective awareness of one's own bucco-facial gestures

Anosognosia is a multifaceted, neuro-psychiatric syndrome characterized by defective awareness of a variety of perceptuo-motor, cognitive or emotional deficits. The syndrome is also characterized by modularity, i.e., deficits of awareness in one domain (e.g., spatial perception) co-existing with spared functions in another domain (e.g., memory). Anosognosia has mainly been reported after right hemisphere lesions. It is however somewhat surprising that no studies have thus far specifically explored the possibility that lack of awareness involves apraxia, i.e., a deficit in the ability to perform gestures caused by an impaired higher-order motor control and not by low-level motor deficits, sensory loss, or failure to comprehend simple commands. We explored this issue by testing fifteen patients with vascular lesions who were assigned to one of three groups depending on their neuropsychological profile and brain lesion. The patients were asked to execute various actions involving the upper limb or bucco-facial body parts. In addition they were also asked to judge the accuracy of these actions, either performed by them or by other individuals. The judgment of the patients was compared to that of two external observers. Results show that our bucco-facial apraxic patients manifest a specific deficit in detecting their own gestural errors. Moreover they were less aware of their defective performance in bucco-facial as compared to limb actions. Our results hint at the existence of a new form of anosognosia specifically involving apraxic deficits.

Finger recognition and gesture imitation in Gerstmann's syndrome.

We report the association between finger agnosia and gesture imitation deficits in a right-handed, right-hemisphere damaged patient with Gerstmanns syndrome (GS), a neuropsychological syndrome characterized by finger and toe agnosia, left–right disorientation and dyscalculia. No language deficits were found. The patient showed a gestural imitation deficit that specifically involved finger movements and postures. The association between finger recognition and imitation deficits suggests that both static and dynamic aspects of finger representations are impaired in GS. We suggest that GS is a disorder of body representation that involves hands and fingers, that is, the non-facial body parts most involved in social interactions.

Contextual bottom-up and implicit top-down modulation of anarchic hand syndrome: A single-case report and a review of the literature

Anarchic hand syndrome (AHS) is a rare neurological condition characterized by seemingly purposeful, goal-directed hand movements which the person afflicted by the syndrome is not, however, in control of. By extensively examining a patient with AHS we provide novel neuropsychological and lesion mapping data that shed new light on the possibility of modulating specific symptoms associated with AHS, in particular unilateral apraxia and magnetic apraxia. Moreover, we compared lesion mapping data with an in depth analysis of previous studies in order to explore the neural network responsible for the complex symptomatology associated with this syndrome. We found that non-primarily motor variables (e.g. the nature of the object to be grasped and integration of visuo-spatial feedback in action) play an important role in determining AHS symptomatology. Moreover, we found that lesions involving various different parts of the motor control network (the corpus callosum, the anterior cingulate cortex and the supplementary motor area, the parietal areas and thalamus) are closely linked to partially differing AHS symptoms. The comparison of our data with those reported in previous studies indicate that AHS is a multifaceted and complex syndrome in which the influence of non-primarily motor, emotional and higher-order components may be largely underestimated.