Aplasia

Motor theories of action comprehension claim that comprehending the meaning of an action performed by a conspecific relies on the perceiver’s own motor representation of the same action. According to this view, whether an action belongs to the motor repertoire of the perceiver should impact the ease by which this action is comprehended. We tested this prediction by assessing the ability of an individual (DC) born without upper limbs to comprehend actions involving hands (e.g., throwing) or other body parts (e.g., jumping). The tests used a range of different visual stimuli differing in the kind of information provided. The results showed that DC was as accurate and fast as control participants in comprehending natural video and photographic presentations of both manual and non-manual actions, as well as pantomimes. However, he was selectively impaired at identifying point-light animations of manual actions. This impairment was not due to a difficulty in processing kinematic information per se. DC was indeed as accurate as control participants in two additional tests requiring a fine-grained analysis of an actor’s arm or whole-body movements. These results challenge motor theories of action comprehension by showing that the visual analysis of body shape and motion provides sufficient input for comprehending observed actions. However, when body shape information is sparsely available, motor involvement becomes critical to interpret observed actions. We suggest that, with natural human movement stimuli, motor representations contribute to action comprehension each time visual information is incomplete or ambiguous.

A B S T R A C T Aplasia cutis congenita (ACC) is a rare disorder which is characterized by the absence of a localized, or less commonly, a widespread area of skin involving the epidermis, dermis and subcutaneous tissue with an incidence of 3/10,000 newborns. Most commonly it manifests as an isolated defect of the scalp, but can also affect other parts like the trunk and limbs. The lesions range from superficial erosions to involving deeper structures like the underlying muscle, periosteum and bone. The dura mater may be affected in 20%-30% of cases. Many embryological malformations like abdominal wall defect, duodenal atresia and biliary atresia may also be associated with it. Majority of foetuses with extensive ACC, manifest with fetus papyraceus. Multiple mechanisms including genetic aberrations, like trisomy 13 and 4p deletion have also been proposed for it's development. The larger defects have a stronger association with the autosomal dominant trait whereas the syndromic pattern show an X linked inheritance. Presently, treatment is largely conservative although skin grafting in cases of large defects involving the scalp is desirable. We report the case of a preterm male neonate with skin defects on the scalp and bilateral flanks. This was IVF (In-Vitro Fertilization) conceived pregnancy with triplets with one fetal reduction done at 15 weeks. The reported case is one of surviving DCDA (Di-chorionic Di-amniotic) twins. No one theory can be used to explain all the lesions of ACC, it is thought to be the phenotypic outcome of multiple disease processes. Fetal reduction is a reported risk factor for ACC.

Phantom limb experiences demonstrate an unexpected degree of fragility inherent in our self-perceptions. This is perhaps most extreme when congenitally absent limbs are experienced as phantoms. Aplasic phantoms highlight fundamental questions about the physiological bases of self-experience and the ontogeny of a physical, embodied sense of the self. Some of the most intriguing of these questions concern the role of mirror neurons in supporting the development of self–other mappings and hence the emergence of phantom experiences of congenitally absent limbs. In this paper, we will examine the hypothesis that aplasic phantom limb experience is the result of an ontogenetic interplay between body schemas and mirror neuron activity and that this interplay is founded on embedding in a social context. Phantom limb experience has been associated with the persistence of subjective experience of a part of the body after deafferentation through surgical or traumatic removal. We maintain that limited association is inconsistent with the extent to which phantom limb experience is reported by aplasic individuals.

BACKGROUND AND OBJECTIVE: Agenesis and hypoplasia of the paranasal sinuses is an anatomical variation that often occurs in frontal sinuses but this rarely happens combined with other paranasal sinuses. The present study was conducted to report a rare case of hypoplasia of the paranasal sinuses and atrophy of all three turbinates in Iran. CASE REPORT: In this study, we report the case of a 28-year-old man who referred with trauma to the head and anosmia. The patient had no complaints of nasal obstruction or congestion, cerebrospinal fluid leakage before or after trauma. He also had no previous history of rhinosinusitis or olfactory disorder. CT scans of nose and paranasal sinuses showed some findings such as bilateral middle and inferior concha atrophy, bilateral hypoplasia of maxillary, ethmoid, sphenoid, and right frontal sinuses and left frontal sinus aplasia. To the best of our knowledge, the number of reports about the combination of abnormal variations of paranasal sinuses was less than 5 and in the present case report, all sinuses had hypoplasia and at the same time, there was turbinate atrophy, while the patient had no clinical symptoms. CONCLUSION: According to the present study, pneumatization of sinus is not necessarily associated with clinical symptoms and other factors play a role in sinus function.

Several studies have reported that, when subjects have to judge the laterality of rotated hand drawings, their judgment is automatically influenced by the biomechanical constraints of the upper limbs. The prominent account for this effect is that, in order to perform the task, subjects mentally rotate their upper limbs toward the position of the displayed stimulus in a way that is consistent with the biomechanical constraints underlying the actual movement. However, the effect of such biomechanical constraints was also found in the responses of motor-impaired individuals performing the hand laterality judgment task, which seems at odds with the “motor imagery” account for this effect. In this study, we further explored the source of the biomechanical constraint effect by assessing the ability of an individual (DC) with a congenital absence of upper limbs to judge the laterality of rotated hand or foot drawings. We found that DC was as accurate and fast as control participants in judging the laterality of both hand and foot drawings, without any disadvantage for hands when compared to feet. Furthermore, DC’s response latencies for hand drawings were influenced by the biomechanical constraints of hand movements in the same way as control participants’ response latencies. These results suggest that the effect of biomechanical constraints in the hand laterality judgment task is not strictly dependent on “motor imagery” and can arise from the visual processing of body parts being sensitive to such constraints.

The sensory-motor theory of conceptual representations assumes that motor knowledge of how an artifact is manipulated is constitutive of its conceptual representation. Accordingly, if we assume that the richer the conceptual representation of an object is, the easier that object is identified, manipulable artifacts that are associated with motor knowledge should be identified more accurately and/or faster than manipulable artifacts that are not (everything else being equal). In this study, we tested this prediction by investigating the identification of manipulable artifacts in an individual, DC, who was totally deprived of hand motor experience due to upper limb aplasia. This condition prevents him from interacting with most manipulable artifacts, for which he thus has no motor knowledge at all. However, he had motor knowledge for some of them, which he routinely uses with his feet. We contrasted DC’s performance in a timed picture naming task for manipulable artifacts for which he had motor knowledge versus those for which he had no motor knowledge. No detectable advantage on DC’s naming performance was found for artifacts for which he had motor knowledge compared to those for which he did not.  This finding suggests that motor knowledge is not part of the concepts of manipulable artifacts.