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C Rabb

Publications and source records attributed to C Rabb.

7 recordsLinked to original sources

What determines choice of limb for unimanual reaching movements?

Currently, relatively little is known about what drives the choice of limb for goal-oriented reaching. Traditionally, the explanation has been tied predominately to motor dominance as manifested in handedness. This article offers data and an argument suggesting that handedness can be modified by attentional (spatial) information. Although motor dominance may be the controlling factor in the programming and execution of reaching movements at the midline and hemispace ipsilateral (same side) to the dominant limb, attentional information alters the programming of movements in what would be contralateral space. The general trend of behavior is characterized by reaching on the same side as the stimulus, in ipsilateral fashion, a phenomenon explained by kinesthetic efficiency and hemispheric bias.

Attention↗

Attentional effects on reaching in hemispace.

Previous evidence notes that attentional information in the form of visually guided stimuli can override motor dominance when programming reaching-to-grasp movements in contralateral hemispace. The present experiment verified these effects for 135 university students, using an auditory stimulus, and the pattern of behavior in the two modalities was quite similar.

Adult↗

Attentional stimuli and programming hand selection: a developmental perspective.

This experiment examined the use of attentional stimuli for reaching in hemispace by strong right-dominant adults and children. Driving the hypothesis was the notion that developmental factors associated with use of attentional information may affect the programming of reaching movements in hemispace. Although the general pattern of responses was similar for both samples, children did not use attentional cues to program reaching movements in contralateral hemispace as effectively as adults. This result suggests that motor dominance and perhaps other factors were pivotal in motor programming for children. One possible explanation for the general behavior observed underlies an attentional hemispheric bias for a tendency to use the hand that is on the same side as the stimulus.

Adult↗

A lateralized comparison of handedness and object proximity.

This study was motivated by the emerging hypothesis that right-handers are more strongly lateralized and perform better on various aspects of functional asymmetry than do left-handers. Right- and left-handers were observed for hand selection responses to a unimanual task of reaching for a small cube in positions of right- and left hemispace, prompting hemispheric decision-making related to hand dominance and attentional (visuospatial) stimuli. As predicted, left-handers did not respond with their preferred limb as consistently across positions as did right-handers. Additional inspection of the task suggests that being lateralized may not be a disadvantage in this context, and that environmental influence may play a significant role in hand selection for a particular motor event.

Adult↗

Isolated cerebral mucormycosis: case report and therapeutic considerations.

Cerebral mucormycosis (without associated involvement of and invasion from the nasal sinuses and turbinates) is an extremely rare opportunistic infection of the central nervous system. We report the case of an intravenous drug abuser (who was negative for the human immunodeficiency virus) who presented with hemiparesis on the right side, slurred speech, altered mental status, and an unsteady gait. Imaging studies revealed a large left-side basal ganglia lesion. A stereotactic biopsy obtained a tissue sample that revealed wide, nonseptated hyphal fragments with granulomatous inflammation. The patient was treated with 3 gm of amphotericin B during a 5-month period. The patient had no residual neurological dysfunction after treatment. Open surgical resection was not employed. This case suggests that stereotactic biopsy followed by long-term amphotericin B therapy, in lieu of open surgical resection, represents a viable treatment option for this rare disorder.

Adult↗

Complex technical methodologies and their applications in the surgery of intracranial meningiomas.

As neurosurgery moves into the twenty-first century, improved visualization/localization techniques, neuromonitoring, and advanced instrumentation will become standards of care for all intracranial procedures. This article has focused on current available technologies that can be used to facilitate operations on intracranial meningiomas. Preoperative anatomic localization with MR imaging, CT, MR angiography, and angiography are standard techniques. Preoperative functional assessments with MR imaging, magnetic source imaging, PET, and functional MR imaging are crucial to recognize and preserve eloquent adjacent cortex. Pathologic correlations with preoperative imaging (i.e., MR imaging) may help to predict the histopathology. Perioperative rehearsal of the operation can be performed. Intraoperative anatomic localization is important to minimize the craniotomy, dural opening, and passage through normal neural structures. An impressive array of new technologies are currently available, including real-time ultrasonography, frame-based stereotaxy (CT, MR imaging PET), frameless stereotaxy (acoustic localization, neuronavigators, real-time visualization), robotics, neuroendoscopy, and intraoperative dye administration. Increased understanding of the function and individual variability of the human cortex underscores the importance of intraoperative functional localization by electrocorticography and optical imaging. Continuous intraoperative neuromonitoring of sensory (SSEPs, BAERs, visual evoked potentials) and motor evoked potentials is now standard during many intracranial procedures. Complex adjunctive instrumentation, such as the ultrasonic aspirator and the laser, are part of the contemporary armamentarium for meningioma surgery. As we have stated in a previous article, "Developmental trends imply realization of three major directions of technical neurosurgery: (1) precise preoperative simulation, (2) minimization or avoidance of transcranial operative corridors, [and] (3) increased refinement of technical adjuvants--both physical and molecular." The end point of these technical advances is to improve precision and safety and will enhance the outcome in each surgical procedure so that one day we will be able to operate on patients with intracranial lesions with minimal morbidity.

Brain↗

Imagined and actual limb selection: a test of preference.

Imagined and actual motor performance were compared to determine what factor(s) drive limb selection for programming movements in contralateral hemispace. Forty right-handed blindfolded subjects were asked to 'reach' via auditory stimulus for a small object placed at multiple locations in hemispace. Two conditions were included: arms uncrossed and arms crossed. With the uncrossed condition, responses were similar. With arms crossed, subjects had the choice of keeping the limbs crossed, reacting to proximity, or uncrossing the arms to reach ipsilaterally. In this condition subjects 'imagined' that they would maintain the crossedposition and reach with the hand closest to the stimulus in both right and left hemispace. However, during 'actual' reaching, responses differed. For left-field stimuli, participants kept the arms crossed, but in response to right-field stimuli, subjects preferred to uncross the limbs in order to reach with the dominant hand. These findings suggest that while motor dominance is the primary factor in limb choice for action in ipsilateral hemispace, it appears that object proximity drives limb selection for reaching in contralateral hemispace.

Adult↗