Biomedical subjects
Publications and source records attributed to R M Camarda.
A 33-year-old woman three weeks after a febrile illness presented with a syndrome of ophthalmoplegia, ataxia and areflexia (SOAA) that characterizes clinically both Bickerstaff and Miller Fisher syndromes. The normality of the electrophysiological tests performed, the CSF findings and the magnetic resonance images proved that the syndrome stemmed from brainstem pathology.
The mesial agranular frontal cortex that lies rostral to area 4 (F1) is formed by two distinct cytoarchitectonic areas: F3, located caudally, and F6, located rostrally. In the present experiments we investigated the organization of F3 and F6 by observing the motor responses evoked by their intracortical electrical microstimulation. Our main purpose was to find out whether the cytoarchitectonic subdivision of the mesial agranular frontal cortex into two areas has a physiological counterpart. The result showed that F3 (the caudal area) contains a complete motor representation with hindlimb movements located caudally, forelimb movements located centrally, and orofacial movements located rostrally. The great majority of limb movements involved proximal joints. With respect to F1, F3 showed the following functional characteristics: (1) lack of segregation between proximal and distal movements, (2) larger percentage of complex movements, and (3) higher excitability threshold. Movements were more difficult to elicit from F6 (the rostral area) than from F3. However, by using a longer stimulus train duration (100 ms) 39.3% of tested sites produced body movements. This percentage increased (50.5%) when the electrical stimulation was applied during monkey natural movements instead of when the monkey was still in its chair. Most of the evoked movements concerned the forelimb. More rarely, neck and upper face movements were observed. Unlike F1 and F3 where most movements were fast, slow movements were frequently observed with stimulation of F6. Many of them mimicked natural movements of the animal. Eye movements were evoked from F7 (superior area 6) but not from F6. An additional motor representation was found in the dorsocaudal part of area 24 (24d). This area is topographically organized with a forelimb representation located caudally and ventrally and a hindlimb representation located rostrally and dorsally. The excitability threshold of area 24d is higher than that of F1 and F3. Evoked movements were occasionally observed also after stimulation of area 24c. In conclusion, on the mesial cortical wall rostral to F1, there are at least three independent motor representations. On the basis of somatotopic organization and excitability properties, we propose that the term supplementary motor area (SMA-proper) should be reserved to F3.
Explore the source record for details and available documents.
Single neurons were recorded from the rostral part of the agranular frontal cortex (area 6a beta) in awake, partially restrained macaque monkeys. In the medialmost and mesial sectors of this area, rostral to the supplementary motor area, neurons were found which were activated during arm reaching-grasping movements. These neurons ("reaching-grasping neurons") did not appear to be influenced by how the objects were grasped nor, with some exceptions, by where they were located. Their activity changed largely prior to the arm movement and continued until the end of it. The premovement modulation (excitatory or inhibitory) could start with stimulus presentation, with the saccade triggered by the stimulus or after stimulus fixation. The distance of the stimulus from the monkey was an important variable for activating many neurons. About half of the recorded neurons showed a modulation of the same sign during movement and premovement period. The other half showed an increase/decrease in activity which was of the opposite sign during movement and premovement period or part of it. In this last case the discharge changes were of the same sign when the stimulus was close to the monkey and when the monkey moved its arm to reach the objects, whereas they were of opposite sign when the stimulus was outside the animal's reach. Microstimulation of area 6a beta and the reconstruction of the locations of eye movement and arm movement related cells showed that the arm field was located more medially (and mesially) than the eye field described by Schlag and Schlag-Rey (1987). It is suggested that, unlike inferior area 6, which is mostly involved in selection of effectors on the basis of the physical properties of the objects and their spatial location (Rizzolatti and Gentilucci 1988), area 6a beta plays a role in the preparation of reaching-grasping arm movements and in their release when the appropriate conditions are set.
We observed a patient with the hypereosinophilic syndrome that showed as a prominent clinical feature peripheral nerve dysfunction. The neuropathy evolved over 4 months and affected sensory and motor functions. Nerve conduction studies and EMG were compatible with axonal neuropathy. Nerve and muscle biopsies revealed severe axonal degeneration with neurogenic atrophy of muscle. Morphometry of peroneal nerve showed marked axonal loss, more prominent in large myelinated fibers. There was no evidence of vasculitis process. Neuropathy is produced by eosinophil-released substances exerting a neurotoxic effect through direct altered vascular endothelial permeability and local mast cell histamine release.
Single unit recording has revealed the same orientation sensitive cell classes in cat area 18 as are to be found in area 17. These include particularly the various types of hypercomplex cell belonging to the S, C, and B cell families.
Explore the source record for details and available documents.