Maria Salerno

The role of the claustrum in the bilateral control of frontal oculomotor neurons in the cat.

SummaryThe effect of claustrum (CL) stimulation on the spontaneous unitary activity of ipsi and contralateral frontal oculomotor neurons, was studied in chloralose-anaesthetized cats. A total of 205 units was bilaterally recorded in the medial oculomotor area, homologous of the primate “frontal eye fields” 127 neurons were identified as projecting to the superior colliculus; for 33 of these last units stimulation of the ipsilateral CL provoked an excitatory effect lasting 10–25 ms and appearing with a latency of 5–15 ms; on 8 units the excitatory effect was followed by an inhibition lasting 100–250 ms. Ninety-eight of the 127 neurons were also tested through activation of the contralateral CL: 13 cells showed an excitatory effect lasting 10–35 ms and appearing with a latency of 20–50 ms. In three of the thirteen units the excitatory effect was followed by an inhibition lasting 100–150 ms. Complete section of the corpus callosum abolished the contralateral CL effect, suggesting the existence of a direct claustro-contralateral oculomotor cortex pathway running through the corpus callosum. The results could support the hypothesis that the CL may play a role in the bilateral control of the visuomotor performance.

Direct stiffness matrices of BEs in the Galerkin BEM formulation

Abstract In the analysis of an elastic two-dimensional solid body by means of the Symmetric Galerkin Boundary Element Method (SGBEM), difficulties arise in the computation of some terms of the solving system coefficients. In fact these coefficients are expressed as double integrals with singularities of order 1/ r 2 , r being the distance between the field and source points. In order to compute these coefficients a strategy based on Schwartzs distribution theory is employed. In this paper the direct stiffness matrix related to the generic node of the free boundary are computed in closed form.

Functional relationship between claustrum and pyramidal tract neurons, in the cat

Electrophysiological relationships between the claustrum and the motor cortex were studied in cats preliminarily anesthetized with ketamine and then with chloralose. Single shock electrical activation of the claustrum induced a decrease of the spontaneous unitary activity of the pyramidal tract neurons (PTNs) both in area 4 and in area 6. Eighty percent of the total number of PTNs was inhibited whereas the remaining 20% was unaffected. The inhibitory effect lasted about 200 msec and appeared about 19 msec after claustrum activation. The results show a functional linkage between the claustrum and the efferent cells of the motor cortex. This relationship suggests the hypothesis that the claustrum, a multisensory structure, may be involved in motor activity integration.

Effects of claustrum stimulation on spontaneous bioelectrical activity of motor cortex neurons in the cat

Electrophysiologic interactions between claustrum and motor cortex neurons were investigated in the cat. A total of 136 neurons was recorded from the motor cortex in area 4 (90 cells) and in area 6 (46 cells). Ninety-eight of the total neurons were identified as pyramidal tract neurons (PTNs). Stimulation of the claustrum by single shocks or by trains of stimuli imposed on the tested PTNs a pure long-lasting inhibition, or a long-lasting inhibition preceded by a short early activation, or no effect. No functional localization of the effects of claustrum activation were found within the motor areas. The observed results are consistent with the hypothesis that the claustrum may play a role in movement organization.

Claustral influence on ipsi- and contralateral motor cortical areas, in the cat

The electrophysiological relationships between the claustrum and the contralateral motor areas of the cerebral cortex were studied in anaesthetized cats. The extracellular unitary activity of 207 pyramidal tract neurons (PTNs) was recorded from area 4 (125 cells) and area 6 (82 cells). Single shock activation of the contralateral claustrum affected 26% of the total tested PTNs, causing long lasting inhibition (44 PTNs) or long lasting inhibition preceded by early excitation (10 PTNs). Forty-three neurons of the 54 were also influenced by ipsilateral claustrum stimulation. Surgical removal of motor and insular cortices ipsilateral to the stimulated claustrum did not modify claustrum inhibition on contralateral PTNs, whereas section of the corpus callosum abolished this effect, suggesting the existence of a direct claustro-contralateral motor cortex pathway passing through the corpus callosum. These results support the hypothesis that the claustrum may exert a bilateral control on motor coordination.

Effect of claustrum activation on the spontaneous unitary activity of frontal eye field neurons in the cat

The influence of claustrum stimulation on spontaneous unitary activity of the ipsilateral frontal oculomotor area was analyzed in anesthetized cats. Sixty-five neurons were isolated, 37 of which (57%) were identified as projecting to the superior colliculus; on 12 of these last units (32%), electrical activation of the dorsal claustrum provoked an excitatory effect, which appeared after a latency of 5-15 ms and lasted 10-25 ms. These data could suggest the involvement of the claustrum in the visuomotor coordination function.

Electrophysiological relationship between claustrum and contralateral area 4 and 6 pyramidal tract neurons

The connections between the claustrum and the contralateral motor areas were electrophysiologically investigated in cats under chloralose anesthesia. The extracellular unitary activity of 81 pyramidal tract neurons (PTNs) was recorded; 22 PTNs were inhibited by activation of the contralateral claustrum; inhibition was preceded by an early activation of 4 out of the 22 inhibited PTNs. Section of the corpus callosum abolished the contralateral claustrum effect, while the action of the ipsilateral homologous structure persisted.

Effect of claustrum stimulation on neurons of the contralateral medial oculomotor area, in the cat

In chloralose-anaesthetized cats, the extracellular spontaneous unitary activity was recorded from 157 neurons, located in the medial oculomotor area. 98 units were identified as projecting onto the superior colliculus. Electrical stimulations of the contralateral claustrum provoked, on 13 of these cells, an excitatory effect, lasting 10-35 ms and appearing with a latency of 20-50 ms. Full length section of the corpus callosum totally abolished the contralateral claustrum effect. The results suggest that in the cat, the claustrum may have a role in the bilateral control of the visuo-motor performance.