Résumé
Peripheral nerve injury of a limb usually causes functional reorganization of the contralateral somatosensory cortex.However, the patients with an operation of the contralateral seventh cervical nerve (C7) transfer to an injured arm with brachial plexus root avulsions usually have the sole tactile sensibility of the healthy hand when the injured hand is touched at the early stage after the operation. Then, at later stage they gradually get normal sense from the injured and the normal hands independently. Mimicked the process in a rat model based on the above operation, representations of the injured forepaw and the healthy forepaw in the somatosensory cortex were studied by means of somatosensory evoked potential (SEP) recording. Somatosensory function shown in SEP response amplitude and peak latency of the injured forepaw gradually recovered with time after the operation due to the contralateral C7 regeneration toward the injured limb, accompanied with the recovery process of limb movement. The somatosensory representation of the injured forepaw was observed exclusively in the ipsilateral somatosensory cortex since the 5th month after the operation. Accordingly, the overlapped representation of the injured and healthy forepaws emerged in the ipsilateral somatosensory cortex of 13 rats studied except one with separated representation though the SEP latency and response amplitude were different in responding to stimuli on the two forepaws. It is concluded that the contralateral peripheral nerve transfer to the injured arm can cause dynamically functional reorganization in the ipsilateral somatosensory cortex suggesting a remarkable plasticity of the brain function induced by an alteration of sensory input between two sides of the body in adult rats.
Résumé
Peripheral nerve injury of a limb usually causes functional reorganization of the contralateral somatosensory cortex.However, the patients with an operation of the contralateral seventh cervical nerve (C7) transfer to an injured arm with brachial plexusroot avulsions usually have the sole tactile sensibility of the healthy hand when the injured hand is touched at the early stage after theoperation. Then, at later stage they gradually get normal sense from the injured and the normal hands independently. Mimicked theprocess in a rat model based on the above operation, representations of the injured forepaw and the healthy forepaw in thesomatosensory cortex were studied by means of somatosensory evoked potential (SEP) recording. Somatosensory function shown inSEP response amplitude and peak latency of the injured forepaw gradually recovered with time after the operation due to thecontralateral C7 regeneration toward the injured limb, accompanied with the recovery process of limb movement. The somatosensoryrepresentation of the injured forepaw was observed exclusively in the ipsilateral somatosensory cortex since the 5th month after theoperation. Accordingly, the overlapped representation of the injured and healthy forepaws emerged in the ipsilateral somatosensorycortex of 13 rats studied except one with separated representation though the SEP latency and response amplitude were different inresponding to stimuli on the two forepaws. It is concluded that the contralateral peripheral nerve transfer to the injured arm can causedynamically functional reorganization in the ipsilateral somatosensory cortex suggesting a remarkable plasticity of the brain functioninduced by an alteration of sensory input between two sides of the body in adult rats.
Résumé
Golgi and Golgi-Cox methods were used to stain the neurones in the II, III layers of 17, 18 areas, lateral suprasylvian area (LS area) of visual cortex and of dorsal lateral geniculate nucleus (LGNd). 298 cells in the II, III layers of 17, 18 areas, 310 cells in the II, III layers of LS area and 168 cells in LGNd were plotted with microscope and camera lucida. Bias was introduced to analyze the properties of dendritic fields of these cells quantitatively. Our results indicated that most of the cells in three areas had elongated and oriented dendritic fields. The proportion of the cells with dendritic fields parallel to the surface of 17, 18 areas was significantly higherthan that of LS area. In LGNd the orientation of dendritic fields of most adjacent cells was similar and the biases of class 3 cells were significantly higher than that of class 1.