Switching of the transmitters that mediate hindbrain correlated activity in the chick embryo.

Widely propagating correlated neuronal activity is a hallmark of the developing nervous system. The activity is usually mediated by multiple transmitters, and the contribution of gap junctions has also been suggested in several systems. In some structures, such as the retina and spinal cord, it has been shown that the dominant transmitter mediating the correlated wave switches from acetylcholine to glutamate during development, although the functional significance of this phenomenon has not been clarified.

Origin of the earliest correlated neuronal activity in the chick embryo revealed by optical imaging with voltage-sensitive dyes.

Spontaneous correlated neuronal activity during early development spreads like a wave by recruiting a large number of neurons, and is considered to play a fundamental role in neural development. One important and as yet unresolved question is where the activity originates, especially at the earliest stage of wave expression. In other words, which part of the brain differentiates first as a source of the correlated activity, and how does it change as development proceeds? We assessed this issue by examining the spatiotemporal patterns of the depolarization wave, the optically identified primordial correlated activity, using the optical imaging technique with voltage-sensitive dyes.

Differential involvement of projection neurons during emergence of spontaneous activity in the developing avian hindbrain.

To better characterize the emergence of spontaneous neuronal activity in the developing hindbrain, spontaneous activity was recorded optically from defined projection neuron populations in isolated preparations of the brain stem of the chicken embryo. Ipsilaterally projecting reticulospinal (RS) neurons and several groups of vestibuloocular (VO) neurons were labeled retrogradely with Calcium Green-1 dextran amine and spontaneous calcium transients were recorded using a charge-coupled-device camera mounted on a fluorescence microscope. Simultaneous extracellular recordings were made from one of the trigeminal motor nerves (nV) to register the occurrence of spontaneous synchronous bursts of activity.

Development of projection-specific interneurons and projection neurons in the embryonic mouse and rat spinal cord.

Interneurons and projection neurons in the lumbar spinal cord of mouse and rat embryos were labeled retrogradely with fluorescent dextran amines from a distance of one segment from the segment of origin [lumbar segment (L) 2]. Six classes with specific axonal projections (ipsilateral ascending, descending, and bifurcating, and commissural ascending, descending, and bifurcating) were identified by differential labeling in both species and followed from embryonic day (E)12 to birth in the mouse. Neurons with shorter projections (intrasegmental interneurons) were not studied.

Optical analysis of depolarization waves in the embryonic brain: a dual network of gap junctions and chemical synapses.

Correlated neuronal activity plays a fundamental role in the development of the CNS. Using a multiple-site optical recording technique with a voltage-sensitive dye, we previously described a novel type of depolarization wave that was evoked by cranial or spinal nerve stimulation and spread widely over the whole brain region in the chick embryo. We have now investigated developmental expression and neuronal network mechanisms of this depolarization wave by applying direct stimulation to the brain stem or upper cervical cord of E5-E11 embryos, which elicited wave activity similar to that evoked by nerve stimulation.

Optical imaging of intrinsic signals induced by peripheral nerve stimulation in the in vivo rat spinal cord.

We examined neural response patterns evoked by peripheral nerve stimulation in in vivo rat spinal cords using an intrinsic optical imaging technique to monitor neural activity. Adult rats were anesthetized by urethane, and laminectomy was performed between C5 and Th1 to expose the dorsal surface of the cervical spinal cord. The median, ulnar, and radial nerves were dissected, and bipolar electrodes were implanted in the forelimb.

Developmental organization of the glossopharyngeal nucleus in the embryonic chick brainstem slice as revealed by optical sectioning recording.

We traced developmental changes in the ventro-dorsal distribution pattern of glossopharyngeal nerve (N. IX) responses by applying an optical sectioning method to thick slice preparations dissected from E4 to E8 chick embryos. We identified the motor and sensory nuclei related to the glossopharyngeal nerve in the rostral and caudal focal planes, respectively.

Optical approaches to functional organization of glossopharyngeal and vagal motor nuclei in the embryonic chick hindbrain.

We investigated the functional organization of the glossopharyngeal and vagal motor nuclei during embryogenesis using multiple-site optical recording with a fast voltage-sensitive dye. Intact brain stem preparations with glossopharyngeal and vagus nerves were dissected from 4- to 8-day-old chick embryos. Electrical responses evoked by glossopharyngeal/vagus nerve stimulation were optically recorded from many loci of the stained preparations.

Intraoperative intrinsic optical imaging of neuronal activity from subdivisions of the human primary somatosensory cortex.

We performed intrinsic optical imaging of neuronal activity induced by peripheral stimulation from the human primary somatosensory cortex during brain tumor surgery for 11 patients. After craniotomy and dura reflection, the cortical surface was illuminated with a xenon light through an operating microscope. The reflected light passed through a bandpass filter, and we acquired functional images using an intrinsic optical imaging system.