The overall goal of this procedure is to propose an effective low cost custom made sensory stimulatory device for fast point like stimulations. This is accomplished by first setting the stimulation device. The second step is to prepare the animal for the electrophysiological recordings by opening a bone window over the primary somatosensory area to allow the positioning of the multi electrode matrix.
The third step of the procedure is to place the stimulation device onto previously identified responsive paw regions. The final step is to find the best spontaneously generated and stimulated LFP and spiking responses. Ultimately, spiking and LFP responses will be evaluated by ad hoc algorithms.
The main advantage of our technique over the existing ones, such as bioelectric stimulators, is that our device is able to produce very fast and point like stimulations over the interested areas. This method can help to answer key question in neurophysiology, such as the fundamental question for the transition from local fin potentials to spikes and vice versa. Demonstrating the animal preparation for the stimulation of the pole will be saini, A PhD student in my lab demonstrating the technical building of the device will be Dr.Antonio Zippo with an assistant of mine in my lab.
In this procedure program, a microcontroller to deliver two paired pulses of current each second, arrange the microcontroller, the breadboard, the mid-range speaker, the driver, and the glue on a table. Next mount a blunt tip, cactus stock orthogonally to the surface of a mid-range speaker. Assemble the speaker and the microcontroller by means of an L 293 DH bridge with basic passive components.
Then connect the microcontroller to a 12 volt rechargeable battery for the stereotaxic surgery. After anesthetizing the rat by IP injection with barbiturate solution mounted on a stereotaxic apparatus, fix its head with the ear bars and mouthpiece. Then maintain the temperature of the stereotaxic pad at 37.5 degrees Celsius by an electronically controlled heating pad.
Afterward, clean the cranial vault carefully with the povidone iodine. Topical antiseptic cut along the midline from the basis of the snout to the occipital bone, and fix the skin by a retractor and two small cocker forceps. Now identify the periosteum and scratch it off the bone vault with a fine tip.
Pen mark bgma at the cross point of the medial sagittal and coronal sutures. Then under the surgical microscope, identify the somatosensory hind limb domain, overlaying the somatosensory cortex, which is contralateral to the posterior paw used in the experiment. Use a fine tip pen to draw a square to deli the hole to be drilled.
Then drill a nine squared millimeter hole on the previously marked square. To remove the bone tile and carefully remove the dura mater. Cover the cortical surface with a surgical sponge soaked in artificial cerebral spinal fluid at 37.5 degrees Celsius.
Next, fix the electrode matrix to a holder connected to an electronic micro manipulator. Connect the head of the matrix to the pre amplifier by a micro connector. Re under the surgical microscope, lower the electrode matrix to the cortical surface manually without touching it.
Then turn on the audio amplifiers and continue to lower the electrode matrix until it touches the cortical surface, which will be indicated by a clear noise. Subsequently lower the electrode matrix by electronically controlled steps at two micron per step until the cortical layer four at a depth of 350 to 400 microns is reached. Then check the responsiveness of neurons by light touches on the contralateral posterior paw.
Adjust the depth by a few further steps until a clear spiking response is observed. Set the software band pass filter to 1.0 to 6, 000 hertz and the sampling rate to 32 kilohertz and start the neuronal signal recording. After five minutes of recording, end the experiment and export the recorded data in binary format for post-processing.
Perform the spike sorting procedure by wave underscore plus toolbox. In this procedure, glue the dorsal aspect of the hind paw to a solid frame, exposing the LAR surface and avoiding articular torsions. Afterward, place the tip of the stimulation device onto the desired limb P paw position switch on the stimulation device.
Following this procedure, the researchers can study the information processing in both low and fast somato and stimuli. After the development of this device, researchers and clinicians will be able to analyze and understand the difference and the neural computation and in signal elaboration of light touch simul, both in normal subjects and in.
