From connelly.bill from gmail.com Wed Jul 1 18:46:28 2009 From: connelly.bill from gmail.com (Bill.Connelly) Date: Wed Jul 1 22:47:12 2009 Subject: [Neuroscience] Re: Fiber Volley/Stimulation artifact References: Message-ID: <7814bae1-1bdf-40ad-b7f5-f28be4f544d8@l34g2000vbi.googlegroups.com> Hi B, I just came back from your lovely UCSD campus, I hope it's not being overrun by summer students. It would be a lot easier to make a decisive comment on this if I could see a waveform. My first suggestion is to move from recording fEPSPs to looking at population spikes. Because the reflected EPSP goes in the other direction to to fiber volley, you should have to trouble telling it from the any other parts of the waveform. You stimulus artifact shouldn't be invading your fiber spike. If it is, I would look at the placement of the electrodes, the stimulating electrode or the stimulus isolator. If your electrodes are very close together, then the conduction lag wont be enough to seperate the fibre spike from the stimulus artifact. Furthermore, you are more likely to get capacitive coupling between the electrodes. Hopefully, you're stimulus artifact is mainly monopolar, i.e. it just goes up the page, or down the page, but not both. You should be able to flip the polarity of your stimulus, which should help seperate it from the fiber spike. What kind of stimulating electrode are you using? Monopolar, bipolar, two big fat wires? Theta glass? In my experience, you get the smallest artifact (amp for amp) from a monopolar glass pipette electrode, with the ground somwhere away from your recording site. But of course the resistance is going to go up relative to a wire electrode, so you might not be able to deliver enough current to do the business. The worst artifact I ever saw was when a guy connected the earth from his stimulator to the earth for his recording (exponentially decaying wave with a time constant of 20ms). You need to make sure you're stimulus isolator is still working, and that you're not laying the cable that caries your stimulus pulse over the cables that carry signal. But these are all just general ideas. How broad is your stimulus artifact, and how broad is your stimulus waveform (i.e. whats coming out of the box)? However, you need to remember, fibre spikes are often vaguely hard to see in fEPSPs, and usually invisible if you're above room temperature. If you want them nice and clear, you're going to have to block glutamatergic synaptic traffic (do a google images search for fEPSP if you don't believe me). Hope I've been some help. On Jul 1, 4:29?pm, bmidt...@ucsd.edu wrote: > Hi, > > I am new to the electrophysiology world and am performing ?hippocampal > field recordings on acute slices. ?I am currently getting a nice field > response, however, many times I barely see a fiber volley, (if at all) > which will sometimes decrease as I increase stimulation. ?Additionally, > because they (the fiber volleys) are so small, any tiny variation > radically ?changes the ?input/output slopes. ?My feeling is that this is > due to the large stimulation artifact. ?Does anybody have any ideas on > what may be causing this and how to fix it? > > Thanks, > B~ From connelly.bill from gmail.com Wed Jul 1 22:44:31 2009 From: connelly.bill from gmail.com (Bill) Date: Wed Jul 1 22:47:16 2009 Subject: [Neuroscience] The relationship between gap junction conductance and coupling coefficient? Message-ID: <1ee2be1f-ee60-41f1-8ed0-a2f5897b9290@x5g2000yqk.googlegroups.com> Does anyone know the relationship between gap junction conductance and coupling coefficient? Coupling coefficient is the ratio of the voltage change in cell2 over the voltage change in cell1, when current is injected into cell1. I can see the circuit: Two resistors to ground (Rm of cell 1 and 2), linked by the resistance of the gap junction. I can see that as the resistance of the gap junction drops to 0, the coupling coefficient goes to 1 (Assuming the membrane resistance of the two cells is (close) equal, which is a fiar assumption). I can also see, the coupling coefficient goes to 0 when there is no coupling between the cells. But is it possible to convert the coupling coefficent to a gap junction conductance? From herwin from btinternet.com.invalid Thu Jul 2 01:26:40 2009 From: herwin from btinternet.com.invalid (herwin@btinternet.com.invalid) Date: Thu Jul 2 11:04:11 2009 Subject: [Neuroscience] MiCRAM Website Message-ID: The MiCRAM website has been rehosted at . This site documents the auditory research that Adrian Rees and Harry Erwin are performing collaboratively using EPSRC funding (starting 1 July 2006) as a interdisciplinary project between the University of Newcastle upon Tyne School of Neurology, Neurobiology and Psychiatry and the University of Sunderland School of Computing. The overall goal is to study sound processing in the mammalian brain and to build a computational model which can be tested on a biomimetic robot artefact to refine the neuroscience models. The robotic work is being led by Professor Stefan Wermter at the University of Sunderland. This research involves the collaborative development of a biologically plausible model of auditory processing at the level of the inferior colliculus. This approach potentially clarifies the roles of the multiple spectral and temporal representations that are present at the level of the inferior colliculus and investigate how representations of sounds interact with auditory processing at that level to focus attention and select sound sources for deeper analysis. A key feature of our approach is to maximise the use of existing data from our own and other laboratories. The inferior colliculus has been extensively studied in many species including several non-specialised mammals and echolocating bats. Much of this vast body of data exists in isolation and has not been formally synthesised. This is a severe hindrance, both to our understanding of the colliculus, and our ability to incorporate it into neural models. The goal of building a model with specific outcomes and measurable performance will provide a formal framework to underpin the data synthesis we propose. Our approach of mining existing data will also contribute to Government's objective in the 3Rs (Replacement, Refinement and Reduction) of reducing the number of animals used in experiments. Dr. Reesís knowledge of the inferior colliculus and extensive connections with other researchers in the field will be key to this approach. Where specific information required for the model is not available we will have the capability to address these questions experimentally. The model will in turn have predictive power that will also guide future experiments in the quest for emergent features. From r_s_norman from comcast.net Thu Jul 2 06:20:41 2009 From: r_s_norman from comcast.net (r norman) Date: Thu Jul 2 11:04:15 2009 Subject: [Neuroscience] Re: The relationship between gap junction conductance and coupling coefficient? References: <1ee2be1f-ee60-41f1-8ed0-a2f5897b9290@x5g2000yqk.googlegroups.com> Message-ID: <4t5p45d6c1vdgji4ek7oqdb9oq9nka300m@4ax.com> On Wed, 1 Jul 2009 20:44:31 -0700 (PDT), Bill wrote: >Does anyone know the relationship between gap junction conductance and >coupling coefficient? > >Coupling coefficient is the ratio of the voltage change in cell2 over >the voltage change in cell1, when current is injected into cell1. > >I can see the circuit: Two resistors to ground (Rm of cell 1 and 2), >linked by the resistance of the gap junction. I can see that as the >resistance of the gap junction drops to 0, the coupling coefficient >goes to 1 (Assuming the membrane resistance of the two cells is >(close) equal, which is a fiar assumption). I can also see, the >coupling coefficient goes to 0 when there is no coupling between the >cells. > >But is it possible to convert the coupling coefficent to a gap >junction conductance? The coupling coefficient is simply Rm2/(Rg + Rm2), the membrane resistance of cells 2 divided by the total of the gap resistance and the membrane resistance. If you know Rm2 you can do what you ask since the junction conductance is simply 1/Rg. If you don't know it, you can't. From connelly.bill from gmail.com Thu Jul 2 21:47:14 2009 From: connelly.bill from gmail.com (Bill.Connelly) Date: Thu Jul 2 22:53:41 2009 Subject: [Neuroscience] Re: The relationship between gap junction conductance and coupling coefficient? References: <1ee2be1f-ee60-41f1-8ed0-a2f5897b9290@x5g2000yqk.googlegroups.com> <4t5p45d6c1vdgji4ek7oqdb9oq9nka300m@4ax.com> Message-ID: <791f70e6-3422-4aca-aa9f-e47fc0cec3a9@k13g2000prh.googlegroups.com> I knew it would be something simple like that. Thank you very much, it fits perfectly with what I have measured. On Jul 2, 11:20?pm, r norman wrote: > On Wed, 1 Jul 2009 20:44:31 -0700 (PDT), Bill > > > > wrote: > >Does anyone know the relationship between gap junction conductance and > >coupling coefficient? > > >Coupling coefficient is the ratio of the voltage change in cell2 over > >the voltage change in cell1, when current is injected into cell1. > > >I can see the circuit: Two resistors to ground (Rm of cell 1 and 2), > >linked by the resistance of the gap junction. I can see that as the > >resistance of the gap junction drops to 0, the coupling coefficient > >goes to 1 (Assuming the membrane resistance of the two cells is > >(close) equal, which is a fiar assumption). I can also see, the > >coupling coefficient goes to 0 when there is no coupling between the > >cells. > > >But is it possible to convert the coupling coefficent to a gap > >junction conductance? > > The coupling coefficient is simply Rm2/(Rg + Rm2), the membrane > resistance ?of cells 2 divided by the total of the gap resistance and > the membrane resistance. ?If you know Rm2 you can do what you ask > since the junction conductance is simply 1/Rg. ?If you don't know it, > you can't. From r_s_norman from comcast.net Sat Jul 18 07:13:11 2009 From: r_s_norman from comcast.net (r norman) Date: Sat Jul 18 13:31:36 2009 Subject: [Neuroscience] Re: Are the dorsal roots parts of the somatic nervous system? References: <74467c1d-99d8-49ab-9d8b-63d6e8265d0f@d9g2000prh.googlegroups.com> Message-ID: <14e365h6ar5mpo3jq99nbhjtprudc7ude0@4ax.com> On Fri, 17 Jul 2009 20:57:44 -0700 (PDT), GreenXenon wrote: >Hi: > >Are the dorsal roots parts of the somatic nervous system? The distinction between somatic and autonomic is primarily a functional one. Do you say that the spinal cord is part of the somatic nervous system? Both somatic and autonomic use the spinal cord and both somatic and autonomic use the dorsal roots. So the dorsal roots are sensory, both somatic and autonomic. However the sensory side of the autonomic system at the spinal level is often ignored in elementary treatments, leaving the impression that the dorsal roots are somatic. From r_s_norman from comcast.net Sat Jul 18 10:32:21 2009 From: r_s_norman from comcast.net (r norman) Date: Sat Jul 18 13:31:41 2009 Subject: [Neuroscience] Re: Are the dorsal roots parts of the somatic nervous system? References: <74467c1d-99d8-49ab-9d8b-63d6e8265d0f@d9g2000prh.googlegroups.com> <14e365h6ar5mpo3jq99nbhjtprudc7ude0@4ax.com> <6fa64c41-fbcb-44c1-be9b-3794563bbc31@g1g2000pra.googlegroups.com> Message-ID: On Sat, 18 Jul 2009 08:05:58 -0700 (PDT), GreenXenon wrote: >On Jul 18, 5:13 am, r norman wrote: > > >> On Fri, 17 Jul 2009 20:57:44 -0700 (PDT), GreenXenon >> >> wrote: > > >> >Hi: >> >> >Are the dorsal roots parts of the somatic nervous system? >> > > >> The distinction between somatic and autonomic is primarily a >> functional one. Do you say that the spinal cord is part of the >> somatic nervous system? > > >The spinal cord is part of the central nervous system. The somatic >nervous system is a division of the peripheral nervous system. So >*no*, the spinal cord is *not* part of the somatic nervous system. >However, the dorsal roots are part of the peripheral nervous system, >so I was wondering if they are also part of the somatic division of >the peripheral nervous system. > > >> Both somatic and autonomic use the spinal >> cord and both somatic and autonomic use the dorsal roots. So the >> dorsal roots are sensory, both somatic and autonomic. However the >> sensory side of the autonomic system at the spinal level is often >> ignored in elementary treatments, leaving the impression that the >> dorsal roots are somatic. > > >Are there any purely-somatic afferent nerve roots in the human body? I always found that defining "somatic" to be strictly peripheral a rather questionable and arbitrary notion. Does a single sensory neuron entering the dorsal root suddenly become "non-somatic" the instant it plunges into the spinal cord? Does a motor neuron axon suddenly acquire the "somatic" label only as it enters the ventral root? Two microns this way a cell is somatic, two microns the other way the same cell is not. However, to answer your question, the facial and trigeminal cranial nerves are generally considered to be somatic sensory without autonomic sensory function and the special sensory cranial nerves: vision, olfaction, audition and balance, taste might be considered sort of somatic. Of course these are not spinal roots. There are sensory cells in the gut which are considered autonomic and enter the spinal cord through the dorsal roots but I really don't know exactly how they are distributed across each level of the spinal column. It is also difficult to make absolute generalizations about anything in biology or physiology. There are lots of very small nerve fibers all over the place, there are efferent fibers in supposedly purely sensory nerves and there are reports about dorsal root efferents and ventral root afferents. From r_s_norman from comcast.net Sat Jul 18 12:18:53 2009 From: r_s_norman from comcast.net (r norman) Date: Sat Jul 18 13:31:45 2009 Subject: [Neuroscience] Re: Are the dorsal roots parts of the somatic nervous system? References: <74467c1d-99d8-49ab-9d8b-63d6e8265d0f@d9g2000prh.googlegroups.com> <14e365h6ar5mpo3jq99nbhjtprudc7ude0@4ax.com> <6fa64c41-fbcb-44c1-be9b-3794563bbc31@g1g2000pra.googlegroups.com> <1b9404b5-5783-49ee-b90a-4f659e510587@l35g2000pra.googlegroups.com> Message-ID: On Sat, 18 Jul 2009 09:52:08 -0700 (PDT), GreenXenon wrote: >On Jul 18, 8:32 am, r norman wrote: > >> Does a single sensory >> neuron entering the dorsal root suddenly become "non-somatic" the >> instant it plunges into the spinal cord? > > >That's another question I find interesting. Sadly, I don't know. > > >> However, to answer your question, the facial and trigeminal cranial >> nerves are generally considered to be somatic sensory without >> autonomic sensory function and the special sensory cranial nerves: >> vision, olfaction, audition and balance, taste might be considered >> sort of somatic. Of course these are not spinal roots. > > >Sorry. I forgot to specify my question. > >Are there any purely-somatic *tactile* afferent nerve roots in the >human body? > >Tactile = pertaining to sensory phenomenon other than vision, smell, >hearing, taste, or balance. IOW, 'tactile' pertains to senses of >touch, tickle, pain, temperature, pressure, itch, movement and pretty >much any physical sensory entity. > >All afferent nerves in the arms, legs, feet, hands, abdomen, chest, >back and neck are "tactile" nerves. In the head and face are both >tactile and non-tactile afferent nerves. > >Another question is, are there any nerve "roots" outside of the head, >face, and spine? The central nervous system consists of the brain and spinal cord so the only connection to the periphery is through the cranial nerves to the brain and the dorsal/ventral roots to the spinal cord. There are more senses than the ones you list. There are chemical sensors detecting a variety of things. There are mechanoreceptors that don't serve "touch" but are part of the proprioceptive system monitoring position of the body, force on the tendons, distension of the gut and other body organs and membranes. Generally sensors connected with digestion, defecation, micturation (urination), and the cardiovascular system are considered autonomic. As I said, these autonomic receptors are scattered around the body and I don't know whether they are restricted to particular spinal roots or are all over the place. From connelly.bill from gmail.com Mon Jul 27 00:58:35 2009 From: connelly.bill from gmail.com (Bill) Date: Mon Jul 27 11:44:45 2009 Subject: [Neuroscience] Warm slicing Message-ID: Hi Guys, I thought I would post the result of a little experiment I tried today. After reading: http://www.precisionary.com/products_faq.html#q9 I tried making some cortical slices (250um thick) in a cutting chamber heated with a 35 degree water bath (in sucrose aCSF) from 20 day old tissue. While the brain was so much more fluid than at 4 degrees, but the cells were wonderfully visible and healthy looking. Just a suggestion that I thought someone might be interested in.