Neuroscience 2004 Abstract
| Presentation Number: | 857.10 |
|---|---|
| Abstract Title: | Effects of a representational border on the synaptic efficacy of horizontal connections in adult rat primary somatosensory cortex (S1). |
| Authors: |
Hickmott, P. W.*1
1Dept Psych, UC Riverside, Riverside, CA |
| Primary Theme and Topics |
Sensory Systems - Tactile/Somatosensory -- Barrels |
| Session: |
857. Barrels I Poster |
| Presentation Time: | Wednesday, October 27, 2004 9:00 AM-10:00 AM |
| Location: | San Diego Convention Center - Hall A-H, Board # Q5 |
| Keywords: | barrel cortex, cortical plasticity, minimal stimulation |
In rat S1, stimulation of connections that stay within a representation (NCB) yields responses that are larger than stimulation of those that cross into an adjacent representation (CB; Hickmott & Merzenich, 1997). Such differences may reflect the fact that there are fewer axons that cross a representational border than project within a representation (Mason et al, SFN Abstr. 2002). In this abstract we investigated whether the synaptic efficacies of NCB connections are larger than those of CB connections.
The border between the forepaw and lower jaw representations was mapped in adult rats (>P90) using in vivo recording and marked with DiI. Coronal slices were taken from the marked region and maintained in vitro. Whole-cell recordings were obtained from layer 2/3 neurons close to the border. Horizontal connections within layer 2/3 were electrically stimulated; stimuli were either at a site that was across the border from the neuron (CB) or at an equivalent site within the representation (NCB). The synaptic efficacies of these 2 populations of connections were determined in 2 ways: 1) CB and NCB connections were stimulated minimally to activate synapses of a single axon; EPSP amplitudes from such stimuli reflect the synaptic efficacy of the axon; 2) CB and NCB connections were stimulated with short (15 pulses) trains of stimuli ranging from 5 to 40 Hz. Based on the model of Tsodyks and Markram (1997) modified by Finnerty et al (1999), synaptic efficacies were determined based on the steady-state amplitude and falling kinetics of the trains. The minimal EPSP amplitudes (n=3) were .38±.064 mV for CB and .51±.061 mV for NCB, while the efficacies calculated from the train stimuli (n=3) were .14±.073 for CB and .26±.1 for NCB. These data indicate that the mean synaptic efficacy of CB connections was smaller than that of NCB connections. Thus, the presence of a representational border affects synaptic efficacy
Supported by NINDS NS42241.
The border between the forepaw and lower jaw representations was mapped in adult rats (>P90) using in vivo recording and marked with DiI. Coronal slices were taken from the marked region and maintained in vitro. Whole-cell recordings were obtained from layer 2/3 neurons close to the border. Horizontal connections within layer 2/3 were electrically stimulated; stimuli were either at a site that was across the border from the neuron (CB) or at an equivalent site within the representation (NCB). The synaptic efficacies of these 2 populations of connections were determined in 2 ways: 1) CB and NCB connections were stimulated minimally to activate synapses of a single axon; EPSP amplitudes from such stimuli reflect the synaptic efficacy of the axon; 2) CB and NCB connections were stimulated with short (15 pulses) trains of stimuli ranging from 5 to 40 Hz. Based on the model of Tsodyks and Markram (1997) modified by Finnerty et al (1999), synaptic efficacies were determined based on the steady-state amplitude and falling kinetics of the trains. The minimal EPSP amplitudes (n=3) were .38±.064 mV for CB and .51±.061 mV for NCB, while the efficacies calculated from the train stimuli (n=3) were .14±.073 for CB and .26±.1 for NCB. These data indicate that the mean synaptic efficacy of CB connections was smaller than that of NCB connections. Thus, the presence of a representational border affects synaptic efficacy
Supported by NINDS NS42241.
Sample Citation:
[Authors]. [Abstract Title]. Program No. XXX.XX. 2004 Neuroscience Meeting Planner. San Diego, CA: Society for Neuroscience, 2004. Online.
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