Adaptation in thalamic barreloid and cortical barrel neurons to periodic whisker deflections varying in frequency and velocity
Adaptation in thalamic barreloid and cortical barrel neurons to periodic whisker deflections varying in frequency and velocity
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DOI：
10.1152/jn.00257.2004
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发表时间：
2004-12-01
影响因子：
2.5
通讯作者：
Simons, DJ
中科院分区：
文献类型：
--
作者：
Khatri, V;Hartings, JA;Simons, DJ
啮齿动物须-桶通路中的第IV层电路在空间和时间上转换丘脑输入信号。兴奋性和抑制性桶神经元显示反应特性，彼此不同，从他们共同的丘脑输入。在这里，我们进一步研究丘脑皮质反应的转换，通过表征个别丘脑barreloid神经元和假定的兴奋性和抑制性皮质桶神经元的周期性晶须偏转频率从1到40 Hz的变化。固定偏转幅度的脉动和正弦周期性刺激用于评估丘脑皮层单位（TCU）、快峰桶单位（FSU：假定抑制性神经元）和规则峰桶单位（RSU：假定兴奋性神经元）的刺激诱发适应。在丘脑和皮层神经元中观察到高（脉动）和低（正弦）速度偏转列车中的第二次和后续刺激的单调，频率依赖性减少。RSU和FSU的适应能力大大超过了丘脑输入神经元，在所有频率下，FSU的发射率都高于其他两种细胞类型。例如，在40 Hz时，TCU的响应幅度降低了34%，FSU降低了72%，RSU降低了78%。在不同频率下，RSU和FSU对于（高速）脉动性比（低速）正弦偏转显示出更多的逐周期夹带和锁相响应;对于TCU，两种刺激的锁相等效，但夹带更高对于正弦偏转。强烈的前馈抑制，与突触抑制，使发射的桶神经元稀疏，但暂时忠实于重复的晶须偏转的发生，特别是当他们是高速的。
Layer IV circuitry in the rodent whisker-to-barrel pathway transforms the thalamic input signal spatially and temporally. Excitatory and inhibitory barrel neurons display response properties that differ from each other and from their common thalamic inputs. Here we further examine thalamocortical response transformations by characterizing the responses of individual thalamic barreloid neurons and presumed excitatory and inhibitory cortical barrel neurons to periodic whisker deflections varying in frequency from 1 to 40 Hz. Both pulsatile and sinusoidal periodic stimulation of fixed deflection amplitude were used to assess stimulus-evoked adaptation of thalamocortical units (TCUs), fast-spike barrel units (FSUs: presumed inhibitory neurons), and regular-spike barrel units (RSUs: presumed excitatory neurons). Monotonic, frequency-dependent reductions in firing were observed in thalamic and cortical neurons to the second and subsequent stimuli in trains of high (pulsatile)- and low (sinusoidal)-velocity deflections. RSUs and FSUs adapted substantially more than their thalamic input neurons, and at all frequencies, FSUs fired at higher rates than the other two cell types. For example at 40 Hz, response magnitudes of TCUs decreased by 34%, FSUs by 72%, and RSUs by 78%. Across frequencies, RSUs and FSUs displayed more cycle-by-cycle entrainment and phase-locked responses for (high velocity) pulsatile than (lower velocity) sinusoidal deflections; for TCUs, phase-locking was equivalent for both stimuli, but entrainment was higher for sinusoidal deflections. Strong feed-forward inhibition, in conjunction with synaptic depression, renders the firing of barrel neurons sparse but temporally faithful to the occurrence of repetitive whisker deflections, especially when they are of high velocity.