Biella G, Panzica F, de Curtis M
Dipartimento di Neurofisiologia, Istituto Nazionale Neurologico, via Celoria 11, 20133 Milano, Italy.
Eur J Neurosci. 1996 Jul;8(7):1350-7. doi: 10.1111/j.1460-9568.1996.tb01597.x.
The interaction between synaptic potentials generated by the activation of separate sets of associative fibres was investigated in the piriform cortex of an in vitro isolated guinea pig brain preparation. Restricted regions of the piriform cortex served by separate contingents of afferent fibres of the lateral olfactory tract were isolated surgically. The activity generated by these patches of cortex in response to afferent stimulation propagates to remote cortical regions along cortico-cortical associative fibres. Current source density (CSD) analysis of field potential laminar profiles evoked by lateral olfactory tract stimulation confirmed that the synaptic sinks induced by distinct associative fibre contingents converge on the apical dendrites of piriform cortex neurons in the superficial lb layer. Pairing between potentials evoked by activation of two separate sets of associative fibres resulted in an almost linear summation when the two responses coincided. For interstimulus intervals of <100 ms, heterosynaptic pairing of independent associative inputs induced a facilitation of the conditioned associative potential, which correlated with an increase in the associative sink located in layer lb, as demonstrated by CSD analysis. The evaluation of the pairing intervals suggests that the heterosynaptic facilitation of the conditioned associative potentials may be due to the summation of local and remote associative synaptic events. It is concluded that separate associative inputs converge on the apical dendrites of piriform cortex pyramidal neurons to generate synaptic potentials through the activation of spatially close but independent synapses. The role of associative synaptic integration in the functional organization of the olfactory cortex is discussed.
在体外分离的豚鼠脑制备物的梨状皮质中，研究了由不同组联合纤维激活所产生的突触电位之间的相互作用。通过手术分离出由外侧嗅束传入纤维的不同分支所服务的梨状皮质的特定区域。这些皮质区域对传入刺激产生的活动沿着皮质 - 皮质联合纤维传播到较远的皮质区域。对外侧嗅束刺激诱发的场电位层状分布进行电流源密度（CSD）分析证实，由不同联合纤维分支诱导的突触汇汇聚在浅表层lb层梨状皮质神经元的顶端树突上。当两组独立联合纤维激活诱发的电位同时出现时，它们的配对会产生几乎线性的总和。对于刺激间隔小于100毫秒的情况，独立联合输入的异突触配对会诱导条件性联合电位的易化，如CSD分析所示，这与位于lb层的联合汇增加相关。对配对间隔的评估表明，条件性联合电位的异突触易化可能是由于局部和远程联合突触事件的总和。得出的结论是，不同的联合输入汇聚在梨状皮质锥体神经元的顶端树突上，通过激活空间上紧密但独立的突触来产生突触电位。文中还讨论了联合突触整合在嗅觉皮质功能组织中的作用。
