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Alexander Thiele, Jose Herreo, Alwin Gieselmann; Differential contribution of cholinergic and glutamatergic receptors to attentional modulation in V1. Journal of Vision 2012;12(9):1400. doi: 10.1167/12.9.1400.
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In V1, attentional modulation of firing rates is dependent on cholinergic (muscarinic) mechanisms (Herrero et al., 2008). Modelling suggests that appropriate ACh drive enables top-down feedback from higher cortical areas to exert its influence (Deco & Thiele, 2011). The implementation of such feedback at the transmitter/receptor level is poorly understood, but it is generally assumed that feedback relies on ionotropic glutamatergic (iGluR) mechanisms. We investigated this possibility by combining iontophoretic pharmacological analysis with V1 cell recordings while macaques performed a spatial attention task. Blockade or activation of iGluR did not alter attention-induced increases in firing rate, when compared to attend away conditions. However, attention reduced firing rate variance as previously reported in V4 (Mitchell, Sundberg, Reynolds, 2007), and this reduction depended on functioning iGluRs. Attention also reduced spike coherence between simultaneously recorded neurons in V1 as previously demonstrated for V4 (Cohen & Maunsell, 2009; Mitchell et al., 2007). Again, this reduction depended on functional iGluR. Thus overall excitatory drive (probably aided by feedback), increased the signal to noise ratio (reduced firing rate variance) and reduced redundancy of information transmission (noise correlation) in V1. Conversely, attention induced firing rate differences are enabled by the cholinergic system. These studies identify independent contributions of different neurotransmitter systems to attentional modulation in V1.
Meeting abstract presented at VSS 2012
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