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that plays a role of inhibitory interface or “attentional gate”, regulating a stream of
information from the thalamus to neocortex (Montero, 2000).
Figure 2. Dopamine-dependent selection of neocortical pattern by the cortico - basal ganglia -
thalamocortical loop. Selection is the result of amplification of activity of cortical cells that “strongly”
activate striatum and suppression of activity of cortical cells that “weakly” activate striatum during
visually-evoked dopamine release (suppression is not shown). PFC, prefrontal cortex; Th, thalamus;
NAcc, nucleus accumbens; SNr, substantia nigra pars reticulata; GP, external part of the globus
pallidus; VP, ventral pallidum; SN and SP, GABAergic striatonigral and striatopallidal cells that
express D1 and D2 receptors, and give rise to the “direct” disinhibitory and “indirect” inhibitory
pathways through BG, respectively; cells in the SNr and GP/VP are GABAergic, large grey circles
dopaminergic cells; small triangles and square, potentiated (LTP), and depressed (LTD) synapses,
respectively; thick and thin lines, strong and weak inputs, respectively. Other abbreviations as in Figure
1.
However, accepted models mostly do not take into account that thalamic nuclei
(including the reticular nucleus) are also under inhibitory influence from the output basal
ganglia (BG) nucleus, the substantia nigra pars reticulata (SNr) (Parent and Hazrati, 1995)
(Fig. 1, 2). In turn, neurons in the SNr are inhibited by spiny cells of the input BG nucleus
striatum (caudatum/putamen) that receives excitation from the neocortex and thalamus (Fig.
2). The involvement of striatum in attentional precesses is evident from the data that that
spiny cells discharge in relation to cues reorienting spatial attention (Kermadi and Boussaoud,
1995). Participation of the cortico-striatal inputs in attention is specified by the data that
disconnection between the medial PfC and the ventral striatum named nucleus accumbens
(NAcc), or bilateral lesion of the NAcc produces a significant reduction in the accuracy of
performance of attentional task (Christakou et al., 2001; Christakou et al., 2004). Remarkably,
that during voluntary attention neuronal activity is strengthened before the real stimulus
appearance not only in the prefrontal and visual cortical areas but also in the striatum
