Taken together, lesion studies point to the critical involvement of the pulvinar in a number of fundamental cognitive

functions, including orienting responses and the exploration of visual space, spatial coding of visual information necessary for feature binding, the filtering http://www.selleckchem.com/products/Fludarabine(Fludara).html of unwanted information, and visually guided behavior. These studies indicate that the pulvinar is an integral subcortical part of multiple large-scale networks that regulate behavior. The findings from lesion studies are corroborated by physiology and neuroimaging studies showing that neural responses in the pulvinar reflect the behavioral relevance of stimuli. In human neuroimaging studies, modulation of responses has been shown in several different parts of the human pulvinar, including dorso-medial

and inferior regions, using selective attention tasks that emphasized directing attention to a spatial location (Kastner et al., 2004), filtering of unwanted information (LaBerge and Buchsbaum, 1990), and shifts of attention across the visual field (Yantis et al., 2002). In monkey physiology studies, it has been demonstrated that spatial attention click here modulates the response magnitude of neurons in dorsal, lateral, and inferior parts of the pulvinar (Bender and Youakim, 2001 and Petersen et al., 1985). Neural responses typically increased by up to 25% or more and, in some cases, spontaneous activity was also affected. In addition to response magnitude, the timing and variability of pulvinar responses is likely to influence information transmission to the cortex. Accordingly, pulvinar neurons

show reduced response variability during peripheral attention and saccade tasks (Petersen et al., 1985). Like other thalamic cells, pulvinar neurons are able to respond in burst or tonic firing modes. Because the activity of the low-threshold calcium channel depends on cell membrane potential, modulatory inputs to the pulvinar may influence the firing mode. Cholinergic inputs will probably depolarize most pulvinar neurons, switching their firing from burst to tonic mode (Varela and Sherman, 2007). Thiamine-diphosphate kinase However, unlike the LGN, muscarinic activation hyperpolarized about one-fifth of rat pulvinar neurons, suggesting that cholinergic inputs can induce bursting in these neurons (Varela and Sherman, 2007). In addition, inhibitory input to the pulvinar from sources such as the TRN, the anterior pretectal nucleus, and the zona incerta (Bokor et al., 2005 and Power et al., 1999) may sufficiently hyperpolarize pulvinar neurons, to enable burst firing. Although data on the relationship between pulvinar burst firing mode and behavior is lacking, it has been shown that pulvinar neurons are more frequently in burst firing mode than LGN neurons (Ramcharan et al., 2005), and thus burst firing may play a larger role in cortico-cortical transmission than retino-cortical transmission.