Figure 8.

A, Depth profile of recordings. Graph superimposed on coronal section through midline thalamus shows frequency distribution pooled across all electrodes for estimated depths of recorded neurons with different types of activity relative to the first neuron recorded on each electrode, which was assumed to approximate the beginning of the PVT. Blue, Neurons with response to visual cue that was numerically larger in reward (C→R) than no-reward (C→X) blocks; orange, neurons with simple lick-related activity; red, neurons with lick responses only to the first lick postsolenoid. Thick, tailed arrows indicate projections to key targets from different midline regions, with intensity of shading indicating relative strength of the connections and thin black arrows indicating intramidline connections, all derived from van der Werf et al. (2002). Atlas section is adapted from Paxinos and Watson (2007). CP, Caudate putamen (dorsal striatum); CM, central medial nucleus; D3V, dorsal third ventricle; HIPP, hippocampus; IMD, interomediodorsal nucleus; Re, reunions nucleus; Rh, rhomboid nucleus; SMC, sensorimotor cortex. B, Schematic of how integration across various dimensions could account for patterns of lick-related activity in midline thalamus neurons. Crossed circles on the process diagrams (left) represent neurons in midline thalamus integrating putative inputs (providing information in square boxes) at three successive levels of complexity to generate lick-related activity (black PETH peaks). Right, Respective patterns of lick-related activity. Black and blue lines show stylized PETHs of neural and licking activity, respectively. Yellow bar indicates visual cue and droplet symbol and green line show solenoid activation time. First-lick postsolenoid is indicated by black circle. For each level of integration, the top pair of PETHs represent trials with established conditioned licking in response to cue and the bottom pair show trials where a new sequence of licks was initiated in response to the solenoid. Asterisks on the traces for each level indicate failures to respond to lick events that were responded to on the level above.