Variable cardiac responses in rhesus macaque monkeys after discrete mediodorsal thalamus manipulations

Figures

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  Figure 1. Effect of microstimulation in the magnocellular (MDmc, left column) and parvocellular (MDpc, right column) subdivisions of the mediodorsal thalamus on the heart rate (HR). (Top and middle row) The moment the microelectrode was positioned in the corresponding structure is pointed out with a downward arrowhead. Periods when microstimulation was administered are shown with a grey background. Also shown is the percent concentration of gaseous anaesthesia (isoflurane %) administered throughout the experiment (grey line). The asterisk * in the top left panel indicates a moment when the animal was taken out of the scanner bore and showed a change in muscle tone, likely causing the brief increase in heart rate. (Bottom row) Individual HR measurements during the baseline and stimulation periods for each MD subdivision.

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  Figure 2. (A) Mean percent heart rate change difference scores as a function of brain manipulation type. (B) Correlation showing effect of age in years at time of neurosurgery on the mean percent heart rate change difference score. (C) Mean age in years at time of neurosurgery for each brain manipulation group. Bilateral: bilateral cytotoxin infusions of NMDA and ibotenic acid to the mediodorsal thalamus (either magnocellular MD (MDmc) or parvocellular MD (MDpc)); Unilateral: unilateral cytotoxin infusions of NMDA and ibotenic acid to the MDmc; Control: bilateral ablations to the retrosplenial cortex, fornix transection, or a combined unilateral ablation to orbitofrontal and ventrolateral prefrontal cortex.

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  Figure 3. Schematic diagram outlining the brain structures implicated in cardiovascular control in response to physiological or emotional stimuli. The structures within this circuit are highly interconnected providing an effective basis for the integration of multiple information streams necessary for cognitive or emotional processing. Furthermore, the magnocellular subdivision of the mediodorsal thalamus (MDmc) with its diverse array of inputs and reciprocal connections to the frontal lobes and insular cortex appears to be well positioned as an important node within this extended neural circuitry. The main (not exhaustive) connections of this circuit are indicated with directional arrows. Reciprocal connections are in grey with double arrowheads and unidirectional connections are in black with a single arrowhead. Connections that require further verification are shown as dashed black lines with a single arrowhead. The larger blue-gray boxes group each structure into the broader category of the brain region it belongs to. *Not all the basal ganglia (BG) connections are indicated. Abbreviations: ACC, anterior cingulate cortex; HPC, hippocampus; Hypothal., hypothalamus; mPFC, medial…