Rostral Intralaminar Thalamic Deep Brain Stimulation Triggered Cortical and Hippocampal Structural Plasticity and Enhanced Spatial Memory.

BACKGROUND/AIMS: Rostral intralaminar thalamic nucleus (ILN) has been shown to modulate cognition through indirect connection with the hippocampus and prefrontal cortex. We explored the effects of deep brain stimulation (DBS) to the rostral ILN on spatial memory acquisition, brain neuronal activation and cortical and hippocampal synaptic changes in rats.

METHODS: The Morris water maze (MWM) task was used to evaluate the spatial memory of the rats. The expression of c-fos, an immediate early gene, was used to identify neural activation in the cerebral cortex and hippocampus. Synaptic changes in the somatosensory cortical and hippocampal neurons were explored with dendritic spine analysis following Golgi-Cox staining.

RESULTS: Our results showed that a barrage of DBS to the rostral ILN of normal rats significantly shortened their escape latency in MWM compared with sham-stimulated and untreated control rats. Rats with enhanced spatial memory had more c-fos immunoreactive cells in layer IV of the somatosensory cortex. Layer III cortical and CA1 hippocampal pyramidal neurons showed over 50% increase of dendritic spines, while only the proximal apical dendrites of layer V cortical pyramidal neurons had more dendritic spines.

CONCLUSIONS: Rostral ILN-DBS activated neurons in the cerebral cortex and triggered cortical and hippocampal structural plasticity in association with spatial memory enhancement.