Conditioned morphine tolerance promotes neurogenesis, dendritic remodelling and pro-plasticity molecules in the adult rat hippocampus.

Structural neuroplasticity of the hippocampus in the form of neurogenesis and dendritic remodelling underlying morphine tolerance is still less known. Therefore, in this study, we aimed to assess whether unconditioned- and conditioned-morphine tolerance can trigger structural neuroplasticity in the dorsal and ventral parts of the adult male rat hippocampus. Evaluation of the levels of neurogenesis markers (Ki67 and DCX) by immunohistochemistry shows that conditioned morphine tolerance is sufficient to increase the baseline topographic level of hippocampal neurogenesis in adult rats. Dendritic spine visualization by Golgi staining shows that the behavioural testing paradigms themselves are sufficient to trigger the hippocampus subregion-specific changes in the dendritic remodelling along the apical dendrites of hippocampal CA1 pyramidal neurons and dentate granule cells in adult rats. Quantitative reverse transcription polymerase chain reaction of Bdnf, Trkb, Rac-1 and RhoA mRNA levels as pro-plasticity molecules, shows that the conditioned morphine tolerance is effective in changing Bdnf and RhoA mRNA levels in the ventral hippocampus of adult rats. In summary, we demonstrate that the acquisition of morphine tolerance promotes adult neurogenesis, dendritic remodelling and pro-plasticity molecules such as Bdnf/Trkb in the rat hippocampus. Indeed, the structural neuroplasticity of the hippocampus may underlie the newly formed aberrant memory and could provide the initial basis for understanding the neurobiological mechanisms of morphine-tolerance plasticity in the hippocampus.

Bodies in motion: Unraveling the distinct roles of motion and shape in dynamic body responses in the temporal cortex.

The temporal cortex represents social stimuli, including bodies. We examine and compare the contributions of dynamic and static features to the single-unit responses to moving monkey bodies in and between a patch in the anterior dorsal bank of the superior temporal sulcus (dorsal patch [DP]) and patches in the anterior inferotemporal cortex (ventral patch [VP]), using fMRI guidance in macaques. The response to dynamics varies within both regions, being higher in DP. The dynamic body selectivity of VP neurons correlates with static features derived from convolutional neural networks and motion. DP neurons' dynamic body selectivity is not predicted by static features but is dominated by motion. Whereas these data support the dominance of motion in the newly proposed "dynamic social perception" stream, they challenge the traditional view that distinguishes DP and VP processing in terms of motion versus static features, underscoring the role of inferotemporal neurons in representing body dynamics.