Involvement of the spino-parabrachio -amygdaloid and -hypothalamic pathways in the autonomic and affective emotional aspects of pain.

Publisher Summary This chapter discusses various aspects of pain pathways. The pain pathways and brain structures involved in pain processing, have been clearly emphasized by the powerful modern anatomical tracing techniques, which have allowed not only a better visualization of the “classical” ascending pathways, but also revealed numerous “novel” ascending tracts that participate in pain integration. Among the so-called “pain pathways”, the spinothalamic tract seems to be highly implicated in sensory-discriminative aspects of pain. The functional roles of other ascending pathways such as the spino-cervico-thalamic tract, the postsynaptic dorsal column fibers and the various components of the spinoreticular and spino-reticulo-thalamic tracts are poorly understood. The electrophysiological properties of neurons recorded in some parts of the pathways and the connections of the three termination sites that is, the central nucleus of the amygdala, the ventromedial nucleus/retrochiasmatic area and the bed nucleus of the stria terminalis indicate that these pathways are strongly implicated in autonomic, affective-emotional and emotional-memory aspects of pain. More specifically, the large output of these nociceptive pathways toward the periaqueductal grey matter, the vagal motor, the ambiguous and the pedunculopontine tegmental nuclei emphasizes the involvment of these nociceptive pathways in the emotional motor control.