| Popis: |
All mammals possess the capacity to affect appropriate responses to “escapable” or “inescapable” stressors, and to facilitate recovery and healing once the stress passes. Different stressors possess, to varying degrees, physical and psychological components. A substantial body of evidence has been reviewed, which supports the concept that the Periaqueductal Gray (PAG) is divisible into a number of distinct, longitudinal neuronal columns each of which lies embedded within a circuit that extends rostrally to include specific prefrontal cortical (PFC) and hypothalamic areas. These PFC-PAG/hypothalamic circuits, in turn project caudally to affect somatic and autonomic pre-motor neurons within the ventrolateral medulla and and ventromedial (raphe) and paramedian medullary neural pools. The evidence reviewed suggests that different PAG columns (and their distinctive forebrain and brainstem connections) play important roles in coordinating distinct emotional coping strategies for dealing with different classes of stress. Specifically, it has been proposed: (i) that the lPAG column (and its associated circuit) is activated preferentially by “escapable” physical stressors to which an active defensive reaction(s) is the primary response; (ii) that the dlPAG column (and its associated circuit) is activated preferentially by “escapable” psychological stressors to which an active defensive response is the primary response; and (iii) that the vlPAG column (and its associated circuit) is activated: (a) by “inescapable” physical or psychological stressors for which passive coping behavior is the primary response; or (b) as a delayed/secondary response, to promote recovery and healing following any stressor. |
