The extrathalamic relay from the brainstem reticular formation to the cerebral cortex in the basal forebrain has been thought to be constituted predominantly, if not exclusively, by cholinergic neurons. In contrast, the septohippocampal projection has been shown to contain an important contingent of gamma-aminobutyric acid (GABA)ergic neurons. In the present study, we investigated whether GABAergic neurons also contribute to the projection from the basal forebrain to neocortical regions, including the mesocortex (limbic) and the isocortex in the rat. For this purpose, retrograde transport of cholera toxin (CT) was examined from the medial prefrontal cortex for the mesocortex and from the parietal cortex for the isocortex and was combined with dual-immunohistochemical staining for either choline acetyltransferase (ChAT) or glutamic acid decarboxylase (GAD) in adjacent series of sections. Retrogradely labelled GAD+ neurons were codistributed with retrogradely labelled ChAT+ neurons through the basal forebrain from both the prefrontal and the parietal cortex, suggesting parallel, widespread cortical projections. The GAD+ cortically projecting cells were similar in size to the ChAT+ cells, thereby indicating that they comprise a contingent of the magnocellular basal cell complex. The proportions of retrogradely labelled neurons that were GAD+ (approximately one-third) were equal to or greater than those that were ChAT+ from both the prefrontal cortex and the parietal cortex. In addition, the total of GAD+ and ChAT+ neurons did not account for the total number of cortically projecting cells, indicating that another equivalent proportion of chemically unidentified noncholinergic neurons also contributes to the basalocortical projection. Accordingly, as in the allocortex, GABAergic, cholinergic, and other unidentified noncholinergic neurons may have the capacity to modulate activity in the mesocortex (limbic) and the isocortex through parallel, widespread projections.
The extrathalamic relay from the brainstem reticular formation to the cerebral cortex in the basal forebrain has been thought to be constituted predominantly, if not exclusively, by cholinergic neurons. In contrast, the septohippocampal projection has been shown to contain an important contingent of gamma-aminobutyric acid (GABA)ergic neurons. In the present study, we investigated whether GABAergic neurons also contribute to the projection from the basal forebrain to neocortical regions, including the mesocortex (limbic) and the isocortex in the rat. For this purpose, retrograde transport of cholera toxin (CT) was examined from the medial prefrontal cortex for the mesocortex and from the parietal cortex for the isocortex and was combined with dual-immunohistochemical staining for either choline acetyltransferase (ChAT) or glutamic acid decarboxylase (GAD) in adjacent series of sections. Retrogradely labelled GAD+ neurons were codistributed with retrogradely labelled ChAT+ neurons through the basal forebrain from both the prefrontal and the parietal cortex, suggesting parallel, widespread cortical projections. The GAD+ cortically projecting cells were similar in size to the ChAT+ cells, thereby indicating that they comprise a contingent of the magnocellular basal cell complex. The proportions of retrogradely labelled neurons that were GAD+ (approximately one-third) were equal to or greater than those that were ChAT+ from both the prefrontal cortex and the parietal cortex. In addition, the total of GAD+ and ChAT+ neurons did not account for the total number of cortically projecting cells, indicating that another equivalent proportion of chemically unidentified noncholinergic neurons also contributes to the basalocortical projection. Accordingly, as in the allocortex, GABAergic, cholinergic, and other unidentified noncholinergic neurons may have the capacity to modulate activity in the mesocortex (limbic) and the isocortex through parallel, widespread projections.
The author discusses memory from the point of view of the neurosciences and molecular biology, proposing an integration with the psychoanalytic theory of the unconscious. The discovery of the implicit memory has extended the concept of the unconscious and supports the hypothesis that this is where the emotional and affective--sometimes traumatic--presymbolic and preverbal experiences of the primary mother-infant relations are stored. They could form the ground structure of an early unrepressed unconscious nucleus of the self. Identifying the unconscious with the memory leads to a theory about its morpho-functional organization. The unrepressed unconscious can be brought to the surface in analysis through the 'musical dimension' of the transference, characterized by the voice (its intonation and rhythm) and the prosody of the language. Dreams can symbolically transform pre-symbolic and preverbal experiences, so that they can be put into words and thought about even without their recollection. Dreams can also create images to fi ll the gap of the absence of representation which characterize the unrepressed unconscious. The description of a segment of analysis of a patient suffering from death anxiety provides a clinical illustration of the theories discussed. The interpretation of her voice and of the prosody of her language, besides the work on dreams, reproduced the emotional essence of the analysand's traumatic childhood experiences. This reconstruction enabled her to speak and think about them even without the actual recollection.
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