Psychic Dissociation

PSYCHIC DISSOCIATION, disruption of coherence in mental processes, resulting from both the breaking of associative connections and a general decrease in mental tone; a frequent symptom of the most diverse mental illnesses, especially characteristic of schizophrenia (see Psychic Duality). (symptom complex of disconnection of sensory perceptions), presence of disorders of certain types of sensitivity while others remain intact. The symptom complex of D. c. arises due to selective damage to certain sensory pathways (fibers), while others remain unaffected by the pathological process. The latter is possible only because different types of sensitivity are conducted along different nerve fibers, and the pathways for conducting various sensory stimuli are topographically isolated from each other (see figure on next page). In peripheral nerves, the pathways for conducting painful, thermal, tactile stimuli, localization and stereognosis are part of both superficial (cutaneous) and deep spinal nerves; however, excitations for sensations and perceptions of weight, bone, vibration sensitivity, determination of the position of the body or limbs in space, maintenance of muscle tone, coordination and balance are conducted exclusively through deep nerves (joints, muscles, tendons, periosteum, bones). In the spinal cord, the pathways for conducting deep sensitivity lie in the posterior columns (position of limbs, awareness of posture, bone sensitivity, stereognosis); they remain on the same side of the spinal cord as they enter through the posterior roots. The pathways for conducting pain and temperature sensitivity, upon entering the spinal cord, soon cross to the opposite side and ascend to the brain in the anterior parts of the lateral column. Tactile sensitivity follows a pathway located in the anterior part of the anterolateral column (touch) of the opposite side and partly in the posterior columns (localization) of the same side. Subconscious regulation of tone, balance and coordination occurs through pathways going in the cerebellar bundles of Gowers and Flechsig. In the brainstem, there is also D. in the arrangement of sensory conducting pathways. In the medial lemniscus, pathways for deep sensitivity, stereognosis and localization of sensations go; near the trigeminal nerve nucleus are located pathways for pain and temperature sensitivity; adjacent to it is Gowers' bundle, and Flechsig's bundle passes into the corpus restiforme. At the level of the thalamus, dissociation of sensory conducting pathways is again observed: in the thalamus, the pathways for pain sensitivity and partly for temperature, vibration and tactile sensitivity end completely; other pathways, in particular those for deep sensitivity (position of limbs, stereognosis, localization), continue from the level of the thalamus to the parietal lobes and to the posterior central gyrus of the cerebral cortex. D. c. is observed in cases where there is selective damage to the aforementioned pathways for conducting sensory stimuli. This is observed in various diseases, both general and focal, with localization of the process in the peripheral nervous apparatus, spinal cord, brainstem, thalamus, cerebral cortex. In peripheral D. in various cases of neuritis, neuralgia, various D. c. are observed; as the most striking D. should be named anaesthesia dolorosa, causalgia, polyneuritis leprosa. D. c. observed in tabes dorsalis, syringomyelia, gliomatosis, hematomyelia, tumors of the spinal cord and other diseases of it are characteristic. - The picture of dissociation depends on the location of damage to the sensory pathways by the pathological process. In tabes, there is a characteristic predominant loss of deep sensitivity, awareness of the position of the limb, ability to localize skin irritation. In diseases of the gray matter of the spinal cord, the classic dissociation is observed in the form of loss of pain and thermal perceptions. Similar disorders are also found in diseases of the brainstem. For lesions of the sensory zone of the cerebral cortex, astereognosis - a disorder of deep sensitivity - is characteristic.