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The biology of depression is the attempt to identify a biochemical origin of depression, as opposed to theories that emphasize psychological or situational causes. Scientific studies have found that different brain areas show altered activity in humans with major depressive disorder (MDD). [1]
Growth and development of new neuron; The neurogenesis hypothesis of depression posits that: [3] Stressful experiences have a negative effect on the process of neurogenesis in the subgranular zone of the dentate gyrus. Alternations in the rate of neurogenesis play a fundamental role in the pathology and treatment of major depression.
Decreased brain-derived neurotrophic factor (BDNF) is known to be associated with depression. Research suggests that increasing BDNF can reverse some symptoms of depression. For instance, increased BDNF signaling can reverse the reduced hippocampal brain signaling observed in animal models of depression.
The neurotrophic hypothesis of depression [1] proposes that major depressive disorder (MDD) is caused, at least partly, by impaired neurotrophic support.Neurotrophic factors (also known as neurotrophins) are a family of closely related proteins which regulate the survival, development, and function of neurons in both the central and peripheral nervous systems.
One reason depression is thought to be a pathology is that it causes so much psychic pain and distress. However, physical pain is also very distressful, yet it has an evolved function: to inform the organism that it is being damaged, to motivate it to withdraw from the source of damage, and to learn to avoid such damage-causing circumstances in the future.
This finding is not as clear though as supporters of adult neurogenesis suggest; the dentate gyrus cells stained with DCX have been shown to have a mature morphology, contrasting the idea that novel neurons are being generated within the adult brain. [17] The role of new neurons in human adult brain function thus remains unclear.
A neural pathway connects one part of the nervous system to another using bundles of axons called tracts. The optic tract that extends from the optic nerve is an example of a neural pathway because it connects the eye to the brain; additional pathways within the brain connect to the visual cortex.
In neurophysiology, long-term depression (LTD) is an activity-dependent reduction in the efficacy of neuronal synapses lasting hours or longer following a long patterned stimulus. LTD occurs in many areas of the CNS with varying mechanisms depending upon brain region and developmental progress.