![]() Similar but attenuated blood flow increases occurs during anxiety attacks.ĭestructive lesions such as ablation of the amygdala cause an effect opposite to the irritative lesions of temporal lobe epilepsy. PET scans have shown an increase in blood flow to the parahippocampal gyri, beginning with the right parahippocampal gyrus. Panic attacks are brief spontaneously recurrent episodes of terror that generate a sense of impending disaster without a clearly identifiable cause. In its extreme form irritative lesions of temporal lobe epilepsy can cause a panic attack. ![]() Irritative lesions of temporal lobe epilepsy have the effect of stimulating the amygdala. Stimulation of the amygdala causes intense emotion, such as aggression or fear. The central nucleus of the amygdala also produces conscious perception of emotion primarily through the ventral amygdalofugal output pathway to the anterior cingulate cortex, orbitofrontal cortex, and prefrontal cortex. The central nucleus of the amygdala produces autonomic components of emotion (e.g., changes in heart rate, blood pressure, and respiration) primarily through output pathways to the lateral hypothalamus and brain stem. The stria terminalis also projects to the habenula, which is part of the epithalamus. Just as in the case of the two hippocampi communicating with each other through the anterior commissure, the two amygdala communicate with each other through the anterior commissure. Whereas the postcommissural branch of the fornix projects to mammillary bodies of the hypothalamus, the postcommissural branch of the stria terminalis projects to the lateral nucleus and ventral-medial nucleus of the hypothalamus.Īs with the fornix, some fibers enter anterior commissure cross to the contralateral side. The postcommissural branch goes to the hypothalamus. The precommissural branch goes to the septal area. Like the fornix, the stria terminalis has precommissural and postcommissural branches in relation to the anterior commissure. The stria terminalis overlaps with the ventral amygdalofugal pathway in that it also connects to the septal nuclei and hypothalamus and thus forms a loop.(Connection to cortical structures is through the ventral amygdalofugal pathway.) The stria terminalis connects only to subcortical structures.Stria is a Latin word that means line, groove, or band. Thus by way of analogy one can say that the stria terminalis is to the amygdala as the fornix is to the hippocampus. The stria terminalis is similar in form, function, and location as the fornix for the hippocampal pathway.That is where responses are associated with appetitive and aversive consequences that is rewards and punishers. In this case this is the link whereby associative learning takes place. ![]() It is also a link whereby responses are learned. ![]() The ventral amygdalofugal pathway is important because it is a link whereby motivation and drives, through the limbic system, can influence responses. ![]() The ventral amygdalofugal pathway also connects to the hypothalamus and septal nucleus, but the amygdala's major connection to the hypothalamus and septal nucleus is through the stria terminalis. Projections from the ventral striatum are links in a basal ganglia circuit that are important in stimulus-response associative learning. The ventral striatum includes part of the caudate, putamen, and the nucleus accumbens septi (nucleus that reclines on the septum). This pathway continues to the anterior olfactory nucleus, anterior perforated substance, piriform cortex, orbitofrontal cortex, anterior cingulate cortex, and ventral striatum. The term "fugal" comes from the word fuge-to drive away-as in fugitive. Directly to the dorsomedial nucleus of the thalamus.Outputs or efferents from the amygdala via the stria terminalis, ventral amygdalofugal pathway, and direct pathways.Ħ.3 Major Output Pathways of the Amygdala ![]()
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |