NEURO 375 LIMBIC SYSTEM |34 QUESTIONS AND ANSWERS 2024

what is the main function of the limbic system - emotionally significant stimuli activate SENSORY pathways that trigger the HYPOTHALAMUS to modulate the ANS response (heart rate, blood pressure...) - accumpanying ANS changes to emotional response (amygdala → hippocampus → fornix) - information about emotionally significant stimuli also conveyed to the cortex directly (from hypothalamus) and indirectly (via cingulate) to integrate a motor response to these stimuli - memory and learning also involved limbic system players - amygdala - hippocampal formation (dentate gyrus, formix, hippocampus) - cingulate gyrus - hypothalamus - anterior, LD and DM thalamus - limbic association areas anygdala - in frontal portion of temporal lobe - formation and storage of info related to emotional events - plseasure responses initiate learning and LTM formation - helps us recognize when we are in danger or fearful of something injury to anygdala memory formation impairments, emotional sensitivity, depression, anxiety fornix connects hippocampus to hypothalamus (mammilary bodies) - crus = superior ascent - body = roof of third vemtrical - columns = near interventricular foramen hippocampus location - parahippocampal gyrus of temporal lobe - floor of lateral ventricle in temporal lobe entorhinal cortex - projects to input region of the hippocampus (the dentate gyrus) -carries info from limbic system, neocortex and amygdala CA1 - Houses the cell bodies that form the fornix - output region of hippocampus Limbic association corticies - medial surface of the frontal, parietal and temporal lobes (mesolimbic structure) - cingulate cortex - orbitofrontal cortex - parahippocampal gyrus - entorhinal gyrus - subcallosal and paraterminal gyri stria terminalis axon tract from amygdala to hypothalamus Papez circuit 1. amygdala → Dentate/hippocampus (eg. via emotional appraisal of smell sent to amygdala from olfactory cortex) 2. Hippocampus (CA1) → fornix (crus→body→columns) 3. fornix → mammilary bodies 4. Mammilary bodies send axon tracts to thalamus (anterior, DM, LD thalamus) 5. Thalamus projects to regions of the cortex (Ie. cingulate) via anterior limb of INTERNAL CAPSULE 6. cingulate projects thalamic info to rest of cortex ... 7. Cingulate receives info from cortex 8. cingulum = axon tracts from cingulate to parahippocampal gyrus 9. parahippocampal gyrus → hippocampus stimulate amygdala fear/apprehention lesion amygdala fearlessness lateral amygdala linked to neocortex - stimulate = anxiety - stimulate further = fear anterior commissure connects two amygda medial amygdala - linked to striatum - connects to motor and brainstem - PD and HD electrodes into lateral hypothalamus extream pleasure = pleasure centre electrodes in MFB (amygdala+hypothalamus) press bar and ignore food ventromedial hypothalamus apprehention centre Limbic system cycle 1. limbic association cortex receives information from higher order sensory areas (eg prefrontal cortex) 2. limbic association cortices convey this information to the amygdala and hypothalamus (via cingulum axon tract) 3. the amygdala uses this sensory info to link stimuli (such as seeing something or hearing a sound) with particular emotions 4. the hippocampus receives more integrated sensory info to reflect more complex features of the environment such as spatial awareness Eg of limbic response Stimuli: see a snake - visual association cortices (dorsal and ventral streams) coney their information to the amygdala and hippocampus (ie. via entorhinal cortex) - the amygdala uses this information to link particular stimuli with particular emotions to give rise to a programed and organized response - the hippocampus recieves more integrated sensory info (ie via amygdala) to reflect more complex features of the environment (such as spatial releationships) in order to learn about the complex environment setting ans the context in which the snake was seen Hippocampal afferents - amygdala - prefrontal / orbital cortices - cingulate - lateral cortex (temproral or posterior parietal) - entorhinal / parahippocampal hippocampal efferents 1. fornix 2. mammilary bodies - Eg to act on ANS 3. thalamus (mammothalamic tract) 4. cingulate gyrus 5. association corticies 6. septal nuclei (reward centres) .. 7. amygdala 8. entorhinal cortex