Basal Ganglia - UBC Flexible Neuroanatomy - Season 1 - Ep 7

deep in the for grains did a group of nuclei that integrate all cortical activity into one behavioral output these are the basal ganglia these deep nuclei are interconnected with each other and with all areas of the CNS a series of parallel circuits regulates different aspects of behavior one circuit is primarily involved in the integration of motor output another circuit plays a major role in learning and cognition and finally a third circuit regulates emotional aspects of behavior so what does this mean you can tell when someone's having a good day or a bad day by their posture body language and even their tone of voice the sum of all experiences hours of practice memory emotion reward seeking and the plan for a particular movement are all integrated and result in one behavioral output due to the coordinated activity within the basal ganglia now let's go and have a look how these structures work together to influence our behavior the goal of all our movements is that they be fluid efficient and target oriented in order to achieve this motor Association and sensory cortices send their input to the basal ganglia essentially asking them to make a decision of whether or not to execute this movement and then streamline the plan to do so while one pathway will facilitate goal-oriented movements another one will suppress all competing movement this results in motor output that is sleek and appears effortless this motor loop is active primarily when a task has been well learned together with association areas of the cortex it helps to put together a routine for established motor output this is the circuit that is active in these dancers now as they perform a well-rehearsed fluid routine you afferents from motor and sensory areas of the cortex reach the putamen here in the information is processed all movements that are part of the integrated plan are facilitated through the direct pathway and all competing movements are inhibited through the indirect pathway the signal that reaches the thalamus is a balance of these pathways from here projections back to the motor cortex result in measured and coordinated output the cognitive or Association rule is particularly important for higher cortical functions and motor learning we try out different strategies for accomplishing a desired movement and think about the different possibilities once we have refined our movements the activity in this loop will decrease and the motor loop will take over the cognitive loop is active in the hours of training and rehearsing these dancers have gone through to achieve a beautiful performance the cognitive loop is this training loop afferents from various cortical areas reach the caudate nucleus and in particular the nucleus accumbens which contains reward affirming dopaminergic connections these connections provide the rewarding feeling following the successful completion of a task from the nucleus accumbens and caudate projections reach the thalamus via the direct and indirect pathways the thalamus in turn projects back to the cortical areas you can almost consider this circuit to be a consulting service that streamlines cognitive processes by separating the successful ones from the unsuccessful ones during learning finally the limbic circuit links the basal ganglia with areas of the brain that process emotionality postures gestures and facial expressions related to emotion are mediated by this circuit everyone around us can pick up on these emotions that we display as we go through our day the motor expression of emotions is evident in everything we do in the limbic circuit the hippocampus the amygdala and the limbic lobe all project to the caudate nucleus and again the nucleus accumbens with its dopaminergic projections from here the direct and indirect pathways project to the thalamus as to which behaviors to facilitate and which ones to inhibit the thalamus of course projects back to the limbic areas of the cortex this circuit adds the emotional component to behavior and colors all of our cortical output from motor performance to cognition here we have dissected away parts of the lateral surface of the cortex to show the corona radiata as it projects to all area of the brain this here is the insula underneath the insula lie the putamen and the Globus pallidus the putamen together with the caudate nucleus is called the striatum and is the main input to the basal ganglia you can see the fibers of the corona radiata converging behind these nuclei to form the internal capsule here we have removed the putamen and Globus pallidus to show the internal capsule you can see the anterior limb and the posterior limb of the internal capsule the caudate nucleus lies deep to the internal capsule it is best shown on this medial view of the brain here we have opened up the lateral ventricle from a medial aspect this bulge here in the floor of the anterior horn of the lateral ventricle is the caudate nucleus it's body follows the curvature of the ventricles into the roof of the inferior horn here we have removed the lining of the ventricles to show you the caudate nucleus as it swings around following the shape of the lateral ventricle there are two additional structures that play an important role in the basal ganglia circuitry the substantia and the subthalamic nucleus the substantia is located in the cerebral peduncles of the midbrain and can be easily found due to its black pigmentation of the dopaminergic neurons these neurons project to the putamen and caudate to influence motor output additionally dopamine release from the substantia facilitates cortical output and feelings of reward the subthalamic nucleus which you can see right here functions like a pacemaker for the basal ganglia circuitry defining the rhythm of output through inhibitory influences it is located in fear early and a bit lateral to the thalamus so you can see in this coronal section so here's the thalamus and this is the subthalamic nucleus let's have a look at the anatomy of all nuclei in cross-section this is how we commonly view these structures using MRI or CT scanning technologies this is a coronal section through the brain let's have a look at our landmarks here's corpus callosum these are the lateral ventricles this here is the third ventricle and the thalamus is on either side of the third ventricle here's the inferior horn of the lateral ventricle this bundle of projection fibers is the internal capsule and here is on the other side here this is the internal capsule it's the posterior limb of the internal capsule because it separates the thalamus from the putamen and Globus pallidus here in the floor of the lateral ventricle is the body of the caudate nucleus here lateral to the internal capsule is the putamen and Globus pallidus with its internal and external parts now let's have a look at these nuclei in a horizontal section let's begin with our landmarks again this here is corpus callosum that big commercial fiber bundle and this is the posterior aspect of corpus callosum also called forceps major these here are the lateral ventricles here's the anterior horn of the lateral ventricle on either side and here's the posterior horn this nucleus here is the thalamus and here's the thalamus on the other side now the thalamus is separated from the putamen and Globus pallidus through the posterior limb of the internal capsule here's the posterior limb on the other side the anterior ylim of the internal capsule separates the head of the caudate nucleus from the putamen and Globus pallidus so here's the anterior of the internal capsule and here's the anterior ylim of the internal capsule on the other side this here in the floor of the anterior horn of the lateral ventricle is the head of the caudate nucleus here's the head of the caudate nucleus on the other side this here is the Globus pallidus with its internal and external parts and this here is the putamen lateral to the putamen is the cortex of the insula now it's really interesting on this section is you can see that the head of the caudate and the putamen are fused here and this is the nucleus accumbens a solid understanding of the alignment of these nuclei in both the coronal and horizontal planes is a key skill in interpreting cross-sectional anatomy in all types of neural imaging all of our cortical output is integrated in the basal ganglia none of these loops works independently everything needs to feel right in order to have the perfect performance the basal ganglia are like a funnel that takes in all of our cortical activity they integrate this activity with our motivation our goals and our general mood and result in one behavioral output

Channel: UBC Medicine - Educational Media

Views: 423,986

Rating: 4.9523444 out of 5

Keywords: Neuroanatomy (Anatomical Structure), UBC, Claudia Krebs, Zachary Rothman, Gross Anatomy Laboratory, delia brett, basal ganglia, motor coordination, motor loop, Cognitive Neuroscience (Field Of Study)

Id: InJByqg1x-0

Length: 14min 29sec (869 seconds)

Published: Fri Feb 28 2014