This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.Today, you'll get to explore the ins and outs of your professor's brain from the comfort of your own computer! The objectives of this lab are:
Click on the hyperlinks for bookmarked views, and follow the instructions in the VHD below.
There are four ventricles in the brain: the two lateral ventricles, the third ventricle, and the fourth ventricle. The main function of the ventricles is to store and produce cerebrospinal fluid (CSF) via the choroid plexus. CSF acts as a shock absorber, protecting the brain from injury. Additionally, CSF "lavages" or washes the brain parenchyma removing waste around the clock but especially when you sleep.
When CSF circulation is blocked or, less commonly, if CSF is overproduced, hydrocephaly occurs and enlarges the ventricular system. Do you remember how this condition is treated?
View the ventricles in the VHD.
Rotate the 3D structure and orient yourself to the caudal, rostral, ventral, and dorsal directionality of the ventricles.
1. Identify the following structures:
2. Trace the pathway of 1 drop of CSF through the ventricular system, starting at a choroid plexus in the lateral ventricle.
3. Next, overlay the coronal cross-section.
4. Next, overlay the transverse (axial) cross-section and remove the coronal section.
5. Now overlay the sagittal cross-section and remove the transverse section.
Observe all of the highlighted grey matter structures on the 3D model and in the cross-sections. We will explore specific structures in detail below.
The basal ganglia is important for initiating motor movements. It is comprised of the caudate, putamen, globus pallidus, substantia nigra, and subthalamic nucleus. In the VHD, only the caudate, putamen, and globus pallidus are clearly visible. This lab focuses on these structures which comprise the telencephalic portion of the basal ganglia.
The basal ganglia are associated with disorders like Parkinson's and Huntington's Diseases. Both diseases have hallmark symptoms involving disordered movement. You will learn more about how the basal ganglia changes with these diseases later.
Start here (scroll up a bit to get back to the instructions).
1. Use the highlight tool to identify and highlight the caudate, putamen, and globus pallidus on the left side of the brain (remember you can use the highlight or dissect tool and hover over structures to see their names).
2. Orient yourself to ventral, dorsal, rostral, and caudal. Rotate the model and describe the relationships of the caudate, putamen, and globus pallidus to each other and to the ventricles.
3. Next, observe the sagittal cross-section overlaid on the 3D model.
4. Use the highlight tool on the sagittal cross-sections to add in the corresponding structures on the right side of the 3D model.
5. Next, add in the MRI cross-sections.
6. We can also locate an important structure, the nucleus accumbens, where the caudate and putamen come together anteriorly. Use the highlight tool on the transverse (axial) cross-section to identify and highlight the nucleus accumbens.
The thalamus relays sensory, motor, and limbic information. There are two thalami in the brain, one on each side. The two thalami sandwich the 3rd ventricle and are connected by a flattened band of tissue called the interthalamic adhesion. Use the highlight tool on the coronal cross-section to identify and highlight the left, then right thalamus (the apparent "hole" in the 3rd ventricle marks the location of the interthalamic adhesion). Each thalamus deals with contralateral body and ipsilateral cortex. Among the many subnuclei in the thalamus, 5 are relay nuclei. Do you remember what they are and what they do?
The thalamus also plays a role in sleep, wakefulness, and consciousness. Damage or degeneration of the thalamus can result in coma or insomnia, respectively.
1. Rotate the model and describe the relationship of the thalamus to the caudate, putamen, globus pallidus, and ventricles.
2. Next, add in the MRI cross-sections.
The hypothalamus maintains homeostasis and biological set points in the body by controlling the autonomic nervous system. It regulates appetite, thirst, body temperature, sweating, the circadian clock, and mating and maternal behavior. The hypothalamus does this through several specialized functional subnuclei with inputs and outputs throughout the CNS, as well as hormonal and neuronal inputs to the pituitary gland. Think of the hypothalamus as a master switchboard for primal functions.
Damage to the hypothalamus can result in a malfunctioning pituitary gland, disrupting many basic bodily functions, which can be treated via hormone therapy. Damage to the hypothalamus can also result in Horner's syndrome, a disorder of the autonomic nervous system (which can have many other causes as well). The classic symptoms are ptosis, miosis, and anhidrosis on one side of the face.
1. Use the highlight tool to identify and highlight the hypothalamus on the 3D model.
2. Rotate the model and describe the relationships of the hypothalamus to other structures. Particularly, take note of the relationship to the 3rd ventricle and the thalamus.
3. Next, add in the MRI cross-sections.
The hippocampus is a part of the limbic system. Its main functions involve learning and memory. It consolidates declarative short-term memory, for instance memorizing all the neurotransmitters for your exam. The hippocampus is also involved in consolidating spatial relationship memories, as evidenced by the finding that successful cab drivers have larger hippocampal regions. The hippocampus does not store memories, however, but it is a critical transit station for the formation of memory.
Damage or degeneration of the hippocampus can occur in Alzheimer's disease and traumatic brain injury, resulting in amnesia, where the patient loses the ability to form new memories and/or experiences memory loss. In milder trauma cases, patients will regain their memories due to the brain's incredible plasticity.
1. Identify and highlight the left and right hippocampus on the 3D model.
2. Rotate the model and describe the relationship of the hippocampus to the other structures, particularly the amygdala and the thalamus.
3. Next, add in the MRI cross-sections.
The amygdala is a part of the limbic system. It is mainly responsible for emotional memory. That is, associating an emotion to a memory, like fear to a shock, or joy to a cute dog. It has long been known to play an important role in our processing and response to fear, but newer findings show that the amygdala plays a role in processing intense emotions. Research shows that amygdala over-activation plays a role in anxiety disorders1. Conversely, early experiments which involved removing the amygdala from monkeys resulted in absent fear responses.
Start here.
1. Use the dissect tool on the axial, sagittal, or coronal cross-sections to identify and add the left and right amygdala to the 3D model.
2. Rotate the model and describe the relationship of the amygdala to the other structures. Take special note of the relationship between the amygdala and the hippocampus, as well as to the hypothalamus.
3. Next, add in the MRI cross-sections.
Observe all of the highlighted white matter structures on the 3D model and in the cross-sections. We will explore specific structures in detail below.
The internal capsule is the white matter tracts that run through the grey matter between the caudate and putamen causing a "striped" appearance. Hence the name striatum. Broadly, it contains both ascending and descending tracts, running from the cerebral cortex to the spinal cord (or spinal cord to cerebral cortex). You will learn more about these tracts in the next unit.
Since this white matter tract plays a major role in the brain-body connection, lesions here can result in paralysis, weakness, and/or somatosensory loss on the contralateral side of the body.
1. Use the highlight tool on the coronal cross-section to identify and highlight the internal capsule on the left and right sides of the brain.
2. Rotate the model and describe the relationship of the internal capsule to the basal ganglia.
3. Next, add in the MRI cross-sections.
The corpus callosum is a large bundle of white matter tracts that connect the left and right cerebral hemispheres and facilitates communication between the two sides of the brain.
In epilepsy, electrical seizures can spread from one side of the brain to the other. As a last resort, the corpus callosum can be surgically severed. Deficits that result from this surgery are explained by the sidedness of the human brain. For example, the left hemisphere (in most individuals) controls speech. If a patient sees an object only in the left half of their visual field (which is processed in the right occipital lobe), they cannot verbalize what they are looking at after this surgery because that information cannot reach the language areas in the left hemisphere.
1. Use the highlight tool to identify and observe the corpus callosum in the 3D model.
2. Rotate the model and describe the relationship of the corpus callosum to the other structures (thalamus, ventricular system, etc).
3. Next, add in the MRI cross-sections.
The anterior commissure is a bundle of white matter tracts that connects the left and right temporal lobes, including the amygdala. Its function is to facilitate communication between the two sides of the brain in the temporal lobe region. It also serves to connect the olfactory tracts across the midline2.
1. Use the highlight tool to identify and observe the anterior commissure in the 3D model. Zoom in and out of the cross-sections to appreciate this bilateral structure in all three image planes.
2. Rotate the model and describe the relationship of the anterior commissure to the other structures (thalamus, hippocampus, etc).
3. Next, add in the MRI cross-sections.
The fornix is part of the limbic system. It consists of a bundle of white matter tracts that connect the hippocampus to the mammillary bodies. Note that it connects rostral-ventral structures, not left and right structures (in other words, it's not a commissure!).
1. Rotate the model and describe the relationship of the fornix to the other structures.
2. Next, add in the MRI cross-sections.
View this model to test your knowledge! See if you can identify each colored structure (you can use the highlight tool to check your answers).
Also, scroll through the MRI cross-sections and see if you can identify each colored structure on both sides of the brain.
Resources:
1. Adhikari A. Distributed circuits underlying anxiety. Front Behav Neurosci. 2014;8:112. Published 2014 Apr 1. doi:10.3389/fnbeh.2014.00112
2. Brunjes, Peter C. (2012). The mouse olfactory peduncle. 2. The anterior limb of the anterior commissure. Frontiers in Neuroanatomy, 6, 51
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.