Anatomy - Cerebrum and Diencephalon / Neuroanatomy of Language

Telencephalon and Diencephalon

The cerebrum is divided into 2 major regions, called?

Forebrain (prosencephalon)

Cerebrum is formed from the ____________ which will give rise to telencephalon (cerebral hemisphere) and diencephalon (core)

Brain stem

Mesencephalon + rhombencephalon. Connects the cerebrum and cerebellum to the spinal cord

Cerebrum

Largest part of the central nervous system (CNS). It has 2 basic poles: Anterior (frontal) pole - more rounded, Posterior (occipital) pole - more pointed

Cerebrum

It is contained within the cranial cavity, covered by the three layers of meninges, and bathed with a cerebrospinal fluid (CSF) which will act as cushion to the brain

Subarachnoid space

Space found within the layers of meninges covering the brain. Filled with CSF which bathes the entire CNS and serves as a cushion to the brain.

Axon, Soma, Dendrites, Myelin Sheath

What are the basic parts of a neuron?

Synapse

Junction between two neurons

Nuclei

Group of cell bodies with common functions. Embedded within the CNS

Ganglion

Group of cell bodies with common functions. Embedded outside the CNS

Gray matter

Brown, peripheral part. Contains cell bodies

White matter

White, central part. Contains axons

Gray Matter (Cerebral Cortex)

Located on the periphery. Represents the location of the cell bodies of the neurons which gives it a grayish appearance

Subcortical Nuclei

If you look closely on the central region of the cerebrum, it has aggregates of gray matter which are formed by clusters of cell bodies called?

White Matter

Found underneath the cortex. Represents the bundles of axons traveling to and from the cerebral cortex and other areas of the central nervous system. These axons are covered with myelin sheath, making it appear white

Myelin Sheath

Produced by Schwann cells in the PNS, and Oligodendrocytes in the CNS

Commissural Fibers

These are the white matter tracts that link or connect the left and right cerebral hemispheres

Anterior Commissure

Commissural fibers that interconnects the limbic system

Posterior commissure

Commissural fibers that interconnects visual pathway since it is important in the pupillary light reflex

Association Fibers

Fascicles or bundles of white matter connecting one region or lobes on one side of the cerebrum. They remain within a single cerebral hemisphere, unlike the commissural fibers which cross between hemisphere

Short

Connects the adjacent regions or gyrus. Example: Uncinate fibers

Long

Connects the lobes of the cerebral hemisphere. Example: Fronto-occipital bundle (connects the frontal and occipital lobe)

Projection Fibers

White matter tracts or bundles that connects the cerebrum to other parts of the central nervous system like the brainstem, spinal cord, or the cerebellum

Corona Radiata

White fibers that are immediately formed just below the cerebral cortex. Carries signals both to and from the cerebral cortex. Pathways may originate in the cerebral cortex and travel to other parts of the central nervous system (CNS). Alternatively, signals can begin in other areas of the CNS and ascend to the cerebral cortex

Internal Capsule

As the fibers reaches the central core of the cerebrum, it organizes to form a more solidified bundle of white matter called the?

Internal Capsule

Becomes more compact and more organized as compared to the corona radiata. It is embedded or blends within the subcortical gray matter of the cerebrum. Boomerang in shape (if seen from a horizontal view)

Anterior Limb, Genu, Posterior Limb

What are the 3 basic parts of the the internal capsule?

Genu

The one that connects the anterior and posterior limb

Left Hemisphere

Controls sensation and movement of the RIGHT side of the body. Analysis and calculations. Time and sequencing. Recognition of words, letters, and numbers. Logic

Right Hemisphere

Controls sensation and movement of the LEFT side of the body. Creativity and spatial ability. Context / perception. Recognition of faces, places, and objects. Artistic expression and music appreciation

Dominant hemisphere

Speech, language, and comprehension is on what hemisphere?

Left Hemisphere

The most dominant hemisphere?

Handdedness

Cerebral dominance is determined by?

Frontal, Parietal, Occipital, Temporal, Insular

What are the 5 general cerebal lobes?

Cerebral gyri (gyrus)

Are the bumps or elevations of the brain

Cerebral sulci (sulcus)

Cerebral fissures are the depressions found between the gyri

Longitudinal (Sagittal) Fissure

Is the groove that separates the left and right cerebral hemisphere

Central Sulcus (Sulcus of Rolando)

Between the precentral gyrus found anterior to the sulcus and postcentral gyrus posteriorly. Separates the frontal lobe from the parietal lobe

Lateral Fissures (Sylvian Fissure)

Separates the frontal from the temporal lobe. A prominent and easily identifiable groove on the surface of a brain specimen

Parieto-Occipital Fissure

Found posteriorly and separates the parietal lobe from the occipital lobe.

Calcarine Sulcus

Perpendicular to the parieto-occipital fissure. Separates the occipital lobe from the temporal lobe. We can only appreciate the sulcus on the medial side of the cerebrum

Insular Lobe

Often called the “hidden lobe” is located deep within the lateral sulcus, covered by parts of the frontal, parietal, and temporal lobes

Lateral Sylvian Fissure

The frontal lobe is separated from the parietal lobe via the central sulcus and to the temporal lobe via the?

Primary Motor Cortex (Precentral Gyrus) - BA4

The gyrus anterior to the central sulcus. It is on the territory of the frontal lobe. Exclusive to skeletal muscle. Periphery of the cerebral hemisphere. Contained within the precentral gyrus. Responsible for the voluntary movement or contraction of all the skeletal muscles on the contralateral side of the body

Paresis

Damage on the Broca’s Area 4 causes this weakness on opposite/contralateral side

Motor Homonclus

Specifically depicts the motor representation within the primary motor cortex

Somatotopic Arrangement

The body is mapped onto the cerebral cortex in a specific arrangement: Medial Aspect: represents the lower limbs. Upper Lateral Surface: represents the trunk and upper limbs. Lower Lateral Surface: represents the face (head and neck)

Phantom limb sensation

Even if the area is amputated, there’s still a present of feeling in that area

White Matter

These are bundles of white myelinated axons of the neurons coming from the cerebral cortex. Since these fibers will course to the other regions of the CNS, it is classified as projection fibers

Corticospinal Tract

From cortex to opposite side of the spinal cord. Supplies the lower limbs, trunks, and upper limbs. Internal Capsule: Posterior Limb

Corticobulbar Tract

From cortex to brainstem. Supplies the head and neck (bulbar means stem). Internal Capsule: Genu

Brodmann Area 4

The primary motor cortex which controls our voluntary movement is located in the precentral gyrus designated as?

Corticobulbar Tract

Will terminate in the brainstem → give rise to the motor cranial nerves → will supply the head and neck musculature

Corticospinal Tract

Will course until it reaches the spinal cord → forms the spinal nerve → will supply upper and lower limbs

Anterior Cerebral Artery (ACA)

Mainly supplies medial side of the cerebrum including medial side of the frontal lobe. Courses along the longitudinal fissure. On top of corpus callosum and follows its shape

Middle Cerebral Artery (MCA)

Supplies the lateral side of cerebrum. Courses inferiorly and exits at the lateral sylvian fissure. Direct continuation of the internal carotid artery

Damaged ACA

Manifestation is greater in lower limb than in upper limb. As ACA supplies the medial side and lower limb is located on the medial side of the homunculus as well

Damaged MCA

Manifestation is greater in upper limb than in lower limb. Muscles of the head and neck will also be affected. If dominant hemisphere, it can also have issues with speech

Cerebrovascular Disease (CVD)

Insult to cerebral arteries. Can present in two ways: Ruptured blood vessel (hemorrhagic), Obstructed blood vessel (ischemic)

Stroke

A vascular event that can happen in any part of the body. Blood supply is affected. Appropriate term: Cerebrovascular disease (CVD)

Hemorrhagic Stroke

“Hemorrhagic” - rupture of blood vessel. Happens in cases of: Severely elevated blood pressure (e.g., 230/90). Cerebral aneurysms or spontaneous rupture secondary to a defect in the arterial wall. Cranial cavity space is very limited, such that if blood clot forms, the brain will be compressed

Ischemic Stroke

“Ischemic” - obstruction of blood vessel. Happens in cases of impeded blood flow leading to decrease blood supply to the area being supplied by the blocked blood vessel, secondary to either:

Atherosclerosis

Or plaque formation inside the blood vessel

Cerebral Embolism

Wandering object or substance that eventually can block the arterial blood vessels. These objects can be a dislodged clot from other areas (such as in deep vein thrombosis), an air or fat globules

Myocardial Infarction

Is an obstruction of a vessel supplying the heart.

CT Scan

Is one of the most widely used (common) diagnostic imaging (modality) to confirm the diagnosis of a hemorrhagic or ischemic strokes. A series of slices is made on the head (with a specific millimeter thickness) in order to give a full picture of the brain

Hemorrhagic Stroke (Intracerebral Hemorrhage)

Reference point is the bone as it is hyperdense. If there is white in an unusual place (e.g. inside the white matter), it typically indicates accumulation of blood clot in the brain. Since the cavity of the skull is very limited, the blood accumulating inside pushes the other brain structures to the opposite side. Hence, the midline structures are now deviated

Ischemic Stroke

Parts of the brain scan appear black, as it is hypodense due to poor or no blood supply. Analyzing the CT scan will give the idea that a major artery was blocked. The scan on the right is a massive ischemic stroke affecting entirely half of the cerebrum

MCA Obstruction

If MCA is blocked, you expect the patient to have weakness and loss of sensation on the opposite side. Especially the upper limbs, head, and neck [FE]. If it is the dominant hemisphere, expect for a speech problem

ACA Obstruction

If ACA is blocked, expect for difficulty in walking due to a lower limb problem

BA 6: Motor Association Cortex

Located anterior to the precentral gyrus. Adjacent to Brodmann Area 4. Output is the final product (or electrical impulse) which has already been refined, calculated, and free of errors

BA 6: Motor Association Cortex

Responsible for the planning, sequencing, and execution of movement. Blueprint of the motor system. Ensures that the only desired movement will happen

Cerebellum and Basal Ganglia

The motor association cortex (BA6) has connections with other parts of the CNS such as the?

Horizontal Eye Gaze

An intact frontal eye field and this is responsible for the voluntary rapid eye movement

BA 8: Frontal Eye Field

Stimulating this BA on one side will result in the movement of the eye away from the stimulated side. If the right side of the brain is stimulated, then both eyes will move to the left

Both eyes

An insult to BA8 will result in an abnormal preferential gaze such that ___ (both or just one) eye/s will be looking on the same side with that of the lesion

Preferential gaze

The eyes will be looking at the side of the lesion. Patient look toward the affected side

BA 9, 10, 11: Prefrontal Cortex

Biggest area of the frontal lobe. One of the most important areas of the cerebrum as it governs the higher brain function. Has a lot of connections with other parts of the central nervous system (i.e. limbic system, basal ganglia, hypothalamus, parietal lobe, etc.)

BA 9, 10, 11: Prefrontal Cortex

BA involved in: Memory and planning, Planning of movement – connects with BA6, Personality and behavior, Cognition, Decision making, Reasoning, Judgement

Sterno schizophrenia

Problem with prefrontal cortex. Depression and bipolar disorder are all attributed to problems in the prefrontal cortex

BA 44: Broca’s Area

Last area in the frontal lobe. Seen on the inferior region of Area 4 and Area 6. Regarded as the motor speech area or speech expression area

BA 44: Broca’s Area

This region of the cortex will send fibers to the brainstem nuclei that will give rise to the cranial nerves that will supply the muscles of speech: Vocal cords, Pharyngeal (articulatory) muscles, Facial (cheek) muscles, Tongue muscles

Broca’s Aphasia

An insult or a problem involving the Broca’s region. An expressive type of aphasia. They can understand what you are saying and what they are reading, but they cannot blurt the words out of of their mouth because the articulatory muscles or speech muscles are affected

BA 3, 1, 2: Primary Somatosensory Cortex (Postcentral Gyrus)

Somatosensation or somatic sensation. Refers to the sensory systems of the body, particularly those related to touch such as: Temperature sense, Pain sensation, Proprioception, Two-point discrimination, Vibration sense, Pressure sense

BA 3, 1, 2: Primary Somatosensory Cortex

Involved in processing sensory information related to touch. Recognizes the tactile sensation of the body

Sensory Homunculus

Similar to the motor homunculus, Area 3, 1, 2 has its own topographic arrangement. Depicts the relative size and location of different body parts based on their sensitivity to touch

Thalamus

All sensory modalities, except for olfaction, will pass the _____ before projecting to the cortex

Trigeminal nerve

In the head and neck region, the impulses of pain, temperature, light touch, and proprioception will be carried by the only pathway that will carry the somatosensation of the head and neck before it reaches BA 3, 1, 2

Spinothalamic pathway

(from spinal cord to thalamus): Carries the pain, temperature, & light touch sensation

Dorsal Column-Medial Leminiscus

Carries proprioception

Contralateral

A lesion involving the cerebral cortex will manifest with sensory loss (contralateral/ipsilateral) to the side of the lesion

BA 5: Somatosensory Association Cortex

Allows people to interpret the sensation received by Area 3, 1, 2. Next to the primary somatosensory association cortex. Allows us to analyze somatosensory sensations as to size, texture, weight, and position in 3D space. This area also allows us to store this information in our memory for pattern recognition 

Pattern Recognition

Involves matching the information received with the information already stored in the brain. The reason why one can identify an object in the absence of a visual stimulus is because one has an intact association sensory cortex

Stereognosis

Ability to perceive and recognize the form of an object. The ability to identify the shape and form of a three-dimensional object, and therefore its identity, with tactile manipulation of that object in the absence of visual and auditory stimuli.

Astereognosis

Inability to identify an object (e.g., key or ball) on his/her hand while eyes are closed. Inability to determine or discriminate the size and shape of an object as well as to recognize objects by touch. Implies an impaired functionality of the primary somatosensory cortex and somatosensory association cortex

Graphesthesia

Ability to recognize writing on the skin purely by the sensation of touch. Ability to recognize symbols written on the skin

Agraphesthesia

Inability to identify the writing on the skin purely by the sensation of touch. Impaired ability to recognize letters or numbers drawn by an examiner's fingertip on the patient's skin

Statognosia

Ability to identify the position of the body parts in space without visual stimulus

Astatognosia

Inability to identify the position of the body parts (or finger) without visual stimulus

Barognosis

Ability to evaluate and differentiate weight of same or different objects by just holding or lifting them