Brain Anatomy: Lobes and Sulci

Brain Overview

• The brain includes the cerebrum, brainstem, and cerebellum.

Major Sulci

• The central sulcus of Rolandus separates the frontal lobe from the parietal lobe.
• The lateral sylvian fissure separates frontoparietal lobes from the temporal lobe.
• The parietooccipital fissure separates the parietal lobe from the occipital lobe.

Longitudinal Fissure & Corpus Callosum

• The longitudinal fissure is located between the two cerebral hemispheres.
• The corpus callosum links the two hemispheres

Anatomical Lobes

• Frontal Lobe
• Parietal Lobe
• Temporal Lobe
• Occipital Lobe
• Limbic Lobe

Frontal Lobe

• The anterior location lies above the lateral sylvian fissure.
• Center for motor function.
• Responsible for initiative, abstract reasoning, creativity and socially appropriate behaviors.
• The central sulcus separates the frontal lobe from the parietal lobe.

Precentral Gyrus

• The location is parallel to the central sulcus
• It is as associated with the paracentral lobule.

Sulci Dividing the Frontal Lobe

• Superior frontal separates the superior frontal gyrus from the medial frontal gyrus.
• Inferior frontal sulcus separates the middle frontal gyrus from the inferior frontal gyrus.

Inferior Frontal Gyrus

• The parts include pars orbitalis, pars triangularis, and pars opercularis.

Superior Frontal Lobe

• It lays superior to the frontal sulcus.
• Includes the precentral gyrus' most posterior part with an anterior portion.
• Designated as BA 6.
• Premotor area.
• Responsible for controlling programmed activities.

Middle Frontal Gyrus

• Located between the superior and inferior frontal sulcus.
• Forms the frontal eyefield areas.
• Controls conjugate eye movements.

Inferior Frontal Gyrus Details

• Pars orbitalis (BA 47)
• Pars triangularis (BA 45)
• Pars opercularis (BA 44)

Precentral Gyrus Details

• Immediately anterior to the central sulcus.
• Posterior to the precentral sulcus.
• Primary motor area.
• Designated as BA 4

Parietal Lobe Overview

• Found between the central and post-central sulcus
• Located immediately posterior to the central sulcus.
• Superior to the lateral sulcus.
• Contains BA 3, 1, and 2.
• Known as the primary somesthetic area.

Superior Parietal Gyrus

• BA 5: Receives input from the primary somesthetic area.
• BA 7: Receives input from the motor and visual cortex.

Inferior Parietal Gyrus

• Lies within the intraparietal sulcus.
• Part of parietal association areas which process tactile and visual information.
• Helps with the awareness of the body itself and surrounding objects.
• Components include supramarginal and angular gyrus

Supramarginal Gyrus

• Located at the termination of the sylvian fissure.
• Designated as BA 40.

Angular Gyrus

• Found at the termination of the superior temporal sulcus.
• Designated as BA 39.

Temporal Lobe

• Located inferior to the lateral sylvian fissure.
• Gyri include superior, middle, inferior, and transverse temporal gyri.

Superior Temporal Gyrus

• Located superior to the superior temporal sulcus.
• Known as the auditory association area.
• BA 22

Middle Temporal Gyrus

• Located between the superior temporal sulcus and the inferior temporal sulcus.

Inferior Temporal Gyrus

• Located inferior to the inferior temporal sulcus.

Transverse Temporal Gyri (Heschl's Gyri)

• Buried in the floor of the lateral fissure.
• Designated as BA 41.
• Primary auditory area.

Occipital Lobe

• Located posterior to the parietooccipital fissure.
• Bisected by the calcarine fissure.
• The upper portion of the calcarine fissure is called the cuneus.
• BA 17 is the primary visual or visual striate area.

Visual Association Areas

• Areas 18 & 19 are designated as visual association areas.
• They are responsible for complex visual perceptions related to movement and direction of objects.
• Area BA 18 is adjacent to the striate area
• Area 19 surrounds the striate & parastriate areas.

Corpus Callosum Details

• Largest interhemispheric commissure
• Integrates and transfers information from both cerebral hemispheres.
• Aids in processing sensory, motor, & high-level cognitive signals.
• Parts:
  • Genu (anterior curved portion)
  • Body (arched portion)
  • Splenium (thickened posterior portion)

Callosal Sulcus

• Depression located above the corpus callosum.
• Separates the corpus callosum from the cingulate gyrus.

Cingulate Gyrus

• It is parallel to the corpus callosum and lies above the callosal sulcus.
• Component of the limbic system and processes the regulation of emotions and behavior

Precuneus

• Commences on the posterior end of the cingulate sulcus.
• It terminates at the anterior portion of the parieto-occipital sulcus.
• Facilitates the recall of episodic memories including past episodes related to the self.

Cuneus

• Represents the inferior quadrants of the visual field

Lingual Gyrus

• Also known as the lateral occipitotemporal gyrus.
• Important role in identifying and recognizing words.
• Modulates visual stimuli.

Fusiform Gyrus Details

• Also known as the medial occipitotemporal gyrus.
• Located on the basal surface.
• Included in anatomical atlases.
• A key structure for high-level vision computations such as face perception, object recognition, and reading.

Prefrontal Area

• Occupies the lateral, medial, and inferior surfaces of the frontal lobe.
• Also called the frontal association area. Subdivided into two main regions:
  • Orbital region
  • Lateral region

Orbital Region

• Also called the orbitofrontal region.
• Designated as BA 11 & 47.
• Includes the orbital gyrus.
• It is associated with visceral and emotional activities.

Lateral Region

• Dorsolateral area, gyri Infront of BA 8 & 45
• Concerned with intellectual abilities of conceptualizing, planning judgment & problem solving.

Limbic Lobe

• Lobe on the medial surface of the cerebral hemisphere.
• Borders the corpus callosum and the rostral brainstem

Limbic Lobe Composition:

• Cingulate gyrus and anterior extension
• Septal region
• Parahippocampal gyrus

Ventricles

• Lateral ventricles
• Interventricular foramen
• Third ventricle
• Cerebral aqueduct
• Fourth ventricle
• Central canal

Cerebellum Functions:

• Controls balance.
• Aids in posture coordination of skilled voluntary movements.
• Contributes to movement planning
• Aids in the command to move

Cerebellar Lobes:

• Archicerebellum (oldest):
  • Consists of the flocculonodular lobe.
  • Regulates equilibrium and posture.
  • Receives input from the vestibular nerve and medial vestibular nuclei.
• Paleocerebellum (anterior lobe):
  • Associated with proprioceptive and exteroceptive inputs from head and body.
  • Regulates muscle tone.
• Neocerebellum (largest and newest, posterior lobe):
  • Associated with the neocortex of the cerebrum, pontine nuclei, and inferior olivary nucleus of medulla.
  • Aids in the muscle coordination of phasic movements.

Cerebellar Nuclei:

• Fastigeal nucleus - most medial containing small & large multipolar neurons
• Globose nucleus - contain small & large multipolar neurons
• Emboliform nucleus - wedge shape mass composed of large multiform nucleus with dendrites
• Dentate nucleus - largest & most lateral and appearing as convoluted mass composed of large multipolar neurons and branching dendrites

Cerebellar Peduncles:

• Connects the cerebellum with the midbrain, pons, and medulla.
• Superior cerebellar peduncle (brachium conjunctivum):
  • Connects the cerebellum to the midbrain
  • Forms the largest cerebellar efferent bundle. Fibers arise from dentate, emboliform & globose nuclei
• Middle cerebellar peduncle (brachium pontis):
  • Connects the cerebellum to the pons
  • Fibers arise from pons via the pontocerebellar tract and consist of afferent fibers.
• Inferior cerebellar peduncle (brachium restiformins):
  • Connects the cerebellum with the medulla. Conveys unconscious proprioceptive and exteroceptive information to the cerebellum.

Brainstem

• Regions of the brainstem:
  • Midbrain
  • Pons
  • Medulla Oblongata

Midbrain

• It is for motor control, eye movements and processing of vision and hearing.

MidBrain - Anterior Surface

• Regions include the crus cerebri and the interpeduncular fossa
• The Corpora quadrigemina contains 2 superior colliculi involved in visual processing and 2 inferior colliculi involved in auditory processing

Pons

• Plays an essential role in regulating respiration.