Neuroanatomy: Cerebrum Structure and Function

Largest brain part located in the anterior and middle cranial fossae.
Comprised of two major parts: diencephalon (central core) and telencephalon (cerebral hemispheres), separated by the longitudinal cerebral fissure.
The fissure contains the falx cerebri and anterior cerebral arteries and hosts the corpus callosum, which connects hemispheres.

Recognized poles: frontal pole (anterior), temporal pole (between frontal and occipital), occipital pole (posterior).
Each cerebral hemisphere has three borders: superomedial, inferolateral, and inferomedial.
The inferomedial border is further divided into the medial orbital border (anterior) and the medial occipital border (posterior).

The hemispheres have three primary surfaces: superolateral, medial, and inferior surfaces.
The inferior surface is subdivided into an anterior orbital part and a posterior tentorial part.

The lobes are distinguished by key sulci, including the posterior ramus of the lateral sulcus and the central sulcus for localization.
Frontal lobe: Anterior to the central sulcus; includes areas for higher cognitive functions.
Parietal lobe: Behind the central sulcus; handles sensory information and spatial awareness.
Temporal lobe: Below the lateral sulcus; involved in processing auditory information and memory.
Occipital lobe: Behind the parieto-occipital sulcus; primarily responsible for visual processing.

Gyri are ridges, and sulci are grooves of the cerebral cortex; collectively known as Gyrencephalic brain in higher mammals.
Frontal lobe features include the precentral sulcus and division into superior, middle, and inferior frontal gyri.
Temporal lobe contains superior and inferior temporal sulci dividing it into respective gyri.
Parietal lobe is segmented by the postcentral sulcus and intraparietal sulcus into superior and inferior parietal lobules.

Significant sulci include the cingulate sulcus, dividing the gyrus cinguli from the corpus callosum.
The medial surfaces contain the paracentral lobule and the cuneus, defined by the parieto-occipital and calcarine sulci.

Inflected by the olfactory sulcus, associated with olfactory tracts, and further detailed into gyri and sulci like the lingual gyrus and uncus.

The highly evolved cerebral cortex consists of neurons and neuroglia, comprising about 14 billion neurons with layered organization.
It includes three divisions based on evolutionary significance: archicortex (primitive), paleocortex (intermediate), and neocortex (major, complex functions).

Involved in perception, response, sensory integration, and higher-order functions like memory and learning.
Composed of a grey matter layer covering the hemispheres, facilitating larger surface area due to folds and sulci.

Composed of myelinated fibers known as medullary substance, divided into association, commissural, and projection fibers.
Association fibers interconnect regions within one hemisphere, while commissural fibers connect equivalent regions across hemispheres (e.g., corpus callosum, anterior commissure).
Projection fibers connect the cortex to subcortical structures, involving cortico-thalamic pathways and descending fiber tracts.

Corticofugal fibers: Efferent pathways projecting from cortex to subcortical centers.
Corticopetal fibers: Afferent pathways projecting from subcortical regions to the cortex, primarily through thalamic connections.

Different areas of the cortex serve specific functions, identified via sulcal and gyral structures.
Brodmann's map classifies cerebral areas numerically from 1 to 47, detailing functional localizations across various lobes.### Motor Area
Located in the precentral gyrus and anterior part of the paracentral lobule, on the superolateral and medial surfaces of the hemisphere.
Corresponds to Brodmann area 4 and part of area 6.
Specific regions control movements of different body parts:
- Lower limbs activated by stimulation of the paracentral lobule.
- Upper limbs and trunk represented in the upper precentral gyrus.
- Face and head represented in the lower precentral gyrus.

Positioned just anterior to the motor area, encompassing the posterior parts of the superior, middle, and inferior frontal gyri.
Corresponds to Brodmann areas 6 and 8 in superior and middle frontal gyri.
Area in the inferior frontal gyrus corresponds to Brodmann areas 44 and 45 (motor speech area of Broca).
Stimulation results in more intricate movements compared to the motor area.

Located in the inferior frontal gyrus (Broca's area) and involves areas 44 and 45.
Injury leads to aphasia, an inability to speak, despite intact muscular control.

Found in the postcentral gyrus, correlating with Brodmann areas 1, 2, and 3.
Extends on the medial surface into the posterior paracentral lobule.
Responds to stimulation of different body parts, allowing mapping of bodily representation.

Positioned mainly in the occipital lobe, particularly above and below the calcarine sulcus, corresponding to area 17.
Area 17 extends into the cuneus and lingual gyrus.
Continuous with areas 18 and 19, which are involved in interpreting visual stimuli.

Located in the temporal lobe, within the superior temporal gyrus near the posterior lateral sulcus.
Includes the anterior transverse temporal gyrus (area 41) with limited extension onto the superior temporal gyrus (areas 41, 42).

Lesion in Brodmann area 4 leads to hemiplegia (paralysis on the opposite side of the body).
Damage to the premotor area results in apraxia, affecting skilled voluntary movements.
A cerebrovascular accident (stroke) is defined as a sudden loss of brain function lasting over 24 hours, caused by hemorrhage or ischemia.

Frontal lobe: Personality changes, behavioral issues, problem-solving difficulties.
Parietal lobe: Attention deficits, such as hemispatial neglect syndrome.
Temporal lobe: Recognition deficits like auditory agnosia and prosopagnosia.
Occipital lobe: Visual field defects, e.g., contralateral hemianopia or quadrantanopia with macular sparing.
Global lesions: Severe cognitive deficits, impacting basic question responses (e.g., name, date).