ANATOMIA FUNCIONAL DO CÓRTEX PARTE 1

Functional Anatomy of the Cerebral Cortex

Overview of Cortical Areas

• The cerebral cortex is divided into projection areas and association areas, with primary areas being sensory and motor.

• Primary sensory areas include somatosensory, auditory, gustatory, olfactory, vestibular, and visual regions; the primary motor area is also noted.

Secondary and Tertiary Areas

• Secondary motor areas include premotor and supplementary motor areas related to movement planning. Sensory secondary areas mirror primary ones (e.g., secondary auditory and gustatory).

• Tertiary areas encompass the prefrontal cortex, posterior parietal cortex, insular cortex, language-related regions, concluding this section of the lecture.

Somatosensory Cortex

• The primary somatosensory area is located in the postcentral gyrus within the parietal lobe; Brodmann's areas 1, 2, and 3 are relevant here.

• Research by neurosurgeon Wilder Penfield revealed a somatotopic organization where specific body parts correspond to distinct cortical regions in the postcentral gyrus.

Homunculus Representation

• The homunculus illustrates how different body parts occupy varying amounts of space in the cortex based on sensitivity; larger representations indicate greater sensitivity (e.g., lips occupy significant cortical area).

• Damage to these cortical regions can lead to deficits in sensory functions associated with those body parts.

Neural Pathways for Sensation

• Sensory information from one side of the body is processed in the opposite hemisphere due to crossing pathways; spinothalamic tracts convey this information to the thalamus before reaching the cortex.

Understanding Sensory Areas of the Brain

Overview of Sensory Processing

• The post-central area is linked to areas 5 and 7, receiving sensory references. This connection involves short fibers that facilitate communication between different brain regions.

• There is a significant relationship between S1 (primary somatosensory cortex) and S2, where S2 plays a crucial role in interpreting tactile sensations.

Tactile Memory and Interpretation

• S2 is responsible for processing tactile memory, which includes understanding movements and sensations. It projects to the temporal lobe and insular cortex, aiding in tactile learning.

• An example of tactile interpretation: when a letter is drawn on a person's palm with their eyes closed, they can identify it through touch alone.

Discrimination Skills

• Individuals can differentiate objects by touch, such as distinguishing between a coin and an olive from a stethoscope while blindfolded. This ability highlights the discriminative function of secondary sensory areas.

Vestibular Area Functions

• The vestibular area located near the face region (area 3 and part of area 7) processes information about head movement and spatial orientation, contributing to proprioceptive sensitivity.

Visual Processing in the Brain

Primary Visual Cortex

• The primary visual cortex (area 17), located at the calcarine sulcus, has retinotopic organization—meaning there’s a direct correspondence between retinal input and cortical representation.

• Visual information travels from photoreceptors through the optic nerve to various brain structures including the lateral geniculate body before reaching the visual cortex via optical radiation.

Object Recognition

• The primary visual cortex outlines object contours, providing initial impressions that are refined by secondary visual areas for more detailed perception.

Secondary Visual Areas

• Secondary visual areas (V2, V3, V4, V5), primarily located in the occipital lobe but also extending into parts of the temporal lobe, play critical roles in processing complex aspects of vision like color recognition and motion detection.

Dorsal vs. Ventral Pathways

Dorsal Pathway Functions

• The dorsal pathway (V3/V5 regions), associated with motion perception and spatial awareness, helps determine how objects move relative to one another within space.

Ventral Pathway Functions

• In contrast, the ventral pathway (V2/V4 regions), focuses on object identification including color recognition and facial recognition—essentially answering "what" an object is versus "where" it is or how it's moving.

Understanding Brain Functionality and Sensory Processing

Lesions and Sensory Recognition

• The discussion begins with the concept of lesions in secondary areas of the brain, particularly relating to prosopagnosia, which is the inability to recognize faces despite being able to see them.

• Individuals with this condition can perceive their surroundings but lack recognition of familiar people, highlighting a disconnection between visual perception and memory.

Auditory Processing Areas

• The anatomical location of auditory processing is identified in the transverse temporal gyrus, specifically Brodmann areas 41 and 42, which are crucial for sound frequency mapping (tonotopy).

• Sounds of specific frequencies correspond to distinct parts of the cochlea, indicating a structured representation within these auditory regions.

• The pathway from the cochlea through various nuclei leads to projections that reach the medial geniculate body and ultimately connect to primary auditory areas.

Secondary Auditory Area Functions

• The secondary auditory area (A2), located in the superior temporal gyrus, plays a role in recognizing sounds such as words and melodies.

• This area processes various sound intensities and characteristics, contributing to semantic understanding related to what is heard.

Olfactory System Overview

• The olfactory area is anatomically situated at the anterior part of the brain's structure, linked with Brodmann areas 34 and 35 responsible for smell perception.

• Olfactory receptors project signals through pathways leading to connections with the olfactory bulb before reaching higher cortical areas for further processing.

Gustatory Processing Insights

• The gustatory area is located in the posterior insula and operculum. It integrates taste information from different sources within its anatomical context.

Understanding the Insular Cortex and Gustatory Perception

The Role of Area 43 in Sensory Processing

• The insula has a central sulcus that divides its anterior and posterior portions, with area 43 linked to long-term sensory processing.

• Area 43 is located inferiorly to the somatosensory area, specifically between the parietal lobe and lateral sulcus.

• This area projects to both primary gustatory regions and insular areas, although there is some ambiguity regarding its topography as noted by researchers like Angelo Machado.

Multimodal Sensory Integration

• Both Machado and Murilo Menezes discuss how area 43 contributes to somatosensory perception related to food, including temperature and texture.

• Gustation involves multiple modalities; not only chemical (taste), but also mechanical (texture), thermal (temperature), and olfactory aspects contribute to overall flavor perception.

• The interaction between gustatory and olfactory senses enhances flavor experience, indicating a complex integration of sensory modalities.

Complexity of Gustatory Perception

• Gustatory perception is linked with olfactory functions, emphasizing the need for an integrated approach in understanding taste experiences.

• Functional MRI studies reveal activation across multiple brain areas during gustation, highlighting the complexity of this sensory process.

Motor Functionality: Understanding Primary Motor Areas

Primary Motor Cortex Overview

• The primary motor cortex is associated with voluntary movement initiation, particularly in distal limb musculature.

• Located in the pre-central gyrus within the frontal lobe, it plays a crucial role in executing motor commands.

Pathways of Motor Control

• The corticospinal tract originates from this area; it travels through various brain structures before reaching spinal levels where it influences muscle activity.

• Approximately 75% of fibers cross at the pyramidal decussation while others remain ipsilateral; this anatomical feature affects clinical outcomes following lesions.

Clinical Implications of Lesions

• Upper motor neuron lesions above the pyramids result in contralateral symptoms while those below lead to ipsilateral manifestations.

• Understanding these pathways aids in diagnosing conditions affecting motor control based on lesion location.

Homunculus Representation: Mapping Sensory-Motor Functions

Sensory-Motor Homunculus Concept

• A homunculus representation illustrates how different body parts are mapped onto cortical areas responsible for sensation and movement.

Specific Body Part Representation

• In the pre-central gyrus, regions corresponding to foot, leg, trunk, arm, face, tongue, and oropharynx are organized medially to laterally.

Interconnectivity Between Areas

Motor Control and Planning in the Brain

Overview of Motor Pathways

• The cerebellum and basal ganglia are key organs that control movement, projecting to the thalamus, which then connects to the primary motor area.

• The primary motor cortex sends projections through the corticobulbar and corticospinal tracts, influencing lower motor neurons for movement execution.

Secondary Motor Areas

• The supplementary motor area (SMA), located in Brodmann area 6 on the medial aspect of the superior frontal gyrus, is involved in planning complex movements, particularly those involving fingers.

• This area is crucial for preparatory movements and ensuring precise activation of distal musculature.

Role of Prefrontal Cortex

• The SMA has reciprocal communication with the primary motor area and receives input from the prefrontal cortex, which provides context and meaning to movements.

• The prefrontal cortex helps determine the objectives behind movements, guiding how they should be executed by secondary motor areas.

Coordination Between Motor Areas

• Secondary motor areas plan specific muscle activations necessary for executing a movement while the primary motor area directly activates these muscles.

• The pre-motor area also plays a role in determining why a movement is performed, adding an additional layer of complexity to motor planning.

Influence of Additional Brain Structures

• Both premotor and supplementary areas are influenced by various brain structures including cerebellum and thalamus; they coordinate large muscle groups for mass movements.

• These areas have multiple projections that facilitate communication with other regions like reticular formation and red nucleus to influence axial muscle activity.

Mirror Neurons and Learning

• Mirror neurons are found in several brain regions including SMA, parietal lobe, Wernicke's area, Broca's area, V5 (visual motion), indicating their role in observational learning.

The Role of Caregivers in Empathy and Emotional Understanding

Understanding Empathy in Caregiving

• Caregivers play a crucial role not only in physical activities but also in fostering empathy, which is essential for emotional support.

• Empathy involves recognizing complex emotional states, such as when someone is angry or sad, highlighting the importance of emotional intelligence in caregiving.

• The ability to respond appropriately to different emotional cues—like anger expressed through accusations or sadness shown through tears—is vital for effective caregiving.

• This discussion emphasizes that caregiving extends beyond mere task completion; it encompasses understanding and responding to the emotional needs of individuals.