Cognition and the Association Cortex

Cognition and the Association Cortex

• Primary sensory and motor cortical regions occupy about one-third of the neocortex.
• The association cortex, which makes up the remaining two-thirds of the neocortex, is located in the frontal, temporal, parietal, and occipital lobes.
• Association cortex is responsible for producing cognition.
• Association cortex differs from primary sensory and motor areas due to its unique connection patterns.
• Input to all cortical areas primarily comes from the thalamus, located atop the brainstem.
• The primary sensory cortex receives input from thalamic nuclei, which then relays information from the body’s sense organs.
• The association cortex gets input from other thalamic and cortical areas, resulting in highly processed information compared to the primary sensory and motor cortex.
• Temporal association regions produce cognition related to visual and auditory processing because of their close relationship with visual and auditory sensory regions.
• Parietal cortex is closely linked to somatosensation and movement control.
• Frontal cortex coordinates information from parietal and temporal association regions, which receive information from subcortical regions.
• Prefrontal cortex (PFC) includes dorsal, lateral, orbital, and medial regions.
• Activity in each prefrontal region is correlated with cognitive processing.
• Anterior cingulate cortex (ACC), another frontal lobe region, serves as an interface between emotion and cognition.

Knowledge About Objects

• The brain's seeing of objects is more compartmentalized than perceptions.
• Damage to areas such as visual area V4 leads to inability to perceive color.
• Damage to areas like V5 results in inability to perceive movement.
• Perception of a milk carton's rectangular shape remains constant despite changes in its visual form.
• The brain ignores changes in shape information received by the retinas, concluding that the object remains the same milk carton.
• Knowledge about milk cartons is represented in the temporal association cortex.
• Temporal association cortex forms the ventral stream of visual processing
• Damage to temporal association causes visual agnosia.
• Knowledge about what things are is stored in the temporal lobe.
• Knowledge of how to grasp objects is stored in the parietal lobe.

Multisensory Integration

• Knowledge about the world is attained through multisensory channels.
• The brain combines shape, color, and details when looking at a face.
• The brain contains visual areas that analyze various components of an object.
• These visual areas are not all connected.
• Philosophers identified the "binding problem," which questions how the brain integrates sensory and motor events into unified perceptions.
• Multimodal regions in the association cortex address sensory integration by housing neurons that respond to multiple sensory modalities.
• Multimodal regions combine stimuli characteristics across different senses.
• Synesthesia, where one sensory modality stimulation induces another, is viewed as an exaggerated solution to the binding problem.

Spatial Cognition

• Spatial cognition is knowledge about the environment that helps determine locations, navigate, interpret spatial relations, and communicate about space.
• Conceptualization of space includes defining body, grasping, distal, and cognitive space.
• Types of space include allocentric (object-to-object) and egocentric (self-to-object) space, and abstract cognitive space.
• Navigating an unfamiliar park involves organized movement and the ability to retrace steps using a mental representation of the physical environment.
• The ability to mentally manipulate visual images likely arose in parallel with the ability to navigate in space.
• Skill evolution in mental manipulation is linked to the evolution of physical movements.
• The dorsal stream in the parietal lobes is central to controlling vision for action and likely provided a basis for spatial cognitive skills.
• Human parietal association regions expanded more than in other primates, enabling complex spatial operations.

Deficits of Spatial Behavior

• The posterior parietal cortex plays a role in spatial behavior.
• Right posterior parietal lesions can cause spatial deficits.
• Topographic disorientation is an inability to use environmental cues to navigate.
• Egocentric disorientation is a type of topographic disorientation involving difficulty perceiving relative locations of objects.
• Individuals with spatial deficits struggle with mental manipulation of objects.
• Damage to the posterior cingulate cortex and medial temporal regions can also cause deficits in spatial behavior.
• The parietal cortex forms the major component of the dorsal stream.
• Bilateral injuries to the posterior parietal cortex can cause Bálint syndrome, which impairs spatial processing, eye gaze control, and object comprehension.
• Individuals with Bálint syndrome struggle with judging locations, estimating distances, and discerning spatial features.
• The temporal cortex, especially medial temporal regions, is implicated in spatial behavior.
• The dorsal and ventral streams converge on the hippocampus.
• Navigation expertise correlates with the size of the posterior hippocampal region.
• London taxi drivers have larger posterior hippocampal regions than bus drivers.
• Posterior hippocampal region activation increases during virtual navigation in taxi drivers.
• Hippocampi can shrink when taxi drivers retire, suggesting structural changes due to navigation expertise reverse with disuse.

Attention

• The narrowing or focusing of awareness to a part of the sensory environment or a class of stimuli defines attention.
• Attention helps to enhance neural activity related to specific information and decrease neural activity related to extraneous information.
• Attention can be directed selectively to thoughts and sensory stimuli.
• Research has identified neurons in the cortex and midbrain that show enhanced firing rates to particular locations or visual stimuli during attention tasks.
• A stimulus can activate a neuron at one time but not at another, depending on the focus of attention.
• Monkeys trained to attend to stimuli in a particular area of the visual field can have varied cell responses based on stimulus location.
• Neurons in visual area V4, sensitive to color and form, respond differently based on these attributes.
• The frontal lobes are central to attention
• Frontal lobe injuries can cause individuals to become overly focused on environmental stimuli.
• Frontal association cortex controls the ability to direct attention.

Neglect and Attention Deficits

• Parietal association cortex is key in other aspects of attention.
• Neglect is where a person ignores sensory information that should be considered important.
• Contralateral neglect affects only one side of the body.
• Neglect is a failure of attention, not sensory pathways.
• Right hemisphere parietal association cortex damage may cause neglect of the left side of their world.
• Anosognosia is when a patient is unaware of their illness.
• Neglect involves damage to the parietal association cortex, as distinct from loss of proprioception.
• People with neglect may ignore information on one side of the body when presented with similar information simultaneously on the other side.
• Extinction is a symptom where a person ignores stimuli on one side when presented simultaneously with stimuli on the other side.
• Neglect involves a failure to pay attention to one side of the physical world and the world represented in their mind.
• Contralateral neglect is usually linked to parietal lobe injury, it can also result from other injuries.
• Amygdala plays a role in directing attention to the eyes to identify facial expressions.

Planning and Executive Function

• Executive function involves the planning and generation of novel actions in changing circumstances.
• Executive functions include attentional control, planning, reasoning, working memory, problem-solving, abstract thinking, and self-monitoring.
• Executive function includes other cortical regions such as the parietal cortex, which are connected with the prefrontal cortex through several networks
• Frontal lobe injuries can cause an inability to organize behavior.
• The Wisconsin Card Sorting Test demonstrates deficits caused by frontal lobe injury.
• The participant must sort cards into piles based on stimulus cards.
• The correct sorting category is unstated, participants must figure out the solution.
• Shifting response strategies is particularly difficult for people with frontal lobe lesions.
• Perseveration involves the tendency to emit the same verbal or motor response, and is common in young children and people with frontal lobe injury.

Imitation and Understanding and Mirror Neurons

• Verbal and nonverbal communication requires a shared understanding between sender and receiver.
• The processes of producing and perceiving a message must share representation in the brains of the sender and receiver.
• Giacomo Rizzolatti and colleagues discovered mirror neurons.
• Mirror neurons in the premotor cortex discharge during both movement execution and observation of the same movement in others.
• Mirror neurons represent actions and enable appropriate responses by for imitation and understanding
• Mirror neurons provide the link between sender and receiver.
• A mirror neuron system (MNS) is distributed throughout the brain and includes cortical areas and can be subdivided into areas related to different types of movements
• MNS forms a basis of understanding actions.
• Data from brain mapping methods reveal the complexity of the MNS, modulated by factors involving the action, actor, observer, relationship, and context.
• The strength of neural activity is mediated by racial and ethnic congruence as well as by interpersonal liking and eye contact

Mirror Neuron Studies

• Studies of the MNS demonstrate that the brain understands actions and facilitates making movements quickly and more accurately.
• The concept of the MNS is being applied to rehabilitation interventions.
• Action observation treatment (AOT) involves watching a video and imitating the actions and aides in the recovery of impaired motor ability and improves motor control in neurologically normal participants.