Cerebral cortex and higher cognitive functions

Functional anatomy of the cerebral cortex

Based on their functions, areas within the cerebral cortex can be divided into primary (sensory or motor), unimodal association and multimodal association (or integration).

• Primary areas send motor outputs (motor cortex) and receive sensory inputs (eg: somatosensory, auditory and visual cortices).
• Unimodal association areas further process sensory inputs and motor outputs of the primary areas. 
• Multimodal association areas integrate information from different areas of the brain and mediate higher functions.

Functions are often localized in specific cortical areas. Examples of functions and corresponding primary and unimodal association areas include:

• Movement: motor cortex in the frontal lobe
• Sensory information: somatosensory cortex in the parietal lobe
• Hearing: auditory cortex in the temporal lobe
• Vision: visual cortex in the occipital lobe

Take a closer look at the structures of the brain in this study unit about the anatomy of the nervous system.

Cognition and Language

Cognitive functions include recognizing, processing and responding to environmental stimuli as well as the initiation of voluntary responses. These processes are responsible for higher mental functions like the sense of self, attention, problem-solving and other behaviors. The cortical areas involved in these processes are usually multimodal association areas.

Some examples include:

• Personality and movement planning: prefrontal cortex in the frontal lobe
• Spatial awareness: areas in the parietal lobe
• Recognition: areas in the temporal lobe

Some functions are lateralized, meaning that their cortical areas are located in the left or the right hemisphere. For instance, attention and facial recognition tend to be localized in the right hemisphere, whereas language and speech are located in the left hemisphere in most people.

Language is one of the most studied higher mental functions. Two main multimodal integration cortices are involved in language understanding and production.

• Wernicke’s area is located in the temporal lobe, at the intersection with the parietal lobe, and is responsible for understanding the meaning of language stimuli like written or spoken words.
• Broca’s area is located in the frontal lobe and is responsible for producing language, for instance choosing the appropriate word order when speaking or writing.

Loss of function in either of these areas leads to specific language deficits such as an inability to understand language (receptive aphasia) or produce language (expressive aphasia).

Learn more about the function of different brain areas in the study unit Broadmann areas. The video also includes clinical notes about aphasia.

Learning and Memory

Whenever we are exposed to new information or try to perform a new motor task, we create new memories. These learning processes occur in multimodal association areas in various regions of the brain. Different types of memory can be defined based on the type of information they contain and for how long the information is stored.

Based on the type of information they contain, memories can be divided into:

• Declarative (or explicit) memory; pieces of information that can be recalled consciously, important for cognitive functions like judgment and evaluation
• Nondeclarative (or implicit) memory; skills and procedures that are mostly unconscious, such as the motor skills required to drink from a cup

Based on storage duration, memories can be divided into:

• Immediate memory; a few seconds
• Short term (working) memory; a few minutes
• Long term memory; months or longer

Need a refresher on the anatomy of the nervous system? Test yourself with our Nervous system anatomy practice: Quizzes and more!

The transfer of memories from short to long term is called consolidation.

This process likely involves the formation of new connections and changes to synaptic connectivity. An important cellular mechanism is long term potentiation, where repeated stimulation of associated neurons induces structural (growth of neuron dendrites) and chemical (more neurotransmitters released) alterations that strengthen the synaptic connections.

Consolidation primarily occurs in the hippocampus and temporal lobe for declarative memory, whereas motor cortex, cerebellum and basal nuclei are more likely to contribute to the consolidation of nondeclarative memories. Long term memories are often stored in the area most relevant for the type of information (eg: visual memories in the occipital lobe, motor memories in the motor circuits).

Sleep and Wakefulness

At the end of the day, when it is time to rest, we go to sleep. The reason we sleep is unclear, but experts suggest that it may be helpful to reduce our energy demands, to repair our bodies and for functions related to brain plasticity.

While sleep is not strictly a higher cognitive function, sleep patterns greatly influence how the brain works. For instance, a lack of sleep often impairs higher cognitive functions, especially attention and decision-making. It is also thought that some sleep phases are important for memory consolidation.

Like other body functions, sleep follows a circadian rhythm, meaning that periods of wakefulness and sleep alternate over 24 hour cycles. A key structure for our circadian rhythms is the suprachiasmatic nucleus of the hypothalamus, which functions as an internal ‘biological clock’ by measuring the passage of time based on how long it takes to degrade a specific protein.

Information from the suprachiasmatic nucleus is integrated with inputs from photoreceptors; when the amount of light in the environment decreases and the sleep generation process starts, the suprachiasmatic nucleus activates a pathway that decreases the communication between the thalamus and the cortex. Since most of the sensory pathways relay in the thalamus, this process effectively reduces the amount of sensory information reaching the cortex and therefore reduces consciousness.