Chapter 58: Cerebral Cortex, Intellectual Functions of the Brain, Learning, and Memory

Guyton & Hall + K2

What is the thickness of the functional layer of the cerebral cortex?

2-5 mm

How many neurons are estimated to be in the cerebral cortex?

~80 billion

What are the three main types of neurons in the cerebral cortex?

Granular (stellate), pyramidal, fusiform

What is the function of granular (stellate) neurons?

Interneurons for local processing (some excitatory, some inhibitory)

Which neurotransmitters are released by granular neurons?

Glutamate (excitatory), GABA (inhibitory)

In which cortical areas are granular neurons most concentrated?

Sensory and association areas

Which cortical neurons are responsible for most output from the cortex?

Pyramidal and fusiform cells

Which type of neuron has the longest axons that reach the spinal cord?

Pyramidal neurons

What type of fibers connect adjacent cortical areas?

Horizontal fibers

What type of fibers connect the cortex with lower brain areas or distant cortex?

Vertical fibers

In which cortical layer do most sensory signals terminate?

Layer IV

Which cortical layer sends output to the brainstem and spinal cord?

Layer V

Which cortical layer sends output to the thalamus?

Layer VI

Which cortical layers are responsible for intracortical connections?

Layers I, II, III

What is the importance of the thalamus in cortical function?

Thalamic excitation is necessary for almost all cortical activity

What happens when both the thalamus and cortex are damaged?

Greater functional loss than cortex damage alone

Which sensory pathway does not pass through the thalamus?

Olfaction

What are the primary functions of the primary motor cortex?

Direct control of discrete muscle movements

What is the function of the primary sensory areas?

Detect visual, auditory, and somatic sensations

What is the role of secondary sensory areas?

Interpretation and processing of sensory signals

What are the three major association areas of the cerebral cortex?

Parieto-occipitotemporal, prefrontal, limbic

What is the function of the parieto-occipitotemporal association area?

Interprets complex sensory information from surrounding areas

What is the function of the spatial coordination area?

Calculates body and environmental positioning

Where is Wernicke’s area located?

Posterior superior temporal gyrus

What is the primary function of Wernicke’s area?

Language comprehension and intellectual processing

What is the function of the angular gyrus?

Initial processing of visual language (reading); connects visual input to Wernicke’s area.

Damage to the angular gyrus leads to which condition?

Alexia (inability to read) and agraphia (inability to write).

What is the role of Wernicke’s area?

Higher-level language comprehension and interpretation of auditory and visual information.

Where is Wernicke’s area located?

Posterior superior temporal lobe, near the parietal and occipital junction.

What condition results from damage to Wernicke’s area?

Wernicke’s aphasia—fluent but nonsensical speech, impaired comprehension.

What is the function of Broca’s area?

Motor control of speech production.

What is the result of damage to Broca’s area?

Broca’s aphasia—nonfluent, effortful speech with intact comprehension.

What is prosopagnosia, and which brain region is affected?

Inability to recognize faces; damage to the medial occipitotemporal (fusiform gyrus).

What is the limbic association area responsible for?

Behavior, emotions, and motivation.

Which hemisphere is typically dominant for language in most people?

Left hemisphere (in 95% of right-handed individuals).

What is the importance of the corpus callosum in brain function?

Connects both hemispheres for coordinated sensory and motor function.

A 45-year-old man presents with difficulty reading and writing after a stroke. His speech and auditory comprehension remain intact. MRI reveals a lesion in the angular gyrus. Which condition is most likely responsible for his symptoms?

Alexia with agraphia

A patient presents with an inability to recognize familiar faces, despite having intact vision and memory. Which brain region is most likely affected?

Fusiform gyrus (medial occipitotemporal region)

A neurosurgeon stimulates a specific cortical area in a conscious patient, causing the patient to recall a childhood memory vividly. Which brain region is most likely being stimulated?

Limbic association area

A bilingual patient suffered a stroke affecting the Broca’s area of his left hemisphere. He learned both languages at different times in life. What is the expected speech impairment?

Greater impairment in the first language

A right-handed individual presents with difficulty in forming coherent speech after a head injury. Imaging reveals damage to the left inferior frontal gyrus. Which of the following functions is most affected?

Speech production (Broca’s aphasia)

What is the main role of Wernicke’s area?

Language comprehension.

How is written language processed in the brain?

Visual input → Angular gyrus → Wernicke’s area.

What happens if Wernicke’s area is damaged?

Impaired reading, writing, math, and logical reasoning.

What functions does the non-dominant hemisphere control?

Music, spatial awareness, body language, and voice intonations.

What is the role of the prefrontal cortex in intellectual function?

Decision-making, planning, goal-setting, and complex thought.

What are the effects of prefrontal cortex damage?

Poor problem-solving, social dysfunction, mood instability.

What is the purpose of prefrontal lobotomy?

Used historically to treat psychotic depression.

What were the effects of prefrontal lobotomy?

Loss of ambition, inappropriate social behavior, erratic mood swings.

What is the function of the prefrontal cortex?

Higher-order thinking, planning, decision-making, and working memory.

What happens if the prefrontal cortex is damaged?

Loss of logical sequencing, distractibility, poor decision-making.

What is "working memory"?

Short-term retention of information for problem-solving and planning.

Which brain area is responsible for prognostication and moral reasoning?

Prefrontal cortex.

What is Wernicke’s aphasia?

Fluent but nonsensical speech due to superior temporal gyrus damage.

What is global aphasia?

Severe language impairment from widespread cortical damage.

What is Broca’s aphasia?

Inability to produce speech while comprehension is intact.

What is motor aphasia?

Inability to vocalize words due to Broca’s area damage.

What is articulation?

Coordination of speech muscles by the motor cortex, basal ganglia, cerebellum.

What is the pathway for hearing and speaking?

Auditory area → Wernicke’s area → Broca’s area → Motor cortex → Speech.

What is the pathway for reading and speaking?

Visual area → Angular gyrus → Wernicke’s area → Broca’s area → Motor cortex → Speech.

What is the role of the arcuate fasciculus?

Connects Wernicke’s area to Broca’s area for language processing.

What is conduction aphasia?

Damage to the arcuate fasciculus causing poor repetition but intact comprehension.

What is the role of the corpus callosum?

Transfers sensory, motor, and cognitive information between hemispheres.

What happens when the corpus callosum is severed?

Split-brain syndrome, affecting interhemispheric communication.

What structure connects the temporal lobes between hemispheres?

Anterior commissure.

What is the holistic theory of thoughts?

Thoughts arise from widespread neural activation, not a single brain area.

Which brain structures contribute to consciousness/thoughts?

Cerebral cortex, thalamus, limbic system, and reticular formation.

Which brain areas determine the general nature of a thought?

Thalamus, limbic system, and reticular formation.

Which brain structure is essential for detailed visual thought?

Visual cortex.

What is consciousness?

Continuous awareness of surroundings or sequential thoughts.

How long does short-term memory last?

Seconds to minutes.

What are the two main theories of short-term memory?

Reverberating circuits and synaptic facilitation/inhibition.

How long does intermediate long-term memory last?

Minutes to weeks.

How can intermediate long-term memories become permanent?

Through repeated activation and reinforcement.

What are the mechanisms of memory at the synaptic level?

Chemical and physical changes in presynaptic terminals or postsynaptic membranes.

What is habituation?

Decreased neuronal response to repeated, insignificant stimuli.

What is facilitation in memory?

Strengthening of synaptic transmission following a strong stimulus, lasting up to weeks.

What causes habituation at the molecular level?

Progressive calcium channel closure → decreased neurotransmitter release.

What neurotransmitter mediates facilitation?

Serotonin.

How does serotonin enhance synaptic transmission?

Increases cAMP → blocks K+ channels → prolongs action potential → increases Ca2+ influx → more neurotransmitter release.

What is required for long-term memory formation?

Structural synaptic changes (more vesicles, terminals, dendritic modifications).

What happens if protein synthesis is blocked during long-term memory formation?

No structural synaptic changes → no permanent memory trace.

What principle governs early neuronal connectivity?

"Use it or lose it."

What happens if neurons fail to connect properly?

They degenerate.

What happens if a newborn’s eye is covered for weeks?

Cortical neurons for that eye degenerate → permanent vision loss.

How long does minimal memory consolidation take?

5-10 minutes.

How long does strong memory consolidation take?

1 hour or more, requiring RNA and protein synthesis.

What can prevent memory consolidation?

Brain concussion, anesthesia, or electrical brain convulsions.

How does rehearsal affect memory consolidation?

Strengthens the transfer of short-term memory into long-term memory.

Why is deep study better for memory than superficial study?

Focused learning enhances retention more than large amounts of shallow study.

What role does alertness play in memory consolidation?

Being awake enhances consolidation, while fatigue impairs it.

How are new memories stored during consolidation?

Codified and linked with related old memories for better retrieval.

What is anterograde amnesia?

Inability to form new long-term declarative memories (hippocampal damage).

Why is the hippocampus crucial for memory?

It determines which experiences are important for storage based on reward/punishment signals.

What is retrograde amnesia?

Loss of past memories due to hippocampal or thalamic lesions.

How does thalamic damage affect memory?

Impares memory retrieval without necessarily affecting memory storage.

Can people with hippocampal damage learn new motor skills?

Yes, because reflexive (skill) learning does not require the hippocampus.

What type of learning remains intact in hippocampal lesions?

Reflexive learning (e.g., sports, physical skills).