PCB3703 chapter 20

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Questions and Answers

What is the primary composition of EEG waveforms?

Individual action potentials from cortical neurons

Intrinsic electrical activity of individual neurons

Extracellular currents from cortical EPSPs and IPSPs (correct)

Magnetic fields generated by brain structures

Which EEG wave type is primarily associated with relaxed wakefulness, especially with eyes closed?

Delta waves

Theta waves

Beta waves

Alpha waves (correct)

What characteristic of REM sleep includes physiological changes?

Increased muscle tension throughout the body

Increased synchronized EEG activity

Decreased heart rate and blood pressure

Phasic contractions of selected muscles like the eyes (correct)

What type of waves are predominantly observed in the deepest stages of non-REM sleep?

Delta waves Signup and view all the answers

Which of the following factors does NOT affect the dominant frequency of EEG waves?

Geographical location Signup and view all the answers

What is the significance of evoked potentials in clinical settings?

They assess the integrity of sensory pathways Signup and view all the answers

Which phenomenon describes the brain's readiness to respond to stimuli during different sleep stages?

Fluctuating responsiveness depending on sleep stage Signup and view all the answers

What is commonly associated with persistent isoelectric EEG activity?

Brain death Signup and view all the answers

Which statement accurately describes the characteristics of REM sleep?

The periods of REM sleep increase in length with sleep duration. Signup and view all the answers

What is the primary role of the left hemisphere in cerebral dominance?

Performing analytical and computational tasks Signup and view all the answers

What major observation was made during split-brain experiments?

Patients cannot describe objects in the left visual field despite being able to locate them. Signup and view all the answers

Which statement is true regarding the changes in heart rate during the sleep stages?

A decrease in heart rate is observed predominantly in stage 4. Signup and view all the answers

What effect do neurotransmitters like serotonin and acetylcholine have on sleep?

They can impact the regulation of the sleep-wake cycle. Signup and view all the answers

What is a common consequence of long-term sleep deprivation on cognition?

Impairment of cognitive functions and memory consolidation Signup and view all the answers

Which of these statements regarding delta waves is correct?

They indicate the presence of deep sleep. Signup and view all the answers

Which aspect of the split-brain procedure is highlighted by the results observed in patients?

Functional independence of the hemispheres leads to specific deficits. Signup and view all the answers

What best explains the behavior observed when a split-brain patient is shown the word ‘Rub’ in their left visual field?

The left hand will scratch the right hand spontaneously. Signup and view all the answers

Which response is characteristic of a split-brain patient when asked to vocalize what they see in a chimeric image?

They will refer to the first object their right hemisphere perceives. Signup and view all the answers

What does the phenomenon of neuron plasticity refer to?

Neuron processes and synaptic connections being flexible and dynamic. Signup and view all the answers

How does attention affect the activity of the frontal lobe?

It enables frontal neurons to filter out distractions. Signup and view all the answers

What is true about the stages of sleep concerning physiological changes?

Non-REM sleep is associated with restoration and tissue growth. Signup and view all the answers

Which best describes the relationship between learning mechanisms and long-term potentiation?

Long-term potentiation is a cellular mechanism that enhances synaptic efficacy. Signup and view all the answers

What does cerebral lateralization imply about brain function?

Certain cognitive tasks are predominantly managed by one hemisphere. Signup and view all the answers

What can be concluded about the brain structure regarding learning and memory?

Modular organization allows for diverse cognitive functions across the brain. Signup and view all the answers

Study Notes

Electroencephalogram (EEG)

EEG records potential oscillations from electrodes on the scalp.
EEG is used in clinical neurology and epilepsy diagnosis.
EEG wave forms result from extracellular currents from cortical EPSPs and IPSPs.
EEG spike does not reflect cortical action potentials, but reflects activity of many cortical pyramidal cells.
EEG wave size or polarity does not reflect excitation or inhibition of cells.

Dominant Frequency

EEG dominant frequency is affected by age, state of consciousness, recording site, drug action, and disease.

Wave Classification

Alpha waves (8-13 Hz) are recorded in the posterior brain when awake and undisturbed, and in relaxed individuals with eyes closed.
Beta waves (more than 13 Hz) are present when the nervous system is active and occur during sensory input and mental activity.
Theta waves (4-7 Hz) are commonly observed in sleep and young children, and sometimes occur with mental disorders.
Delta waves (less than 4 Hz) are primarily seen in adults during deep sleep and are occasionally present in awake, young children.

Brain Death

Brain death is indicated by a persistent isoelectric EEG in the absence of depressants.

Sleep-Wake Cycle

The sleep-wake cycle is a circadian process with an endogenous 25-hour cycle.
The cycle can be interrupted by time zone changes or environmental shifts.
Sleep stages include non-REM and REM sleep.
Non-REM sleep involves stages of drowsiness, light sleep, early sleep, and deepest sleep, characterized by different EEG wave patterns.
REM sleep occurs approximately every 90 minutes and is associated with rapid eye movement, desynchronized EEG activity, and dreaming.

Non-REM Sleep Stages

Stage 1: Drowsiness (theta waves)
Stage 2: Light sleep (slow waves interspersed with sleep spindles and K complexes)
Stage 3: Muscle tone decreases, heart rate slows (some delta waves)
Stage 4: Deepest sleep, difficult to arouse (delta waves)

REM Characteristics

REM periods increase in length with sleep duration.
In newborns, REM sleep makes up 50% of sleep, but decreases with age.
REM sleep is believed to be the period of most dreaming.

Sleep Mechanism

The purpose of sleep is unknown, but sleep deprivation is debilitating.
Neurotransmitters like serotonin, norepinephrine, and acetylcholine can affect the sleep-wake cycle.

Evoked Potential

EEG changes elicited by stimuli (visual, acoustic, or peripheral nerve).
Waveforms are largest over the appropriate brain region.
Used clinically to assess sensory pathway integrity.

Cerebral Dominance

Each hemisphere of the brain receives and analyzes information, but one hemisphere is dominant for certain functions.
The left hemisphere is dominant for speech, writing, analytical, and computational activities.
The non-dominant hemisphere specializes in non-verbal, emotional, artistic, and intuitive activities.
Many individuals have a larger left temporal lobe than the right.

Sodium Amytal Test

In this test, Sodium amytal (fast-acting barbituate) is injected into the carotid arteries.
This demonstrates which hemisphere is dominant for speech.
The majority of right-handed and left-handed people have their speech in the left hemisphere.
Lateralization may be weaker or absent in some left-handed people.

Split Brain Experiments

Commissurotomy is performed to alleviate severe epilepsy by severing the corpus callosum and anterior commissure.
This procedure prevents the spread of epileptic activity and allows each hemisphere to function independently.
There are no significant changes to patients after the procedure, but there is an increased risk of sagging of the brain lobes due to lack of support.

Classical Studies on Split-Brain Patients

Objects presented to one visual field are processed by the contralateral hemisphere.
Persons can only locate objects with their hand that corresponds to the same hemisphere as the presented visual field.
Persons often deny seeing anything in the other hemisphere.

Presentation of Conflicting Images

When conflicting images are presented to the visual fields in split-brain patients, the responses differentiate the function of each hemisphere.

Chimeric Image Presentation

Split-brain patients are presented with face images, half of which is presented to each side of the brain.
In these studies, the dominant hemisphere determines which feature is the response, either "man" or "woman."

Summary

Humans have two brains that have strengths and weaknesses, but each can operate cooperatively.
When the two hemispheres are separated, each develops mechanisms to work together.

Biological Basis of Learning and Memory

Within the first six months of life, the human brain fully complements with the addition of neuron growth processes.
Supportive and protective cells (glia) are also added.
We are not hard-wired; neuron processes and synaptic connections are dynamic.
Processes strengthen when used and weaken when inactive.
Learning may be related to the stabilization of useful circuits.

Brain Modules

The brain is modular anatomically and functionally.
It can listen to lectures, take notes, look at images, and simultaneously think of other topics (e.g. lunch).
Interest, need or curiosity prompts us to pay attention, activating the frontal lobe.
Signals can be attenuated when concentrating, while gating promotes passage to gnostic areas in the frontal cortex.

Memory Categorization

Memory is categorized into declarative and procedural types.
Declarative memory involves storing and retrieving conscious information.
Procedural memory involves unconscious motor skills.

Temporal Categorization of Memory

Short-term memory is located primarily in the anterior portion of the frontal lobe and thalamus, relying on ongoing neural activity.
Recent memory involves the hippocampus and allows easy recall of events over the past few days.
Long-term memory is stored diffusely in both hemispheres and requires repeated recall.

Engram and Stages of Memory

An engram is the site of change in the nervous system associated with learning.
Profound memory deficits can occur when the hippocampus is damaged.
Short-term memory is processed into long-term memory via a process called long-term potentiation (LTP).
LTP requires gene induction and is potentially blocked by inhibitors of protein synthesis.

Learning

Neural circuitry involved in learning in mammals is complex.
Researchers have studied the cellular bases of learning in simpler organisms like aplysia.
Example: the gill-withdrawal reflex in aplysia (monosynaptic) is subject to short-term and long-term potentiation.
Single tail shock activates serotonergic neurons, increasing sensory neuron transmitter release, through mechanisms such as increasing cAMP, decreasing K conductance and depolarizing neurons.

Long-Term Potentiation

Stimuli over 1.5 hours lead to sensitization that lasts days to weeks.
This is related to induced protein synthesis, increased RNA transcription, and the increased presence of neuronal cell adhesion molecules (NCAMs), increased dendritic density and second messenger activity, and long-term facilitated transmitter release.

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