Epigenetics, Developmental Disorders, and Sensory Systems: Ch. 8–9

What is epigenetics?

The study of lasting changes in gene expression caused by chemical modifications of DNA or its associated proteins, without altering the DNA sequence.

How can early-life experiences affect gene expression?

Experiences can change gene expression patterns, influencing behavior and potentially leading to long-lasting consequences.

This has chnaged how we think about the biology of early experience

What are two common ways experience affects gene expression?

1. DNA methylation - prevents gene expression at specific sites. 2. Histone modification - alters histone proteins to increase gene accessibility for expression.

Histones may be acetlyated because the addition of the acetyl group to the histone protein makes the DNA more easily accessed to increase gene expression.

What role do epigenetic mechanisms play in mental health?

They account for how early life stress or trauma can increase the risk of major depression and other mental illnesses.

DNA methylation and histone acetlylation that shift how strongly a particular genes to express. Why?

Experience can leave a lasting mark on gene expression without changing the DNA sequence

What is a developmental disorder? And what are the 3 main environmental aspect to them?

A disorder that involves complex etiology, often influenced by multiple genes and environmental factors, such as epigenetics.

- Autism spectrum disorder (ASD)

-Attention deficit/ hyperactivity disorder (ADHD)

-Schizophrenia (onset is not until late teen years,

but is now regarded as a developmental disorder...

will cover later)

What is Autism Spectrum Disorder (ASD)?

A class of neural development disorders characterized by impaired social interaction, communication, and restricted interests, typically evident by age 3.

Causes of ASD are not understood but people think it has to deal with genetic component

What is the teratogenic (vaccines) basis for ASD? Who made it?

A theory proposed---Andrew Wakefiled)--in a fraudulent study suggesting vaccines cause ASD, which has been disproven by large studies.

Andrew lost his medical license

What is the one leading hypothesis of ASD?

There is abnormal development of interneruons in the cerebral cortex, but it is poorly understood.

What is Attention Deficit/Hyperactivity Disorder (ADHD)? And why people say that is either over or under diagnosed?

1. A disorder characterized by symptoms present before age 12, affecting about 5-10% of children, with complex genetic and environmental components.

2. People think that because it has increased a lot in the us and has even risen and also saying that the stimulant is part of it.

What brain differences are associated with ADHD?

Some differences have been noted in the prefrontal cortex and the dopamine mesolimbic pathway.

Which stimulant drug helps with ADHD?

Amphetamine

Chapter 8

Overview of the Sensory Systems

- Our perceptions are abstractions based upon the

biasing of sensory information processing to extract

meaningful information

- By meaningful, we mean information that is relevant

for the individual, or that which has evolved to

promote fitness, or optimize adaptation

What is sensory adaptation?

The process by which sensory receptors become less sensitive to constant stimuli over time.

Examples of the sensory systems

-sensory adaptation (olfactory, tactile)

-even important input can be suppressed when something else takes

priority — pain during an emergency

-processing is non-linear - perception is not proportional to the physical

stimulus

-context matters - the response at one point depends on its neighbors

(more on this later

What is the law of specific nerve energies?

The principle that specific receptors and neural channels for each sense are independent and can only produce one sensation.

What is transduction in sensory systems?

The conversion of physical energy by a receptor into an electrochemical pattern in neurons.

What is an adequate stimulus?

The specific type of energy that a sensory receptor is most sensitive to, such as light for the eye or sound waves for the ear.

What is hierarchical processing in sensory systems?

The representation of sensory information at multiple levels of the central nervous system.

What is cortical representation?

The specific areas of the cortex that process each sensory modality.

What is the significance of topographical mapping in sensory systems?

Neighboring points on the sensory surface are represented at neighboring points in the brain, maintaining spatial relationships.

What is the role of tonic activity in sensory neurons?

It provides a broader dynamic range of responses, allowing for modulation of action potential frequency based on sensory receptor activation.

How does context affect sensory perception?

The response to a stimulus can depend on its surrounding stimuli, demonstrating that perception is not solely based on the physical stimulus.

What is the impact of evolution on sensory processing?

Evolution favors sensory systems that can distill and alter information to enhance meaningful perception and promote adaptive behavior.

What is integration in sensory systems?

Integration refers to how sensory systems combine information, usually in association cortical regions.

What is coding in sensory systems?

Coding is the neural activity patterns that simplify and represent information for efficient transmission.

What does rate coding measure?

Rate coding measures how many action potentials (APs) occur per second, encoding stimulus intensity.

What is labeled line coding?

Labeled line coding is when individual sensory receptors respond to only a single quality for a particular sense, with information traveling to the CNS on its own afferent pathway.

What is across-fiber coding?

Across-fiber coding occurs when each receptor responds to a range of stimuli, with the quality encoded by the pattern across many receptors.

What is somatosensation?

Somatosensation is the sense of touch, which includes the detection of body sensations like touch and pain.

How is stimulus location determined in somatosensation?

Stimulus location is determined from the position of the activated receptors, mapping onto a representation of the body's surface in the cerebral cortex.

What is the pacinian corpuscle?

The pacinian corpuscle is a touch receptor that detects sudden displacement or high-frequency vibrations on the skin.

What happens when pressure is applied to the pacinian corpuscle?

When pressure is applied, the pacinian corpuscle changes shape, opening Na+ channels and producing a generator potential.

What is adaptation in sensory systems?

Adaptation is the progressive loss of response to a maintained stimulus, allowing for the representation of changes in the environment.

What are tonic receptors?

Tonic receptors show slow or no decline in action potential frequency.

What are phasic receptors?

Phasic receptors display adaptation and decrease the frequency of action potentials.

What is a receptive field?

A receptive field is the region of space or range whereby the presence of a stimulus will alter the firing of a sensory neuron.

What is the primary somatosensory cortex (S1)?

The primary somatosensory cortex (S1) receives touch information from the opposite side of the body.

What is the secondary somatosensory cortex (S2)?

The secondary somatosensory cortex (S2) maps both sides of the body.

What is audition?

Audition refers to our sense of hearing, which depends on our ability to detect sound waves.

What are the properties of sound waves?

Sound waves are periodic compressions of air, water, or other media and involve longitudinal oscillations in air pressure.

What is pitch in sound perception?

Pitch is the term used to define the perception of a sound, usually in terms of frequencies.

What defines loudness in sound?

Loudness is defined by the amplitude or height of the sound wave, usually measured in decibels (dB).

What is Fourier analysis?

Fourier analysis is a set of mathematical formulas for deconstructing complex waveforms into separable sine waves.

What are the three main parts of the ear?

The three main parts of the ear are the outer ear (pinna), middle ear (tympanic membrane and ossicles), and inner ear (cochlea).

What role does the cochlea play in hearing?

The cochlea contains hair cells that transduce sound vibrations into neural activity.

What is the organ of Corti?

The organ of Corti is the collective name for structures within the cochlea that convert sounds into neural activity.

What is temporal coding in sound processing?

Temporal coding (frequency theory) is when the basilar membrane vibrates at the frequency of the sound, and hair cells drive action potentials at that same rate.

What is the volley principle?

The volley principle states that groups of neurons fire in alternation, tracking sound frequencies up to about 4,000 Hz.

What is place coding?

Place coding covers the highest frequencies, with each region of the basilar membrane having hair cells most sensitive to one frequency.

What is the primary auditory cortex (A1)?

The primary auditory cortex (A1) is located in the superior region of the temporal lobe and is the destination for most information from the auditory system.

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