PSYC304: Sensory Processing and Pain Principles

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Questions and Answers

Which brain region is primarily involved in processing unattended information?

Occipital lobe

Frontal cortex

Hippocampus

Cingulate cortex (correct)

What is one of the key features of neurons in the brain?

They remain dormant unless stimulated.

They can adapt to interpret nearly any input. (correct)

They operate independently without the need for rewiring.

They can only process stimuli from sensory organs.

What is the term used for the phenomenon of experiencing cross-modal stimulation?

Neuroplasticity

Multisensory processing

Synesthesia (correct)

Nociception

What type of receptors are tonic receptors?

Slow-adapting receptors Signup and view all the answers

Which sensory pathway primarily conducts information through the thalamus?

The dorsal column system Signup and view all the answers

Which type of receptor is primarily involved in sensing temperature?

Thermoreceptors Signup and view all the answers

What role does pain serve beyond just withdrawal from harmful stimuli?

It aids in recuperation and learning. Signup and view all the answers

What kind of organization does the primary somatosensory cortex (S1) exhibit?

Contralateral and somatotopic organization Signup and view all the answers

What does neuroplasticity refer to in the context of sensory processing?

Reorganization of neural pathways through experience Signup and view all the answers

How is congenital insensitivity to pain caused?

Due to mutations in voltage-gated sodium channels. Signup and view all the answers

Which synesthetic pairing is given as an example?

Grapheme-color synesthesia Signup and view all the answers

What specialized sensory structure do some animals use for tactile navigation?

The barrel cortex Signup and view all the answers

What phenomenon can occur in response to injury where individuals perceive sensation in non-existent limbs?

Phantom pain syndromes Signup and view all the answers

What does the McGill Pain Questionnaire assess?

The multifaceted nature of pain. Signup and view all the answers

Which principle describes the way sensory pathways convey information?

Labelled lines Signup and view all the answers

What is the implication of cortical magnification in sensory mapping?

Increased representation of highly sensitive body regions Signup and view all the answers

What is the main difference between sensation and perception?

Sensation is the initial detection of stimuli, while perception is the interpretation of that information. Signup and view all the answers

Which processing method is characterized by starting with sensory input and building a more complex understanding?

Bottom-up processing Signup and view all the answers

How do the four main types of somatosensory receptors function?

They transduce environmental energy into neural signals via specific mechanisms. Signup and view all the answers

What happens when sensory neurons are wired incorrectly, such as auditory neurons to the visual system?

Unusual sensations or experiences occur because the brain does not receive typical input. Signup and view all the answers

What is meant by the term 'receptive field' in sensory processing?

The range of stimuli that can activate a receptor or neuron. Signup and view all the answers

What role does neural coding play in determining the intensity of a stimulus?

Intensity is communicated by the rate of action potentials generated by the sensory neurons. Signup and view all the answers

Why is it beneficial for our sensation to diminish with constant stimulation?

It helps conserve energy and prevent sensory overload. Signup and view all the answers

What is a potential drawback of managing pain through pharmacological means?

They can lead to dependency or have side effects. Signup and view all the answers

Study Notes

PSYC304: General Principles of Sensory Processing, Touch, and Pain

The course covers the general principles of sensory processing, including touch and pain.
The lecture outline covers principles of sensory processing, types of somatosensation, and pain, thermosensation, and itch.
Learning objectives include differentiating sensation and perception, top-down vs. bottom-up sensory processes, the number and type of senses, how neural information is interpreted, and how the brain codes for sensory information.
Learning objectives also include understanding sensation diminishment with constant stimulation, receptive fields, plasticity in the brain, pain, different types of nociceptors and thermoceptors, and pain management.

Basic Concepts of Sensation and Perception (part 1)

Sensation and perception are parts of a continuous process.
Sensation involves receiving sensory stimulation.
Perception involves interpreting sensory information.

Basic Concepts of Sensation and Perception (part 2)

Bottom-up processing involves detecting specific features of stimuli and combining them into more complex forms.
Top-down processing involves forming perceptual hypotheses, selecting features to check these hypotheses, and recognizing the stimulus itself.

Basic Concepts of Sensation and Perception (part 3)

Sensory systems receive stimulation through specialized receptor cells.
Sensory input is transduced into receptor potentials (e.g. PSPs).
This process is often driven by ionotropic receptors, but sometimes, metabotropic receptors are used.
Receptor cells deliver neural information to the brain.

The Five Senses

Sensory systems use different modalities and adequate stimuli to receive signals.
Mechanical senses detect physical contact or deformation.
Visual senses involve visible radiant energy.
Chemical senses involve substances dissolved in air or water.
Electrical senses detect differences in electrical current density.

Sensory Receptor Organs

Sensory systems have a restricted range of responsiveness.
Receptor organs detect energy or substances.
Sensory systems respond to a range of wavelengths and frequencies.

Intensity Coding

Intensity coding occurs with different thresholds for the three types of neurons.
The brain uses range fractionation to determine stimulus intensity, which involves multiple neurons acting in parallel.
More neurons are recruited if the stimulus increases.

Sensory Adaptation

Sensory adaptation is the progressive loss of response to maintained stimuli.
Tonic receptors are slow-adapting, while phasic receptors are fast-adapting.

Receptive Fields

Each cortical neuron has a receptive field that is stimulated when a stimulus is applied.
Cortical neurons respond to inputs in a specific location; if stimulation occurs in the surrounding region, they inhibit in response.

Receptors in the Skin

Skin receptors include free nerve endings, Merkel's discs, Meissner's corpuscles, Ruffini's endings, and Pacinian corpuscles. These all come in both large and small variations based on their function.
Each receptor is responsible for detecting a specific stimulus such as temperature, vibration, or pressure and delivers this information to the brain.

Example: The Pacinian Corpuscle

Pacinian corpuscles detect vibration.
Transduction occurs via stretch receptors, similar to muscle spindles (proprioception).
Receptor potentials and action potentials carry information for the stimulus.

Receptor Potentials and Action Potentials

Receptor potentials lead to action potentials when they surpass a certain threshold.

The Four Main Skin Receptors

The four main skin receptors are Pacinian corpuscles (vibration), Meissner's corpuscles (light touch, fast-adapting), Merkel's discs (fine touch, slow-adapting), and Ruffini's endings (stretch, slow-adapting).

Afferent Axons from Skin Receptors

Afferent axons carry sensory information to the CNS.
Different types of neurons carry information about touch, proprioception, pain, temperature, and itch.
A alpha (Αα), A-beta (Αβ), A-delta (Αδ), and C fibres have different lengths, diameters, and conduction speeds.

Pathways: The Dorsal Column System

Sensory information from the body travels through the dorsal columns of the spinal cord and makes its way to the brain via distinct pathways.
Information is relayed through the medulla, thalamus, and travels to the primary somatosensory cortex.

Dermatomes

Dermatomes are specific body regions where incoming and outgoing nerves meet.
Corresponding dorsal roots innervate different dermatomes in the body.
Many dermatomes may overlap, making it possible for nerves connected to one area of the body to also send information from other areas.

Sensory Pathways

Sensory pathways are segregated ("labelled lines").
Signals arrive at the spinal cord or brainstem.
Most signals travel through the thalamus and are processed by the cerebral cortex.

Cortical Organization of Sensory Information

Information from different body parts is organized somatotopically in the primary and secondary somatosensory cortex.
Primary somatosensory cortex (S1) is contralaterally organized.
Secondary somatosensory cortex (S2) has more complex processing and may use bilateral information.

Somatotopic Organization (Sensory Homunculus)

The sensory homunculus maps body parts to cortical areas.
The size of the map area reflects the density of sensory receptors in that part.
More sensitive areas (e.g. hands, face) have a larger cortical representation.

Special Systems for Special Animals

Special sensory systems like whiskers and the barrel cortex in certain animals are responsible for processing sensory input relevant to their environment.

Cortical Representation

Cortical representation maps to the body and has flexible receptive fields.
Representation is based on the use of specific parts.

Neuroplasticity (due to damage)

The brain adjusts and modifies itself in response to sensory deprivation, injuries, and other alterations to the body.
The brain can compensate for damage done to sensory input by transferring the responsible function to another area.

Neuroplasticity (due to use)

Experience (e.g., use/practice) can change the brain.
The amount of use directly affects the size and/or function of the responsive area in the cortex.

Neuroplasticity (due to cortical damage)

After cortical damage, constraint-induced therapies can promote recovery.
Reorganization occurs, as the brain restructures itself to compensate for this damage.

Phantom Limbs

Phantom limb sensations show large-scale plasticity.
The brain reorganizes cortical maps to represent lost limbs.
This leads to the sensation of feelings in the missing limb, despite the fact there is no physical stimulation to the area.

Are Cortical Sensory Neurons Specialized for Their Type of Sensation?

Cortical sensory neurons are not specialized in terms of the type of sensation, as neurons in different brain regions can detect nearly any input type.
The specialized processing stems mainly from differing wiring.

The Brain that Kind of Changes Itself

Brain plasticity and the organization's limited capacity for change.
Plasticity is less flexible than previously believed.

Attention: Manipulating Sensory Processing

Attention enhances specific messages, using the attenuator and filtering unattended messages.
Attentional processing is carried out by the posterior parietal and cingulate cortex, as well as other regions.

"Association" Cortex

AKA tertiary cortex is multimodal.
It comprises a large portion of the brain.
Is often considered sensory and motor.

Cross-modal stimulation is characterized by an involuntary sensory experience involving stimuli that don't usually evoke that particular sensation.
It's thought to be driven by learning rules and related to evolutionary processes.

How to Test for Synesthesia

Testing for synesthesia involves determining if a perceived stimulus is real or imagined (malingering) to assess whether the user is experiencing it genuinely.
Difficult search tests take longer than basic searches, which can reflect the intensity of the feeling.

Unpleasant but Adaptive

Pain is associated with tissue damage that results in an unpleasant experience.
Congenital insensitivity to pain is caused by a voltage-gated sodium channel mutation.
Pain is necessary for the body's well-being, allowing for recovery from damage, inducing learning experiences, and communicating to others.

Pain Serves Many Functions

Pain induces withdrawal, recovery, learning from experiences, and communicating with others.
A simple pain reflex is carried out quickly, while conscious pain processing is delayed.

Pain is Multifaceted

Pain perception, cognitive processing (e.g. no pain, mild, excruciating experience), motivational affective systems (such as feeling tired/fearful), and the sensory discriminative system (e.g., throbbing, and shooting pain).
The McGill Pain Questionnaire is commonly used to assess different types of pain.

Nociceptors

Nociceptors are sensitive to temperature and chemicals released by tissue damage.
These receptors transmit information about pain to the central nervous system.
Important components like histamine, serotonin, prostaglandins, and leukotrienes act on these receptors to trigger pain signals.

Different Receptors for Different Temperatures

Nociceptors with components TRPV1 (hot), TRPM3 (cold), and CMR1 (cold).
These thermoreceptors differ in their sensitivity, response patterns, and receptor types.

Itch: A Complicated Sensation

Itch is a multifaceted sensation with multiple receptors and pathways.
Itch receptors do not exclusively respond to pain.
Itch cells contain histamine receptors in some cells, but some do not.
Itch signals are involved in pain.

Pathways: The Spinothalamic System

The spinothalamic system carries pain and temperature information.
It crosses the midline in the spinal cord before ascending to the thalamus.

Phantom Limb Pain

Dorsal horn neurons can become hyperexcitable after damage.
This can result in phantom limb pain.

Pain Isn't a Physical Sensation

People may experience pain due to social rejection.
All types of pain activate the anterior cingulate cortex.
Painkillers can reduce the pain of social rejection.

Pain Management: Drugs

Analgesia is the absence or reduction of pain, and many different drugs have been developed to address this issue.
NSAIDs affect COX, prostaglandins.
Opioids (endogenous and exogenous) act on spinal cord, descending pathways, and higher brain sites.

Pain Management: PAG

The periaqueductal gray (PAG) in the midbrain is involved in pain modulation.
Stimulation in the PAG can block incoming pain signals.
Endogenous mechanisms involve natural pain relief.

Pain Management: Placebo

Placebos have shown effectiveness in pain management, suggesting psychological factors are influential in pain perception.
Placebo's effects vary with expectations and contexts, but likely involve endogenous opioids.

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Description

This quiz assesses your understanding of the principles of sensory processing, specifically focusing on touch and pain. Topics include sensation versus perception, somatosensation types, and neural interpretation of sensory information. Prepare to differentiate key concepts and apply your knowledge of pain management techniques.