Workshops

What are the three main types of stimuli that can elicit acute pain?

Mechanical, thermal, and chemical stimuli.

How do mechanical, thermal, and chemical stimuli activate nociceptors?

Mechanical stimuli open mechanically gated ion channels; thermal stimuli open thermally gated ion channels; chemical stimuli activate ligand-gated ion channels or G-protein coupled receptors.

List some common transducers involved in nociception.

TRP channels, ASICs, P2X receptors, PIEZO channels.

What is a receptive field?

The area of sensory surface (e.g., skin) that elicits a neuronal response in a single sensory neuron.

Define a dermatome.

A region of skin innervated by a single spinal root.

How many pairs of spinal nerves are there?

31 pairs of spinal nerves.

How many vertebral bones are there?

30 vertebral bones.

How many dorsal root ganglia (DRG) are there?

31 dorsal root ganglia.

Why are there only 30 dermatomes?

Because there is no C1 dermatome.

What is another anomaly in the dermatome map?

There is no spinal dermatome on the face; it is supplied by the trigeminal nerve.

Where are the dorsal root ganglia located?

In the intervertebral foramen between adjacent vertebrae.

Where is the trigeminal ganglion located?

In Meckel’s cave within the dura mater.

Can nociceptors respond to more than one type of stimulus?

Yes, polymodal nociceptors can respond to mechanical, thermal, and chemical stimuli.

Which DRG innervates the big toe?

L4 dorsal root ganglion.

What are the three branches of the trigeminal nerve that form the facial dermatome?

Ophthalmic (V1), Maxillary (V2), and Mandibular (V3) branches.

What is congenital insensitivity to pain?

A rare genetic disorder where individuals cannot feel physical pain.

What is the function of the PRDM12 gene?

It encodes a transcriptional regulator essential for the development of nociceptors.

How does a PRDM12 mutation cause congenital analgesia?

Individuals lack functional nociceptors due to disrupted developmental specification.

How does a SCN9A mutation lead to congenital analgesia?

SCN9A encodes the NaV1.7 sodium channel required for action potential conduction in nociceptors; its loss prevents signal transmission to the CNS.

Which laminae of the spinal cord dorsal horn receive sensory afferent inputs?

Laminae I, II, and V.

Through which structure do NS and WDR axons cross the spinal cord midline?

The anterior white spinal commissure.

In which white matter column do pain and temperature fibers ascend?

The anterolateral white column.

Which receptor is prominent in lamina I neurons receiving peptidergic input?

NK1 receptors (bind substance P).

What is the termination site and function of the spinothalamic tract?

Ventrobasal thalamus; conveys crude sensation and relays to the cortex.

What is the termination site and function of the spinoreticular tract?

Brainstem reticular formation and raphe nuclei; involved in pain modulation and autonomic responses.

What is the termination site and function of the spinomesencephalic/spinotectal tract?

Midbrain structures such as the colliculi and periaqueductal gray; involved in pain modulation and orienting to pain.

What is the difference between the neospinothalamic and paleospinothalamic tracts?

The neospinothalamic tract is newer, has fewer synapses, and conveys fast, discriminative pain; the paleospinothalamic tract is older, more multisynaptic, and conveys slow, crude pain.

In Brown-Sequard syndrome, why is pain and temperature loss contralateral but proprioception loss ipsilateral?

Pain/temperature fibers cross in the spinal cord (anterolateral system), while proprioceptive fibers cross in the medulla (dorsal column system).

Why is motor control affected ipsilaterally in Brown-Sequard syndrome?

Because corticospinal tracts cross in the medullary pyramids, not the spinal cord.

What is the pain matrix?

A network of brain regions collectively responsible for processing the sensory and affective dimensions of pain.

Which thalamic nuclei are involved in the lateral and medial pain systems?

VPL and VPM nuclei (lateral pain system), and mediodorsal (MD) nucleus (medial pain system).

What input does the VPL thalamic nucleus receive and where does it project?

Receives neospinothalamic input and projects to Brodmann areas 3, 1, and 2 in the postcentral gyrus.

What is different about the VPM compared to the VPL?

VPM receives trigeminothalamic input conveying facial sensory information, including taste from the solitary tract.

What structure lies between the temporal and parietal lobes when separated?

The insular cortex.

Which cortical layer receives thalamic sensory inputs?

Layer 4 of the primary somatosensory cortex.

What is the role of the secondary somatosensory cortex (SII)?

Integrates sensory information from both body halves, attention, learning, and sensorimotor integration.

Which regions form the medial pain system?

Insula, anterior cingulate cortex, and limbic structures.

How do chronic pain states alter neural processing?

Chronic pain changes gene expression and neuronal phenotype, creating unique neurochemical signatures that complicate treatment.

What is the main descending pain control system called?

The endogenous analgesia system.

Which brainstem nuclei are key components of the descending analgesia pathway?

Periaqueductal gray (PAG), rostral ventromedial medulla (RVM/raphe magnus), and locus coeruleus.

What are the neurotransmitters used by PAG, RVMM, and LC?

PAG: opioids; RVMM: serotonin (5-HT); LC: noradrenaline (NA).

What are the functions of the periaqueductal gray besides analgesia?

Autonomic regulation, bladder control, vocalization, respiration, and emotional responses.

Name five forebrain regions that influence descending pain control.

Prefrontal cortex, anterior cingulate cortex, insula, amygdala, and hypothalamus.

What is the thermal grill illusion?

A sensory illusion where interlaced warm and cool stimuli produce a burning pain sensation without tissue damage.

What does the thermal grill illusion suggest about pain mechanisms?

It indicates that simultaneous activation of warm and cool pathways can aberrantly activate nociceptive circuits through disinhibition.

What is central inhibition in the context of temperature and pain?

Cool-sensitive pathways inhibit nociceptive pathways to prevent pain during normal temperature sensations.

What real-life example supports central inhibition?

Applying a cool cloth to an injury reduces pain by engaging inhibitory cooling pathways.

What is central disinhibition in the thermal grill illusion?

Simultaneous warm and cool stimulation suppresses the inhibitory cool pathway, disinhibiting nociceptive neurons and creating pain.

Which cortical areas are involved in processing the thermal grill illusion?

Insular and cingulate cortices.

What role does the insula play in pain processing?

Integrates sensory, affective, and cognitive components of pain and other sensations.

Describe the key features and lesion site of Wernicke’s aphasia.

Characterized by fluent but meaningless speech, poor comprehension, and lack of awareness of deficits; lesion in the posterior superior temporal gyrus (Wernicke’s area) of the dominant hemisphere.

Describe the key features and lesion site of Broca’s aphasia.

Characterized by non-fluent, effortful speech with intact comprehension and awareness of deficits; lesion in the inferior frontal gyrus (Broca’s area) of the dominant hemisphere.

How does recovery of language in Broca’s aphasia typically present, and what does it suggest about comprehension?

Partial recovery may allow limited speech but continued difficulty forming grammatically correct sentences; comprehension of complex syntax often remains impaired, indicating distributed processing beyond Broca’s area.

What evidence suggests that aphasia is associated with damage to the left hemisphere?

Aphasia typically co-occurs with right-sided motor deficits following left-hemisphere stroke, indicating lateralization of language to the left hemisphere.

Explain how the structure of the retina limits reading ability.

Reading depends on the fovea, which covers only a few degrees of the visual field; peripheral vision has poor resolution, requiring frequent saccades to move the fovea across text.

Describe the role of saccades in reading.

Saccades are rapid eye movements that reposition the fovea across text lines; they enable sequential word processing but introduce brief periods where no visual information is taken in.

Explain how visibility of text to the right of fixation affects reading performance.

Visible text to the right allows for ‘parafoveal preview,’ facilitating prediction and reducing fixation duration; obscuring right-hand text reduces reading efficiency and comprehension.

Compare the Rapid Serial Visual Presentation (RSVP) method to normal reading.

RSVP presents words sequentially at a fixed fixation point, eliminating saccades and allowing faster reading, but may reduce comprehension due to loss of parafoveal preview and context integration.

Differentiate between the phonological and lexical routes in reading.

The phonological route involves decoding graphemes into phonemes, while the lexical route recognizes entire words as visual symbols; the lexical route is faster and used for familiar words.

Explain why lexical recognition is generally faster than phonological decoding.

Lexical recognition allows holistic word identification, bypassing grapheme-phoneme conversion and internal speech articulation, leading to quicker semantic access.

Outline the neural sequence involved in a simple reading reaction-time task.

Light activates retinal photoreceptors → bipolar and ganglion cells → LGN → V1 → higher visual areas (V2, V4, IT) → cognitive processing in temporal and frontal regions → motor planning (SMA, premotor cortex) → M1 and spinal motor neurons for response.

Explain why reaction times differ for real words versus pseudo-words.

Real words are recognized faster due to activation of stored lexical representations; pseudo-words require phonological analysis and comparison against the lexicon, increasing processing time.

Discuss whether the lexical or phonological route is primarily used to discriminate between real and pseudo-words.

Both routes are used, but pseudo-words rely more on the slower phonological route since no pre-existing lexical entry exists.

Explain what the similarity in reaction time between semantic tasks (e.g., food vs non-food words) implies about lexical processing.

It suggests that semantic evaluation occurs automatically during word recognition; comprehension and classification likely occur in parallel rather than as separate sequential processes.

Discuss the effect of word length on recognition speed and its implications for reading models.

Longer words may be processed slightly slower than short words, but differences are minimal; this supports a parallel processing model of word recognition rather than serial letter-by-letter decoding.

What aspect of reading does the word-length experiment primarily test?

It tests both the spatial limitations of the fovea and the efficiency of lexical recognition across different visual spans.

Define semantic priming and explain its effect on word recognition speed.

Semantic priming is the facilitation of word recognition when a preceding stimulus is related in meaning or sound; it activates associative networks in language regions, reducing recognition latency.

Describe the types of word relationships that can produce priming effects.

Semantically related words, antonyms, synonyms, homophones, and words that co-occur in common phrases can all elicit priming effects.

Explain how subliminal priming demonstrates pre-conscious language activation.

Even when the prime word is presented too briefly for conscious awareness, it can still facilitate recognition of related targets, showing that lexical-semantic processing occurs automatically below awareness.

Discuss whether priming mechanisms operate during natural reading.

Yes, predictive priming likely occurs as readers anticipate upcoming words based on context and syntax, enhancing comprehension efficiency.

Explain why visual signals from the right visual field are processed only in the left hemisphere.

The right visual field projects to the nasal retina of the right eye and the temporal retina of the left eye. Nasal fibers cross at the optic chiasm, so all right-field information is sent to the left hemisphere.

How can visual stimuli be used to investigate split-brain function?

In intact brains, each hemisphere shares visual information via the corpus callosum. In split-brain patients, the severed callosum prevents this sharing, allowing researchers to test each hemisphere’s cognitive abilities independently.

Name the five major commissures that connect the cerebral hemispheres.

Corpus callosum, anterior commissure, posterior commissure, hippocampal commissure, and habenular commissure.

Which commissure is primarily responsible for interhemispheric sharing of visual information?

The corpus callosum.

Which smaller commissure is often damaged during corpus callosotomy?

The hippocampal commissure, as it lies immediately ventral to the corpus callosum.

Define the term 'dominant hemisphere'.

The hemisphere controlling the preferred hand for fine motor tasks; typically the left hemisphere in right-handed individuals.

Compare language abilities between the dominant and non-dominant hemispheres.

The left hemisphere can interpret and generate complex speech. The right hemisphere primarily processes prosody and emotional tone and may have limited reading and writing capacity.

Summarize hemispheric lateralisation for key cognitive and perceptual functions.

Left: language, logic, and fine motor control. Right: visuo-spatial processing, emotional and musical interpretation, face recognition, and global perception.

Besides commissures, what other neural pathways permit hemispheric communication?

Interhemispheric connections exist through the basal ganglia, cerebellum, brainstem, and spinal cord.

Describe the expected effects of cutting the corpus callosum on motor, sensory, and language function.

Motor: difficulty coordinating bimanual actions. Somatosensory: confusion near midline. Vision: disrupted perception of central objects. Language: inability to name objects in the left visual field. Memory: mild impairment if hippocampal commissure is cut.

Why can a split-brain patient like Joe perform two independent tasks simultaneously, one with each hand?

Each hemisphere controls its contralateral hand independently; without callosal competition, two separate motor programs can run in parallel.

Why could Vicki’s right hemisphere write the word 'telephone' even though she could not say it?

Her right hemisphere recognized the object and accessed the corresponding word form for writing, despite lacking verbal output capacity.

Which hemisphere likely produced Vicki’s incorrect verbal guess 'skipping rope', and why?

Her left hemisphere, which handles speech, fabricated a plausible answer despite not having visual access to the image shown to the right hemisphere.

Summarize the sensory and motor capabilities of each hemisphere in a split-brain patient like Vicki.

Left hemisphere: receives right visual field, controls right hand, produces speech. Right hemisphere: receives left visual field, controls left hand, limited speech but can write or draw responses.

Why does performance of the 'split-brain student' model differ when eyes are open versus closed?

With eyes open, visual feedback allows intermanual coordination, partially substituting for the missing corpus callosum.

In the split-brain experiment, if 'bell' is shown to Joe’s left visual field and 'music' to his right, which word would he report seeing aloud?

He would say 'music', since the left hemisphere receives the right visual field and controls speech output.

If Joe is asked to point to what he saw using his left hand, which object would he select and why?

He would point to 'bell', because the left hand is controlled by the right hemisphere that perceived the left visual field stimulus.

Explain why Joe’s left hemisphere confabulates a story about why he pointed to 'bell' after seeing 'music'.

The left hemisphere, unaware of the right hemisphere’s perception, invents a rational explanation based on limited information—demonstrating the brain’s tendency to 'interpreter' behaviour.

What does Joe’s drawing of a 'toadstool' reveal about right hemisphere language processing?

It shows that the right hemisphere can recognize and interpret simple words and integrate them into meaningful representations despite lacking full linguistic output.

Why do individuals with agenesis of the corpus callosum often differ from surgical split-brain patients?

Developmental plasticity allows alternative interhemispheric connections to form, so their deficits are less pronounced than in surgically split brains.

Why should hemispheric specialisation not be viewed as absolute?

While one hemisphere may dominate a function, the other typically retains partial capacity; real brains show graded lateralization and compensatory interaction through remaining pathways.

Explain why MRI is considered non-invasive and why this is important for neuroscience research.

MRI visualises internal organs and tissues without physical interference such as cutting or inserting instruments. It is safe, repeatable, and allows researchers to study the living brain without altering its function or structure.

List the three standard anatomical planes used in MRI imaging.

Horizontal (axial), coronal, and sagittal planes.

Describe the relationship between slices, voxels, and pixels in MRI.

MRI captures 3D volumes as slices composed of voxels. Each voxel corresponds to one pixel in the 2D image; thus, one pixel represents the signal from one voxel.

Why is spatial resolution important in structural MRI?

High spatial resolution determines how much anatomical detail is visible, enabling detection of small structural abnormalities or fine anatomical boundaries.

What are the typical brightness characteristics of tissues in T1-weighted MRI?

White matter appears bright due to lipid-rich myelin; grey matter is intermediate; cerebrospinal fluid appears dark because it is water-based with low signal intensity.

What is the main purpose of structural MRI?

To examine brain anatomy and detect morphological changes due to trauma, disease, or development. It provides a detailed map of brain structures for diagnostic and research use.

How are 3D MRI reconstructions produced, and are they a different type of scan?

3D models are generated using computer graphics applied to 2D slice data. The underlying MRI acquisition is the same; additional thin slices improve reconstruction accuracy.

What is the finest level of structure currently visible with state-of-the-art MRI?

Current MRI can resolve structures around 0.5 mm, sufficient to distinguish cortical layers or medium-sized cortical columns.

Define spatial resolution and temporal resolution in the context of MRI.

Spatial resolution describes how finely brain structures can be imaged; temporal resolution refers to how quickly changes in brain activity can be detected over time.